No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Experimental and numerical study of double-skin aluminium foam sandwich panels in bending
Abstract
Metal foams are engineered materials with attractive mechanical properties such as lightness, energy dissi-pation capacity, high resistance and stiffness. To date, the applications of these materials are mainly limited to aeronautic and mechanical engineering. However, their features can provide significant advantages also for the development of new products for structures and infrastructures in the field of civil engineering. This consideration has motivated the study described in this paper, which is mainly devoted to assessing the performance of double-skin composite sandwich panels made of steel sheets and aluminium foam to be used as the deck in civil structures. To this aim, as the first step of ongoing research activity, both experimental and finite element (FE) simulations are carried out verifying the applicability of the proposed type of sandwich panel. Both tests on material specimens and three-point bending tests on the double-skin composite sandwich panels are performed, and the main results are discussed. FE analyses are carried out enlarging the range of investigated and monitored parameters assessing their influence on the bending and shear response of the panels. The outcomes of the study show the effectiveness of the proposed type of sandwich panel and allow selecting the most effective type of adhesive to bond the steel plates to the aluminium foam core. The obtained results are complemented with simple design equations that allow satisfactorily predicting both stiffness and strength of the sandwich panels.
... Samples of aluminium foams prod by the Canadian company Cymat Technologies Ltd. (Mississauga, ON, Canada) tested to characterise their bending and shear resistance. For the sake of brevity, the re of two specimens for the bending test and two for the shear test are reported, but a tional and detailed information is included in Latour et al. [18,19]. Coupon tests were formed to characterise the material properties of the steel skins. ...
... Samples of aluminium foams produced by the Canadian company Cymat Technologies Ltd. (Mississauga, ON, Canada) were tested to characterise their bending and shear resistance. For the sake of brevity, the results of two specimens for the bending test and two for the shear test are reported, but additional and detailed information is included in Latour et al. [18,19]. Coupon tests were performed to characterise the material properties of the steel skins. ...
... The panel connected with screws can effectively address the challenges assoc with adhesive-based types, which often involve the loss of adhesion shortly after su sing the steel's yield strain. In this paper, for comparison purposes, some results fr previous experimental campaign [18,19] were reported to compare the overall behav of the sandwich panels equipped with two connection typologies: screwed and g sandwich panels. The results were analysed and compared to assess the best choi terms of the overall behaviour of the sandwich panel. ...
Metal foams are newly developed engineered materials with attractive mechanical properties such as lightness, high resistance-to-weight ratio, and insulation capabilities. Lately, applications of these technologies have demonstrated the possibility of obtaining high-performance sandwich panels with steel skins and metal foam core, with potential applications across various fields. Within this framework, this work aims to assess the response of sandwich panels made of steel and aluminium foam to develop a new system of dry-assembled composite floors. The present study investigates a novel screwed steel–aluminium foam–steel (SSAFS) sandwich panel. This paper mainly describes and discusses the results of experimental tests devoted to evaluating the structural performance, mechanical properties, and suitability for practical applications of SSAFS. The fabrication process and the detailing of the steel skins and aluminium foam core assembly are also described. The results from the experimental tests revealed the potentialities of using SSAFS sandwich panels in terms of strength and stiffness, thus making them suitable for lightweight structural systems.
... AFSs prepared directly with carbon fiber/epoxy composite laminates as the upper and lower panels also have certain bonding strengths [11,22]. [23] and (b) adhesive detail diagram [24]. Reprinted with permission from ref. [23,24]. ...
... Figure 4 shows an AFS prepared by the adhesivity method, where there is an obvious gap between the panel and core. [23] and (b) adhesive detail diagram [24]. Reprinted with permission from ref. [23,24]. ...
... [23] and (b) adhesive detail diagram [24]. Reprinted with permission from ref. [23,24]. Copyright 2022 Elsevier. ...
Closed-cell aluminum foam has a porous structure and metal properties due to its unique composition. As a structural material, it has the advantages of being lightweight, having a large specific surface area, and having high specific strength and stiffness. As a functional material, it can be used for sound and noise reduction, heat insulation, electromagnetic shielding, damping, and energy absorption, but it also has poor mechanical properties and poor surface flatness, and can be easily corroded. Considering the abovementioned problems, researchers have gradually extended their research on foam materials. Under the research of many international scholars, studies have shifted from simple aluminum foam preparation to improving and optimizing aluminum foam composite structures (AFCSs). From the perspective of development prospects, AFCSs have better application prospects than single aluminum foam. In this paper, the research progress on the preparation technology of AFCSs in recent years was reviewed based on the performance enhancement mechanism of aluminum matrix composites and the structural characteristics of aluminum foam. The morphology and pore structures of closed-cell AFCSs under different preparation methods were summarized. However, due to the limitations of existing experimental conditions, this paper only considered the advantages and disadvantages of AFCS preparation methods. The improvement of AFCS preparation technology, the development of the potential properties of AFCSs, and the promotion of AFCS industrial applications were also considered.
... Recent studies have also been made on panels with metal skins and different types of foam. Latour et al. [20] investigated sandwich panels made of steel sheets and aluminium foam for decking in civil constructions. Zhao et al. [21] performed experimental and numerical analyses to explore the dynamic behaviour of aluminium foam sandwich panels subjected to low-velocity impacts. ...
... Analytical calculations are used to compare the bending resistance of the panels [20]. Considering the specific test conditions, the bending moment is evaluated through simple equilibrium conditions: ...
... All conditions showed a region of local indentation (see Fig. 5) in the mid-span on the compressive side of the beam. Unlike [20,47], the debonding between the aluminium skin and the PET foam core is not observed in all tested specimens. This result can be explained by the relatively high shear strength of the adhesive found in the single-lap tests. ...
This work describes a methodology for the multi-objective optimisation of sandwich structures made of aluminium skins and recycled PET foams with perforated architecture. The designs are evaluated using a nonlinear finite element (FE) model validated by comparing the load, displacement and final shape of a representative sandwich panel against related experimental results. An extensive number of experiments characterise the mechanical performance of sandwich panels in pristine and perforated architected foams, the latter with perforations distributed following cubic and hexagon packing. A single lap joint test assesses the bonding between the aluminium skins and the epoxy adhesive system. Three-point bending and drop tower impact tests are performed to characterise the foams and the panels. Aluminium sheets are also tested for comparison purposes. Analysis of variance and Tukey test are used to compare the results from a statistical standpoint. The validity of the optimisation process is demonstrated through the design of sandwich panels made of hexagonal architectures of foam perforations and subjected to impact load. The sandwich panel is optimised to minimise mass and maximise the absorbed energy by using a custom routine integrated with a genetic algorithm. The results demonstrate that sandwich panels in pristine conditions provide enhanced bending performance, while panels with perforated foams have larger impact resistance. The optimisation indicates that the proposed methodology can support the design of lightweight perforated sandwich panels with superior structural performance.
... By examining three design criteria specified in the standard ISO 22502:2020 isostatic, integrated, and dissipative Marco Lamperti Tornaghi et al. [8] concentrated on the practical connections for the horizontal cladding panel. Previous research has extensively studied various core materials, such as tubular structures, aluminum foam, and composite sandwich panels, to enhance the energy absorption and impact resistance properties of cladding sandwich panels [3,9]. However, there has been limited research on the use of honeycomb cores for these applications. ...
... Such honeycomb plates are practically feasible to manufacture. The modelling procedure involved assembling the plate, honeycomb, and frame components within the Abaqus Assembly module while ensuring proper global coordinate alignment [1 3,7]. Several significant steps were implemented to ensure accurate results. ...
This research aims to investigate the performance of honeycomb sandwich panels under cyclic loads, to identify the most suitable configuration for specific applications. The study involves material characterization, finite element modeling, dynamic analysis, and design optimization to assess the stiffness, strength, and vibration-damping properties of cladding sandwich panels (14mm overall wall thickness) with different types of honeycomb cores. The considered variants of honeycomb cores like hexagonal, circular, and triangular cells with various cell sizes (10mm, 20mm, and 30mm) and cell thicknesses (0.6mm, 0.8mm, and 1mm) were tied within two skin plates of the same size (220mm×220mm×2mm) and the assemble panels were mounted within a steel frame sized 220mm×220mm×10mm. Steel materials were assigned to the honeycombs and the plates. The findings of this study could help create better lightweight and energy-efficient structures in the construction sector. The study shows that the thickness of the panel's core cells has a significant impact on the behavior of panels with triangular and hexagonal cores, while the one with the circular core; the effect of variant cells thicknesses is minor. Overall, the study demonstrates that varying the height, diameter, and thickness of such panels has a significant impact on their behavior. The findings of this study provide an important overview of the design and optimization of cladding sandwich panels with honeycomb cores for dynamic loading applications.
... In addition, integrating the MSFs with higher strength shells was considered to increase their strength and load bearing capacity. To this end, two types of structures have been investigated in the literature: (i) sandwich structures [20][21][22][23][24] and (ii) the foam-filled tube structures [25][26][27][28]. In the case of sandwich structures, face sheets like steel, Al alloy, carbon reinforced plastic were attached to the surfaces of the MSFs. ...
... In the case of sandwich structures, face sheets like steel, Al alloy, carbon reinforced plastic were attached to the surfaces of the MSFs. This method is mostly used to improve the bending properties of the MSF composites [20][21][22][23][24]. In the latter case, a tube is reinforced by an MSF using either in-situ or ex-situ manufacturing methods. ...
This research provides a comparative study between metal syntactic foams (MSFs) manufactured using two different infiltration casting techniques. Counter-gravity infiltration (CGI) and low-pressure infiltration (LPI) casting methods are employed to manufacture aluminium alloy matrix MSFs with embedded lightweight expanded clay aggregate particles. The cast MSFs from both methods are then used as the core material in the empty aluminium tubes with or without adhesive to produce foam-filled tube (FFT) samples. The MSFs manufactured using the LPI technique show higher density compared to their CGI cast counterparts. The quasi-static compression of the MSFs in axial and lateral loading directions showed the shearing of the MSFs during their deformation. The deformation of the FFTs in axial compression was influenced by the type of adhesive material, while in their lateral compression, the effect of adhesive type was insignificant. The mechanical properties of the MSFs and FFTs using the LPI technique showed higher values. For both casting techniques, the mechanical properties of the MSFs and FFTs in axial compression outperformed their structural values obtained from lateral compression.
... An aluminum foam sandwich tube is a thin-walled structure composed of metal and an aluminum foam core; this material stands out for its remarkable capacity to absorb energy efficiently, ensuring high resilience against impacts while maintaining an impressively lightweight construction [5][6][7]. Numerous studies have shown that aluminum foam core tubes have better blast resistance compared with single solid tubes [8][9][10][11][12][13]. At the same time, when evaluating the antiexplosion performance of sandwich tubes, several crucial parameters [14] cannot be ignored, such as maximum displacement, total energy absorption capacity, and the specific energy absorption rate. ...
In this paper, we numerically investigate the dynamic response and explosion resistance of gradient aluminum foam sandwich tubes subjected to external blast loads. Based on 3D-Voronoi technology, we construct density-graded aluminum foam cores to systematically explore the influence of core density distribution, density gradient, and average relative density on the protective performance of these structures. Our primary objective is to identify optimal design parameters that maximize explosion mitigation capabilities while balancing energy absorption and specific energy absorption capacities. The research results show that a positive gradient core configuration exhibits superior anti-explosion performance, significantly outperforming its uniform and negatively graded counterparts, particularly when the gradient value is substantial. For the positive gradient cores, an increase in the gradient value leads to a corresponding enhancement in explosion resistance. Conversely, in negatively graded cores, a higher gradient value diminishes the anti-explosion performance. Furthermore, while augmenting the relative density of the core layer does improve the overall explosion resistance of the sandwich tube, it comes at the cost of reduced energy absorption and specific energy absorption capabilities, highlighting the need for a delicate balance among these competing factors.
... Xu et al. [52] utilize experiments and finite element simulations to optimize the mechanical properties of a foam-filled re-entrant aluminum honeycomb composite structure. A numerical and experimental study was performed to study the bending and shear response characteristics of the double-skin composite sandwich panels made of Al-foam core and steel sheets in terms of three-point bending tests [53]. In a subsequent article, a multimaterial composite sandwich structure was designed and fabricated by Yang et al. [54]. ...
In the field of lighter substitute materials, sandwich plate models of composite and hybrid foam cores are used in this study. Three core structures: composite core structure and then the core is replaced by a structure of a closed and open repeating cellular pattern manufactured with 3D printing technology. It finally integrated both into one hybrid open-cell core filled with foam and employed the same device (WBW-100E) to conduct the three-point bending experiment. The test was conducted based on the international standard (ASTM-C 393-00) to perform the three-point bending investigation on the sandwich structure. Flexural test finding, with the hybrid polyurethane/polytropic acid (PUR/PLA) core, the ultimate bending load is increased by 127.7% compared to the open-cell structure core. In addition, the maximum deflection increased by 163.3%. The simulation results of three-point bending indicate that employing a hybrid combination of PUR-PLA led to an increase of 382.3%, and for PUR–TPU by 111.8%; however, the highest value recorded with PUR/PLA, which has the slightest stress error among the tests. Also, it is reported that when the volume fraction of reinforced aluminum particles is increased, the overall deformation becomes more sufficient, and the test accuracy improves; for example, rising from 0.5% to 3%, the midspan deflection of composite (foam-Al) is increased by 40.34%. There were noticeable improvements in mechanical properties in the 2.5% composite foam-Al.
... Supplemental energy dissipation devices are widely used to control the structural response to earthquakes and wind forces. Differently from the traditional systems, where the energy is dissipated by the plastic deformation of structural elements [15][16][17][18][19][20], passive systems, such as friction devices, offer a wide variety of features such as ease of maintenance and are easily replaced in the event of having damage [21][22]. Moreover, such a system can be a potential solution to one of the major criticisms of EC8-compliant steel MRFs which is their large overdesign due to the strict requirements for P-Delta effects and serviceability checks [23]. ...
... A joint synergy between different engineering fields can lead the path of innovation and hence making our constructions increasingly safe, sustainable and comfortable. Recent research activities have highlighted the ability of Steel Structures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and, in particular, Lightweight Steel (LWS) systems made of Cold Formed Steel (CFS) profiles [19][20][21][22][23][24][25][26][27][28][29][30][31], to guarantee high performances, both from structural and environmental point of view. In this perspective, a research project has been just concluded at University of Naples "Federico II" in cooperation with Lamieredil S.p.A. Company, which aims to develop innovative technological solutions with higher structural and environmental performances. ...
... In this context, the study of strengthening systems through steel exoskeletons orthogonal to the facade of the building to be protected is of great interest [16]. In fact, the use of steel as a construction material allows for sustainable, high-performance, and fast application interventions [17][18][19][20][21][22][23][24]. The high structural performance of steel systems is widely reported in numerous works in literature [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. ...
... The simplification of the design aspects changed the investigation from a quite complex analysis to an analysis with appropriate results. A numerical analysis of sandwich panels with a new type of element was proposed by Ya Ou et al. [9]. The element they used comprised two face layers connected by another layer. ...
In the field of engineering materials, lightweight and ultra-lightweight composites are used in real time to a greater extent, with high-performance targeting for tailor-made systems in aerospace, automotive, and biomedical applications. Sandwich composites are among the most popular lightweight materials used in structural and vehicle-building applications. In the present investigation, one such sandwich composite laminate composed of aluminum face sheets and a high-density polyethylene core was considered to analyze sandwich composites’ flexural and buckling behavior experimentally and numerically. The influence of aspect ratios, such as length to thickness and width to thickness, on the flexural and buckling performance of sandwich composite laminates was explored in the study. Laminates with different widths, namely, 10, 12, and 15 mm, and a uniform thickness and length of 3 mm and 150 mm, respectively, were used for flexural analysis, whereas laminates with widths of 10, 12, and 15 mm and a uniform thickness and length of 3 mm and 350 mm, respectively, were used for buckling analysis. The geometrical influence of the laminates on mechanical performance was studied through performance measures such as critical bending load, flexural stiffness, inter-laminar shear stress, and critical buckling load. A significant influence of aspect ratio on the mechanical behavior of the laminates was observed using both experimental and numerical approaches. Flexural behavior was observed to be better at greater widths, namely, 15 mm, and with a minimum support span of 90 mm due to reduced spring back effects and increased bending resistance. A maximum width of 15 mm allowed for a higher buckling load capacity similar to that of bending resistance. A critical buckling load of 655.8 N seemed to be the maximum and was obtained for the highest aspect ratio, b/t = 5. The soft core and ductile metal face sheets offered combined resistance to both bending and buckling. A lower aspect ratio (span to thickness) rendered these sandwich laminates better in terms of both bending and buckling.
... The tests were performed on a portal counterforce frame with loading devices from top to bottom: hydraulic jacks, pressure transducers, distribution beams, and supports. The ATS380 test system was used to collect data [38]. The deflection, cracks, and strains of concrete, longitudinal reinforcement, and reinforcement of the specimens were mainly tested in the experiment. ...
(1) Background: to study the differences in flexural performance and failure characteristics of spontaneous combustion gangue coarse aggregate concrete (SCGAC) laminated slabs and ordinary concrete laminated slabs, comparative flexural performance tests of one ordinary concrete laminated slab and four spontaneous combustion gangue coarse aggregate concrete laminated slabs (SCGACLSs) full-scale specimens were carried out. (2) Methods: The loading method was four-point unidirectional static loading; the failure mode, load–deflection curve, load–reinforcement strain curve, and load–concrete strain curve of each specimen were analyzed. In addition, the load–deflection curve of the five slabs were predicted by ABAQUS. (3) Results: The five laminated slabs showed similar behaviors in terms of failure mode, load–strain curve, load–deflection curve, and deformation and all the properties satisfied the Chinese standard GB50010 (2010). Compared with ordinary concrete laminated slabs, the cracking load of SCGACLS with a precast layer of SCGAC(C30) decreased by 15.2% and the span deflection increased by 28.3% in the ultimate condition; however, when the strength grade of SCGAC of the precast layer was increased to SCGAC(C40), the cracking load increased by 7.8% and the span deflection was similar to that of the ordinary concrete laminated slabs. All specimens conformed to the planar section assumption. In addition, the finite element model (FEM) prediction results showed that the maximum relative errors of load and deflection were <5% and <10%, respectively, indicating that the established FEM had high prediction accuracy. (4) Conclusions: The defects of reduced load-carrying capacity and uncoordinated deformation caused by the different elastic modulus of precast and cast-in-place layer concrete can be compensated by appropriately increasing the strength grade of precast layer concrete of SCGACLSs. The application of SCGACLSs in structures is feasible.
... Consequently, it is imperative that the axial compression properties of auxetic circular and square tubes are fully compared. In addition, aluminum foam is a lightweight porous material with superior physical properties and performs excellently in areas such as energy absorption, cushioning and explosion protection [44][45][46][47][48]. Simultaneously, auxetic tubes also fulfill these aforementioned areas well, but the two have never functioned together in combination. ...
The incorporation of aluminum foam in auxetic tubes can significantly enhance the overall stability, stiffness and energy absorption properties. In this work, a comparative study of the mechanical properties between auxetic circular and square tubes was conducted. The foam-filled auxetic square tube (FFAST) has the best specific energy absorption (SEA) up to 1.45 among the four auxetic tubes, and exhibits a pronounced auxetic effect throughout the minor deformation under compression, with a symmetrical and stable deformation mode. The experimental and simulated results are in excellent agreement. Hence, the finite element method is subsequently applied to the parametric analysis of FFAST, including the effects of wall thickness, height and ellipticity. Firstly, it is found that the thinner the wall thickness of FFAST is, the weaker the peak force and the greater the specific energy absorption would be. Secondly, within the same minor strain of different heights, SEA remains almost the same. Finally, with the decrease in ellipticity, the yield load of the bore tube gradually grows and SEA progressively increases. It can be concluded that FFAST with the ellipticity of 1.69 has both a high SEA and non-peak force. These findings are useful for fabricating FFAST for individual scenarios of energy absorption requirements. Such composite tubular structures will have practical applications in, e.g., protective engineering, vehicle engineering and aerospace engineering.
... There are five prominent failure modes at a three-point bending load: crush, shear damage of the foam core, fracture of the bottom panel, indentation, and delamination. Different strength analysis models are established for different failure modes [12][13][14][15]. The dynamic mechanical behavior of AFS is also an inescapable element needing to be paid more attention to, as the AFS is generally used to resist impact load in some situations, such as aerospace, shipbuilding, and highspeed rail. ...
The aluminum foam sandwich (AFS), which perfectly combines the excellent merits of an aluminum foam core and face sheet materials, has extensive and reliable applications in many fields, such as aerospace, military equipment, transportation, and so on. Adhesive bonding is one of the most widely used methods to produce AFS due to its general applicability, simple process, and low cost, however, the bonding interface is known as the weak link and may cause a serious accident. To overcome the shortcomings of a bonded AFS interface, short carbon fiber as a reinforcement phase was introduced to epoxy resin to reinforce the interface adhesion strength of AFS. Single lap shear tests and three-point bending tests were conducted to study the mechanical behavior of the reinforced interface and AFS, respectively. The failure mechanism was studied through a macro- and microanalysis. The result showed that after the reinforcement of carbon fiber, the tangential shear strength of the interface increased by 73.65%. The effective displacement of AFS prepared by the reinforced epoxy resin is 125.95% more than the AFS prepared by the unreinforced epoxy resin. The flexure behavior of the reinforced AFS can be compared with AFS made through a metallurgical method. Three categories of reinforcement mechanisms were discovered: (a) the pull off and pull mechanism: when the modified carbon fiber performed as the bridge, the bonding strength improved because of the pull off and pull out of fibers; (b) adhesion effect: the carbon fiber gathered in the hole edge resulted in epoxy resins being gathered in there too, which increased the effective bonding area of the interface; (c) mechanical self-locking effect: the carbon fiber enhanced the adhesive filling performance of aluminum foam holes, which improved the mechanical self-locking effect of the bonding interface.
... Their results show a significant difference between the experimental and theoretical values (Timoshenko, 1921). Latour et al. (2021) look into double-skin aluminum foam sandwich panels in bending. They used three types of glue to create the specimens and discovered through three-point testing that shear strength and modulus of specimens differ according to the kind of adhesive. ...
Due to their mechanical properties, metal foams are used in various fields. The aim of the present research is to collect different studies about the important mechanical properties of metal foams, such as Young’s modulus, tensile and shear strength, relative density, etc. under tensile and shear loading. Gaps were identified in the methodological embodiments of the experiments due to the use of different standards, as well as in the calculation of mechanical properties through mathematical relations in tensile and shear, which led to deviations between the experimental results and these. Furthermore, this work records sequences and connections between experimental results of different tasks as well as solutions to the aforementioned issues.
... It can absorb a large amount of energy before being crushed to a stable stage or before failure, with excellent energy absorption and impact resistance, and has been widely used in explosion-proof and impact protection fields [1][2][3]. Compared with the single-foam material, the foam sandwich structure can show better anti-explosion performance under the explosion load [4][5][6][7][8][9]. ...
In this paper, the dynamic response of continually density-graded aluminum foam sandwich tubes under internal explosion load was studied. A 3D mesoscopic finite-element model of continually density-graded aluminum foam sandwich tubes was established by the 3D-Voronoi technology. The finite-element results were compared with the existing experimental results, and the rationality of the model was verified. The influences of the core density distribution, the core density gradient, and the core thickness on the blast resistance of the sandwich tubes were analyzed. The results showed that the blast resistance of the sandwich tube with the negative-gradient core is better than that of the sandwich tube with the uniform core. While the blast resistance of the sandwich tube with the positive-gradient core or the middle-hard-gradient core is worse than that of the sandwich tube with the uniform core. For the sandwich tube with the negative-gradient core, the core density gradient increased, and the blast resistance decreased. Increasing the thickness of the core can effectively decrease the deformation of the outer tube of the sandwich tube, but the specific energy absorption of both the whole sandwich tube and its core also decreases.
... Several studies were carried out in the last decades on the mechanical behavior of sandwich structures made of aluminum foam as core and polymer matrix composites or metallic solids as skins [8,9]. To the authors' best of knowledge, very few works have been carried out on reinforced aluminum foam samples with the skins constituting the sandwich made of lightweight metallic grid. ...
Metals foams are attracting great interest in aerospace, automotive and military fields. Particularly, the closed-cells aluminum foams are characterized by peculiar properties, such as low specific weight coupled with high energy absorption capacity, high specific stiffness and strength and reduced thermal and electrical conductivity. For the above reasons, aluminum foams can be effectively used as core of sandwich structures, replacing the traditional honeycomb and polymer-based foams. However, under specific loading conditions, the foam core was proved to collapse because of the bubble-cell structure, so affecting the mechanical performance of the sandwich constructions. Different solutions have been studying in literature to reinforce the foam-based core; for example, the authors in previous studies investigated the possibility to use a metal grid inside the core as a corrugated skeleton, to improve its behavior under compression. Therefore, based on these premises, the aim of this work is to improve understanding of the mechanical behavior of innovative reinforced aluminum foam panels through an experimental approach consisting of three-point bending tests. In particular sandwich structures with and without a corrugated grid structure, acting as skeleton inside the core, were manufactured. The bending properties were estimated also considering two different types of steel grid employed for the corrugated structure and for reinforcing the skins.
... Simple honeycomb-based sandwich panels are generally made by the corrugation manufacturing process [7]. The other commonly used sandwich cores with different structures are grid [8], foams [9], web [10], end-grain balsa wood [11], and hybrid lonitrile Butadiene Styrene (ABS) is the commonly used material. It possesses high strength and toughness and has potential applications in the aircraft and ship's body. ...
In this study, the flexural performance of the novel bird's feather-inspired cellular panels has been studied. All the panels are fabricated using the fused filament fabrication (FFF) method with acrylonitrile butadiene styrene (ABS) plus material. Both the in-plane and out-plane flexural response is studied under a three-point bending load. The panels were designed to study the effect of unit cell length and orientation on stiffness, strength, energy absorption, and crack propagation. The in-situ digital image correlation (DIC) technique has been used to visualize the deflection field of the panels. Furthermore, finite element modeling (FEM) is also used to visualize the plastic strain and stress in the panels. Results showed an increase in stiffness and flexural strength with a decrease in the unit cell length. The change in orientation of the unit cell length can significantly increase the flexural performance of both the in-panels and out-plane loaded panels. The panels loaded in the in-plane three-point loading showed higher energy absorption, whereas panels loaded in out-plane three-point loading showed higher stiffness and flexural strength. Finally, the flexural performance of the new bionic panels is compared with the other type of panels reported in the literature. The new bionic panels show significant improvement over the previous designs. The current study provides novel lightweight panels with improved flexural properties, which can also be helpful for researchers working in the design field. From the design point of view, novel designs can be used in applications like ship floors, aircraft bodies, construction, etc.
... Wan et al. [17] investigated the structural behavior, strength and design of coldformed steel C-and Z-section beams under the action of combined bending and torsion. Latour et al. [18] studied double-skin aluminum foam sandwich panels in bending experimentally and numerically. Both experimental and finite element (FE) simulations were carried out verifying the applicability of the proposed type of sandwich panel. ...
Side beams are among various types of structures used for reinforcing the safety of automobiles against lateral collisions which have been widely explored. In this study, it was attempted to increment the energy absorption capacity of the beam by creating a non-uniform cross-section with a cosine function at the upper part of the beam. This study was conducted both experimentally and numerically. The numerical investigations were achieved by finite element software of LS-DYNA and the simulation results were validated by experimental three-point flexural tests. By creating a non-uniform cross-section, it was tried to augment the energy absorption capacity as much as possible. NSGA-III and MOEAD algorithms were also used for optimization purposes to select the best beam with superior efficiency. Obtained results showed that non-uniform thin-walled beams can increase specific energy absorption (SEA) of a simple beam up to 71%.
... Tahmoorian [2] utilized high density polyethylene (HDPE) foam core as well as two continuous layers of HDPE skins and analyze shear strength. On the other hand, Latour et al [3] used metal foam as the core sandwiched between double layered skin and comes out with the suggestion on the best adhesive to prevent delamination. ...
Although rigid foam core structures have gotten a lot of attention, there have only been a few researches on foam reinforced sandwich panels with aluminum alloy A6061 sheets as face-sheets. In this research, the sandwich concept was applied to develop lightweight panels for roofing system. Analysis on the influences of core thickness, density, and foam layer arrangement on energy absorption, bending strength and displacement of sandwich panel under the quasi-static three-point bending test were investigated. Sandwich panel core is made of closed-cell polyurethane foam with densities of 40 kg/m ³ , 60 kg/m ³ , and 80 kg/m ³ . The quasi-static three-point bending tests were conducted in accordance to ASTM C-393 Standard and the polyurethane foam cores are design accordingly to the guideline of National Institutes of Standards and Technology (NIST). Load–displacement curves and mechanical properties are shown using data from experimental works. Results demonstrate that increased in thickness of the sandwich panel, also increased the bending strength, energy absorption and displacement. Furthermore, the sandwich panel with 50 mm thickness and 60 kg/m ³ density foam core has the maximum bending strength.
... Regarding core structures, there are many forms, such as web [18][19][20][21], honeycomb [22][23][24][25][26][27][28], grid [29,30], foams [31][32][33][34][35][36][37][38], end-grain balsa wood [39,40] and combined cores [41,42]. Additionally, regarding the mechanical properties, the compressive properties [43][44][45], flexural properties [46][47][48], vibration properties [14,49,50], anti-impact properties [16,51], and blast resistance [52] have been widely studied. ...
This paper studies the flexural mechanical behaviour of grid beetle elytron plates (GBEPs), which are lightweight and high-strength bionic structures with excellent compressive properties, for the first time. The flexural properties, failure modes and flexural mechanism of 3D-printed GBEP, grid plate (GP) and honeycomb plate (HP) specimens with the same wall thickness are investigated via three-point bending experiments. The results show that the flexural strength per unit mass and energy absorption per unit mass of the GP and GBEP are greatly improved and that the stress per unit mass corresponding to elastic stage I in the serviceability state is improved over those of typical lightweight and high-strength HPs. The fracture location and range of the GBEP are affected by the diameter of the trabecula. The experimental results indicate that the grid group effectively solves the problem of insufficient core shear strength in HPs through the regular grid core structure, which successfully converts core failure in shear of the HP to face failure in tension of the GBEP and GP. The flexural mechanisms of the three types of plates are revealed from multiple perspectives, such as the relationship between the facing stress and core shear stress and the tension field effect induced by the film force. This work provides useful instruction for designing lightweight sandwich structures, further develops the application of beetle elytron plates used in many fields such as aircraft bodies and ship floor, and presents a scientific basis for rational selection among GPs, GBEPs and HPs in practical engineering.
The generation of micro-nano structures on a polymer is a growing industrial-sector application due to its utility in optics, microfluidic chips, photovoltaic, and medical sectors. The filling behavior of polymers in micro-nano dies differs significantly from that of bulk polymer deformation due to the scaling law effect. Deformation at various scales affects the mechanical, electrical, and other properties of polymers. As the demand for micro and submicron components grows, it becomes increasingly important to develop a process for producing small components at a lower cost and in less time. As a result, understanding the dynamics of polymer behavior/deformation in micro-nano cavities (or dies) and various forming methods capable of mass-producing such micro components becomes critical. As a result, the goal of this chapter is to give the reader a basic understanding of the hot embossing micro-nano forming process in comparison to other micro-forming polymer techniques. The process parameters associated with the hot embossing process are thoroughly discussed, as is their impact on the process. In addition, the mathematical description of viscoelastic behavior and polymer viscosity will pave the way for a better understanding of the process simulation later in this chapter.
In this study, one-piece glass cenospheres/aluminum core sandwich is prepared using a pressure infiltration method. In comparison to adhesive bonding, the layers combined by metallurgical bonding are straight and smooth, and the sandwich shows high shear stress of 80.4 MPa. The failure mode is analyzed through a combination of mises stress distribution simulated using the finite element analysis and in-situ strain
distribution obtained from a digital image correlation system. After cracks initiated at
interfaces, they propagate to nearby layers in the sandwich structure, which can delay the shear failure by avoiding significant damage of core layer.
Metal foam is a relatively new and potentially revolutionary material due to its properties such as the low weight‐to‐stiffness ratio, high damping and energy dissipation capacity. Even if this material is widely used in mechanical, aerospace and automotive industries, it is still not frequently used in civil engineering applications. The large energy dissipation capacity that metal foams possess could be exploited to control the seismic performance of structures, but only few research investigations have been focused on this matter. Within this context, the present paper investigates a possible solution to realize dissipative aluminium foam dampers to be applied in X‐braced steel structures for concentrically braced steel frames (CBFs). The bracing system consists of a steel rod or tube linked to an aluminium foam damper. The damper device is constituted by aluminium foam that provides the structure with dissipation capacity when activated under compression. The permanent deformations of the aluminium foam are absorbed by a wedge device, avoiding a pinching behaviour in the global response. Analytical equations governing the global behaviour of the bracing system are herein presented. An X‐braced steel frame complying with Eurocode 8 provisions is designed and considered as case‐study. The structure is subsequently upgraded by introducing the dissipative device into the bracings. The results of preliminary experimental and numerical tests on the components of the device are herein presented, showing the potentiality of the solution.
The additively manufactured bio‐inspired lattice structures have various superior properties in comparison to their solid counterparts as they are lightweight and suitable for fabricating various parts in aerospace sectors. This study limits the investigation of triply periodic minimal surface (TPMS)‐based diamond sheet and solid cellular structures with varying densities (25%, 35%, 45%, and graded) under flexural loading conditions. The sandwich panel structures are made using acrylonitrile butadiene styrene material utilizing the fused filament fabrication (FFF) process. In‐plane flexural performances of the FFF fabricated bio‐inspired TPMS diamond sandwich panels are investigated for the first time. The panels are created to investigate how density and unit cell geometry affect stiffness, strength, and energy absorption. The digital image correlation approach is used to visualize the deflection of the panels subjected to three‐point bending. Also, a theoretical analysis is done to find out the deflection of the sandwich panel structures. An Ashby chart shows the comparison of the specific energy absorption of the TPMS diamond sandwich panels used in this study with several other cellular core sandwich panels available in the literature. This study provides a valuable contribution to the improved energy absorption performance of additively manufactured cellular materials.
The glass cenosphere/Al syntactic foam core sandwich with steel and aluminum sheets was successfully synthesized using the spark plasma sintering method, it owns metallurgical interfaces between the foam core and the metal sheets. The aluminum foil placement between the glass cenosphere-aluminum mixture powder and steel sheet in the preparing process facilitated the Fe-Al diffusion to form a double-layer reaction metallurgical interface containing Fe4Al13 and Fe2Al5. While for the foam core-aluminum sheet, an excellent fusion of aluminum was achieved at the interface. Both foam core-steel sheet and foam core-aluminum sheet showed good interfacial shear strength. There is a significant difference in the interfacial shear behavior between the foam core-steel sheet and the foam core-aluminum sheet due to their different metallurgical interfaces. The stable fusion of aluminum at the foam core-aluminum sheet interface can be conducive to the interfacial load transfer, resulting in a better interfacial bonding than that of the foam core-steel sheet.
In the present study, Al/Al2O3 foams were prepared to increase the energy absorption capacity by enlarging the densification strain. Analysis of the mechanical characteristics was performed and the energy absorption ability was calculated on the samples. The deformation process of the inner and outer-layer cells was investigated on the micro- and macro-scales to clarify the optimisation mechanism of the densification strain. The stress–strain curves demonstrated that the ceramic/aluminium foam exhibited an extended plateau region (densification strain of 0.63), resulting in high energy absorption capacity and efficiency. Analysis of the deformation process illustrated that the oxide layer played a dominant role in the brittle deformation of the outer-layer cells. The evolution of crack formation, propagation, and coalescence in cells provided randomly distributed “defects” in foams, resulted in the scattered plastic deformation zones in inner cells. The strain hardening effect of the cell wall was suppressed based on this typical deformation mode of foam, which resulted in increased densification strain and improved energy absorption capacity. Moreover, the Al/Al2O3 foams exhibited superior corrosion resistance compared to the Al foams.
The flexural behaviour of sandwich panels with basalt fiber-reinforced polymer (BFRP) facesheets was investigated. A total of 10 sandwich panels were subjected to six-point flexural tests to simulate uniformly distributed loading conditions. The variable parameters were the core thickness (30, 50, 60 and 100 mm), core category (polyurethane [PU], extruded polystyrene [XPS], rock-mineral wool [RW]), and hybrid core (PU+RW and XPS+RW). Finally, the shear distribution coefficient of core material for sandwich panels with BFRP facesheets was modified depending on the experimental data. The experimental results showed that an increase in the PU core thickness significantly increased the flexural strength and rigidity of the sandwich panels. For different core materials, the maximum loads of the panels were positive with the shear strength of the core materials. Whereas, XPS+RW hybrid core not only can significantly decreases the costs, but also exhibits the highest bearing capacity and stiffness as compared with the PU+RW hybrid and PU cores.
The plastic behaviour (PB) of fully clamped foam-filled X-shaped core sandwich beams (SBs) is researched analytically and numerically. Considering the strengths of X-shaped core and foam, the yield criterion of foam-filled X-shaped core sandwich structure is presented. Taking into account the interaction between traction and bending moment caused by large deflection, the analytical solution of foam-filled X-shaped core SBs loading laterally under a punch is derived. The numerical results calculated by Abaqus/Standard software are in great accordance with the analysis. The influences of geometrical parameters and foam strength about the load-bearing capability and absorbed deformation energy capability of the foam-filled X-shaped core SB are clearly discussed. The results show that the axial stretching caused by large displacement has a significant impact on load-bearing capability and absorbed deformation energy of foam-filled X-shaped core SBs. This analysis approach could be used to predict the PB of foam-filled X-shaped core SB.
The metal slabs studied in this work are used to protect the walls of the motorway tunnels and to improve the lighting conditions inside the tunnel. Their installation causes an increase in the cost of the work, consequently, the coatings must be resistant to corrosion and must not require frequent maintenance in order to be functional for long periods. The material chosen to produce these artifacts is aluminum, but despite this metal being generally resistant to chemical attack, the analyzed coating still suffered corrosion. The sampled and analyzed slab was covered with white titanium-based paint on the side facing the street and a transparent protective resin on the side facing the wall. This preliminary study uses a different approach through microanalysis of metal slabs. For this reason, the corroded slab was studied through different analytical techniques (microscope, SEM-EDS, XRF and Raman analyses) in order to identify the causes of corrosion of the metal slab. The observations made it possible to hypothesize a corrosion process divided into different stages.
The paper presents an automated continuous production line (7 m × 1.5 m × 1 m) of high-quality metallic foams using a powder metallurgical method. This continuous production line was used to obtain metal foam parts and/or components by heating the foamable precursor material at melting temperatures close to the temperature of the metallic matrix and cooling the formed liquid metallic foam (in liquid state), which then results in a solid closed-cell metallic foam. This automated continuous production line is composed of a continuous foaming furnace, a cooling sector and a robotic system. This installation has enabled a technological breakthrough with many improvements solving some technical problems and eliminating the risks and dangers related to the safety of workers due to the high temperatures involved in this process. The whole process becomes automatic without any need for human intervention.
This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also taking into account costs and feasibility considerations. These properties are the motivation and basis of related applications. Finally, a summary of the most relevant applications showing a large number of actual examples is presented. Concluding, we can forecast a slow, but continuous growth of this industrial sector.
The present paper introduces the manufacturing process and industrial applications of Alantum metal foams having a complete open-pore structure. Wide spectrum of foam products, based on several distinguished properties of metal foams is described. Examples of Alantum foam products, transited to the industrial applications are provided with the roles of foams during their performances.
Der Beitrag geht auf das Stabilitätsverhalten von biegebeanspruchten Sandwichelementen ein. Es wird mittels der Methode der Finiten Elemente der Einfluß der Schaumorthotropie, der Haftfestigkeit zwischen Deckschicht und Schaumkern und der Schaumkerndicke auf die Knitterspannung untersucht. Die Approximation numerisch für Sandwichelemente mit gesickten Deckschichten ermittelter Knitterspannungen führte zu einem Formelausdruck, mit dem der Stabilitätsnachweis derartiger Elemente erfolgen kann. Es ist schließlich eine experimentelle Verifikation vorgenommen worden.
The history of metallic foams and the key innovations that have led to the variety of processing methods known today are reviewed. It is evident that the idea of foaming metals is very old and that most of the techniques used today have been proposed already in the 1950s. The most important milestones in the development of foaming technologies and the some of the attempts to commercialize metal foams are reviewed. The history of metallic foams dates back to 1926. Most of the techniques used today were proposed in the 1950s, but refinement of methods to a state allowing for industrial application has taken place only recently. Based on earlier developments, many new processing routes have been proposed. These and attempts to commercialize metal foams are reviewed.
The objective of this paper is to provide and verify a new design method for the in-plane compressive strength of steel sandwich panels comprised of steel face sheets and foamed steel cores. Foamed steel, literally steel with internal voids, provides enhanced bending rigidity, exceptional energy dissipation, and the potential to mitigate local instability. In this work, Winter's effective width expression is generalized to the case of steel foam sandwich panels. The generalization requires modification of the elastic buckling expressions to account for panel non-composite bending rigidity and shear deformations. In addition, an equivalent yield stress is introduced to provide a single parameter description of the yielding behavior of the steel face sheets and steel foam core. The provided analytical expressions are verified with finite element simulations employing three-dimensional continuum elements and calibrated constitutive models specific to metallic foams. The developed closed-form design expressions are employed to conduct parametric studies of steel foam sandwich panels, which (a) demonstrate the significant strength improvements possible when compared with solid steel, and (b) provide insights on the optimal balance between steel face sheet thickness and density of the foamed steel core. This work is part of a larger effort to help develop steel foam as a material with relevance to civil engineering applications.
The objective of this paper is to provide and verify a new design method for the in-plane compressive strength of steel sandwich panels comprised of steel face sheets and foamed steel cores. Foamed steel, literally steel with internal voids, provides enhanced bending rigidity, exceptional energy dissipation, and the potential to mitigate local instability. In this work, Winter’s effective width expression is generalized to the case of steel foam sandwich panels. The generalization requires modification of the elastic buckling expressions to account for panel non-composite bending rigidity and shear deformations. In addition, an equivalent yield stress is introduced to provide a single parameter description of the yielding behavior of the steel face sheets and steel foam core. The provided analytical expressions are verified with finite element simulations employing three-dimensional continuum elements and calibrated constitutive models specific to metallic foams. The developed closed-form design expressions are employed to conduct parametric studies of steel foam sandwich panels, which (a) demonstrate the significant strength improvements possible when compared with solid steel, and (b) provide insights on the optimal balance between steel face sheet thickness and density of the foamed steel core. This work is part of a larger effort to help develop steel foam as a material with relevance to civil engineering applications.
The objective of this paper is to provide a state-of-the-art review for the structural application, manufacturing, material properties, and modeling of a new material: steel foam. Foamed steel includes air voids in the material microstructure and as a result introduces density as a new design variable in steel material selection. By controlling density the engineering properties of steel components may be altered significantly: improvement in the weight-to-stiffness ratio is particularly pronounced, as is the available energy dissipation and thermal resistivity. Full-scale applications of steel foams in civil structures have not yet been demonstrated. Therefore, existing applications demonstrating either proof-of-concept for steel foam, or full-scale use of aluminum foams in situations with clear civil/structural analogs are highlighted. Adoption of steel foam relies on the manufacturing method, particularly its cost, and the resulting properties of the steel foam. Therefore, published methods for producing steel foam are summarized, along with measurements of steel foam structural (modulus, yield stress, etc.) and non-structural (thermal conductivity, acoustic absorption, etc.) properties. Finally, existing models for predicting foamed steel material properties are summarized to highlight the central role of material density. Taken in total the existing research demonstrates the viability of steel foams for use in civil/structural applications, while also pointing to areas where further research work is required.
Recent advances in manufacturing methods open the possibility for broader use of metal foams and metal matrix composites (MMCs) for heat exchangers, and these materials can have tailored material properties. Metal foams in particular combine a number of interesting properties from a heat exchanger's point of view. In this paper, the material properties of metal foams and MMCs are surveyed, and the current state of the art is reviewed for heat exchanger applications. Four different applications are considered: liquid-liquid, liquid-gas and gas-gas heat exchangers and heat sinks. Manufacturing and implementation issues are identified and discussed, and it is concluded that these materials hold promise both for heat exchangers and heat sinks, but that some key issues still need to be solved before broad scale application is possible.
The emphasis of this work is on the use of metal foams in automotive design for weight reduction with the purpose of studying the mechanical behaviour and possible project alternatives, through the modelling and subsequent computer simulation according to the case study – chassis of the “Sabiá 5”. The “Sabiás” are hyper-economic vehicles created to compete in an energy-economy racing circuit (Shell Eco-marathon). For the structural analysis, the finite element software Abaqus/CAE is used. The tests performed are static and dynamic tests simulating the vehicle passing across a rough track and crash test. According to the results of the computational tests, metal foams demonstrated to be a good choice for the studied application, presenting the necessary weight reduction with the expected structural performance.
Lotus-type porous metals whose long cylindrical pores are aligned in one direction were fabricated by unidirectional solidification in a pressurized gas atmosphere. The pores are formed as a result of precipitation of supersaturated gas when liquid metal is solidified. The lotus-type porous metals with homogeneous size and porosity of the evolved pores produced by a mould casting technique are limited to the metals with high thermal conductivity. On the other hand, the pores with inhomogeneous pore size and porosity are evolved for metals and alloys with low thermal conductivity such as stainless steel. In order to obtain uniform pore size and porosity, a new “continuous zone melting technique” was developed to fabricate long rod- and plate-shape porous metals and alloys even with low thermal conductivity. Mechanical properties of tensile and compressive strength of lotus-type porous metals and alloys are described together with internal friction, elasticity, thermal conductivity and sound absorption characteristics. All the physical properties exhibit significant anisotropy. Lotus-type porous iron fabricated using a pressurized nitrogen gas instead of hydrogen exhibits superior strength.
The study of metallic foams has become attractive to researchers interested in both scientific and industrial applications.
In this paper, various methods for making such foams are presented and discussed. Some techniques start from specially prepared
molten metals with adjusted viscosities. Such melts can be foamed by injecting gases or by adding gas-releasing blowing agents
which cause the formation of bubbles during their in-situ decomposition. Another method is to prepare supersaturated metal-gas
systems under high pressure and initiate bubble formation by pressure and temperature control. Finally, metallic foams can
be made by mixing metal powders with a blowing agent, compacting the mix, and then foaming the compact by melting. The various
foaming processes, the foam-stabilizing mechanisms, and some known problems with the various methods are addressed in this
article. In addition, some possible applications for metallic foams are presented.
This paper presents an application of a simplified assessment approach to steel structures which takes into account sustainability requirements. The proposed approach is based on a time-dependent, multi-performance-based design methodology. The simplified procedure is organized in three main steps concerning the environmental conceptual design, the ordinary structural design and the life-cycle analysis devoted to defining service life scenarios in order to assess the structural, economic and environmental performances of structures during their entire life-cycle. Three different seismic-resistant steel structural typologies are designed for a multi-storey residential building and compared in terms of sustainability. Those comprise Moment Resisting Frames (MRF), Concentrically Braced Frames (CBF) with removable Chevron braces and Eccentrically Braced Frames (EBF) with removable shear links. The structural, environmental and economic performances of the three examined design options are assessed and compared in order to evaluate their sustainable potentialities and criticalities for two design scenarios, namely an ordinary condition characterized by an expected deterioration and an exceptional case in which a seismic event hits the structures during their service life.
A comprehensive bending performance and energy absorption capability of aluminium alloy tubes filled with different cost-effective cellular metal cores were experimentally evaluated for the first time. The following cellular metal cores were evaluated: i) Advanced Pore Morphology (APM) foam, ii) hybrid APM foam and iii) Metallic Hollow Sphere Structures (MHSS). The results have been compared also with the performance of aluminium alloy tubes filled with (ex-situ and in-situ) closed-cell aluminium alloy foam. The three-point bending tests have been performed at two loading rates (quasi-static and dynamic) and supported by infrared thermography to evaluate the deformation mechanism, damage progress and failure modes. A thorough heat treatment sensitivity (due to the fabrication procedures of composite structures) study on the aluminium tubes has been performed as well. The results show that a reliable and predictable mechanical behaviour and failure can be achieved with proper combination of tubes and cellular metal core. A low scatter of bending properties and energy absorption capability has been observed. The hybrid APM and the ex-situ foam filled tubes achieved the highest peak load. However, they also exhibit a rapid load drop and abrupt failure once the structure has reached the peak load. The APM, MHSS and in-situ foam filled tubes show more ductile behaviour with a predictable failure mode.
Aluminium honeycomb sandwich panels are an interesting lightweight structural solution for several applications such as marine structures, aerospace, automotive and aeronautics.
In many of these applications, in-service conditions produce fatigue loadings: as a result, safer use of aluminium honeycomb sandwich structures requires a deep knowledge of their fatigue response, which was seldom studied in previous literature.
The aim of the current study is to evaluate the fatigue response of aluminium honeycomb sandwich panels subjected to three-point bending loading conditions.
The experimental investigation was performed on a commercial aluminium honeycomb sandwich structure with an overall thickness of 11 mm.
A preliminary static analysis was performed both under three and four point bending conditions. The static tests allowed the identification of the static bending strength and the absence of a significant strain rate influence. Crashworthiness parameters were evaluated and a slight better performance was found under four point bending. The combination of static tests with Computed Tomography analysis resulted in the observation of the phenomena involved in static bending response of aluminium honeycomb sandwich structures, which are mainly dependent on cell walls buckling.
Fatigue tests were conducted under three-point bending conditions. The influence of boundary conditions on fatigue life and on collapse modes were investigated by considering different supports spans. For one condition the S-N curve was obtained and its equation was compared to literature results.
Two different collapse mechanisms were observed depending on the supports span: for larger supports span a fracture of the tensioned skin was observed, whereas lower supports span produced core shear. The former mode differed significantly from static failure with the same boundary conditions. In both cases, failure occurred suddenly and this should be taken into consideration in industrial applications. An analytical model was applied to predict fatigue collapse modes and limit loads. A fatigue failure map describing the relationship between supports span, collapse modes and fatigue limit loads was obtained, in order to provide a quantitative tool for aluminium honeycomb sandwich structures design. The fatigue failure map was able to accurately predict the experimental results.
The goal of this study is to investigate the effectiveness of Composite Metal Foam (CMF) armors against 0.50 caliber ballistic threats. A hard armor was manufactured using a sandwich panel construction consisting of a ceramic faceplate, a CMF core, and a thin aluminum back plate. The hard armor system was tested against 0.50 caliber (12.7 × 99 mm) ball and armor piercing (AP) rounds. The CMF armors were tested with a variety of areal densities at impact velocities between 500 and 885 m/s. The armors stopped the threats at speeds up to 819 m/s without penetration. The CMF layer was found to absorb 73–76% and 69–79% of the kinetic energy of the ball and AP round respectively. When compared to rolled homogeneous steel armor (RHA), the CMF hard armors, in their current unoptimized condition, have a mass efficiency ratio of approximately 2.1. The CMF armor offers a much needed weight savings without sacrificing protection. Finite element analysis was completed using ANSYS/AUTODYN Explicit Dynamics solver to study the material interactions and impact. The results are shown to be in good agreement with the experimental findings.
The aluminium foam sandwich (AFS), prepared through the traditional adhesive or brazing methods, usually exhibits a low flexural strength due to the poor combination among the face sheets and the aluminium foam core. In this work, a new method, named friction stir welding (FSW), was utilized to fabricate AFS. The results demonstrated that the joining of the face sheets and aluminium foam was achieved through the plasticized metal flow. In addition, the AFS prepared through FSW possessed high flexural strength and impact resistance, as well as good sound absorption and reduction performance. This demonstrated that the FSW was a good method to prepare AFS.
The perforation behaviour of Cymat© aluminium foam at various impact loading rates was studied both experimentally and numerically. Perforation tests were performed with an inverse perforation setup using a split Hopkinson pressure bar (SHPB) system at speeds up to 40 m/s. Compared with a quasi-static test using the same specimen and clamping system, a significantly enhanced piercing force was found under impact loading. Numerical simulations of the perforation test were carried out using LS-DYNA code, and the material models available in this code were benchmarked. Good agreement was found between the experimental and simulated force/displacement curves when using the honeycomb material model with an appropriate failure criterion. The simulation revealed that a strain discontinuity front propagated ahead of the perforator when the impact velocity of the perforator exceeded 20 m/s. The significance of this numerical model is that it demonstrates that the main feature (average perforation force) can be reproduced with a rather simple pre-implemented material law for a homogeneous specimen. An analytical model using the concept of a shock front with a power law densification assumption is proposed to describe the enhancement in the impact piercing force.
Honeycomb sandwich structures have excellent energy absorption capabilities, combined with good mechanical properties and low density. These characteristics make them ideal for the transportation industry, which has a growing interest in reaching higher safety standards. The purpose of the present paper is the introduction of lightweight and more efficient crashworthy structures. Double-layer honeycomb sandwich structures were analysed and their energy absorption capabilities were evaluated by means of low-velocity impact tests. The specific energy absorption of double-layer panels was compared to single-layer honeycomb and other lightweight panels, in order to assess the effectiveness and the convenience of the introduced solution for lightweight and crashworthy devices. The impact absorption mechanism was evaluated through Computed Tomography images and visual inspection. A theoretical evaluation was applied to investigate the mono-layer impact response. The results were compared to those obtained with different boundary conditions and with a full-scale test. Contact parameters were influenced by boundary conditions since they depend on the specimens stiffness. Double-layer panels displayed a progressive collapse sequence, depending on the core arrangement and on the cell size. Honeycomb with larger cell size showed a better distribution of the impact loading which generated an almost uniform compression of the core. Such observations suggested the possibility to obtain energy absorber devices with a controlled deformation. Preliminary considerations on the existence of a size effect were drawn, since it was observed a relation among the contact parameters and the geometrical characteristics of the honeycomb and the indenter.
This paper presents results of an experimental study on the processing and mechanical characterisation of plain and in-situ carbon-steel bar reinforced cylindrical Al-alloy foams. The reinforcement is incorporated into the foam-structure during the foaming-process which is based on the powder metallurgy method. Some key technical issues concerning the manufacturing procedure are discussed. A technical solution to design moulds to prepare high-quality foam parts with longer lengths is proposed. This has been achieved by constructing moulds with varied mould-wall thickness. Such an approach enabled to control the foaming-process and subsequent the foam-filling in different regions of the mould cavity. A series of plain and in-situ reinforced foams with two different lengths (150 and 200 mm) and the same diameter (25 mm) were fabricated. Uniaxial compressive and three-point bending behaviour was studied, exploring their deformation and failure mechanisms. The results demonstrate that the carbon-steel bar increases the compressive behaviour of the foams but does not significantly influence their bending behaviour in terms of peak load. Under bending loads, the stress-strain curves are shifted along the strain axis in comparison to the plain foams. The deformation and failure mode of both specimens under compressive and bending loads is similar. The results indicate the potential of reinforced materials.
This classic manual on structural steel design provides a major source of reference for structural engineers and fabricators working with the leading construction material. Based fully on the concepts of limit state design, the manual has been revised to take account of the 2000 revisions to BS 5950. It also looks at new developments in structural steel, environmental issues and outlines the main requirements of the Eurocode on structural steel.
Sandwich panels are being used increasingly as the cladding of buildings like factories, warehouses, cold stores and retail sheds. This is because they are light in weight, thermally efficient, aesthetically attractive and can be easily handled and erected. However, to date, an authoritative book on the subject was lacking. This new reference work aims to fill that gap. The designer, specifier and manufacturer of sandwich panels all require a great deal of information on a wide range of subjects. This book was written by a group of European experts under the editorship of a UK specialist in lightweight construction. It provides guidance on: materials used in manufacture thermal efficiency and air- and water-tightness acoustic performance performance in fire durability special problems of sandwich panels in cold stores and chill rooms architectural and aesthetic considerations structural design at the ultimate and serviceability limit states additional structural considerations including fastenings, the effect of openings and the use of sandwich panels as load-bearing walls test procedures The book concludes with some numerical design examples and is highly illustrated throughout.
This book introduces the design concept of Eurocode 3 for steel structures in building construction, and their practical application. Following a discussion of the basis of design, including the limit state approach, the material standards and their use are detailed. The fundamentals of structural analysis and modeling are presented, followed by the design criteria and approaches for various types of structural members. The following chapters expand on the principles and applications of elastic and plastic design, each exemplified by the step-by-step design calculation of a braced steel-framed building and an industrial building, respectively. Besides providing the necessary theoretical concepts for a good understanding, this manual intends to be a supporting tool for the use of practicing engineers. In order of this purpose, throughout the book, numerous worked examples are provided, concerning the analysis of steel structures and the design of elements under several types of actions. These examples will provide for a smooth transition from earlier national codes to the Eurocode.
An analytical solution for the failure modes of foam-core sandwich beams subjected to three-point bending is presented in this study and a failure model is established to predict the failure modes and estimate the initial failure loads for each failure mode, i.e. face yield, core shear and indentation. Quasi-static three-point bending experiments have been carried out to verify the predictions of the theoretical analysis. Analytical predictions of the failure mode and the ultimate load compare well with the experimental results and better accuracy than the previous model is achieved.
The application of advance materials to manufacture hard armor systems has led to high performance ballistic protection. Due to its light-weight and high impact energy absorption capabilities, composite metal foams have shown good potential for applications as ballistic armor. A high-performance light-weight composite armor system has been manufactured using boron carbide ceramics as the strike face, composite metal foam processed by powder metallurgy technique as a bullet kinetic energy absorber interlayer, and aluminum 7075 or Kevlar™ panels as backplates with a total armor thickness less than 25 mm. The ballistic tolerance of this novel composite armor system has been evaluated against the 7.62 × 51 mm M80 and 7.62 × 63 mm M2 armor piercing projectiles according to U.S. National Institute of Justice (NIJ) standard 0101.06. The results showed that composite metal foams absorbed approximately 60–70% of the total kinetic energy of the projectile effectively and stopped both types of projectiles with less depth of penetration and backplate deformation than that specified in the NIJ 0101.06 standard guidelines. Finite element analysis was performed using Abaqus/Explicit to study the failure mechanisms and energy absorption of the armor system. The results showed close agreement between experimental and analytical results.
Sandwichbauteile mit dünnen metallischen Deckschichten und einer leichten, wärmedämmenden Kernschicht, z. B. aus Polyurethan-Hartschaum oder Mineralwolle, werden hauptsächlich als tragende Wand- und Dachbauteile eingesetzt. Die einzelnen Schichten der Paneele sind schubsteif miteinander verbunden, so daß insgesamt ein Verbundquerschnitt mit hoher Tragfähigkeit zur Wirkung kommt. Der praxisgerechte Einsatz dieser Bauteile ist in Deutschland durch Allgemeine bauaufsichtliche Zulassungen geregelt, in denen auch die erforderlichen Standsicherheits- und Gebrauchsfähigkeitsnachweise angegeben sind. Nachfolgend werden die zugehörigen Grundlagen für die rechnerischen Nachweise nach der Sandwich-Theorie (nachgiebiger Verbund), auch für die zusätzlich anzusetzenden Einwirkungen aus unterschiedlichen Deckenblechtemperaturen und Kriechen der Kernschicht, auf der Basis von explizit angegebenen Formeln und speziell entwickelten Diagrammen angegeben. Eine praxisnahe Bemessung, jeweils für ein Wand- und ein Dachteil, ist als Beispiel dargestellt.
Introduction Making Metal Foams Characterization Methods Properties of Metal Foams Design Analysis for Material Selection Design Formulae for Simple Structures A Constitutive Model for Metal Foams Design for Creep with Metal Foams Sandwich Structures Energy Management: Packaging and Blast Protection Sound Absorption and Vibration Suppression Thermal Management and Heat Transfer Electrical Properties of Metal Foams Cutting, Finishing and Joining Cost Estimation and Viability Case Studies Suppliers of Metal Foams Web Sites Index .
Static three-point bending tests of aluminum foam sandwiches with glued steel panel were performed. The deformation and failure of sandwich structure with different thicknesses of panel and foam core were investigated. The results indicate that the maximum bending load increases with the thickness of both steel panel and foam core. The failure of sandwich can be ascribed to the crush and shear damage of foam core and the delamination of glued interface at a large bending load. The crack on the foam wall developed in the melting foam procedure is the major factor for the failure of foam core. The sandwich structure with thick foam core and thin steel panel has the optimal specific bending strength. The maximum bending load of that with 8 mm panel and 50 mm foam core is 66.06 kN.
The focus of this review is on the hierarchy of computational models for sandwich plates and shells, predictor-corrector procedures, and the sensitivity of the sandwich response to variations in the different geometric and material parameters. The literature reviewed is devoted to the following application areas: heat transfer problems; thermal and mechanical stresses (including boundary layer and edge stresses); free vibrations and damping; transient dynamic response; bifurcation buckling, local buckling, face-sheet wrinkling and core crimping; large deflection and postbuckling problems; effects of discontinuities (eg, cutouts and stiffeners), and geometric changes (eg, tapered thickness); damage and failure of sandwich structures; experimental studies; optimization and design studies. Over 800 relevant references are cited in this review, and another 559 references are included in a supplemental bibliography for completeness. Extensive numerical results are presented for thermally stressed sandwich panels with composite face sheets showing the effects of variation in their geometric and material parameters on the accuracy of the free vibration response, and the sensitivity coefficients predicted by eight different modeling approaches (based on two-dimensional theories). The standard of comparison is taken to be the analytic three-dimensional thermoelasticity solutions. Some future directions for research on the modeling of sandwich plates and shells are outlined.
Sandwich panels manufactured using thermoplastic fiber-metal laminates (FML) skins and an aluminum foam core were tested under quasi-static and low-velocity impact loading conditions. The quasi-static properties of the sandwich beams were evaluated using the three-point bend test geometry. Energy absorbing mechanisms such as buckling and interfacial delamination in the FML skin, as well as indentation, crushing, and densification in the aluminum foam have been observed to contribute to the excellent energy absorbing characteristics offered by these systems. The low-velocity impact behavior of the sandwich panels was evaluated using an instrumented dropping weight impact tower and modeled using an energy balance approach. A breakdown of the energy absorption revealed that these sandwich structures absorb much of the impact energy due to contact and bending effects. Finally, four-point bend testing after low-velocity impact revealed that these systems offer excellent residual flexural strength with relative values remaining close to 80% of the original strength after a 32 J impact.
New closed cell composite metal foams are processed using casting and powder metallurgy (PM) techniques. The foam is comprised of steel hollow spheres packed into a random loose arrangement, with the interstitial spaces between spheres occupied with a solid metallic matrix. The characterization of composite metal foams was carried out using monotonic compression, compression–compression fatigue, loading–unloading compression, micro-hardness and nano-hardness testing. The microstructure of the composite metal foams was studied using optical, scanning electron microscopy imaging and electron dispersive spectroscopy. The composite metal foams displayed superior (5–20 times higher) compressive strengths, reported as 105 MPa for cast foams and 127 MPa for PM foams, and much higher energy absorbing capability as compared to other metal foams being produced with similar materials through other technologies.
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.
The feasibility of protecting tall buildings against progressive downwards collapse following catastrophic structural failure at high level is explored and various design suggestions made.
The performance in axial compression of square aluminium columns with aluminium foam filler has been assessed based upon existing design formulas for average crush force, maximum force and effective crushing distance. Using an optimisation algorithm, the combination of (1) foam density, (2) column wall thickness, (3) column width, (4) column material strength and (5) total component length giving the component of minimum mass was determined for specific cases. It was found that optimum foam filled columns compared to the traditionally designed non-filled columns showed smaller cross section dimensions in addition to less weight. As a consequence, mass-, length- and volume reductions are possible by utilising foam filler.
This paper provides an outline of the history since 1971 of EN1994 Eurocode 4: Design of composite steel and concrete structures followed by an account of current work on it. This should lead to publication of its three parts in 2004-2005 and withdrawal of competing national codes five years later. Summaries are given of the code's wide scope and the principal changes in provisions for buildings and bridges (but excluding structural fire design) since the pre-standard ENV versions were completed between 1992 and 1997. Reference is made to implications for practice in the UK and to some pitfalls of calibration work.
In recent years, there has been increasing interest in the use of structural sandwich panels as the cladding of buildings and a good deal of research and development has been carried out. This paper reviews the state of the art with regard to the structural design of elements consisting of two thin metal faces separated by a lightweight core. Various aspects are discussed but two are given particular attention, namely methods of global analysis and the local buckling of compressed face elements. The analysis of sandwich panels under all possible loading and boundary conditions no longer poses any problem. Classical solutions, approximate solutions and numerical methods such as finite elements all have their place and are reviewed in detail. Local buckling phenomena in sandwich elements are similar to those in other thin-walled metal elements with the added consideration that buckling is resisted by the core material. This leads to some quite complex analysis which requires simplification for practical design. The paper includes a useful bibliography of recent references.
The present contribution is concerned with a combined experimental and numerical design of graded cellular materials for multifunctional aerospace application performed in the context of an integrated research project funded by the European Commission. The primary objective is an exploration of the potential of functionally graded materials as sandwich cores for multifunctional application. With particulate advanced pore morphology (APM) foams and hollow spheres assemblies, two different types of particle-based cellular base materials are considered. Based on these constituent materials, functionally graded sandwich cores are designed in a combined numerical and experimental approach. Their properties and their performance in the desired application are investigated and optimized. The performance of the optimized material is compared to the performance of a non-graded sandwich core in the numerical simulation of a bird strike experiment. (C) 2012 Elsevier Ltd. All rights reserved.
The main purpose of this work is to study the bending behavior and deformation mechanisms of sandwich panels with AlSi7-alloy foam cores obtained by the powder metallurgy method. For this purpose, quasi-static three-point bending tests were performed on samples of AlSi7-alloy foam sandwich panels at different cross-head displacement rates: 1, 10, 20, 40 and 80 [mm/min]. Load-deflection values were registered during the bending test and further transformed into bending moment–rotation data. Obtained results show that different failure collapse modes can be obtained for samples with identical nominal dimensions, depending on the cross-head displacement rate.
Interaction between the bending moment and support reaction introduces new failure modes at intermediate supports of continuous sandwich panels. Two different loading cases have to be separated in the design. Positive support reaction causes a compressive contact pressure between the supporting structure and sandwich panel, and negative support reaction tensile forces in the fasteners of the panels. In the paper, the loading case named the positive support reaction is studied by means of analytical models, numerical analyses and experimental results. The analyses result in recommendations for the design at the serviceability state.
Steel foam steel was synthesized by a powder metallurgical route, resulting in densities less than half that of steel. Process parameters for foam synthesis were investigated, and two standard powder formulations were selected consisting of Fe–2.5%C and 0.2 wt.% foaming agent (either MgCO 3 or SrCO 3). Using the PM approach, foams with relative density ranging between 0.38 and 0.64 were obtained. Compression tests were performed on annealed and pre-annealed foam samples of different density to determine mechanical response and energy absorption behavior. The stress – strain response was strongly affected by annealing, which reduced the carbon content and converted much of the pearlitic structure to ferrite. These microstructural changes led to a more ductile response during compressive loading, in which a long stress plateau typically occurred after initial yielding. In fact, annealed steel foams behaved much like aluminum foams under compressive loading, despite pore structures that were considerably more coarse than those reported for aluminum foams.
Structural sandwich elements typically have two thin metal faces and a lightweight core. The core may be polyurethane or polyisocyanurate foamed in situ, or it may be formed from either rigid plastic foam or mineral wool slabstock. It is particularly in the latter case that durability problems may arise which have not been properly addressed by the industry. This paper considers appropriate test regimes for considering the durability of the adhesive bond between the core and the faces. In the case of panels with a core formed of mineral wool lamellae, it also considers possible degradation of the core material. The results of these tests demonstrate that commercially available mineral wools do not have uniform durability. It is necessary to pay particular attention to this factor when choosing core material for structural sandwich panels. Although the research described in this paper was conducted with mineral wool core material in mind, it is believed that the procedures are equally applicable to other materials. They are being codified in European recommendations for sandwich panels with additional recommendations for panels with mineral wool core material, published jointly by the European Convention for Constructional Steelwork (ECCS) and the International Council for Building Research Studies and Documentation (CIB).
The performance of new composite metal foams (CMFs) under bending was evaluated with simultaneous acoustic emission (AE) monitoring
on samples processed by cast and powder metallurgy (PM) techniques. The results showed high maximum strength in all samples
up to 86MPa with more ductile failure in PM samples. Acoustic emission behavior confirmed that the dominating failure mechanism
of cast CMF is the brittle fracture of intermetallic phases that mostly exist at the interface of the steel spheres with the
aluminum matrix, whereas in PM samples (100pct steel), the failure is governed by the propagation of preexisting microporosities
in the matrix resulting in a complete ductile failure. SEM imaging of the fracture surfaces supported these findings.
Nowadays, the construction sector is more and more oriented toward the promotion of sustainability in all its activities.
The goal to achieve is the optimization of performances, over the whole life-cycle, with respect to environmental, economic
and social requirements. According to the latest advances, the concept of sustainability applied to constructions covers a
number of branches such as life-cycle costing, ecology, durability and even structural design. Several procedures and design
tools have been implemented in the framework of international research. Indeed the current trend in civil engineering research
is moving towards life-time engineering, with the aim to implement integrated methodologies to consider as a whole all the
sustainability requirements according to time-dependent multi-performance-based design approaches. Following a general introduction
of the concept of sustainability applied to constructions, this paper presents an overview of life-time engineering methodologies
according to the current state-of-the-art. In particular the methods currently received by International Standards are discussed.
A special focus is devoted to the durability design of metal structures with respect to the degradation phenomena able to
impair the structural capacity over time. Finally a proposal towards an integrated approach to life-time engineering design
of steel structures and needs for further advances are presented.
Keywordssustainability–life-time engineering–performance based design–durability–metal structures
Static and dynamic three-point bending tests were carried out in order to investigate the structural response (collapse modes, energy dissipation, strain rate sensitivity) of two different typologies of aluminium foam sandwich (AFS) panels, consisting of a closed-cell aluminium foam core with either two integral (Schunk) or two glued (Alulight) faces. Impact measurements were performed by a bi-pendulum testing machine designed by the authors. It was found that different collapse modes can be obtained for samples with identical nominal dimensions, depending on the support span distance and on the own AFS properties. Simplified theoretical collapse models were introduced to explain the observed experimental behaviour, showing good agreement between predicted and experimental limit loads. As far as energy dissipation is concerned, no strain rate sensitivity was found for initial impact velocity up to about 1.2 m/s.
Sandwich beams with metallic foam cores can fail by several modes: face yielding, face wrinkling, core yielding and indentation. We estimate the initial failure load, corresponding to the first deviation from linearity in the load–deflection curve as well as the peak load for each mode. Failure mode maps are constructed which illustrate the dominant failure mode for practical beam designs. The results of the analysis are compared with experiments on sandwich beams with aluminum foam cores in three-point bending. The peak loads and the failure modes are described well by the analysis.
Sandwich beams with aluminium face sheets and an aluminium alloy foam core are tested in cyclic four point bend, and S–N fatigue curves are determined for the failure modes of face fatigue, core shear and core indentation. The operative failure mode is dictated by the relative fatigue strength of face sheets to core, and upon the geometry of the sandwich beams. Simple analytical models are developed to predict the fatigue strength for each of the competing failure modes, and a design map is produced to display the fatigue strength and mode of failure as a function of sandwich beam geometry.