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.

A review of recent research on bio-inspired structures and materials for energy absorption applications

This paper treats the dynamic response and energy absorption of aluminum foamfilled
conical tubes under axial impact loading using non-linear finite element
techniques. The influence of geometrical, material and loading parameters on the impact
response is investigated using validated numerical models. Results are quantified in
terms of important impact response parameters and indicate that the foam filler
stabilizes the crushing process and thus improves the energy absorption capacity. The
superior performance of foam-filled conical tubes as impact energy absorbers is evident
from the results. The research information generated will be useful in developing
guidance towards the design of these devices in impact applications.

Dynamic computer simulation and energy absorption offoam-filled conical tubes under axial impact loading

It is widely known that the demand for lightweight structures with excellent energy absorption capacity is paramount in numerous engineering applications. Many publications have revealed that corrugated structures can collapse in a relatively controlled manner with a uniform force-displacement response and have remarkable energy absorption efficiency when compared with traditional structures without corrugations. The present work provides a comprehensive overview of recent advances in the development of corrugated structures for energy absorption applications, also considering the effects of corrugation characteristics on their crashworthiness. Such advanced energy absorbers include corrugated tubes, corrugated tapered tubes, corrugated beam and plates, corrugated honeycombs, corrugated core sandwich panels and other hybrid structures with complex corrugations. This review demonstrates that thin-walled structures with introduced corrugations can achieve more efficient and effective energy absorption. Finally, contemporary challenges of design and manufacture are discussed, as well as future directions for corrugated structures. This synopsis provides a useful platform for researchers and engineers designing corrugated structures for energy absorption applications.

Thin-walled corrugated structures: A review of crashworthiness designs and energy absorption characteristics

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.

Energy absorption of a bio-inspired honeycomb sandwich panel

Honeycombs are ultra-light materials with outstanding mechanical properties, which mainly originate from their unit cell configurations rather than the properties of matrix materials. Honeycombs are triggering in numerous promising applications in the fields of architecture, automotive, railway vehicle, marine, aerospace, satellite, packaging and medical implants, etc. Here we provide an in-depth overview of some important advances in basic structural design to obtain novel honeycombs with various improved mechanical properties. Firstly, the review introduces the classical honeycomb configurations. Then, a clear classification of advanced designs is established and discussed according to the design scale. The designs on the macro scale are divided into hierarchical, graded and disordered, while the designs on the meso scale are grouped as hybrid, curved ligament and reinforced strut. Moreover, the effects of different designs on the mechanical properties of honeycomb are discussed quantitatively. Finally, we summarize the important potential designs to improve the mechanical properties of honeycombs and the challenges in further research.

Advanced honeycomb designs for improving mechanical properties: A review

High energy absorption efficiency of thin-walled conical corrugation tubes mimicking coconut tree configuration

In this paper, an innovative bio-inspired multi-layered graded foam-filled structure (MGFS) mimicking the characteristics of the human skeleton was proposed in an attempt to improve the energy absorption. The proposed structures consisted of three layers of aluminum foam with different densities filled in three concentric aluminum circular tubes. To find out the optimal foam-filled combination and demonstrate the superior energy absorption performance of the proposed structures, a series of quasi-static compression tests were experimentally and numerically carried out. The results showed the proposed structures had higher energy absorption efficiency than that of both uniform foam-filled structures and the empty tubes, and Model-1 with the foam density increasing from the inner tube to the outer tube was the best combination mode. Furthermore, parametric numerical studies on Model-1 revealed that the diameter and thickness of the aluminum tube and the density of the aluminum foam had significant effects on the energy absorption characteristics. Finally, a theoretical model was developed to predict the mean crushing force of the bioinspired MGFS, which was in good agreement with the experimental results. This study provides an effective guideline for designing a foam-filled energy absorber with high energy absorption efficiency.

Energy absorption of bio-inspired multi-layered graded foam-filled structures under axial crushing

Origami structures are commonly constructed by folding a two-dimensional sheet according to a given crease pattern. The existence of abundant crease patterns means that many three-dimensional structures can be fabricated by using a variety of sheet materials, including thin-walled tubes and arcs. Some origami structures can also be used as core structures, sandwich plates, or arcs, whereas other such structures can be stacked to form metamaterials, which are materials designed to possess a property that is not readily available in nature. Because the mechanical performances of these structures are commonly dependent upon their geometry, the properties of these structures can be designed and adjusted through the selection and optimization of the appropriate geometric parameters. This review focuses on the deformation and energy absorption (EA) capability of origami structures subjected to static and dynamic loading. The main characteristics and findings are summarized, and further work in the area is suggested.

Xinmei Xiang

Papers

Energy absorption of a bio-inspired honeycomb sandwich panel

High energy absorption efficiency of thin-walled conical corrugation tubes mimicking coconut tree configuration

Energy absorption of bio-inspired multi-layered graded foam-filled structures under axial crushing

Energy absorption of origami inspired structures and materials

Rectangular sandwich plates with Miura-ori folded core under quasi-static loadings