Article

Structure and mechanical behavior of a toucan beak

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Abstract

The toucan beak, which comprises one third of the length of the bird and yet only about 1/20th of its mass, has outstanding stiffness. The structure of a Toco toucan (Ramphastos toco) beak was found to be a sandwich composite with an exterior of keratin and a fibrous network of closed cells made of calcium-rich proteins. The keratin layer is comprised of superposed hexagonal scales (50 μm diameter and 1 μm thickness) glued together. Its tensile strength is about 50 MPa and Young’s modulus is 1.4 GPa. Micro and nanoindentation hardness measurements corroborate these values. The keratin shell exhibits a strain-rate sensitivity with a transition from slippage of the scales due to release of the organic glue, at a low strain rate (5 × 10−5/s) to fracture of the scales at a higher strain rate (1.5 × 10−3/s). The closed-cell foam is comprised of fibers having a Young’s modulus twice as high as the keratin shells due to their higher calcium content. The compressive response of the foam was modeled by the Gibson–Ashby constitutive equations for open and closed-cell foam. There is a synergistic effect between foam and shell evidenced by experiments and analysis establishing the separate responses of shell, foam, and foam + shell. The stability analysis developed by Karam and Gibson, assuming an idealized circular cross section, was applied to the beak. It shows that the foam stabilizes the deformation of the beak by providing an elastic foundation which increases its Brazier and buckling load under flexure loading.

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... Subsequently he carried out the first studies on the structure and properties of mollusk shells, sea urchin tooth, narwhal tusk, antler and other biological mineralized materials [61][62][63][64][65][66]. More recently, our group has examined the structure and mechanical properties of the abalone [67][68][69][70], crab exoskeleton [71], the toucan beak [72][73][74], the armadillo carapace [75], bird feathers [76], antler [77][78][79], bone [80][81][82], horn [83,84], teeth [85,86], underwater adhesives [87], fish scales [88], and porcupine quills [89]. ...
... This internal foam has a closed-cell structure constructed from bony struts with thin membranes. We summarize here the principal results obtained by our group [72][73][74]456,457]. Fig. 148 shows photographs and schematics of the toucan and hornbill beaks. ...
... We summarize here the principal results obtained by our group [72][73][74]456,457]. Fig. 148 shows photographs and schematics of the toucan and hornbill beaks. This structure was found by Seki et al. [72] to have a bending strength (Brazier moment) that is considerably higher than if all the mass were concentrated in the shell as a solid hollow cylinder by applying the analysis developed by Karam and Gibson [171]. Seki et al. [72,73] showed that the internal cellular core serves to increase the buckling resistance of the beak and demonstrated a synergism between the two components that provides the stability in bending configuration. ...
... Nature has provided an unlimited variety of these structures around and within us. Most common naturally occurring cellular structures are wood [17], bone structure [18], corals and cork [15], toucan beak [19], and many more. Humans get the inspiration from the variety of design and use of these structures, by nature, and adopt them in their construction. ...
... Figure 10a,b shows the strength to mass ratios versus vertical shift of specimens with 70% and 100% infill density. For 100% infill density specimens, a zigzag trend is observed for specimens with frequency f1 (19), and an increasing trend is observed for specimens with frequency f2 (21). The strength to mass ratio of solid specimens is higher than the values of 100% infill density with internal structure specimens, except for the specimen with frequency 21 and vertical shift 0.4, having the same value of strength to mass ratio. ...
... Figure 10a,b shows the strength to mass ratios versus vertical shift of specimens with 70% and 100% infill density. For 100% infill density specimens, a zigzag trend is observed for specimens with frequency f 1 (19), and an increasing trend is observed for specimens with frequency f 2 (21). The strength to mass ratio of solid specimens is higher than the values of 100% infill density with internal structure specimens, except for the specimen with frequency 21 and vertical shift 0.4, having the same value of strength to mass ratio. ...
Article
Full-text available
Additive manufacturing (AM) has a greater potential to construct lighter parts, having complex geometries with no additional cost, by embedding cellular lattice structures within an object. The geometry of lattice structure can be engineered to achieve improved strength and extra level of performance with the advantage of consuming less material and energy. This paper provides a systematic experimental evaluation of a series of cellular lattice structures, embedded within a cylindrical specimen and constructed according to terms and requirements of ASTMD1621-16, which is standard for the compressive properties of rigid cellular plastics. The modeling of test specimens is based on function representation (FRep) and constructed by fused deposition modeling (FDM) technology. Two different test series, each having eleven test specimens of different parameters, are printed along with their replicates of 70% and 100% infill density. Test specimens are subjected to uniaxial compressive load to produce 13% deformation to the height of the specimen. Comparison of results reveals that specimens, having cellular lattice structure and printed with 70% infill density, exhibit greater strength and improvement in strength to mass ratio, as compared to the solid printed specimen without structure.
... The main component of the skeleton of the bird needs to be strong and robust enough to support the reaction force that comes from the large wingspan subjected to lift and drag forces for sustaining flight, while the lightweight of the material is critical to overcome the gravity force. Among birds, a fascinating example are Toucan, who is famous for its large beak taking 1/3 of its total length but showing a weight that is less than 1/20 of the total and with average density surprisingly low, i.e. 1/10 that of water [18,19]. It turned out that the entire beak is foam-like structure covered by a thin layer of keratin, making the structure so light [18][19][20]. ...
... Among birds, a fascinating example are Toucan, who is famous for its large beak taking 1/3 of its total length but showing a weight that is less than 1/20 of the total and with average density surprisingly low, i.e. 1/10 that of water [18,19]. It turned out that the entire beak is foam-like structure covered by a thin layer of keratin, making the structure so light [18][19][20]. ...
... Design and fabrication of high strength, high-porosity materials with continuous porous features can be used directly for energy absorption upon impact loading conditions. Biological materials, including toucan beak, balsa wood and bamboo are fully composed of porous channels [23], which reduce the weight but also enhance their capability to absorb impact energy [18][19][20]. Accordingly, wood materials have been widely used in engineering applications including wind turbines or aviation models made of balsa wood, as well as scaffold structures fabricated with bamboo for infrastructure [55], architecture, and fiber-reinforced composites [56]. All these applications demand good capability of energy absorption to prevent the applied external force from causing catastrophic failure of the material. ...
Chapter
Bone, nacre, and other biological materials exhibit unique hierarchical structures at different length scales, and thereby achieve versatile material functions. The excellent performance of bioinspired designs in materials science has attracted the interest of engineers and scientists to expand this bioinspiration to many other materials, including graphene. Among the different designs that draw significant attention, butterfly wings are particularly noteworthy, whose iridescent colors arise from the interaction of light with highly precise multiscale structures that in some cases correspond to a 3D shape of gyroid geometries. Especially, the combination of gyroid designs with graphene can produce mechanical and thermal functions for carbon porous materials that exhibit superior properties such as strength 10 times higher than mild steel, with only around 4.6% the density of this material, featuring also density-insensitive thermal stability, as well as an outstanding impact energy absorption capability as high as 269 MJ/m³. Based on molecular modeling, the physics and mechanics of graphene-based gyroid structures, as well as their performance in the context of thermal conduction and impact energy absorption are included in our current short review.
... The length of a toucan's beak accounts for 1/3 of the bird's total length, but thanks to its density being approximately 0.1 g/cm 3 , the mass is only one-twentieth of the total bird. Similar to the toucan, the hornbill's beak occupies 1/4 of the bird's total length and the density is about 0.3 g/cm 3 [39,98,99]. Toucan and hornbill beaks are 3D cellular structures made of foam and covered with a hard surface [11]. ...
... Figure 7a, d show toucan and hornbill beaks schematically [11]. The hornbill's beak has a unique casque formed from a cornified keratin layer [11,12,39]. The hard surface (keratin shell) of toucan and hornbill beaks consists of multiple layers of keratin scales (Figure 7e) [39]. ...
... The hornbill's beak has a unique casque formed from a cornified keratin layer [11,12,39]. The hard surface (keratin shell) of toucan and hornbill beaks consists of multiple layers of keratin scales (Figure 7e) [39]. The keratin scales are hexagonal, are glued together and overlap each other. ...
Article
Full-text available
The rise in structural performance requirements in engineering is driving the research and development of stronger, stiffer, and lighter materials. However, most traditional artificial materials are unable to meet the needs of modern industrial and technological development. In fact, multifarious creatures in nature are further ahead in their use of structural materials. There is a fairly limited selection of natural structural materials at ambient temperatures. They usually consist of hard and soft phases arranged in a complex hierarchy with characteristic dimensions ranging from nanoscale to macroscale. The resulting materials usually show a nearly perfect combination of strength and toughness integrated with lightweight characteristics. This is exactly what is required of engineering materials. In this review, different biological materials were divided into the following types in terms of structural elements: 1D fibrous structures, 2D layered structures, 3D cellular structures and heterogeneous interface structures. For each structural element, corresponding structure components and mechanical properties of typical organisms were well described. Abundant sophisticated models of natural biological structures were discussed contrastively. The purpose of this review was to summarize the excellent properties of multi-dimensional biological models with cross-scale features and to reveal the relationship between structure characteristics and function mechanism, which could provide valuable references for the design and optimization of a future biomimetic composite with high mechanical performance. This review is anticipated to not only inspire novel biomimetic design but also offer a window for the deep understanding of existing outstanding structural composites in diversified species, which could provide continuous innovative power for composite renovation in many engineering fields.
... Pomelo peel Non-uniform pore distribution improves impact resistance. [26] Toucan beak Toucan beaks are made from rigid foam inside and keratin outside made it lightweight and strong [27] Hedgehog spines The spines of hedgehogs' function as shock-absorbers when falling. [28] Scientist discovered the non-uniform of the Pomelo peel through the peel thickness can give a good damping and dissipation energy to the fruit. ...
... Although the beak is big as in Figure 5(a) [30], but it was lightweight. This is because of the sandwich structures of a foam covered with a hard layer of keratin showed in Figure 5(b) [27]. Analysis of energy absorbed by the shell and form was higher than the shell and foam separately. ...
Conference Paper
Theory of Inventive Problem Solving (TRIZ) is a tool to solve a technical problem while biomimetic is the imitation of nature in solving the problems. Ongoing research about integration between TRIZ and biomimetic in solving engineering problems can be found in scientific journals database, however, its application for conceptual design stage in product development is still limited and can be further explored. In this paper, a new framework for integrating TRIZ and biomimetic methods in generating design concepts for product development process is proposed. The framework proposed the use of Function-Oriented Search (FOS) by TRIZ combined with biomimetic principles. As a conclusion, the proposed framework was shown able to facilitate in generating innovative design concepts during the product development process.
... These very active species are noted by their disproportionately long and brightly colored beaks. The Toucan's beak is a lightweight and highly vascularized dynamic structure composed of spongy bone with an intricate inner network of trabeculae, a dermis layer attached to the periosteum of the underlying bone, and a germinative layer for the beak's continuous growth (Cornelissen and Ritchie 1994;Cubas 2001;Seki et al. 2005;Worell 2008). Covering the bone structure, there is a thick keratinized epidermal wall called rhamphotheca that is divided into the rhinotheca (maxillary keratin) and the gnathotheca (mandibular keratin) (Cornelissen and Ritchie 1994;Doneley 2016). ...
... Covering the bone structure, there is a thick keratinized epidermal wall called rhamphotheca that is divided into the rhinotheca (maxillary keratin) and the gnathotheca (mandibular keratin) (Cornelissen and Ritchie 1994;Doneley 2016). Because of this composite structure, a Toucan's beak has a low density (approximately 0.1 g cm −3 ), comprising 1/3 of the bird length but only 1/20 of its mass and with a high-energy absorption capacity (Seki et al. 2005), being able to support traction of 270.4 N (for Ramphastos toco, Fecchio et al. 2008). Apart from foraging, their unique beak morphology is known to be related to other physiologic processes and behaviors. ...
Article
Beak fractures in Toucans can be common for different causes and usually treated with prostheses while the bird is kept in captivity up to total beak regrowth. There is no information of Toucans thriving in the wild with this kind of injury. Here, I report a free-living Red-breasted Toucan (Ramphastos dicolorus) recorded on video with an avulsion of half of its upper jaw showing an adapted behavior for feeding. The bird was observed twice in the same area. The apparent absence of caseous content and debris in the injury through the analysis of the frames suggests an old lesion in recovery. Based on the literature on beak injuries, I discuss some potential threats the lesion could pose to the specimen in the wild and suggest further researches that can be done with animals already in captivity recovering from the same injury.
... materials created by Nature, as opposed to "traditional" man-made solids. Extensive research efforts have been directed to such materials, with emphasis on bamboo, [4,5] trees, [6][7][8] mollusks, [9][10][11][12][13][14][15] arthropods, [16][17][18][19][20][21] birds, [22][23][24][25][26][27] fish, [28][29][30][31][32][33][34] mammals, [35][36][37][38][39][40][41][42][43] and human beings, [44][45][46][47][48][49][50][51][52][53] motivated not only by their unique structures and properties/ functionalities, but also by the salient mechanisms and underlying design principles that account for their long-term perfection. ...
... The bird beak provides an illuminating insight into how sufficiently high rigidity and robustness can be achieved in materials with a minimum weight penalty-which is critical for flight-by utilizing expert designs. [22,23,26,27,112,113] A good example here is the red-bellied woodpecker (Melanerpes carolinus) beak which is used to penetrate trees-a beak that functions more like a weapon as compared to the chicken and toucan beaks that are used for grabbing food or crushing fruit (Figure 4a). [23,26] The keratin scales in the rhamphotheca are more elongated along the longitudinal direction than in the chicken and toucan beaks, in order to achieve high friction to dissipate more impact energy. ...
Article
Biological material systems have evolved unique combinations of mechanical properties to fulfill their specific function through a series of ingenious designs. Seeking lessons from Nature by replicating the underlying principles of such biological materials offers new promise for creating unique combinations of properties in man‐made systems. One case in point is Nature's means of attack and defense. During the long‐term evolutionary “arms race,” naturally evolved weapons have achieved exceptional mechanical efficiency with a synergy of effective offense and persistence—two characteristics that often tend to be mutually exclusive in many synthetic systems—which may present a notable source of new materials science knowledge and inspiration. This review categorizes Nature's weapons into ten distinct groups, and discusses the unique structural and mechanical designs of each group by taking representative systems as examples. The approach described is to extract the common principles underlying such designs that could be translated into man‐made materials. Further, recent advances in replicating the design principles of natural weapons at differing lengthscales in artificial materials, devices and tools to tackle practical problems are revisited, and the challenges associated with biological and bioinspired materials research in terms of both processing and properties are discussed. The critical structural and mechanical designs employed by naturally evolved weapons in pursuing their high mechanical efficiency in Nature's evolutionary arms race are reviewed. The materials‐design strategies towards an outstanding synergy of offence and persistence are extracted from such weapons. The challenges and opportunities associated with natural weapons in biological and bioinspired materials research are discussed.
... of collagen fibres embedded in a mineral matrix; being able of absorbing shock energy without damaging his body [28]. ...
... Another light-weight natural material is the toucan and hornbill beaks whose structure consist of an external hard keratin shell with a fibrous closed-cell interior system and a hollow core. Not only this foam-like interior allows energy dissipation under stress and ensuing mechanical stability, but also the shell and foam-like sandwich composite yield high stiffness to the beaks [15,28,166,167]. ...
Article
Full-text available
In Nature, there are a large range of tough, strong, lightweight and multifunctional structures that can be an inspiration to better performing materials. This work presents a review of structures found in Nature, from biological ceramics and ceramics composites, biological polymers and polymers composites, biological cellular materials, biological elastomers to functional biological materials, and their main toughening mechanisms, envisaging potential mimicking approaches that can be applied in advanced continuous fibre reinforced polymer (FRP) composite structures. For this, the most common engineering composite manufacturing processes and current composite damage mitigation approaches are analysed. This aims at establishing the constraints of biomimetic approaches development as these bioinspired structures are to be manufactured by composite technologies. Combining both Nature approaches and engineering composites developments is a route for the design and manufacturing of high mechanical performance and multifunctional composite structures, therefore new bioinspired solutions are proposed.
... [8][9][10][11] As a result, a vast number of studies have been carried out to explore the secret behind nature structures, their shapes, as well as their topologies. [12][13][14][15][16][17] The shape and mechanical properties of seashell, [18] ladybug legs, [19] kingfisher beak, [20] shark teeth, [21] and many others have been studied in greater details. Most of the research has focused on understanding the complex architecture of these Adv. ...
... [8][9][10][11] As a result, a vast number of studies have been carried out to explore the secret behind nature structures, their shapes, as well as their topologies. [12][13][14][15][16][17] The shape and mechanical properties of seashell, [18] ladybug legs, [19] kingfisher beak, [20] shark teeth, [21] and many others have been studied in greater details. Most of the research has focused on understanding the complex architecture of these www.advmat.de ...
Article
Full-text available
Schwartzites are three dimensional porous solids with periodic minimal surfaces having negative Gaussian curvatures and could possess unusual mechanical and electronic properties. We investigated the mechanical behavior of primitive and gyroid Schwartzite structures across different length scales after these geometries were 3D printed at centimeter length scales based on molecular models. Molecular dynamics and finite elements simulations were used to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments. Our results show that these structures hold great promise as high load bearing and impact resistant materials due to a unique layered deformation mechanisms that emerges in these architectures during loading. Easily scalable technique such as 3D printing can be used for exploring mechanical behavior of various predicted complex geometrical shapes to build innovative engineered materials with tunable properties.
... The general trend for keratinous materials is that increasing strain rate increases stiffness and strength, while decreasing the breaking strain (Johnson et al., 2017;Kasapi and Gosline, 1996;Seki et al., 2005;Song et al., 2009). Thus, most keratin materials undergo an elastic to ductile-plastic to brittle transition with an increasing strain rate, as was shown for the toucan rhamphotheca (Seki et al., 2005) and pangolin scales (Wang et al., 2016c). ...
... The general trend for keratinous materials is that increasing strain rate increases stiffness and strength, while decreasing the breaking strain (Johnson et al., 2017;Kasapi and Gosline, 1996;Seki et al., 2005;Song et al., 2009). Thus, most keratin materials undergo an elastic to ductile-plastic to brittle transition with an increasing strain rate, as was shown for the toucan rhamphotheca (Seki et al., 2005) and pangolin scales (Wang et al., 2016c). This rate-dependent behavior has important implications for impact resistance, suggesting that these materials can withstand greater stresses under dynamic conditions and have different failure mechanisms than quasi-static conditions. ...
Article
Full-text available
Keratin is a highly multifunctional biopolymer serving various roles in nature due to its diversified material properties, a wide spectrum of structural designs, and impressive performance. Keratin-based materials are mechanically robust, thermally insulating, lightweight, capable of undergoing reversible adhesion through van der Waals forces, and exhibit structural coloration and hydrophobic surfaces. Thus, they have become templates for bioinspired designs and have even been applied as a raw material for biomedical applications and environmentally sustainable fiber-reinforced composites. This review aims to highlight keratin’s remarkable capabilities as a biological component, a source of design inspiration, and an engineering material. We conclude with future directions for the exploration of keratinous materials.
... Such assembly provides them exceptional strength, toughness, and stiffness compared with their counterparts. [1][2][3][4][5][6][7][8][9] Most recent studies on natural material includes shrimp exoskeleton, 3,4 crab exoskeletons, 10-13 lobsters, 1,2,14,15 ganoid scale of an ancient fish, 16 toucan beak, 17,18 and sea shells such as nacre and mollusk. [19][20][21][22][23][24][25][26][27][28] These studies have revealed interesting features in the design of such biocomposites that makes them much stronger than the constitutive materials. ...
... 1,10,[12][13][14][15]26,29 The spacing between such woven layers is filled with proteins and biominerals. Studies by Seki et al. 17,18 have concentrated on a similar kind of exoskeleton found in the beak of toucan. It was found to be a sandwich structure with the exterior of keratin and a closed cell fibrous network made of calcium rich proteins. ...
Chapter
Crustacean exoskeletons in the form of thin films have been investigated by several researchers in order to understand the role played by the exoskeletal structure in affecting functioning of species such as shrimps, crabs and lobsters. These species exhibit similar design in their exoskeleton microstructure. Bouligand pattern (twisted plywood structure), layers of different thicknesses across cross section, changes in mineral content through the layers etc. are common feature changes. Different parts of crustacean exoskeletons exhibit a significant variation in mechanical properties based on the variation in the above mentioned features. Mechanical properties have been analyzed by authors using imaging techniques such as SEM (Scanning Electron Microscopy), EDX (Energy Dispersive X-ray) and using mechanical characterization based on nanoindentation. Analyses show that the confinement effect arising from interfaces sandwiched in crustacean microstructure layers along with the strain rates of deformation plays a major role in the deformation of such layered systems. A new constitutive model is proposed that couples the effect of strain-rate and confinement to predict interface deformation behavior. The model predictions are validated based on experiments in glass/epoxy interfaces.
... Such assembly provides them exceptional strength, toughness, and stiffness compared with their counterparts. [1][2][3][4][5][6][7][8][9] Most recent studies on natural material includes shrimp exoskeleton, 3,4 crab exoskeletons, 10-13 lobsters, 1,2,14,15 ganoid scale of an ancient fish, 16 toucan beak, 17,18 and sea shells such as nacre and mollusk. [19][20][21][22][23][24][25][26][27][28] These studies have revealed interesting features in the design of such biocomposites that makes them much stronger than the constitutive materials. ...
... 1,10,[12][13][14][15]26,29 The spacing between such woven layers is filled with proteins and biominerals. Studies by Seki et al. 17,18 have concentrated on a similar kind of exoskeleton found in the beak of toucan. It was found to be a sandwich structure with the exterior of keratin and a closed cell fibrous network made of calcium rich proteins. ...
... Parallels in the overall structural organization of the claw can also be found in animal groups other than arthropods. For example, the beaks and claws of birds and the claws of mammals, such as cats, consist of a durable external sheath of longitudinally oriented keratinocytes and mineralized tissue in the center (Seki et al., 2005;Homberger et al., 2009;Soons et al., 2012;Van Hemert et al., 2012). In the toucan beak, the combination of the keratin sheath and the porous core of the beak absorbs energy more efficiently that individual components, suggesting a functional value for this structural organization (Seki et al., 2005). ...
... For example, the beaks and claws of birds and the claws of mammals, such as cats, consist of a durable external sheath of longitudinally oriented keratinocytes and mineralized tissue in the center (Seki et al., 2005;Homberger et al., 2009;Soons et al., 2012;Van Hemert et al., 2012). In the toucan beak, the combination of the keratin sheath and the porous core of the beak absorbs energy more efficiently that individual components, suggesting a functional value for this structural organization (Seki et al., 2005). ...
Article
Skeletal elements that are exposed to heavy mechanical loads may provide important insights into the evolutionary solutions to mechanical challenges. We analyzed the microscopic architecture of dactylus claws in the woodlice _Porcellio scaber_ and correlated these observations with analyses of the claws’ mineral composition with energy dispersive X-ray spectrometry (EDX), electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED). Extraordinarily, amorphous calcium phosphate is the predominant mineral in the claw endocuticle. Unlike the strongly calcified exocuticle of the dactylus base, the claw exocuticle is devoid of mineral and is highly brominated. The architecture of the dactylus claw cuticle is drastically different from that of other parts of the exoskeleton. In contrast to the quasi-isotropic structure with chitin-protein fibers oriented in multiple directions, characteristic of the arthropod exoskeleton, the chitin-protein fibers and mineral components in the endocuticle of _P. scaber_ claws are exclusively axially oriented. Taken together, these characteristics suggest that the claw cuticle is highly structurally anisotropic and fracture resistant and can be explained as adaptations to predominant axial loading of the thin, elongated claws. The nanoscale architecture of the isopod claw may inspire technological solutions in the design of durable machine elements subjected to heavy loading and wear.
... The bird beak rhamphotheca (b-keratin) shows a pull-out fracture mode at low strain rate (5 Â 10 À5 /s) and brittle fracture (keratin scales were torn) at higher strain rate (5 Â 10 À2 /s). The transition of fracture mode was explained in terms of the competition between viscoplastic shear of the interscale glue and tensile fracture of the scales [55]. Since pangolin scales consist of aand b-keratins, the amorphous matrix proteins and the fibrous phase are probably the viscous and elastic components, respectively, and the bonding between keratinized cells/lamellae plays a role in determining mechanical properties. ...
... At relatively high strain rate (10 À1 / s), lamellar movement is restricted, and lamellae are torn and fractured, displaying a smooth fracture surface with crossed-lamellae orientations. Such fracture mode change with increasing strain rate is also observed in hoof wall (a-keratin) [49] and bird beak rhamphotheca (b-keratin) [20,55]. The hoof wall shows highest degree of tubule pull-out fracture at lowest strain rate, and a more brittle surface fractured at impact. ...
Article
Unlabelled: The pangolin has a flexible dermal armor consisting of overlapping keratinous scales. Although they show potential for bioinspired flexible armor, the design principles of pangolin armor are barely known. Here we report on the overlapping organization, hierarchical structure (from the nano to the mesolevel), and mechanical response of scales from ground (Chinese) and arboreal (African tree) pangolins. Both scales exhibit the same overlapping organization, with each scale at the center of neighboring scales arranged in a hexagonal pattern. The scales have a cuticle of several layers of loosely attached flattened keratinized cells, while the interior structure exhibits three regions distinguished by the geometry and orientations of the keratinized cells, which form densely packed lamellae; each one corresponds to one layer of cells. Unlike most other keratinous materials, the scales show a crossed-lamellar structure (∼5μm) and crossed fibers (∼50μm). A nano-scale suture structure, observed for the first time, outlines cell membranes and leads to an interlocking interface between lamellae, thus enhancing the bonding and shear resistance. The tensile response of the scales shows an elastic limit followed by a short plateau prior to failure, with Young's modulus ∼1 GPa and tensile strength 60-100MPa. The mechanical response is transversely isotropic, a result of the cross lamellar structure. The strain rate sensitivity in the range of 10(-5)-10(-1)s(-1) region is found to be equal to 0.07-0.08, typical of other keratins and polymers. The mechanical response is highly dependent on the degree of hydration, a characteristic of keratins. Statement of significance: Although many fish and reptiles have protective scales and carapaces, mammals are characteristically fast and light. The pangolin is one of the few mammal possessing a flexible dermal armor for protection from predators, such as lions. Here we study the arrangement of the scales as well as their hierarchical structure from the nano to the mesolevel and correlate it to the mechanical properties. The study reveals a unique structure consisting of crossed lamellae and interlocking sutures that provide exceptional performance and in-plane isotropy.
... Such assembly provides them exceptional strength, toughness, and stiffness compared with their counterparts. [1][2][3][4][5][6][7][8][9] Most recent studies on natural material includes shrimp exoskeleton, 3,4 crab exoskeletons, 10-13 lobsters, 1,2,14,15 ganoid scale of an ancient fish, 16 toucan beak, 17,18 and sea shells such as nacre and mollusk. [19][20][21][22][23][24][25][26][27][28] These studies have revealed interesting features in the design of such biocomposites that makes them much stronger than the constitutive materials. ...
... 1,10,[12][13][14][15]26,29 The spacing between such woven layers is filled with proteins and biominerals. Studies by Seki et al. 17,18 have concentrated on a similar kind of exoskeleton found in the beak of toucan. It was found to be a sandwich structure with the exterior of keratin and a closed cell fibrous network made of calcium rich proteins. ...
Chapter
Most recent studies on the natural material include shrimp exoskeleton, crab exoskeletons, lobsters, ganoid scale of an ancient fish, toucan beak, and seashells such as nacre and mollusk. Studies focusing on biomimetic materials include development of biomimetic scaffolds for tissue growth and fabrication of tissues from biocompatible, biodegradable polymers, development of the honeycomb plates with design from beetle forewings to eliminate problems of edge sealing, molding process by thoroughly investigating beetle forewing to be able to mimic its design for better sandwich panel structures, and development of high-performance functional nanocomposites from graphene sheets with enhanced thermal conductivity and mechanical stiffness. In the present chapter, basic design principles of the crustaceans and deformation mechanisms responsible for higher strength, stiffness, and toughness are highlighted.
... Studying the structure of a biological material can provide insights to understand its function and mechanical strength [1]. Biological systems strategically construct their structures by means of self-organization/self-assembly [2]. ...
Article
Keratins as fibrous proteins, offer structural integrity to various tissues in providing the functional role of protection or load bearing. This work is a prelude to understand the structure - property correlation for a wide variety of keratins. The kinetics of aggregation of bovine hoof keratin (KF) and horn keratin (KR) were monitored by different biophysical methods. pH dependent studies indicated that initially both keratins existed in pre-aggregated form and the efficiency of aggregation decreased with increasing pH. The size of the aggregates was found to be larger in KF compared to KR. UV-vis and particle size analysis clearly revealed that the pre-aggregated forms of KF and KR dissociated to intermediate transient structures with smaller aggregate size, which acted as stronger nucleating agents for further self association of the keratins to form higher order supramolecular assemblies. Conformational analysis indicated that there was no significant conformational change during the aggregation of KF and KR. Morphology of the KF aggregates showed fractal arrangement while KR aggregates formed an ordered structure with no particular arrangement. To the best of our knowledge, this is the first report which shows an interesting and unique observation on changes in the structure during self-association of keratins.
... Biological structures have received significant attention from engineering researchers over the past few decades due to their unique structural configurations [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. They offer superior mechanical performance [15][16][17][18][19], lightweight and durability to maximize mobility [20,21] and survival under harsh environmental conditions. ...
Article
This paper explores several lamellar structures found in nature, which have been shown to possess superior armor systems. In particular, the hard armor systems of nacre and conch shells, and the flexible armor system of fish scales are the focus of this review due to their high relevance to the protective structural engineering discipline. The structure-function relationships that govern the superior mechanical performance of these systems are attributed to their well-organized composite hierarchical structures. The paper also reviews advancements in additive manufacturing techniques for proof-of-concept prototyping, as well as advanced modeling techniques that have been employed to capture the complex geometries of biological structures and the interactions between their constituents. Finite element modeling and 3D printing were found to be the most popular techniques, as they automate the process of modeling and manufacturing complex bio-mimetic composites from a computer-aided design. Finally, attempts to apply bio-mimicry to the structural engineering discipline have been identified, which remains a new and exciting area of research.
... Meta-materials and biomimetic structures show a kind of ordering in their microstructure [1][2][3]. The ordering introduces functions not achievable in fully stochastic microstructures [4]. ...
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Designing meta-materials and cellular solids with biomimetic structures has received increasing attention in the past few years partially due to advances in additive manufacturing techniques that have enabled the fabrication of advanced materials with arbitrarily complex microarchitectures and novel functionalities. To impact on this trend, it is essential to develop our understanding about the role of microstructure on mechanical responses of these structures. Although a large literature exists on the general subject, the role of microstructure on the post-yield instability is not yet adequately documented. This research introduces a numerical approach to study the post-yield instability in 2D infinite honeycombs as a bottleneck for understanding the instability in more complex 3D systems. Two distinct algorithms are used to systematically vary the ordering in the microstructure of regular hexagonal honeycombs and the mean cell size in the microstructure of Voronoi honeycombs. Finite elements together with a nonlinear homogenization technique are incorporated to quantify the instability responses. Finally, the contribution of microstructure on initial post-yield instability—the slope and magnitude of stress drop after yielding—is statistically investigated. It is found that changing the degree of ordering in the microstructure with respect to a parent symmetry can systematically vary the post-yield instability properties. However, systematic variation of the cell size distribution in absence of ordering in the microstructure cannot remarkably change the post-yield instability in the meta-material. Instead, a tailored cell size distribution can systematically influence its yield strength and plateau stress.
... The motivation for this investigation is the establishment of the mechanisms by which nature develops strong and tough materials using relatively weak (chitin, proteins and calcium carbonate) constituents. A range of hard natural materials has been investigated, such as the intricate tiled structure of the nacreous component of abalone shells [33][34][35], the sandwich structure of toucan beaks [36,37], silk and others [7], yielding results that have significant technological applications. ...
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INTRODUCTION Crab Shell is the second most common natural composite material in the world, and one of the most versatile. Very few mechanical studies have been made on the hard shells (solid cuticle) characteristic of the arthropod integument and it is therefore not yet possible to provide a general model for the mechanical behavior of the exoskeletons of this phylum. Arthropods are the largest animal phylum. They include the trilobites, chelicerates, myriapods, hexapods, and crustaceans. All arthropods are covered by an exoskeleton, which is periodically shed as the animal grows. The exoskeleton of arthropods consists mainly of chitin. In the case of crustaceans, there is a high degree of mineralization, typically calcium carbonate, which gives mechanical rigidity. The various studies carried out on insect solid cuticle[1-4] and prawn shells [5] indicate a number of similarities in the mechanical behaviour of insect and prawn solid cuticle as well as differences apparently due to the fact that the former are two-phase composite materials consisting of chitin fibres in a protein matrix while the latter include another phase, namely inorganic alts, resulting in a three-phase material. In the present review, the mechanical behavior of the solid cuticle of the crab, Scylla serrata, was investigated in order to determine their fracture behavior, micro-hardness properties and general mechanical behavior as composite materials. This crustacean Abstract-The present review describes the development of investigations of mechanical properties of crab shell. The mechanical behavior of crab shell was investigated. There was low strain discontinuity in their bulk tensile stress-strain curves. The crab cuticle fails in an entirely brittle manner. The cutile of the crab is a composite material, the properties of which are closely analogous to those of pre-stressed concrete. The mechanical properties of the exoskeleton of the sheep crab (Loxorhynchus grandis) were investigated earlier. It was found that the crab exoskeleton is a natural composite consisting of highly mineralized chitin–protein fibers arranged in a twisted plywood pattern. It was observed that there is a high density of pore canal tubules in the direction normal to the surface. Tensile tests were carried out on wet and dry specimens in longitudinal as well as normal directions. Samples tested in the longitudinal direction showed a convex shape and no evidence of permanent deformation prior to failure, whereas samples tested in the normal orientation exhibited a concave shape. The results show that the composite is anisotropic in mechanical properties. Micro indentation was performed to measure the hardness through the thickness. It was found that the outer layer is two times harder than the inner layer.
... For example, the skull of a magpie is a double sandwich construction (see Fig. 1.2(a)) whereas the skull of larger birds, such as owls, is a multiple sandwich construction (see Fig. 1.2(b)). Another example is the stiff toucan beak, which constitutes one third of the bird's length, but only one twentieth of its weight (Seki et al., 2005). The first industrial application of a sandwich construction is attributed to Fairbairn (1849) who used iron face-sheets riveted to a wooden core in the construction of bridges. ...
Thesis
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Lattice materials are used as the core of sandwich panels to construct light and strong structures. This thesis focuses on metallic sandwich structures and has two main objectives: (i) explore how a surface treatment can improve the strength of a lattice material and (ii) investigate the collapse response of two competing prismatic sandwich cores employed in ship hulls. First, the finite element method is used to examine the effect of carburisation and strain hardening upon the compressive response of a pyramidal lattice made from hollow tubes or solid struts. The carburisation surface treatment increases the yield strength of the material, but its effects on pyramidal lattices are not known. Here, it is demonstrated that carburisation increases the plastic buckling strength of the lattice and reduces the slenderness ratio at which the transition from plastic to elastic buckling occurs. The predictions also showed that strain hardening increases the compressive strength of stocky lattices with a slenderness ratio inferior to ten, but without affecting the collapse mode of the lattice. Second, the quasi-static three-point bending responses of simply supported and clamped sandwich beams with a corrugated core or a Y-frame core are compared via experiments and finite element simulations. The role of the face-sheets is assessed by considering beams with (i) front-and-back faces present and (ii) front face present, but back face absent. These two beam designs are used to represent single hull and double hull ship structures, and they are compared on an equal mass basis by doubling the thickness of the front face when the back face is absent. Beams with a corrugated core are found to be slightly stronger than those with a Y-frame core, and two collapse mechanisms are identified depending upon beam span. Short beams collapse by indentation and for this collapse mechanism, beams without a back face outperform those with front-and back faces present. In contrast, long beams fail by Brazier plastic buckling and for this collapse mechanism, the presence of a back face strengthens the beam. Third, drop weight tests with an impact velocity of 5 m/s are performed on simply supported and clamped sandwich beams with a corrugated core or a Y-frame core. These tests are conducted to mimic the response of a sandwich hull in a ship collision. The responses measured at 5 m/s are found to be slightly stronger than those measured quasi-statically. The measurements are in reasonable agreement with finite element predictions. In addition, the finite element method is used to investigate whether the collapse mechanism at 5 m/s is different from the one obtained quasi-statically. The predictions indicate that sandwich beams that collapse quasi-statically by indentation also fail by indentation at 5 m/s. In contrast, the simulations for beams that fail quasi-statically by Brazier plastic buckling show that they collapse by indentation at 5 m/s. Finally, the dynamic indentation response of sandwich panels with a corrugated core or a Y-frame core is simulated using the finite element method. The panels are indented at a constant velocity ranging from quasi-static loading to 100 m/s, and two indenters are considered: a flat-bottomed indenter and a cylindrical roller. For indentation velocities representative of a ship collision, i.e. below 10 m/s, the predictions indicate that the force applied to the front face of the panel is approximately equal to the force transmitted to the back face. Even at such low indentation velocities, inertia stabilisation effects increase the dynamic initial peak load above its quasi-static value. This strengthening effect is more important for the corrugated core than for the Y-frame core. For velocities greater than 10 m/s, the force applied to the front face exceeds the force transmitted to the back face due to wave propagation effects. The results are also found to be very sensitive to the size of the flat-bottomed indenter; increasing its width enhances both inertia stabilisation and wave propagation effects. In contrast, increasing the roller diameter has a smaller effect on the dynamic indentation response. Lastly, it is demonstrated that material strain-rate sensitivity has a small effect on the dynamic indentation response of both corrugated and Y-frame sandwich panels.
... Exoskeleton of the arthropod [21] with mineralized chitin layers was effective in crack arrest property. Toucan beak [22] owned the porous interior with a central void region, which decreased the weight of beaks and resisted flexure stresses without buckling. In our previous studies [23], the effect of microstructure on mechanical properties of the white clam shell was investigated. ...
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Based on microstructure characteristics of Meretrix lusoria shell and Rapana venosa shell, bionic coupling layered B4C/5083Al composites with different layered structures and hard/soft combination models were fabricated via hot pressed sintering. The simplified bionic coupling models with hard and soft layers were similar to layered structure and hardness tendency of shells, guiding the bionic design and fabrication. B4C/5083Al composites with various B4C contents and pure 5083Al were treated as hard and soft layers, respectively. Hot pressed sintering maintained the designed bionic structure and enhanced high bonding strength between ceramics and matrix. Compared with B4C/5083Al composites, bionic layered composites exhibited high mechanical properties including flexural strength, fracture toughness, compressive strength and impact toughness. The hard layers absorbed applied loads in the form of intergranular fracture. Besides connection role, soft layers restrained slabbing phenomenon and reset extension direction of cracks among layers. The coupling functions of bionic composites proved the feasibility and practicability of bionic fabrication, providing a new method for improvement of ceramic/Al composite with properties of being lightweight and high mechanical strength.
... In parallel with optimization of the porous foam structures, the external curviplanar contours and overall spherical geometries in natural materials like beaks, nacre and scallop have proved to be the best configuration for enhancing strength and deformation ( Huang et al., 2011;Li et al., 2015;Meyers et al., 2006 ). For instance, the long and thick toucan beak wrapped by a curviplanar keratin shell exhibits a high resistance to buckling deformation and an excellent ability to mitigate impact energy ( Seki et al., 2005 ). As a representative of man-made shell structures, a hollow CdS nanocrystal sphere has been synthesized and proves to approach the ideal shear strength and sustaining considerable deformation ( Shan et al., 2008 ). ...
... A previous study demonstrated differential expression of calmodulin between finches with different beak types [17]. The structure of a toucan beak was found to be a sandwich composite with an exterior of keratin and a fibrous network of closed cells comprising calcium-rich proteins [53]. Lamichhaney [11] found that among the 15 most significant genomic regions related to beak shape, six harbored genes associated with craniofacial and/or beak development in mammals or birds were identified, including calmodulin. ...
Article
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Background Beak deformity, typically expressed as the crossing of upper and lower mandibles, is found in several indigenous chicken breeds, including the Beijing-You chickens studied here. Beak deformity severely impairs the birds’ growth and welfare. Although previous studies shed some light on the genetic regulation of this complex trait, the genetic basis of this malformation remains incompletely understood. ResultsIn this study, single SNP- and pathway-based genome-wide association studies (GWASs) were performed using ROADTRIPS and SNP ratio test (SRT), respectively. A total of 48 birds with deformed beaks (case) and 48 normal birds (control) were genotyped using Affymetrix 600 K HD genotyping arrays. As a result, 95 individuals and 429,539 SNPs were obtained after quality control. The P-value was corrected by a Bonferroni adjustment based on linkage disequilibrium pruning. The single SNP-based association study identified one associated SNP with 5% genome-wide significance and seven suggestively associated SNPs. Four high-confidence genes, LOC421892, TDRD3, RET, and STMN1, were identified as the most promising candidate genes underlying this complex trait in view of their positions, functions, and overlaps with previous studies. The pathway-based association study highlighted the association of six pathways with beak deformity, including the calcium signaling pathway. Conclusions Potentially useful candidate genes and pathways for beak deformity were identified, which should be the subject of further functional characterization.
... This embrittlement at higher strain rates is a manifestation of a ductile-to-brittle transition, which has been observed previously for keratin in the toucan beak. [24] Fracture toughness tests were also conducted at higher loading rates (Section SVII, Supporting Information), demonstrating that the fracture www.advmat.de www.advancedsciencenews.com toughness (J) decreases with increasing loading rate; this is a direct consequence of the ductile-to-brittle transition. ...
... Overall, the multilayered structure of the lingual body is similar to the lingual apex. In the dorsal view, the shape and dimension of the keratin scales in both the lingual apex and body have isotropic shapes, which are comparable to the keratin scales on beaks of other birds [30][31][32], in contrast to the elongated scales found on woodpecker beaks [11]. In comparison, the average ratio of adult chicken cortical bone (1.73 [34]) and bovine femur (2.23-2.31 ...
Article
Statement of significance: Woodpeckers avoid brain injury while they peck at trees, which results in extreme impact conditions. One common adaptation in woodpeckers is the unusual shape of the elongated tongue, also called the hyoid apparatus. The relationship between the structure and mechanical properties of the bony part of the hyoid apparatus has not been previously reported. A three dimensional model of the bony tongue was developed, and the hardness and stiffness were evaluated. A new type of bone structure, which is opposite of typical skeletal bone structure was found. The combined microstructural and mechanical property analysis indicate possible energy absorption routes for the hyoid apparatus and are applicable to the design of engineered structures.
... This area has been suggested to have several functions such as acting as a stress/strain dampener or shock absorber or contributing to an increase in swimming hydrodynamics due to an oil producing gland found at the base of swordfishes' rostrum (Gudger, 1940;Habegger et al., 2015;Videler et al., 2016). Similar composite structures are common in many biological structures, such as toucan beaks and porcupine quills, and improve mechanical performance by providing increased energy absorption (Seki et al., 2005;Yang and Chao, 2013). In addition, in previous experiments, differences in the positioning of the virtual strain gauges compared to their actual placement had explained some differences in validation results, especially in areas where strain gradients are present (Bright and Rayfield, 2011). ...
Article
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Billfishes are large pelagic fishes that have an extreme elongation of the upper jaw bones forming the rostrum. Recent kinematic and biomechanical studies show the rostrum to be associated to feeding, however, it is less clear how the wide range of morphologies present among billfish may affect their striking behavior. In this study we aim to assess the mechanical performance of different rostrum morphologies under loads that simulate feeding and to test existing hypotheses of species‐specific feeding behaviors. We use finite element analysis (FEA) ‐ a physics‐based method that predicts patterns of stress and strain in morphologically complex structures under specified boundary conditions‐ to test hypotheses on the form and mechanical performance of billfish rostra. Patterns of von Mises stress and total strain energy suggest that distinct rostral morphologies may be functionally segregated. The rounder blue marlin rostrum may be better suited for a wide range of slashing motions to disable prey, whereas the more flattened swordfish rostrum appears to be more specialized for lateral swiping during prey capture. The almost homogenous stress distribution along each rostrum implies their possible use as a predatory weapon regardless of morphological differences between species. The mechanical implications of other less commonly reported behaviors such as spearing are discussed, as well as the potential impact of hydrodynamics in shaping the evolution of the rostrum in this lineage. This article is protected by copyright. All rights reserved.
... The intricate arrangements of biological thin-walled cellular structures facilitate lightweight and high energy absorption. These include thin-walled cellular structures that have been optimised over many years of evolution, including those of porous or trabecular bone [1][2][3][4], porcupine quills [5][6][7][8], turtle shells [9][10][11][12] and toucan beak [13][14][15][16]. In particular, trabecular bone ( Fig. 1) shows a unique cellular arrangement that minimises weight whilst meeting the loading demands of the human body. ...
Article
Biological thin-walled cellular structures have intricate arrangements that facilitate lightweight and high energy absorption. A prime example is trabecular bone, which possesses a unique thin-walled cellular structure of connected rods or plates, to minimise weight whilst meeting the loading demands from the body. For example, the femur has a closed cell structure of plates to transmit heavy loads to the ground, whereas a carpal bone has an open cell structure of connected rods. Although existing lightweight thin-walled cellular structures with controlled arrangements have been investigated extensively, such as those with re-entrant geometries, asymmetric instability due to local buckling can hinder their energy absorption capacity. Mimicking the features of trabecular bone can offer the designer a greater degree of control over the buckling and collapse mechanisms of thin-walled cellular structures. This can lead to the development of high-performance protective systems with superior energy absorption capabilities. This study employs 3D printing and finite element analysis techniques to mimic and investigate several key features of the plate-like thin-walled cellular structure of trabecular bone. The performance of the developed bioinspired structure is benchmarked against traditional hexagonal and re-entrant designs. The controlled and progressive buckling and collapse mechanisms observed in the bioinspired structure result in superior energy absorption over its re-entrant and hexagonal counterparts.
... However, the geometries investigated in the archival literature, such as honeycomb and re-entrant, can experience premature local buckling and collapse in the immediate vicinity of the loading, which may amplify the forces on the protected target [1,2]. Some cellular structures that have evolved over millennia and possess unique mechanical characteristics worthy of study, are the trabecular bone [3][4][5], porcupine quills [6][7][8], turtle carapaces [9][10][11] and the beak of the toucan [12][13][14]. All of these structures are lightweight, have high energy absorption per unit weight and have evolved to resist extreme loadings. ...
Article
Re-entrant and honeycomb cellular structures have shown potential for mitigating the effects of extreme loadings such as those imposed by impacts and near-range air blast. However, these cellular geometries can buckle locally and collapse in the immediate vicinity of the loading, which can limit their effectiveness as a protective element. These deficiencies can be addressed by mimicking alternate, naturally occurring, cellular structures, including that of the porcupine quill, which is studied here. The quill possesses several distinct features that effectively counteract buckling and bending, and minimise weight. This study mimics several structural features of the quill to develop a novel cellular design for counteracting air blast loads such as those associated with detonations of high explosives. The performance of the bio-mimetic structure is benchmarked against traditional hexagonal and re-entrant designs, which have been documented in the archival literature. The quill-inspired structure offers more design freedom than the traditional cellular geometries. By iteratively mimicking several of the structural features of the porcupine quill, an optimal balance between local buckling and collapse can be realised, which minimises the reaction on the target below and maximises energy dissipation.
... Most technical lightweight structures, such as typical honeycomb sandwich constructions, lattice structures or steel girders used for planes, buildings, or cranes have mainly regular periodic geometries. However, natural lightweight structures are often complex and show good mechanical properties, like honeycombs of bees [53], the beak of toucans (figure 3.1a) [151,152], cancellous bones (figure 3.1b) [52,53], the southern giant horsetail (figure 3.1c) [161], or the shell structures of plankton organisms [142]. These structures are highly optimised during the process of evolution and usually fulfil different functions. ...
Thesis
Finding the optimal structural design to avoid resonance has been a goal for decades as it is of high interest in many technical areas. Lightweight design structures, in particular, show a high susceptibility to vibration. One approach is to increase (maximise) the structural eigenfrequencies, i.e., to ’detune’ the system. In this work, a detailed literature review on technical lightweight structures and structural optimisations focusing on vibration characteristics is presented. Subsequently, different studies investigate the application of biologically inspired structures and methods to increase eigenfrequencies. It has been observed that diatom shells are shaped according to their vibration mode shapes, which leads to the assumption that these structures are optimised for vibratory loads. Applying this mode shape adaptation strategy to axially constrained beams (1D) and plates (2D) results in strong eigenfrequency increases at constant mass. In addition, the increase of multiple eigenfrequencies is possible. The mode shape adaptation results are compared to evolutionary strategic optimisations and, in the case of the plate, also to topography optimisations. The optimisations using commercially available optimisers successfully increase the targeted eigenfrequencies. However, the single eigenfrequency increases are generally lower than those generated by the mode shape adaptation method, while the evolutionary strategic optimisations lead to higher multiple eigenfrequency increases. With regard to the complex honeycomb and lattice structures found in aquatic plankton organisms, the impact of the structural complexity on the eigenfrequencies is studied. The 1st eigenfrequency of a 2D cellular plate significantly rises using irregular structures. In addition, the application of the mode shape method to the studied cellular plates raises the 1st eigenfrequency even further. Regarding lattice structures, a strong 1st eigenfrequency increase with rising structural complexity is obtained likewise. Additional design constraints allow the development of vibration optimised lattices that can be additive manufactured without support structures. As an example of biologically inspired vibration optimisation, a girder used in synchrotron radiation facilities to support the magnets and to assure a stable particle beam is studied. It is focused on the girder design for the currently planned synchrotron radiation facility upgrade PETRA IV at DESY (German Electron Synchrotron, Hamburg, Germany). In a parametric study, the impact of different boundary conditions on the magnet-girder assembly is investigated, involving varying loading conditions, girder support definitions, and material properties of the girder and bases. Afterwards, a development process for a girder structure installed in a synchrotron radiation facility is generated. Based on a topology optimisation, a parametric beam-shell model including biologically inspired structures is created. The subsequent cross section optimisation using evolutionary strategic optimisation reveals an optimum girder structure. Vibration experiments of the casted girder structure validated the numerical results. Future changes in the specifications can be implemented in the development process to obtain further adapted girder structures.
... Cellular materials such as lattice and open cell foam structures have been developed, inspired by biological structures, such as the stem of giant bird of paradise plant [1], porcupine quills [2], toucan beaks [3] and feather rachis [4], which are all composed of a dense outer layer and a low-density hollow internal structure, thus exhibiting a high stiffness-to-weight ratio. Owing to their distinctive properties, lattice structures have been used in numerous applications and been specially designed to realize materials with functions of energy absorption [5][6][7], weight saving [8], heat transfer and thermal insulation [9] for use in bio-medical implants [10][11] and electrochemical devices [12][13]. ...
Article
The synergy of additive manufacturing (AM) with topology optimization has become a useful method for developing ultralight, ultrastiff structures with high energy absorption capability. To improve the weight-specific stiffness and energy absorption capability of the conventional dome commonly used as the core of sandwich sheets, a new concept of filling the solid part of the dome with stretch-dominated microlattices is proposed. The optimal density distribution of microlattices is obtained by integrating the homogenization-based topology optimization method with the lattice structure. The compressive and bending stiffnesses of the optimized variable-density microlattice domes are demonstrated to be 41.8% and 33.7% higher than those of the conventional solid domes, while the energy absorption of the microlattice dome during compression and three-point bending is increased by 297.5% and 85%, respectively. Investigation of the cell size effect on the mechanical properties of the microlattice dome reveals that a larger cell size contributes more to the weight-specific stiffness and energy absorption capability at a given overall volume fraction constraint. The topology optimization and construction methods described in this paper are universal and can be used for the further development of ultralight, ultrastiff structures with arbitrary macro shapes with microlattices as constituent units.
... A plethora of researchers have followed the protective function of keratin-made body parts to develop additively manufactured composites [9][10][11]. Recent studies on biomimetic composites inspired from hooves [12], horns [8,13], beaks [14,15] and turtle shells [16,17] have shown promising energy absorption characteristics. It has been found that hooves and horns have comparable tubular structures [18,19]. ...
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This paper investigates the quasi-static response of structures inspired by the horse hoof wall structure. The horse hoof wall has a laminated structure which was mimicked to develop a composite structure using the biomimicry design spiral approach. Additive manufacturing technique was used to create the laminated structures. The intermediate layers of the laminated structures were filled with resin material in three different layer configurations with variable angles of 60°, 70°, and 90°. The quasi-static response of the biomimetic structures was investigated using a hemispherical indenter. To further understand the influence of filler material, the structures were also examined without filling the intermediate layers. It was found that the flat layer, i.e. 90°, has a better energy absorption capacity than monolithic and other structures. This research will assist in the development of energy absorbing biomimetic structures as well as the selection of appropriate materials to improve the bonding between layers of 3D printed structures, resulting in increased structural strength.
... Continuous adaptation and optimization of natural structures under evolutionary pressure and/or environmental conditions have led to the development of unique architectures [1,2], such as bone [3], seashells [4], bird beaks [5], shark teeth [6], and many more [7,8], which are known for their complexity yet exceptional structural and mechanical performance. These architectures have a high load-bearing capacity and offer the advantage of being lightweight, thereby, facilitating their mobility and structural purpose [9]. ...
Article
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Extrusion-based additive manufacturing (AM) enables the fabrication of three-dimensional structures with intricate cellular architectures where the material is selectively dispensed through a nozzle or orifice in a layer-by-layer fashion at the macro-, meso-, and micro-scale. Polymers and their composites are one of the most widely used materials and are of great interest in the field of AM due to their vast potential for various applications, especially for the medical, military, aerospace, and automotive industries. Because architected polymer-based structures impart remarkably improved material properties such as low density and high mechanical performance compared to their bulk counterparts, this review focuses particularly on the development of such objects by extrusion-based AM intended for structural applications. This review introduces the extrusion-based AM techniques followed by a discussion on the wide variety of materials used for extrusion printing, various architected structures, and their mechanical properties. Notable advances in newly developed polymer and composite materials and their potential applications are summarized. Finally, perspectives and insights into future research of extrusion-based AM on developing high-performance ultra-light materials using polymers and their composite materials are discussed.
... In other words, the polymer of the composite that better suits an impact load condition would preferably have low mineral content. Furthermore, nature has perfected several other structures to withstand impact solicitations such as multi-layered bones, teeth and horns; or a hard outer shell to distribute impact and retain strength, such as in the case of the toucan's beak [39] or the armadillo's armor [40], which can be applied, for instance, in a state-of-the-art helmet with fiberglass outer skin and a soft polyurethane inner layer [41]. ...
Article
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The development of new materials has always been strictly related to the rise of new technologies and progressively efficient systems. However, cutting-edge materials might not be enough to en-sure the effectiveness of a given product if the design guidelines used do not favor the specific ad-vantages of this material. Polymeric composites are known for their excellent mechanical proper-ties, but current manufacturing techniques and the relatively narrow expertise in the field amongst engineers impose the challenge to provide the most suitable designs to certain applica-tions. Bio-inspired designs, supported by thousands of years of evolution of nature, have shown to be extremely profitable tools for the design of optimized yet structurally complex shapes in which the tailoring aspect of polymeric composites perfectly fit. Bearing in mind the current but old-fashioned designs of auto-parts and vehicles built with metals with little or no topological optimization, the present work addresses how biomimicry is being applied in the mobility in-dustry nowadays to provide lightweight structures and efficient designs. A general overview of biomimicry is made regarding vehicles, approaching how the use of composite materials has al-ready contributed to successful cases.
... These energy-absorbing structures have inspired works aimed at imitating them for developing armour materials that can absorb the impact energy by plastic deformation [20,21]. Recent studies suggest that fish skins [22,23], nacre [24][25][26], turtle shells [5,7,27], bird beaks [28,29], horns [2,30], shark teeth [31], and horse hooves [32] have shown fairly good impact-resistant properties [33]. These unique and excellent properties of biological materials qualify them to inspire improvements to human-made conventional materials. ...
Article
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Nature has a wide range of biological protection strategies that show resilience to impact loading. These strategies also serve certain amount of flexibility that contribute to body movement and locomotion. Consequently, researchers have developed biomimetic engineering structures emulating natural strategies. However, biological entities are often complex and are difficult to replicate with conventional manufacturing technologies. Recent advances in additive manufacturing provide a pathway to emulate the hierarchical architectures of biological materials. In this review paper, we consider biological structures from marine and terrestrial animals that safeguard their body parts from external attack. We also discuss biological structures that are not employed for protective purposes but provide flexibility and have damage tolerant properties suitable for developing strong, tough and lightweight bioinspired armour. Mobility and protection strategies have been considered to enhance the development of bio-inspired designs. Moreover, we discuss how additive manufacturing can be incorporated in the biomimicry design process.
... From nacre composed of strong calcium carbonate platelets glued together with a softer organic matrix 24 to the toucan beak exhibiting a high-resistant and lightweight structure of stiff keratin units with a ductile collagen foam, 25 the diversity of natural materials is truly remarkable. 1 The exceptional properties of these materials arise from their hierarchical structure with a specific organization of the constitutive building blocks at different length scales. Before mimicking the biological structures found in nature, the first step is to thoroughly analyse the structure-function-property relationships in these materials. ...
Thesis
Through evolution Nature has succeeded to form nanocomposite materials with complex anisotropies structures including the helical architectures found in cell walls of wood or in the exoskeleton of Arthropods. The remarkable properties of these materials have inspired our research team to reproduce similar high-performance materials synthetically. We first prepared multilayer films composed of nanocellulose and poly(vinylamine) combining the layer-by-layer assembly and grazing incidence spraying (GIS). Nanocomposite materials with random, unidirectional or helical orientation of cellulose nanoparticles were assembled. The structure and morphology of the resulting films were investigated by electron microscopy while their mechanical and optical properties were determined using dynamic mechanical analysis and circular dichroism spectroscopy. In a second part, we utilized the anisotropic optical properties of oriented silver nanowires (AgNWs) to fabricate a direction-sensitive strain sensor. For this purpose, monolayers of AgNWs were aligned on a stretchable and transparent substrate of poly(dimethylsiloxane). UV-Visible-IR spectroscopy measurements with polarized light revealed that the variation of the optical properties of the oriented AgNW monolayer upon stretching was depending on both the light polarization and stretching direction. A mathematical model was developed for analyzing the optical data and for calculating the applied strain and its direction during linear deformation.
... Lattice structures such as rod-lattices, plate-lattices, or shell-lattices may demonstrate stretching-dominated or appear in nature through biological cellular materials. Cancellous bone, toucan beak, and woodpecker cranial skull all exhibit a combination of rod, plate and shell structures (Mosekilde, 1990;Seki et al., 2005;Wang et al., 2011). ...
Article
The compressive high strain-rate behavior of polymeric Kelvin lattice structures with rod-based or plate-based unit cells was investigated through experimental techniques and finite element simulations. Polymeric lattice structures with 5x5x5 unit cell geometries were manufactured on the millimeter scale using vat polymerization additive manufacturing and tested at low (0.001/s) and high (1000/s) strain-rates. High strain-rate experiments were performed and validated for a viscoelastic split-Hopkinson (Kolsky) pressure bar system (SHPB) coupled with high-speed imaging and digital image correlation (DIC). Experimental results at both low and high strain-rates show the formation of a localized deformation band which was more prevalent in low relative density specimens and low strain-rate experiments. Strain-rate effects of lattice specimens strongly correlate with effects of the base polymer material; both bulk polymer and lattice specimen demonstrated strain-rate hardening, strain-rate stiffening, and decreased fracture strain under dynamic loading. Results show mechanical failure properties and energy absorption depended strongly on the relative density of the lattice specimen and exhibited distinct scaling between relative density and geometry type (rod, plate) and loading rate. High relative density plate-lattices demonstrated inferior mechanical properties to rod-lattices; however, there exists a critical relative density for a given mechanical property (17%–28%) below which plate-lattices outperform rod-lattices of similar mass. High strain-rate explicit finite element simulations were performed and showed good agreement with the mechanical failure trends and deformation modes observed in the experiments.
Chapter
Nature has created materials with characteristics and processes that are far beyond the thinking of the engineering materials industry. Nature is supreme when it comes to architecture and intricate designing. This design does not compromise with the properties of materials. Nature has used inorganic and solid-state materials along with their composites as elements that can be utilized in sensors, precision tools, functional materials, etc. These biogenic materials have undergone millions of years of evolution before their utilization by humankind for various purposes. These natural structural materials are made from a small number of components at room temperature. Various phases are commonly arranged in complicated hierarchical systems, with diameters ranging from nanoscale to macroscale. The hierarchical organization of nature-based materials offers varied characteristics based on weak components, high-performance per unit mass, and varied functions in addition to mechanical capabilities. Bioinspired materials require the development of a fundamental understanding of biological materials and integrating that understanding with current needs as well as manufacturing hierarchically organized materials with improved properties. The current review focuses mainly on bioinspired materials and bioceramics.
Chapter
System characterization through experimental means is the most common (and successful) approach to extract mechanical properties, performance, and behavior from complex biological systems. Experiment—as opposed to simulation, modeling, and theory—has the intrinsic advantage of not requiring any assumptions about material structure. Here, we review common experimental techniques that span scales from nano to macro. Multiple scales are discussed, encompassing single molecule assays (e.g., through optical tweezers) that probe molecular mechanics and reaction pathways, to the many uses of atomic force microscopy (such as protein stretching or bending), to microscale techniques applied to cells (e.g., micropipette aspiration) and tissues (e.g., nanoindentation). A well equipped materiomics “toolbox” is necessary to further our understanding of how the mechanical behavior of a material affects its biological function.
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Bioinspired design is an emerging field that takes inspiration from nature to develop high-performance materials and devices. The sea urchin mouthpiece, known as the Aristotle's lantern, is a compelling source of bioinspiration with an intricate network of musculature and calcareous teeth that can scrape, cut, chew food and bore holes into rocky substrates. We describe the bioinspiration process as including animal observation, specimen characterization, device fabrication and mechanism bioexploration. The last step of bioexploration allows for a deeper understanding of the initial biology. The design architecture of the Aristotle's lantern is analyzed with micro-computed tomography and individual teeth are examined with scanning electron microscopy to identify the microstructure. Bioinspired designs are fabricated with a 3D printer, assembled and tested to determine the most efficient lantern opening and closing mechanism. Teeth from the bioinspired lantern design are bioexplored via finite element analysis to explain from a mechanical perspective why keeled tooth structures evolved in the modern sea urchins we observed. This circular approach allows for new conclusions to be drawn from biology and nature.
Chapter
Inorganic materials made from metals and nonmetals combined by ionic and/or covalent bonds are known as ceramic materials and can be crystalline, amorphous, or mixture of both. When the size goes below 100 nm, it becomes nanostructured ceramic material. Both top-down and bottom-up approaches have been discussed for the synthesis of different types of nanostructured ceramic materials. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and many other techniques have been used to characterize nanostructured ceramic materials. Optical, electronic, electrical, magnetic, and structural properties of nanostructured ceramic material have been discussed. Applications in different sectors such as thermal barrier coatings, sensors, health, capacitors, automotive, batteries, solid electrolytes for fuel cells, catalysts, cosmetics, corrosion-resistant coatings, bioengineering, optoelectronics, computers, and electronics, etc., have been elaborated in detail.
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Natural cellular structures encourage researchers to seek new design inspirations for impact protection engineering materials. The thousands of eyes Bodhi (TEB) is a novel hierarchical cellular structure material, which includes the first order filled-cells, the second order novel-closed-cells, and the third order open-cells. In this study, dynamic compressive tests at different high strain rates in the longitudinal and transverse directions were conducted by a split Hopkinson pressure bar (SHPB), respectively. A high-speed camera was employed to capture the macroscopic deformation mechanisms and a scanning electron microscope (SEM) was employed to study the microscopic failure mechanisms. The dynamic mechanical response and strain rate effects of TEB samples in the transverse and longitudinal directions were investigated. The anisotropic behavior of TEB samples is observed under dynamic compression tests. The tests results show that the dynamic mechanical properties of TEB samples and dynamic deformation behavior of each order cellular structure exist a significant strain rate dependence. The TEB material dissipates the impact energy through the dynamic compression mechanisms of each order cellular structure which improves the energy absorption and impact resistance. Thus, it provides a bio-inspired template for the design of energy absorption and crashworthiness engineering materials.
Article
Various natural materials were used recently for the synthesis of gold nanoparticles (AuNPs). These natural materials are attracting attention because they are more environmentally friendly than conventional chemicals used for AuNP synthesis. Silk sericin (SS) is a protein that is removed during the silk degumming process, and it has been studied for the synthesis of several inorganic materials, such as hydroxyapatite and silica. The present study synthesized AuNPs using SS. To optimize the conditions for the synthesis of AuNPs, the effects of reaction pH, SS concentration, reaction time and temperature during the formation of AuNPs were monitored using visual observation, a UV-Vis spectrophotometer, and energy-filtered transmission electron microscopy (EF-TEM) analysis. When the concentration of HAuCl4 was 1 mM, the optimal conditions for synthesizing AuNPs were an SS concentration of 1 mg/ml, a reaction pH of 7, a reaction temperature of 70 °C and a reaction time of 12 hours. The AuNPs prepared under the optimal conditions had a size of approximately 17 nm, and the particles were well dispersed. When ethanol was added, the secondary structure of SS transitioned to β-sheets, the size of the gold nanoparticles increased to approximately 20 nm, and the amount of AuNPs increased. Amino acids bearing a hydroxyl group or negative charge were effective in the synthesis of AuNPs, and SS has a high content of these amino acids. Therefore, SS reduced gold ions and induced the synthesis of AuNPs. High-resolution TEM (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) revealed that SS remained in a form that capped the synthesized AuNPs.
Chapter
The avian world offers unique aspects of feather structures resulting in colors that stand alone in the natural world. Some birds also have a different structural approach that allow for beaks of amazing strength. Each of these observed attributes is due to nanoscale structures. Applications may provide positive impacts at a global level.
Article
The turtle carapace is a biological composite shield consisting of a hard boney layer covered with a soft keratincollagen bi-layer. The unique microstructure enables the turtle carapace to protect the underlying soft tissues from predator assaults. Recent experiments have shown that when the turtle carapace is subjected to dynamic loading, brittle fracture of the boney layer occurs, which is accompanied by delamination at the keratin-collagen and collagen-bone interfaces. To unveil the role of interfacial delamination, we propose a model of fracture in the multilayered microstructure of turtle carapace, in which brittle cracking in the boney layer, delamination of the soft bi-layer and plastic deformation in the bi-layer are taken into account. Calculations are carried out for crack propagation in the turtle carapace under dynamic loading; it is found that low strength of the keratin-collagen interface can activate large plastic deformation in the collagen layer and promote spreading of damage region in the keratin-collagen interface, which delays fracture of the boney layer. High toughness of the keratin-collagen interface increases plastic deformation in the soft bi-layer and suppresses crack propagation in the boney layer. We further reveal the role of mechanical properties of the collagen-bone interface. It is identified that high strength of the collagen-bone interface enables enhanced plastic dissipation in the soft bi-layer, retarding crack growth in the boney layer. The collagen-bone interface with high toughness plays a role in enhancing plastic deformation in the soft bi-layer, which potentially increases the resistance to crack growth in the boney layer. In addition, we explore the effect of strain rate sensitivity of the soft bi-layer. We show that decreasing the degree of strain rate sensitivity of the keratin layer can mitigate fracture of the boney layer. The findings of this study shed new light on the protection mechanisms of turtle carapace.
Article
The thousands of eyes Bobhis (TEB) is a natural cellular material and has ingeniously evolved hierarchical structures to resist the damage from external environment. In this study, the relationship between cellular structure and mechanical properties of the TEBs is first investigated. SEM studies reveal that the TEB hierarchically exhibit three distinct cellular structures, the filled-cells, novel-closed-cells and open-cells, which is ranging from the macroscopic (>10⁻³ m) to the microcosmic scale (10⁻⁴-10⁻⁶ m) respectively. Compression and shear tests indicate that such hierarchical cellular structure has intimate influence on the mechanical properties of TEB. The loads of TEB samples are decomposed through the three hierarchical cellular structures. Microscopically, the multiple micro-cracks are firstly generated from the open-cells, and the novel-closed-cells are deformed and crushed in which the multiple micro shear bands and cell walls interlocking phenomenon can be found in the tests. Macroscopically, the filled-cells are stretched and damaged with the extrusion of filler. The hierarchical cellular structure of TEB possesses excellent mechanical properties, which hinder the catastrophic failure and increase the toughness and strength. The distinct hierarchical cellular structure of TEB provides a new pathway to design bio-inspired engineering materials.
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Abstract: This paper presents the conceptual design stage in the product development process of a natural fiber composites of the side-door impact beam, which starts from idea generation to the selection of the best design concept. This paper also demonstrates the use of the integrated Theory of Inventive Problem Solving (Function-Oriented Search) (TRIZ (FOS)) and Biomimetics method, as well as the VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method. The aim of this study was to generate design concepts that were inspired by nature and to select the best design concept for the composite side-door impact beam. Subsequently, eight design concepts were generated using the TRIZ (FOS)-Biomimetics method and finite element analysis were used to analyse their performance and weight criteria using ANSYS software. VIKOR method was used as the multiple criteria decision making tools to compare their performances, weight and cost criteria. As a result, design concepts B-03 and C-02 were ranked as the first and second best, with VIKOR value of 0.0156 and 0.1178, respectively, which satisfied the conditions in VIKOR method. This paper shows that the integrated method of TRIZ (FOS)-Biomimetics and VIKOR can assist researchers and engineers in developing designs that are inspired by nature, as well as in selecting the best design concept using a systematic strategy and justified solutions during the conceptual design stage.
Article
Cellular solids are commonly observed in nature and have wide applications in industry. While there is an unavoidable tradeoff between their weight and strength, it is feasible to use carbon nanomaterials as the constituent building blocks to guarantee both strength and lightweight. However, there is a lack of design tools to efficiently consider their hierarchical chemical structures and reveal how they relate to mechanical features. Here, we develop a coarse-grained (CG) model of covalently bonded carbon nanotube (CNT) networks. The CG model includes bead–spring chains for CNTs and nodal beads for carbon junctions. The effect of different nodal connectivities has been parameterized, yielding consistent modulus, tensile strength, and deformation with fully atomic CNT lattices. The CG model can be used to efficiently investigate the mechanics of CNT lattices and reveal their scaling law with density. We notice that all CNT lattices have specific tensile strengths 2 orders of magnitude higher than that of steel, and a larger nodal connectivity generally makes the material stiffer but weaker for the same density. The method can be effectively used to design the mechanics of CNT-based cellular solids as well as other covalently bonded network structures with a large length scale, high complexity, and varying nodal connectivity.
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The European Starling, Sturnus vulgaris, is notable for the marked changes-in bill coloration which occur through its annual cvcle (ea.. Nichols 1945. Wvdowski 1964;Feare 1984).~Frommid-winter through to the breeding season, the bill is pale or yellow. Following breeding, at the onset of molt, the bill becomes dark due to deposition of melanin granules (e.g., Witschi 1961, Filshie and Rogers 1962). For many species, it has been argued that changes in bill color may have been selected as sexual or social signals (e.g., Witschi 196 1, Hardy 1974, Garson et al. 1980, Lawton and Lawton 1985). As an alternative, we propose that changes in bill coloration may have a mechanical func-tion. It is well known that the presence of fillers affect the mechanical properties of polymers (see Ferry 196 1). Furthermore, Averill (1923) noted that white areas of gull primary feather vanes wear more quickly than dark areas. Therefore, we hypothesize that the incorporation of melanin granules into bill keratin may increase wear resistance. Experimental studies of feather abrasion (e.g., Bergman 1982, Burtt 1986) have not considered how melanin affects the material properties of keratins. In this paper, we examine the indentation hardness of melanic and non-melanic bill keratin of the Starling. These measures have direct implications for wear re-sistance because it has been demonstrated previously that the indentation hardness of a material is inversely proportional to its wear rate (e.g., Lipson 1967, Lan-caster 1973. Barwell 1979). That is. a hard material loses less volume than a less-hard material under the abrasive action of an equal force. This has been dis-cussed mainly for metals (Lipson 1967. Barwell 1979). but also holds true for visdoelastic polymers (Lancaster 1973). such as keratin.
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Thin walled cylindrical shell structures are widespread in nature; examples include plant stems, porcupine quills and hedgehog spines. All have an outer shell of almost fully dense material supported by a low density, cellular core. In nature, all are loaded in some combination of axial compression and bending; failure is typically by buckling. Natural structures are often optimized. Here we have analysed the elastic buckling of a thin cylindrical shell supported by an elastic core to show that this structural configuration achieves significant weight saving over a hollow cylinder. Biomimicking of natural cylindrical shell structures may offer the potential to increase the mechanical efficiency of engineering cylindrical shells. The results of the analysis are compared with data in the following, companion paper.
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The compressive flow behavior of Al, Al−7 pct Mg and 7075 Al alloy foams has been determined in structures whose void fraction varies from 0.80 to 0.95 of the total volume. In all cases, a greater than linear increase in flow strength with increase in density was exhibited, indicating that bending stresses within the foam structure are an important feature of the collapse mode. The flow strength did not follow proportionately changes in bulk flow strength in comparisons of either alloy or of heat-treatment conditions. Ancillary tensile and metallographic observations show that this lack of correlation arises because the different foams collapse by different modes with localized fracture becoming dominant in the higher strength 7075 alloy. The energy absorbing efficiency was found to be independent of foam density for all the materials. However, the efficiency was found to be a strong function of the alloy and heat treatment increasing from about 30 pct in Al, to 43 pct in Al−7 pct Mg and to 50 pct in the solution heat treated and aged 7075 alloy. The increase in efficiency occurs because of an increase in the propensity to fracture in the higher strength alloys which introduces the potential for a propagating constant-stress collapse process.
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Thin walled cylindrical shell structures are widespread in nature: examples include porcupine quills, hedgehog spines and plant stems. All have an outer shell of almost fully dense material supported by a low density, cellular core. In nature, all are loaded in some combination of axial compression and bending: failure is typically by buckling. Natural structures are often optimized. Here we have investigated and characterized the morphology of several natural tubular structures. Mechanical models recently developed to analyze the elastic buckling of a thin cylindrical shell supported by a soft elastic core (G.N. Karam and L.J. Gibson, Elastic buckling of cylindrical shells with elastic cores, I: Analysis, submitted to Int. J. Solids Structures, 1994, G.N. Karam and L.J. Gibson, Elastic buckling of cylindrical shells with elastic cores, II: Experiments, submitted to Int. J. Solids Structures, 1994) were used to study the mechanical efficiency of these natural structures. It was found that natural structures are often more mechanically efficient than equivalent weight hollow cylinders. Biomimicking of natural cylindrical shell structures may offer the potential to increase the mechanical efficiency of engineering structures.
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The analysis of the previous, companion paper showed that the buckling resistance of a cylindrical shell with a compliant core is greater than that of an equivalent weight shell without a core. Here, we describe uniaxial compression and four point bending tests on silicone rubber shells with and without compliant foam cores. The analysis describes the results of the mechanical tests well.
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Detailed descriptions of the structural features of bone abound in the literature; however, the mechanical properties of bone, in particular those at the micro- and nano-structural level, remain poorly understood. This paper surveys the mechanical data that are available, with an emphasis on the relationship between the complex hierarchical structure of bone and its mechanical properties. Attempts to predict the mechanical properties of bone by applying composite rule of mixtures formulae have been only moderately successful, making it clear that an accurate model should include the molecular interactions or physical mechanisms involved in transfer of load across the bone material subunits. Models of this sort cannot be constructed before more information is available about the interactions between the various organic and inorganic components. Therefore, further investigations of mechanical properties at the 'materials level', in addition to the studies at the 'structural level' are needed to fill the gap in our present knowledge and to achieve a complete understanding of the mechanical properties of bone.
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Toxoplasma gondii tachyzoites were isolated from an ocular patient in the Republic of Korea and maintained in the laboratory (designated KI-1). In the present study, its genotype was determined by analyzing dense granule antigen 6 (GRA6) gene and surface antigen 2 (SAG2) gene as typing markers. Digestion of the amplification products of GRA6 and of the 5o and 3o ends of SAG2, respectively, with Mse I, Sau3A I, and Hha I, revealed that KI-1 is included in the genotype I, which includes the worldwide virulent RH strain. In addition, when the whole sequences of the coding regions of SAG1, rhoptry antigen 1 (ROP1), and GRA8 genes of KI-1 were compared with those of RH, minor nucleotide polymorphisms and amino acid substitutions were identified. These results show that KI-1 is a new geographical strain of T. gondii that can be included in the genotype I.
Article
Cellular metals have ranges of thermomechanical properties that suggest their implementation in ultralight structures, as well as for impact/blast amelioration systems, for heat dissipation media and in acoustic isolation. The realization of these applications requires that the properties of cellular metals be understood in terms of their manufacturing constraints and that their thermostructural benefits over competing concepts be firmly established. This overview examines the mechanical and thermal properties of this material class, relative to other cellular and dense materials. It also provides design analyses for prototypical systems which specify implementation opportunities relative to competing concepts.
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The multifunctional performance of stochastic (foamed) cellular metals is now well documented. This article compares such materials with the projected capabilities of materials with periodic cells, configured as cores of panels, tubes and shells. The implementation opportunities are as ultra-light structures, for compact cooling, in energy absorption and vibration control. The periodic topologies comprise either micro-truss lattices or prismatic materials. Performance benefits that can be expected upon implementing these periodic materials are presented and compared with competing concepts. Methods for manufacturing these materials are discussed and some cost/performance trade-offs are addressed.
Article
Cellular solids include engineering honeycombs and foams (which can now be made from polymers, metals, ceramics, and composites) as well as natural materials, such as wood, cork, and cancellous bone. This new edition of a classic work details current understanding of the structure and mechanical behavior of cellular materials, and the ways in which they can be exploited in engineering design. Gibson and Ashby have brought the book completely up to date, including new work on processing of metallic and ceramic foams and on the mechanical, electrical and acoustic properties of cellular solids. Data for commercially available foams are presented on material property charts; two new case studies show how the charts are used for selection of foams in engineering design. Over 150 references appearing in the literature since the publication of the first edition are cited. It will be of interest to graduate students and researchers in materials science and engineering. © Lorna J. Gibson and Michael F. Ashby, 1988 and Lorna J. Gibson and Michael F. Ashby, 1997.
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The modeling of material failure in foam-filled beams was explored through numerical analyses with LS-DYNA. The study was based on previous physical tests on bending of square aluminum extrusions filled with aluminum foam. Recently implemented material models including fracture criteria for both extrusion and foam were used in the analyses. The objectives were to verify the numerical model, and to investigate the influence of different fracture criteria on the response.
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An experimental programme consisting of 144 tests was carried out to study the behaviour of triggered, square 80×80mm2 AA6060 aluminium extrusions filled with aluminium foam under both quasi-static and dynamic axial loading conditions. The main parameters in addition to the loading condition were the foam density, the extrusion wall strength and the extrusion wall thickness. Previously proposed design formulas applied to these components under static loading were found to be valid, and a simple modification introduced in order to allow for dynamic load effects.
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Many natural materials have exceptionally high values of the mechanical performance indices described in the previous, companion paper. For beams and plates of a given stiffness or strength, or for a column of a given buckling resistance, woods, palms and bamboo are among the most efficient materials available. Their mechanical efficiency arises from their combination of composite and cellular microstructures. In this paper we analyse the microstructures which give rise to exceptional performance, describe the fabrication and testing of model materials with those microstructures and discuss the implications for design of mechanically efficient engineering materials.
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Many advanced composites can best be described hierarchically. In particular, the biological composites that occur in organisms are generally seen to be organized on discrete scale levels ranging from the molecular to the macroscopic. At each level the components are held together by specific interactions and organized in a way that is optimized for the ultimate function and performance of the overall system. Biological composites typically consist of fibers made from long macromolecules, organized into different structures. One can learn much from biological composites by considering the relationship between their structures and their properties. Whether natural or synthetic, for a composite system to function efficiently its components must be assembled into a specific architecture that gives the required spectrum of properties. Creators of high-performance synthetic composites hope to emulate nature by designing materials that are optimized for their ultimate functions on every scale from the molecular to the macroscopic.
Article
Preliminary investigations of the microstructure/mechanical properties relationship in a mollusk shell—the large conch, Strombus gigas—are reported. Strombus gigas has the well-ordered “crossed lamellar” microstructure and, in four-point bending, is remarkably tough in certain orientations, permitting noncatastrophic (“graceful”) failure. Fractography indicates that several toughening mechanisms are acting in concert, including crack bridging, microcracking, fiber pullout, and microstructurally induced crack arrest branching. Microindentation studies show that this material is very resistant to cracking; the damage zones around the indents strongly reflect the lamellar character of the microstructure.
Article
With a nano-indenter and a microhardness testing machine, nano-indentation hardness and microhardness are measured in a wide load range (0.1–19600 mN) for five materials. Even fused silica and silicon almost have constant hardness during the load range, the nano-indentation hardness of copper, stainless steel and nickel titanium alloy shows obvious indentation size effect, namely that the hardness decreases with the increase of depth. For the measured materials, the nano-indentation hardness is about 10–30% in magnitude larger than the microhardness. The main reasons can be explained as the analysis of the nano-indentation hardness using the projected contact area at peak load Ac instead of the residual projected area Ar, as well as the purely elastic contact assumption describing the elastic/plastic indentation process. The analysis based on a simple model indicates that Ac is always smaller than Ar, and the more heavily the indent piles up (or sinks in), the larger the difference between the nano-indentation hardness and microhardness.
Article
Samples of the keratinous covering of ostrich claw were prepared and were tensile tested. The Young's modulus of the specimens was calculated from the initial, steepest portion of the load-displacement curve. The mean Young's modulus values were 1.84 GPa and 1.33 GPa, respectively along and perpendicular to the claw length. Comparing these values with those reported for hoof keratins from mammals suggest a mechanical anisotropy that arise from the orientation of the keratin. Basic fibrous composite theory then suggests either a structure made of a matrix almost as stiff as the fiber, or the claws and hooves are either laminate or multidirectional composites.
Article
The temperature dependence of the yield stress and energy absorbing capacity of zinc foam, having a density between 0.05 and 0.07 of that of zinc, was determined over a range of temperatures from 0.1 Tm to 0.7 Tm approximately. With increase in temperature over this temperature range, the yield stress and energy absorbing capacity of the foam at first increased, and then subsequently decreased, above room temperature. At low temperatures,e.g. 0.1 Tm, the foam disintegrated into powder, and the energy absorbing efficiency parameters were high and independent of the foam density. In contrast, at the highest temperatures,e.g. 0.7 Tm, the energy absorbing efficiency parameters were lower and decreased with increase in density. The results are interpreted on the basis of the change in deformation mode which occurs in the zinc matrix of the foam over this temperature range,i.e. the transition from cleavage at the low temperature to plastic flow at the high temperature of deformation.
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Despite recent research exploring the elastic properties of avian keratins, data on failure properties are less common in the literature. In this paper we present data on the failure properties and moduli of both avian feather and claw keratin in tension and the modulus of claw keratin in compression. Increased water content acts to decrease stiffness and strength but to increase strain at failure. The modulus of claw did not differ significantly when tested under tension and compression. (C) 2004 Kluwer Academic Publishers.
Article
The effects of two levels of hydration on microhardness and Young's modulus was determined on samples of claw keratin from six ostriches. Young's modulus was calculated from the initial, steepest portion of the stress-strain curve. Specimens were conditioned in the same way as those for microhardness testing. The average water content of ostrich claw keratin was determined by conditioning four samples of keratin in the same way as were the test specimens and measuring mass lost after drying to constant mass at 105 C.
Article
Electrophoretic analysis of soluble φ-keratin protein of beaks (ramphotheca) revealed differences in individuals among maxillary, mandibular and palatal portions. There were no differences in tissue between individual parrots (Psittacus). In morphologically more complex feathers, no differences were found in the molecular mass of the φ-proteins, but greater numbers of charge isomers were present. The distribution of polypeptide size and structural complexity can be related to function, ontogeny, or both.
Article
Quasi-static and dynamic compression and three-point bending tests have been carried out on Haliotis rufescens (abalone) shells. The mechanical response of the abalone shell is correlated with its microstructure and damage mechanisms. The mechanical response is found to vary significantly from specimen to specimen and requires the application of Weibull statistics in order to be quantitatively evaluated. The abalone shell exhibited orientation dependence of strength, as well as significant strain-rate sensitivity; the failure strength at loading rates between 10×103 and 25×103 GPa/s was approx. 50% higher than the quasi-static strength. The compressive strength when loaded perpendicular to the shell surface was approx. 50% higher than parallel to the shell surface. The compressive strength of abalone is 1.5–3 times the tensile strength (as determined from flexural tests), in contrast with monolithic ceramics, for which the compressive strength is typically an order-of-magnitude greater than the tensile strength. Quasi-static compressive failure occurred gradually, in a mode sometimes described as “graceful failure”. The shear strength of the organic/ceramic interfaces was determined to be approx. 30 MPa by means of a shear test. Considerable inelastic deformation of the organic layers (up to a shear strain of 0.4) preceded failure. Crack deflection, delocalization of damage, plastic microbuckling (kinking), and viscoplastic deformation of the organic layers are the most important mechanisms contributing to the unique mechanical properties of this shell. The plastic microbuckling is analysed in terms of the equations proposed by Argon (Treatise of Materials Science and Technology. Academic Press, New York, 1972, p. 79) and Budiansky (Comput. Struct. 1983, 16, 3).
Article
The growth and self-assembly of aragonitic calcium carbonate found in the shell of abalone (Haliotis) is described. This was accomplished through the close examination of laboratory-grown flat pearl samples and cross-sectional slices of the nacreous shell. Further understanding of the sequenced assembly has been obtained. It has been confirmed that the growth of the aragonite component of the composite occurs by the successive nucleation of aragonite crystals and their arrest by means of a protein-mediated mechanism; it takes place in the “Christmas-tree pattern” [Nature 49 (1994) 371]. It is shown that the protein layer is virtually absent where plates on a same plane abut (along lateral surfaces of tiles). This suggests a mechanism of c-axis aragonite growth arrest by the deposition of a protein layer of approximately 20–30 nm that is periodically activated and determines the thickness of the aragonite platelets, which are remarkably constant (0.5 μm). This platelet size was measured for animals with shell diameters of 10, 50, and 200 mm and was found to be constant. The overall growth process is expressed in terms of parameters incorporating the anisotropy of growth velocity in aragonite (Vc, the velocity along c axis, and Vab, the velocity in basal plane). Comparison of laboratory-raised and naturally-grown abalone indicates growth regulated by the level of proteinaceous saturation. Naturally-grown abalone exhibits mesolayers (growth bands) ∼0.3 mm apart; it is proposed that they result from seasonal interruptions in feeding patterns, creating thicker (∼10–20 μm) layers of protein. These mesolayers play a critical role in the mechanical properties, and are powerful crack deflectors. The viscoplastic deformation of the organic inter-tile layers is responsible for the significant improvement of tensile strength over the tensile strength of monolithic aragonite.
Article
Quasi-static and dynamic compression and three-point bending tests have been carried out on Strombus gigas (conch) shells. The mechanical response is correlated with its microstructure and damage mechanisms. The mechanical response is found to vary significantly from specimen to specimen and requires the application of Weibull statistics in order to be quantitatively evaluated. The conch exhibited orientation dependence of strength as well as significant strain-rate sensitivity; the failure strength at loading rates between 10×103 and 25×103 GPa s−1 was approximately 50% higher than the quasi-static strength. Quasi-static compressive failure occurred gradually, in a mode sometimes described as ‘graceful failure’. Crack deflection, delocalization of damage, and viscoplastic deformation of the organic layers are the most important mechanisms contributing to the unique mechanical properties of these shells.
Article
An extensive experimental database has been established for the structural behaviour of aluminium foam and aluminium foam-based components (foam-filled extrusions). The database is divided into three levels, these are: (1) foam material calibration tests, (2) foam material validation tests and finally (3) structural interaction tests where the foam interacts with aluminium extrusions. This division makes it possible to validate constitutive models applicable to aluminium foam for a wide spectrum of loading configurations. Several existing material models for aluminium foam from the literature are discussed and compared. To illustrate the use of the database, four existing material models for foams in the explicit, non-linear finite element code LS-DYNA have been calibrated and evaluated against configurations in the database.
Article
When a low density foam is indented, it is found that the indentation hardness is about equal to the yield strength of the foam in compression. In this, foams differ from fully dense materials which, when plastic, exhibit a hardness which is about three times larger than the yield strength. This is because the foam is compressible: under the indent, a column of foam collapses, in a way which is hardly influenced by the surrounding material. This paper reports analyses of the indentation of compressible foams by cylindrical and spherical indenters, which reasonably account for measurements of the indentation hardness and the shape of the plastic zone beneath the indenter, in polyurethane foams. The results are relevant to the understanding of low density foams and woods, be they elastic, plastic or brittle.
Article
Birds' beaks have an outer shell of hard keratin which consists almost entirely of proteins which are very rich in glycine [about 30 residues per 100 residues (residues %)], contain moderate levels of tyrosine and serine (each about 8 residues %), and which have relatively low contents of cystine (about 2-5 residues %), lysine, histidine, isoleucine and methionine. Major protein fractions in the S-carboxymethyl form isolated from the beaks of six different orders of birds have similar amino acid compositions, isoelectric points (pH 4-2-4-9) and molecular weights (13,000-14,500). Detailed chromatographic electrophoretic and compositional studies of the proteins of kookaburra beak reveal them to be a family of closely related proteins with only limited heterogeneity, in contrast to mammalian keratin systems. The major kookaburra beak fraction is similar in overall composition and molecular weight to fowl epidermal scale, kookaburra claw and turtle scute proteins and shows some resemblance to reptile claw protein. Beaks also contain small amounts of protein which are distinctly different from the major fraction but which resemble feather keratin proteins in composition and size.
1. A number of differences in the phi-keratins have been shown to exist among various avian epidermal structures. 2. There is extensive electrophoretic heterogeneity within tissues and two elemental sizes of monomers. Feathers, natal and definitive down monomers have a weight of 10,500 dalton; scale, break and claw monomers approx 13,500 daltons. 3. Differences in the size of the monomers is due to the presence of an insoluble tryptic peptide high in Gly, Phe, Leu and Tyr. 4. Tissue differences in composition are related to structure and function.
Article
Biomimetics is a newly emerging interdisciplinary field in materials science and engineering and biology in which lessons learned from biology form the basis for novel technological materials. It involves investigation of both structures and physical functions of biological composites of engineering interest with the goal of designing and synthesizing new and improved materials. This paper discusses microarchitectural aspects of some structural biocomposites, presents microstructural criteria for future materials design and processing, and identifies areas of future research.
Article
The mechanical properties of fully hydrated equine hoof wall were examined at various loading rates in compact tension (CT) fracture, tensile and three-point bending dynamic tests to determine possible effects of hoof wall viscoelasticity on fracture toughness and tensile parameters. Four cross-head rates were used in CT tests: 1.7 x 10(-5), 1.7 x 10 (-3), 1.7 x 10(-2) and 2.5ms-1; four strain rates were used in tensile tests: 1.6 x 10(-3), 3.2 x 10(-2), 0.33 and 70s(-1). Speeds for the highest test rates were achieved using a large, custom-built impact pendulum. Bending test frequencies ranged from 0.04 to 200 Hz. In CT tests, both the initial modulus Ei and the stress intensity factor K rose with increasing strain rate (from 0.38 to 0.76 GPa for Ei and from 0.71 to 1.4 MN m-3/2 for K), whereas the fracture toughness parameter J remained constant at 12kJm-2. All tensile parameters except ultimate strain were sensitive to strain rate. Ei, total energy to breakage and maximum stress rose with increasing strain rate from 0.28 to 0.85 GPa, from 5.4 to 9.7 MJm-3 and from 17 to 31 MPa, respectively. Data from low-amplitude dynamic tests agreed well with Ei trends from CT and tensile tests. Direction of crack growth differed through the thickness of the wall, the pattern of which resembled a trilaminar ply. Although scanning electron microscopic examination of fracture surfaces revealed a decreasing pseudo-ductile behaviour with increasing strain rate, and ultimate tensile parameters are positively affected, equine hoof wall viscoelasticity does not appear to compromise fracture toughness at high strain rates.
Article
The flexural stiffness of the rachis varies along the length of a primary feather, between primaries and between species; the possible contribution of variations in the longitudinal Young's modulus of feather keratin to this was assessed. Tensile tests on compact keratin from eight species of birds belonging to different orders showed similar moduli (mean E=2.50 GPa) in all species apart from the grey heron (E=1.78 GPa). No significant differences were seen in the modulus of keratin from primaries 7­10 in any species. There was a systematic increase in the modulus distally along the length of the rachis from swan primary feathers. Dynamic bending tests on swan primary feather rachises also showed that the longitudinal elastic modulus increases with increasing frequency of bending over the range 0.1­10 Hz and decreases monotonically with increasing temperature over the range -50 to +50 °C. The position-, frequency- and temperature-dependent variations in the modulus are, however, relatively small. It is concluded that, in the species studied, the flexural stiffness of the whole rachis is principally controlled by its cross-sectional morphology rather than by the material properties of the keratin.
Article
Feathers are composed of a structure that, whilst being very light, is able to withstand the large aerodynamic forces exerted upon them during flight. To explore the contribution of molecular orientation to feather keratin mechanical properties, we have examined the nanoscopic organisation of the keratin molecules by X-ray diffraction techniques and have confirmed a link between this and the Young's modulus of the feather rachis. Our results indicate that along the rachis length, from calamus to tip, the keratin molecules become more aligned than at the calamus before returning to a state of higher mis-orientation towards the tip of the rachis. We have also confirmed the general trend of increasing Young's modulus with distance along the rachis. Furthermore, we report a distinct difference in the patterns of orientation of beta-keratin in the feathers of flying and flightless birds. The trend for increased modulus along the feathers of volant birds is absent in the flightless ostrich.
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