It is widely known that the availability of lightweight structures with excellent energy absorption capacity is essential for numerous engineering applications. Inspired by many biological structures ...in nature, bio-inspired structures have been proved to exhibit a significant improvement over conventional structures in energy absorption capacity. Therefore, use of the biomimetic approach for designing novel lightweight structures with excellent energy absorption capacity has been increasing in engineering fields in recent years. This paper provides a comprehensive overview of recent advances in the development of bio-inspired structures for energy absorption applications. In particular, we describe the unique features and remarkable mechanical properties of biological structures such as plants and animals, which can be mimicked to design efficient energy absorbers. Next, we review and discuss the structural designs as well as the energy absorption characteristics of current bio-inspired structures with different configurations and structures, including multi-cell tubes, frusta, sandwich panels, composite plates, honeycombs, foams, building structures and lattices. These materials have been used for bio-inspired structures, including but not limited to metals, polymers, fibre-reinforced composites, concrete and glass. We also discussed the manufacturing techniques of bio-inspired structures based on conventional methods, and adaptive manufacturing (3D printing). Finally, contemporary challenges and future directions for bio-inspired structures are presented. This synopsis provides a useful platform for researchers and engineers to create novel designs of bio-inspired structures for energy absorption applications.
Different from conventional materials, materials with negative Poisson's ratios expand laterally when stretched longitudinally. Known as ‘auxetic’ materials, the effect means they possess ...particularly fascinating properties, which have recently attracted considerable attention in the literature. A range of auxetic materials has been discovered, theoretically designed and fabricated. Developments in additive manufacturing (AM) techniques enable fabrication of materials with intricate cellular architectures. This paper outlines recent progress in the development of auxetic materials and structures, and their mechanical properties under quasi-static and dynamic loading are analysed and summarised. Limited experimental studies on 3D printed auxetic materials and structures are given more attention, ahead of extensively finite element (FE) simulations. A special focus is dedicated to their large, plastic deformation behaviour and energy absorption performance, which should be stressed in their engineering applications; no review paper has yet been found regarding this. Finally, this paper provides an overview of current study limitations, and some future research is envisaged in terms of auxetic materials and structures, nano-auxetics and additive manufacturing.
•This paper outlines recent development of auxetic materials and structures.•Limited experimental studies on printed auxetic materials and structures are given more attention.•A special focus is their large deformation behaviour and energy absorption performance.•This paper summaries current limitations and future research regarding AM, auxetic materials and nano-auxetics.
In this study, a novel bio-inspired honeycomb sandwich panel (BHSP) based on the microstructure of a woodpecker’s beak is proposed. Unlike a conventional honeycomb, the walls of the bio-inspired ...honeycomb (BH), which is used as the core of a sandwich panel, are made wavy. Finite element simulation shows that under dynamic crushing the proposed BHSPs exhibit superior energy absorption capability compared with the conventional honeycomb sandwich panel (CHSP). In particular, the specific energy absorption (SEA) of the BHSP increases by 125% and 63.7%, respectively, compared with that of the honeycomb sandwich panel with the same thickness core or the same volume core. In addition, a parametric study of the BHSPs is carried out to investigate the influences of the wave amplitude, wave number and core thickness on the energy absorption performance of the BHSPs. It is found that the BH core with a larger wave number and amplitude shows higher SEA. Furthermore, an increase in core thickness can improve the SEA. These results provide guidelines in the design of a lightweight sandwich panel for high-energy absorption capability.
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•Inspired by the deep-sea glass sponge skeleton, a new multi-cell tubular structure was proposed.•Both high specific energy absorption and high crushing force efficiency are ...achieved.•The mean crushing force of the proposed structure is close to the full-plastic force.•The crushing force efficiency of the proposed structure approaches the ideal value of 1.
The energy absorption potential of conventional thin-walled tubes is compromised by the long-wavelength folding lobes, which result in a mean crushing force that is much smaller than their yield strength. Here, inspired by the characteristics of the skeletal of the glass sponge, a new thin-walled multi-cell tubular structure with modified face-centered cubic (MFCS) cross section is proposed. The compression behaviors and energy absorbing capacity of the proposed structure were compared with those of the traditional multi-cell tube through finite element simulation and experimental tests. Compared with the traditional multi-cell tubes, the proposed MFCS structure exhibits micro-folding lobes with shorter wavelength, resulting in larger energy absorption, higher energy absorption efficiency and a more stable and controllable deformation mode, with the mean crushing force almost reaching that of an ideal energy absorber. Moreover, the effects of the geometric coefficient of MFCS multi-cell tube on the energy absorption performance and deformation pattern were studied parametrically. Through the bionic design, extraordinary energy absorbing performance is achieved, providing guidance for future design of lightweight structures with unprecedented mechanical properties.
Selective Laser Melting (SLM) allows the fabrication of complex geometries with high resolution and robust mechanical properties. However, the manner of manufacture – melting of metallic powder with ...a laser power source – affects microstructure and results in mechanical anisotropy. While some studies have sought to characterise the microstructure and performance of SLM AlSi10Mg, the dynamic response, particularly with regard to anisotropic effects, remains relatively undefined. To overcome this deficit AlSi10Mg specimens were fabricated using SLM with three different build orientations, and quasi-static and dynamic split-Hopkinson tensile bar tests were performed to characterise the tensile properties of the material at strain rates ranging from 3.33 x 10-2 to 2.4 x 103 s-1. The microstructure of as-manufactured specimens and fracture surfaces of failed specimens were analysed. Quasi-static and dynamic results showed little difference between build orientations with regard to strength, but components loaded perpendicular to the build direction were found to be more ductile than other build orientations. Significant scatter was observed in dynamic results, suggesting no strain rate sensitivity of the material in the tested strain rate range. Build orientation was found to affect fracture surface morphology of dynamically tested specimens due to fracture paths following melt pool boundaries. These results assist in the characterisation of the anisotropic effects of build orientation on quasi-static and dynamic behaviours of SLM AlSi10Mg towards the further commercial adoption of the manufacturing technique and material.
Additive manufacturing (AM) techniques such as selective laser melting (SLM) enable the fabrication of complex metallic lattice structures. By tuning geometric and topological parameters, these ...structures can be manufactured to exhibit a range of useful properties, including excellent strength-to-weight ratios and energy absorption capabilities. While the effects of these parameters on various aspects of AM lattice performance have been previously studied, such as the effects of manufacturability, material selection and geometric parameters on the quasi-static performance of AM lattice structures, the effect of topology on the dynamic behaviour of SLM AlSi10Mg lattice structures remains relatively unexplored. Lattice structure specimens with five different topologies were manufactured using SLM AlSi10Mg and tested under quasi-static and dynamic loading conditions. The tested topologies were body-centred cubic with (BCCZ) and without (BCC) z-struts; face-centred cubic with (FCCZ) and without (FCC) z-struts; and body and face-centred cubic with z-struts (FBCCZ). A numerical model was developed to investigate failure modes and collapse mechanisms. Specimens were found to fail by the emergence of diagonal shear planes, and the orientation of which was dependent on topology, due to the uneven concentration of stress in struts across the structure. No significant rate sensitivity was identified for any of the tested topologies in the range of tested strain rates. The FCCZ topology was demonstrated to provide the greatest efficiency in terms of both strength-to-weight and stiffness-to-weight ratios. These results assist in the characterisation of the dynamic behaviour of SLM AlSi10Mg lattice structures and contribute to their further commercialisation.
Thin-walled tubes are a kind of popular design for the energy absorbing devices. However, when they are subjected to axial loading, there exists a large undesirable initial peak force, followed by ...fluctuation in the force–displacement curve. In this paper, the origami patterns are introduced to thin-walled tubes to minimize the initial peak and the subsequent fluctuations. Tubes of square, hexagonal and octagonal cross-sections with origami patterns are investigated by finite element analysis. Numerical results show that compared with the conventional tube, the patterned tubes exhibit a lower initial peak force and more uniform crushing load. The critical states are obtained under which the crushing mode follows the initial origami pattern. The parametric study shows the relationship between the pre-folding angle and the initial peak force as well as the mean crushing force for the tubes with different cross-sections. A prototype of the patterned tube is constructed and tested, showing much lower initial peak force and a smooth crushing process which agrees with the numerical results.
► We introduce origami patterns to thin-walled structures and study their axial crushing. ► Patterned tubes with square, hexagonal and octagonal sections are studied using FEA. ► The peak force decreases as patterns are introduced and the force fluctuates much less. ► A critical initial angle is used to govern if the crushing mode follows the initial pattern. ► An experiment was conducted which verified the idea.
The work aims to study the large, plastic deformation and energy absorption characteristics of zig-zag folded metamaterials, BCHn, under quasi-static in-plane compression, using an analytical method ...and numerical analysis. In analytical modelling, the zig-zag folded materials are assumed as rigid origami in the y direction. The BCHn materials are considered as cellular materials with various topologies defined by the characteristic geometric parameters (a,b,h;α,γ0;n) when the strength at large plastic strains and densification strain are defined. The obtained analytical relationships between material topology and material strength provide an easy way to assess the energy absorption of BCHn materials with various geometric parameters. Particular attention is paid to the compression response of BCH2 and BCH3 materials, and comparisons are made with Miura-ori based materials having the same parameters (a,b,h;α,γ0). It is found that the zig-zag folded materials outperform the Miura-ori based material in terms of energy absorption. Besides, tunable geometric parameters of the BCHn zig-zag folded materials allow better tailoring of their mechanical properties. Comparisons of the energy absorption efficiency between zig-zag folded materials and hexagonal honeycomb materials show that the parameters of the BCHn materials can be selected to obtain metamaterials with superior energy absorption characteristics. Finite element models of zig-zag folded materials are built using ABAQUS/Explicit and numerical simulations of quasi-static compression are carried out to verify the analytical results. The observed agreement in terms of force and deformation confirmed that the analytical models are valid, and the analytical predictions are reliable.
•This work analyses the large, plastic deformation and energy absorption characteristics of BCHn metamaterials to quasi-static compression.•BCHn metamaterials outperform the Miura-ori based materials in terms of energy absorption.•The analytical relationships between topology and strength allow assessing easily the energy absorption of BCHn metamaterials.
The Miura-ori pattern possesses intriguing mechanical features, namely, the one Degree Of Freedom mobility, auxetic in-plane behavior and energy absorption capability, for applications such as core ...to sandwich structure, shock absorber, airless tire, etc. To realize the folding mechanism of Miura-ori, in this paper a Miura-ori patterned sheet was made from copolymer Elvaloy by compression molding, and then its deformation behavior was investigated experimentally and by using finite element analysis. The intrinsic mechanical properties of Elvaloy were obtained by tensile and four-point-bending tests, respectively, and subsequently used in the finite element (FE) simulation. For utilizing the sheet in all the principal directions, three types of tests were conducted: out-of-plane compression, three-point-bending and in-plane compressions. FE simulations using Abaqus/Explicit were carried out to analyze the deformations of the patterned sheet under the same loading as that in the tests. The simulation results were then compared with the tests, which show good agreements. Based on the simulation results, the deformation patterns of the patterned sheet under different loading conditions were examined, as well as the energy absorption capacity.
•The deformation behavior of the Miura-ori patterned sheet is investigated.•The patterned sheet is made of copolymer Elvaloy, capable of elastic deformations.•In-plane properties, not reported before, are investigated.•The energy absorption capacities of the patterned sheet have been investigated.
The tensile properties of the lightweight titanium-based carbon-fibre/epoxy laminates (TI-CF FMLs) were investigated under quasi-static loading. A comprehensive experimental study was conducted for ...eleven different types of the TI-CF FMLs (considering various metal sheet thicknesses, metal volume fractions and fibre orientations) as well as their associated constituent materials (i.e., Ti-6Al-4V and carbon-fibre/epoxy laminates). Specimens were fabricated using vacuum bagging technique in an autoclave. Theoretical predictions using the volume fraction approach based on the rule of mixtures match closely with the measured mechanical properties of the TI-CF FMLs. In addition, tensile failure mechanisms of the specimens were explored in this study.
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•Tensile behaviour of 11 types titanium-based carbon-fibre/epoxy laminate was studied via comprehensive experimental tests.•Strain localization in metal was observed by using Digital Image Correlation technique after initial breakage of 0° fibre.•Two failure modes were categorised in terms of the state of deformation (elastic/plastic/fracture) of constitutive layers.•• Failure was dominated by carbon fibre/epoxy laminate cores (Mode 1) or by Ti-6Al-4 V (Mode 2).
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