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Numerical investigation of compressive behaviour of luffa-filled tubes
... A model were developed to study the failure of 0 laminated composite tubes under static and fatigue loadings [13]. Wang et al. [14] analyzed the behavior of luffa-filled tubes under uniaxial compression numerically using and analytically using finite element analysis and theoretical models, respectively. In addition, they validated FEA models against experimental data. ...
... (17) and the subsequent results into Eqs. (14). The results are given as: ...
... To fully leverage the energy absorption of hierarchical structures of pomelo peel, a bio-inspired hierarchical honeycomb structure was proposed [4]. Other bio-inspired structures mimicking the biological structures such as coconut mesocarp, luffa sponge and palm vascular tissue have attracted tremendous interest among researchers [5][6][7][8]. The energy absorption characteristics of biological and bio-inspired structures and materials were comprehensively reviewed by Ha and Lu [9]. ...
This study explores the influence of dehydration on the energy absorption properties of the mesocarp layer of the tropic fruit durian (Durio zibethinus). Cuboid-shaped mesocarp samples of both fresh and dehydrated durian shells were subjected to axial compression tests. The findings reveal that the fresh mesocarp layer demonstrated heightened densification strain, a stable stress plateau, and enhanced specific energy absorption compared to its dehydrated counterpart. This underscores the crucial role of water and liquid sap in optimizing the energy absorption capacity of the durian mesocarp layer.
... And, the bioinspired structure shows a 29% reduction in the peak load and a 69% increase in energy absorption [23]. Furthermore, other types of structures in nature have also been used by many scholars for the development and application of lattice structures, such as pemelo peel [24], horse hoof [25], luffa-sponge-like hierarchical cellular structures [26][27][28], and bio-inspired Kagome truss [29]. As a result of the mechanical characteristics, biological structures always present inspiration for the development of high-performance mechanical structures [30]. ...
This paper aims to explore the influence of surface curvature distribution on the mechanical properties of lattice structures. In this study, a series of typical structure types were designed to obtain lattice structures with different surface Gaussian curvatures, including BCC (body center cubic) configuration, cross-cube configuration, and diamond lattice structure. Then, the above-mentioned porous structural sample was formed by SLM (selective laser melting), and the relevant mechanical properties were obtained by simulation and experiment. In addition, a characteristic method to describe the surface curvature of discrete triangular plaques is proposed and used to calculate the curvature distribution of the designed lattice structure. The results show that the lattice structure with concentrated Gaussian curvature distribution on the surface has good mechanical properties. Especially, for the cross-cube structure, the elastic modulus of the traditional configuration lattice structure increases by 79%, and the elastic modulus of the stretched structure increases by 70% when the volume fraction increased from 10 to 15%. Meanwhile, the elastic modulus for the traditional structure and the stretched structure increases by 41% and 14%, respectively, when the volume fraction of the structure increases from 15 to 20%. It is noted that the influence of surface curvature distribution on mechanical properties is slightly inferior to the volume fraction, which provides a new idea for the quantitative evaluation and design of porous structural properties. In addition, the BCC structure with concentrated curvature distribution provides a new scheme for the protection device after the stress climb stage after the elastic stage. Furthermore, the influence of surface curvature on the mechanical properties of lattice structures described in this paper will provide new inspiration for lattice structures in the fields of biocompatibility and heat exchange.
... Due to the unique fiber structure, loofah can bear a large load, and Zou [14] made an optimization algorithm on the displacement and stress relationship of the geometric structure. For studying the mechanical properties of loofah, Wang [15] found that the inner surface of the loofah plays a major role in supporting the axial load by conducting the tests of quasi-static compression and dynamic impact on the loofah structure. Elmadih [16] researched the ability of these lattices to provide vibration attenuation at frequencies greater than their natural frequency. ...
To obtain the lattice structure with excellent energy absorption performance, the structure of loofah inner fiber is studied to develop bionic design of lattice structure by experiment and simulation analysis method. From the compression experiment about the four bionic multi-cell lattice structures (bio-45, bio-60, bio-75, and bio-90) and VC lattice structures, we found that all are made of PLA and fabricated by the fused deposition modeling (FDM) 3D printer. The comprehensive performance of bio-90 lattice structure is the best in the performance of the specific volume energy absorption (SEAv), the effective energy absorption (EA), and the specific energy absorption (SEA). Based on the experimental result, the energy absorption performance of bio-90 lattice structure is then studied by the simulation analysis of influence on multiple parameters, such as the number of cells, the relative density, the impact velocity, and the material. The results can provide a reference for the design of highly efficient energy absorption structures.
... Natural hierarchical materials, such as bio-cellular luffa sponges [125][126][127][128][129][130], are an excellent subject for the study of porous structures. They have an incredible level of porosity, and are capable of maintaining a constant stress deformation plateau during crushing. ...
As a result of their mechanical characteristics, biological structures often provide inspiration for the development of high-performance components and devices. Nevertheless, traditional production processes are often incapable of precisely reproducing the intricate and exquisite nature of bio-inspired structures. Modern additive manufacturing techniques provides a pathway to the creation of materials with complex patterns that are inspired by biological processes. In this paper, we identify the different types of biomimetic porous structures seen in nature, many of which are composite in nature, and categorise them. We also identify the natural species with porous structures and illustrate their functions. In addition, the review paper presents the mimicked porous features and their recent and past findings of various researchers. Figures are shown to demonstrate the scale (meso, micro, and nano) at which the porous structures are emulated. As biological porous structures have been successfully mimicked into synthetic materials using additive manufacturing (AM), in this review paper, we classify the different types of porous structures, identify various species in nature, and describe the various types of additive manufacturing processes used to manufacture biomimetic porous structures. This review paper will be of interest to academics looking to design innovative lightweight porous composite structures and use emerging technologies to investigate their energy absorption properties, which have a wide range of engineering applications.
... Compared with conventional material with positive Poisson's ratio, auxetics have superior mechanical properties in energy absorption [3][4][5], shear resistance [6,7], fracture toughness [8,9], in-plane indentation resistance [10,11], synclastic behavior [12,13], negative compliance [14,15] and sound insulation [16,17], thus have multiple applications in medical, aerospace, intelligent materials, civil engineering [18,19] and other fields [20]. Tubular structures have been extensively developed and widely applied in various fields, such as vehicle engineering, energy absorption, aerospace industry, civil engineering, medical equipment, and packaging engineering [21,22]. Introducing auxeticity into the tubular structure could further widen their application prospects [23]. ...
Auxetic materials exhibit interesting deformation characteristics and excellent mechanical properties. A novel combined tubular structure with tunable stiffness is proposed in this work, aiming to improve the bearing capacity and stability by length design of the central column. Specimens were fabricated via 3D printing technique. Experimental test was performed to study their mechanical property and deformation characteristics under uniaxial compression. The validity of the finite element model was proved by comparing the experimental result with simulation prediction. The compression process and stress-strain curve of the tubular structure with tunable
stiffness exhibited four distinct stages (elastic, stiffness change, densification and buckling). Subsequently, a parametrical analysis was conducted to investigate the influences of the central connecting column on the stressstrain response, Poisson’s ratio and stability of the structure. By properly choosing the length of the central connecting column, the tubular structure could possess tunable stiffness, higher stability and compressive capacity. Furthermore, this design concept could be of benefit to the development of adaptive structures, smart devices and applications for civil engineering and protective engineering.
... Mechanical characteristics of an NFC are specified through multiple tests, like hardness, flexural, tensile, compression, impact, etc. [131,132]. The mechanical properties of LNFCs are summarized and discussed in this section. ...
Natural fiber composites (NFCs) are an evolving area in polymer sciences. Fibers extracted from natural sources hold a wide set of advantages such as negligible cost, significant mechanical characteristics, low density, high strength-to-weight ratio, environmental friendliness, recyclability, etc. Luffa cylindrica, also termed luffa gourd or luffa sponge, is a natural fiber that has a solid potential to replace synthetic fibers in composite materials in diverse applications like vibration isolation, sound absorption, packaging, etc. Recently, many researches have involved luffa fibers as a reinforcement in the development of NFC, aiming to investigate their performance in selected matrices as well as the behavior of the end NFC. This paper presents a review on recent developments in luffa natural fiber composites. Physical, morphological, mechanical, thermal, electrical, and acoustic properties of luffa NFCs are investigated, categorized, and compared, taking into consideration selected matrices as well as the size, volume fraction, and treatments of fibers. Although luffa natural fiber composites have revealed promising properties, the addition of these natural fibers increases water absorption. Moreover, chemical treatments with different agents such as sodium hydroxide (NaOH) and benzoyl can remarkably enhance the surface area of luffa fibers, remove undesirable impurities, and reduce water uptake, thereby improving their overall characteristics. Hybridization of luffa NFC with other natural or synthetic fibers, e.g., glass, carbon, ceramic, flax, jute, etc., can enhance the properties of the end composite material. However, luffa fibers have exhibited a profuse compatibility with epoxy matrix.
... The current study of luffa sponge focuses onits mechanical properties. Wang et al. [20] studied the compression behavior of luffa-filled tubes and regard luffa sponge as a part. However, they did not mention the contribution of the I layer. ...
The luffa sponge shows excellent cushion properties. This paper presents a bio-inspired structure of the luffa sponge. The geometry of the bionic structure was built based on the fractal theory by Python programming language and prepared by a 3D printer. Then a series of quasi-static compression tests and finite element analysis were carried out to determine the cushion properties. An optimization design was adopted to determine the best design parameter. The results showed that the influence of length ( a ) on specific energy absorption was more important than the degree ( θ ). The best parameter was found to be length less than 4 mm and angle around 11 degrees. The bionic structure of luffa sponge may show a novel perspective on natural cellular material. The findings demonstrate the great potential for designing hierarchical cellular structures and broad application prospects in the field of cushioning and energy absorption.
... Diameter ratio of the tube increases the thickness. Jianhu Shen et al. investigated the mechanical properties of luffa sponge [24]. Some metallic cellular materials in a similar density range comparable with energy absorption capacities strength and remarkable stiffness of luffa sponge material. ...
The main aim of the present experimental investigation is to evaluate mechanical properties of natural
fibre ridge gourd with polymers laminates prepared with different combinations of fiber and resin.
Laminates were fabricated by hand layup method. The impregnation of laminates is done by epoxy resin
and polyester resin as matrix material. The ridge gourd is cheaper, biodegradable and Eco Friendly and it
is located in all the areas and it can be available during all the seasons. With various structures of patterns
materials characteristics is observed that with different combinations glass, ceramic fibers with ridge
gourd with epoxy resin and polyester resin laminates increases its mechanical properties. In tensile
strength ceramic fiber with epoxy resin and fiber mat shows increase strength such as 140.68 MPa and
77.3 in hardness strength. Likewise compressive strength in natural fiber with ridge guard shows
increased strength.
... In this article, Abaqus/Explicit software is used to carry out the dynamic model thanks to the wide applications of FEA tools in the analysis of dynamic crushing of thin-walled structure and cellular materials. 16,19,26,33,[39][40][41][42] The finite element model is built with four-node reduced integration shell elements with five integration points across the thickness. The contact between the impacting rigid plate and the thin-walled tube is a node-to-surface contact with friction coefficient of 0.2, and the supporting rigid plate and the thinwalled tube are defined as ''tied.'' ...
In this article, a novel multi-cell conical tube is designed. First, a detail analysis about the crashworthiness of three structures, that is, the multi-cell conical tube, multi-cell square tapered tube, and fourfold-cell conical tube, is made and compared at the condition of keeping the same mass with different oblique load angles. Then, the influences of the internal cell walls, load angle, the cone angle, and wall thickness on the performances of crashworthiness are investigated. The multi-cell conical tube has better energy absorption capacity than multi-cell square tapered tube and fourfold-cell conical tube at small load angles. The normalization of average gradients of the cone angle on specific energy absorption reached 48.25% compared with the wall thickness. The full factorial design and the optimal Latin hypercube design method are adopted to define the sample points and error analysis points. A numerical simulation on the sample points and error analysis points are performed using Abaqus/Explicit. According to different working conditions, different optimization objects are determined, and corresponding surrogate models with different indicators are constructed using Kriging method. The accuracy of surrogate model is evaluated. The non-dominated sorting genetic algorithm-II is utilized to optimize the multi-objective problem. Finally, the influence of structural parameters on crashworthiness is discussed.
... Importantly, the loss factors for the Luffa-1, 2, and 3 bio-composite plates used in modal analyses were c,Luffa-1 =2.62%, c,Luffa-2 =2.53%, and c,Luffa-3 =2.57%, respectively, in the frequency range of interest. The Poisson's ratio was assumed to be v = 0.3 (Wang et al. 2015). Overall, the elasticity moduli of the luffa biocomposite plates were Ec,Luffa-1 = 2.55 GPa, Ec,Luffa-2 = 2.45 GPa, and Ec,Luffa-3 = 2.40 GPa. ...
Luffa cylindrica plant fiber is a new biodegradable engineering material. However, the dynamic behaviors of these new green materials or their composites should be explored to consider them for practical applications. The dynamic characteristics including modal behavior and the elastic and sound isolation properties of luffa-based bio-composite plates were explored in this study. Structural frequency response function measurements were conducted using a few luffa bio-composite plates to identify their modal behavior. The modal frequencies and loss factors of the luffa bio-composite plates were identified by analyzing the frequency response function measurements using a few modal analysis methods such as half-power, circle-fit, and line-fit. The same luffa bio-composite structures were modelled using a finite element formulation with damping capability, and the elastic moduli of the composite plates were identified. In addition, the transmission loss levels of the same luffa composite samples were measured using the impedance tube method. The results showed that luffa composite structures have considerably high stiffness (elasticity modulus: 2.5 GPa), damping levels (loss factor: 2.6%), and transmission loss level (25 to 30 dB for a 1 cm thickness), and their mechanical properties are promising as an alternative disposable material for noise and vibration control engineering applications.
... The major bio-fibers including flax, jute hemp, kenaf and sisal were investigated in many studies [3][4][5][6][7][8][9] though there are some challenges such as cultivation and continuity for these plant materials. In the recent years, luffa plant has been recognized as a new potential natural fiber [3,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] though there is a need for more research on the composites of luffa fibers to evaluate and use them for practical applications. ...
New materials as alternatives to petroleum-based composite materials are needed due to adverse effects of chemical materials on nature. On the other hand, there is a need to characterize and evaluate new alternative materials to be effectively used in practical applications. The vibro-acoustic behaviors including damping and elastic properties, sound absorption and transmission loss levels of luffa bio-composites are investigated and their use for practical applications is evaluated in this study. First, the procedure for manufacturing luffa composites is summarized and materials and methods are presented. After that, the acoustic absorption and transmission loss levels of sample luffa composites are explored by using the impedance tube method. The damping and elastic properties of sample luffa composites are determined by using experimental and theoretical modal data. Furthermore, the interface properties of the luffa fibers and matrix are examined by using Scanning Electron Microscope. All the results are evaluated and the potential of the use of luffa composites in practical applications is assessed.
... Another attracting material is natural hierarchical material [15], such as bio-cellular luffa sponges [16][17][18][19][20][21]. The luffa sponge has great porosity and stable deformation plateau in crushing. ...
... The results showed this method effectively retained postharvest quality and extended shelf life of sponge gourd. Wang, Shen, Zuo, Huang, Zhou, and Xie (2015) investigated and analyzed the compressive behavior of luffa sponge and luffa-filled tubes through finite element analysis (FEA) and its model. They found that the optimal density of the luffa as filler for the luffa-filled tubes was equal to the optimal density of the luffa sponge; it increased with the increase of the thickness to diameter ratio of the tube. ...
... They also found that increasing wall thickness could be more efficient to increase specific energy absorption than foam filling. Similarly, Wang et al. [10] investigated the compressive behaviour of luffafilled tubes and found that the deformation would change to concertina mode with the increase of luffa density. ...
Thin-walled tubes are widely used as energy absorption components. In this study, two different origami
patterns were introduced to circular tubes. The influence of the origami patterns on the energy absorption capacity and the deformation mechanism of tubes under uniaxial loading were investigated
both numerically and experimentally. The results showed that the initial peak force of origami tubes
would be significantly reduced, while the energy absorption capacity could be improved or maintained.
Brass tubes with and without origami patterns were fabricated using 3D printing and were tested to
validate the finite element models.
... Bio-cellular materials, observed in biological systems, have hierarchical structures (Lakes 1993;Fratzl and Weinkamer 2007;Chen and Pugno 2013); these materials exhibit excellent mechanical properties at remarkably low density (Taylor et al. 2011;Fan et al. 2014;Wang et al. 2014;Anbukarasi and Kalaiselvam 2015). The luffa sponge is one such material containing a complex, interconnecting pore structure (Shen et al. 2012;Chen et al. 2014). ...
Crushing behaviors of luffa sponges were studied through mechanical experiments. Controlled by four-order hierarchical and anisotropic structures, luffa sponges exhibit anisotropic responses along axial, radial, and circumferential directions. The ultra-thin but stiff inner surface layer dominates the crushing behavior, endowing the axially compressed luffa cylinder with structural integrity, enhancing the elastic deformation and yielding strength. In radial, circumferential, and lateral compressions, after removing the inner surface layer, luffa sponges are compliant and have large quasi-linear deformation before densification, without a plateau characterized by yielding and deformation. Immersed into water, crushed luffa sponge cylinders recover their geometry completely. However, compression strength is only partially restored. Gradual damage of the inner surface layer in water immersing/drying cycles greatly weakens the compression strength. In the case of removal of the inner surface layer, crushed luffa sponge cylinders completely restore their quasi-linear deformation ability during the water immersing/drying cycles.
This article introduces natural composite and nanocomposite panels of Luffa fibers–chitosan resin; and they are subjected to quasi-static penetration tests and compression experiments to discuss their penetration resistance and compression strength. Natural fibers of Luffa cylindrical sponge were used as the reinforcement and natural chitosan resin was produced from shrimp shells. Specimens with various characteristics were produced through hand layup method and they were subjected to penetration test of a blunt-nose punch. Results demonstrated that there is an optimum mass fraction for chitosan and magnetite nanoparticles to achieve the highest penetration strength; and the best layer configuration is as 0 and 90°, alternately. Furthermore, some glass-chitosan composite panels were produced and comparison of their penetration tests and the corresponding Luffa-chitosan composite experiments demonstrated that in a certain condition, the maximum loads of penetrating the punch into the both composite panels are the same. In second type experiments, quasi–static compression tests were performed on some cubic Luffa–chitosan specimens and results showed that the natural composite cube has significant specific absorbed energy; and by selecting its suitable dimensions, a natural energy absorber can be achieved. Development of the natural Luffa–chitosan composite is suggested, based on sustainability considerations; and using it in the bulletproof vests and armors is presented as a creative idea; due to its natural structure, compatibility with human skin, acceptable resistance against the penetration, its biodegradable ability and simple and low cost production process.
The smooth thin shell structure has exhibited significant advantages in light weight and high energy absorption and been widely applied in transportation, aerospace fields. This study proposed the thin-walled square tube filled with hollow aluminum metal spheres (TST-HS) to improve the crashworthiness. In this structure, hollow aluminum spheres were filled into thin-walled square tubes in different stacking modes, such as simple cubic (SC), body-centered cubic(BCC), and face-centered cubic (FCC). A series of quasi-static compression experiments and numerical simulations were conducted to investigate the deformation mechanism and crashworthiness of TST-HS. The results indicated that filled hollow spheres lead to the change in the deformation mode and an increase in the number of plastic hinges of TST-HS. The mean load of TST-HS was increased by 68.98% and 15.6%, respectively, compared to the square tubes and the foam-filled tube of same mass. Parametric studies show that the wall thickness, size and stacking modes of the hollow spheres have major impacts on the crashworthiness of the TST-HS. Energy analysis reveals the contribution of the interaction between hollow sphere and square tube to the total energy absorption of TST-HS.
The impact performance of lightweight structures represents an important design criterion in modern applications. Within this framework, the self-reinforced PET (poly-ethylene terephthalate) materials prove to exhibit large deformations till failure, which enables them to be proper candidates for impact energy absorption. Apart from the advantages offered by the lightweight characteristics, they are made of recyclable materials, an additional reason for their consideration in engineering applications. In this paper, the behavior of a hierarchical sandwich structure made out of self-reinforced PET (matrix & fibre) combined with PET foam is numerically investigated with respect to the specific energy absorption (SEA) capacity in out-of-plane quasi-static loading conditions. The numerical model of the structure is developed and its behavior is firstly validated through experimental tests. The specific energy absorption is further on determined for several geometric configurations of the hierarchical sandwich structure and compared with the behavior of other cellular structures found in the technical literature. A competitive behavior is observed with respect to impact energy absorption.
This chapter presents an overview of the acoustic and mechanical behaviors of luffa fiber-reinforced biocomposites. A growing number of studies are examining the composites of biodegradable fibers such as flax, hemp, kenaf, and luffa because of the adverse effects of their chemical materials on nature. Their low cost and the superior acoustic and acceptable mechanical properties of biocomposites make them attractive for practical applications such as sound and vibration isolation. However, the acoustic and mechanical characteristics of biocomposites and their dynamic behaviors should be fully determined before they are considered for practical applications. In this chapter, acoustic properties such as sound absorption and transmission loss and mechanical properties such as the damping and elasticity of luffa fiber-reinforced composites are presented. Variations in acoustic and mechanical properties owing to different samples and manufacturing processes are explored.
The crashworthiness testing of carbon/epoxy composite tubes is conducted in this study, and the corresponding energy-absorbing parameters and failure morphology are discussed. Considering the anisotropic constitutive relationships of composites, a stiffness degraded model that involves the extended Hashin failure criterion and damage evolution law based on the continuum damage mechanics is proposed to analyze the progressive failure of G803/5224 composite tubes. The progressive failure user subroutine is developed based on the transient dynamics software. The progressive failure numerical analysis combined with the failure criterion is also discussed. The relative error of specific energy absorption and average load is less than 6% compared that of the experimental results. This result indicates that the proposed method can be applied to estimate the energy-absorbing characteristics of composite tubes.
Thin-walled structures have been widely used as key components in automobile and aerospace industry to improve the crashworthiness and safety of vehicles while maintaining overall light-weight. This paper aims to explore the design issue of thin-walled bitubal column structures filled with aluminum foam. As a relatively new filler material, aluminum foam can increase crashworthiness without sacrificing too much weight. To optimize crashworthiness of the foam-filled bitubal square column, the Kriging meta-modeling technique is adopted herein to formulate the objective and constraint functions. The genetic algorithm (GA) and Non-dominated Sorting Genetic Algorithm II (NSGA II) are used to seek the optimal solutions to the single and multiobjective optimization problems, respectively. To compare with other thin-walled configurations, the design optimization is also conducted for empty bitubal column and foam-filled monotubal column. The results demonstrate that the foam-filled bitubal configuration has more room to enhance the crashworthiness and can be an efficient energy absorber.
Foam-filled thin-wall structures have exhibited significant advantages in light weight and high energy absorption and been widely applied in automotive, aerospace, transportation and defence industries. Unlike existing uniform foam materials, this paper introduces functionally graded foam (FGF) fillers to fill thin-walled structures, aiming to improve crashworthiness. In this novel structure, the foam density varies throughout the depth in a certain gradient. Numerical simulations showed that gradient exponential parameter m that controls the variation of foam density has significant effect on system crashworthiness. In this study, the single and multiobjective particle swarm optimization methods are used to seek for optimal gradient, where response surface models are established to formulate specific energy absorption and peak crushing force. The results yielded from the optimizations indicate that the FGF material is superior to its uniform counterparts in overall crashworthiness. The data has considerable implication in design of FGF materials for optimizing structural crashworthiness.
This paper presents a two-stage multi-fidelity (or named variable fidelity) method for surrogate models in honeycomb crashworthiness design. The high/low-fidelity analyses adopt fine/coarse finite element (FE) meshes, respectively. In Stage I, a correction response surface (RS) was constructed from the ratio or difference between high-fidelity and low-fidelity analyses at few sample points. In Stage II, the high-fidelity response is approximated via a radial basis function (RBF), either alone or incorporating with the correction RS model from Stage I. It is shown that the presented two-stage multi-fidelity model is more appropriate than any single-fidelity counterpart in the honeycomb optimization under the same computational cost.
Load-bearing biological materials such as shell, mineralized tendon and bone exhibit two to seven levels of structural hierarchy based on constituent materials (biominerals and proteins) of relatively poor mechanical properties. A key question that remains unanswered is what determines the number of hierarchical levels in these materials. Here we develop a quasi-self-similar hierarchical model to show that, depending on the mineral content, there exists an optimal level of structural hierarchy for maximal toughness of biocomposites. The predicted optimal levels of hierarchy and cooperative deformation across multiple structural levels are in excellent agreement with experimental observations.
This important study focuses on the way in which structures and materials can be best designed to absorb kinetic energy in a controllable and predictable manner. Understanding of energy absorption of structures and materials is important in calculating the damage to structures caused by accidental collision, assessing the residual strength of structures after initial damage and in designing packaging to protect its contents in the event of impact. Whilst a great deal of recent research has taken place into the energy absorption behaviour of structures and materials and significant progress has been made, this knowledge is diffuse and widely scattered. This book offers a synthesis of the most recent developments and forms a detailed and comprehensive view of the area. It is an essential reference for all engineers concerned with materials engineering in relation to the theory of plasticity, structural mechanics and impact dynamics. © 2003 Woodhead Publishing Limited Published by Elsevier Ltd All rights reserved.
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.
Insight into the stimuli-responsive behaviour of biological materials with hierarchical microstructures is essential for designing new sustainable materials and structures. Shape memory, self-healing and self-repairing will become valuable characteristics of advanced materials. Here we report the water-triggered shape recovery of a natural biological material, the luffa sponge. The longitudinally crushed luffa sponge column can recover up to 98% of its original shape after it is immersed in water. The mechanical properties of the luffa sponge can also be recovered, to a large extent, after a subsequent drying process. The effects of strain rate, crushing strains, loading cycles, and temperature/duration of water treatment of the drying process on the shape recovery ratio and the energy dissipation recovery ratio have been investigated. The results from this study have demonstrated that the luffa sponge material possesses remarkable shape memory effects and mechanical recovery features which could be exploited or biomimicked for the design of water-responsive smart materials undergoing large deformations.
Insight into the stimuli–responsive behaviour of biological materials with hierarchical microstructures is essential for designing new sustainable materials and structures. Shape memory, self-healing and self-repairing will become valuable characteristics of advanced materials. Here we report the water-triggered shape recovery of a natural biological material, the luffa sponge. The longitudinally crushed luffa sponge column can recover up to 98% of its original shape after it is immersed in water. The mechanical properties of the luffa sponge can also be recovered, to a large extent, after a subsequent drying process. The effects of strain rate, crushing strains, loading cycles, and temperature/duration of water treatment of the drying process on the shape recovery ratio and the energy dissipation recovery ratio have been investigated. The results from this study have demonstrated that the luffa sponge material possesses remarkable shape memory effects and mechanical recovery features which could be exploited or biomimicked for the design of water-responsive smart materials undergoing large deformations.
This paper presents further investigations into the axisymmetric progressive crushing behaviour of metal tubes subject to quasi-static axial loads. Based on experiments and a finite element analysis, a new, more realistic theoretical model is developed by introducing the concept of effective plastic hinge length which is proportional to tube thickness. The theoretical crushing force history, mean crushing force and plastic half-wavelength are compared with experiments and finite element analysis results. It is found that for normalized mean crushing force, Pm/Mo, better agreement is obtained using the present theoretical model than previous ones. This analysis helps explain the paradox between the D/t exponent calculated from experimental results and previous theoretical predictions. Also, a good estimate of plastic half-wavelength, h, is also obtained.
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.
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.
An experimental investigation was carried out to study the behaviour of square aluminium extrusions filled with aluminium foam under quasi-static loading conditions. Based on the experimental work, simple relations between dimensionless numbers governing the influence of the foam on the characteristics of the crush problem were identified. Furthermore, a simplified set of equations applicable for design of foam-filled components was proposed.
A new method of treating progressive folding of foam filled prismatic columns is developed and compared with available experimental data. Theoretical analysis gives good agreement with experimental results, provided that the interaction between the thin-walled tube and filling foam is taken into account.
The paper presents the first scientific study of the stiffness, strength and energy absorption characteristics of the luffa sponge with a view to using it as an alternative sustainable engineering material for various practical applications. A series of compression tests on luffa sponge columns have been carried out. The stress-strain curves show a near constant plateau stress over a long strain range, which is ideal for energy absorption applications. It is found that the luffa sponge material exhibits remarkable stiffness, strength and energy absorption capacities that are comparable to those of some metallic cellular materials in a similar density range. Empirical formulae have been developed for stiffness, strength, densification strain and specific energy absorption at the macroscopic level. A comparative study shows that the luffa sponge material outperforms a variety of traditional engineering materials.
Thin-walled columns play an important role on passenger safety in vehicular collisions for their progressive deformation patterns and large energy absorptions. A thin-walled column with a large specific energy, i.e., the ratio of energy absorption to its mass, is often desirable to the automotive industry, because such designs could enhance safety and reduce manufacturing cost. Due to the complexity of crash mechanism, obtaining such designs has been a challenge to the trial-and-error approach using physical prototype testing. To this end, combining finite element simulations with optimization methodologies has become the viable means to meet the challenge. In this paper, single- and triple-cell hexagonal columns filled with aluminum foams were optimized for maximum specific energy with simultaneous consideration of section geometry, tube thickness, and foam density. The effects of crushing forces on column designs were analyzed by comparing optimum solutions with and without constraints on the mean crushing forces. The interaction effects between the tube and foam of composite columns and the relative advantages of single- and triple-cell structures were investigated and discussed.
Experimental investigations are carried out in order to study the effects of different tube and filler arrangements on the crushing behaviour of axially compressed tubular crush elements. To this end quasistatic experiments are performed on monotubal and bitubal, empty and filled steel profiles with different materials, dimensions and cross-sectional shapes. Aluminium foam, produced by a powder metallurgical production process, is applied as filler material. The test results confirm that considerable mass efficiency improvements with respect to energy absorption may be obtained, even if reduced stroke lengths, caused by the presence of foam, are taken into account. Distinct differences are pointed out between the different cross-sectional shapes. Bitubal arrangements, consisting of outer and inner profiles with foam in between, are shown to be particularly efficient crush elements, as long as global failure can be avoided. Explanations for the experimental observations are obtained by a simplified analysis of interaction effects. Constraints concerning the appropriate choice of Al-foam densities are summarized, too, in order to provide an aid for the future design of ‘optimally tuned’ crush elements composed of tubular members and Al-foam.
Foam-filled thin-walled tubes are considered to be desirable energy absorbers under axial loading due to their higher energy absorption compared with empty tubes. This paper treats the axial crushing and energy absorption response of foam-filled conical tubes under quasi-static axial loading, using non-linear finite element models. Influence of important parameters such as wall thickness, semi-apical angle and density of foam filler was investigated and the results highlight the advantages of using foam-filled conical tubes as energy absorber. Results also indicate that the crush and energy absorption performances of conical tubes are significantly enhanced by foam filling. The primary outcome of the study is new research information and development of empirical relations which will facilitate the design of foam-filled conical tubes as energy absorbers in impact applications.
An experimental programme consisting of 96 tests was carried out to study the axial deformation behaviour of triggered, circular AA6060 aluminium extrusions filled with aluminium foam under both quasi-static and dynamic loading conditions. The outer diameter and length of the columns were kept constant at 80 mm and 230 mm, respectively. The main parameters in addition to the loading condition were the foam density, the extrusion wall strength and the extrusion wall thickness. Based on the experiments, design formulas for prediction of average force, maximum force and effective crushing distance were suggested.
The effect of low density polyurethane foam on the axial crushing of thin-walled (D/t>600) circular metal tubes is studied under quasi-static and dynamic loading conditions. The mode of deformation of the tube is found to change from irregular diamond crumpling to axisymmetric bellows folding due to the filler. Assuming the axisymmetric mode of crushing and using the model of foam recently developed (M.F. Ashby, Metals Trans.14A, 1755–1769, 1983), the behaviour is analysed. Theoretical predictions agree well with experiments. Numerical results show that there is an optimum foam density which produces a maximum specific energy absorption of the filled cylinders.
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.
Copyright: 2008 Elsevier Ltd This review deals with a recent study of the literature on the various aspects of cellulosic fibres and biocomposites. Cellulosic fibre reinforced polymeric composites are finding applications in many fields ranging from construction industry to automotive industry. The pros and cons of using these fibres are enumerated in this review. The classification of composites into green composites, hybrid biocomposites and textile biocomposites are discussed. New developments dealing with cellulose based nanocomposites and electrospinning of nanofibres have also been presented. Recent studies pertaining to the above topics have also been cited. Finally, the applications of cellulosic fibre reinforced polymeric composites have been highlighted
Although strong and stiff human-made composites have long been developed, the microstructure of today's most advanced composites has yet to achieve the order and sophisticated hierarchy of hybrid materials built up by living organisms in nature. Clay-based nanocomposites with layered structure can reach notable stiffness and strength, but these properties are usually not accompanied by the ductility and flaw tolerance found in the structures generated by natural hybrid materials. By using principles found in natural composites, we showed that layered hybrid films combining high tensile strength and ductile behavior can be obtained through the bottom-up colloidal assembly of strong submicrometer-thick ceramic platelets within a ductile polymer matrix.
Structural enhancement of luffa sponge to increase its energy absorption capacity
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