Beetle Elytron Research Articles

The bending of 3D-printed bio-inspired sandwich panels with wavy cylinder cores

Beetle Elytron Plates (BEPs) represent a new class of biomimetic sandwich cores with excellent mechanical properties inspired by the microstructure of the beetle elytra. The cores have a hexagonal centre-symmetric configuration with through-thickness cylinders in the unit cell. In this work, we describe the behaviour of sandwich panels with novel BEP core configurations possessing wavy cylinders under four-point bending tests. Full-scale simulations are also carried out to validate the experimental data. The results show that all the sandwich panels produced with face skins adhesively bonded have material failure earlier than the adhesive bond failure. BEPs with wavy cylinders have larger peak loads compared to those with straight cylinders, and all BEPs show higher peak loads than those of sandwich panels with classical hexagonal honeycombs. Additionally, all the BEPs exhibit an enhanced ductility compared to honeycomb sandwich panels.

The engineering elastic constants of bio-inspired sandwich cores with wavy cylinders

Beetle Elytron Plates (BEPs) represent a new class of biomimetic sandwich cores with excellent mechanical properties and inspired by the internal structure of the beetle elytra. The cores have a hexagonal centre-symmetric configuration with through-thickness cylinders in the unit cell. The present work describes the behaviour of the engineering elastic constants of an evolution of these BEP topologies that feature cylinders with waviness. These BEP core configurations are simulated using Finite Element models, with periodic boundary conditions for volumetric homogenization. The models are then used to perform a parametric analysis against the geometry characteristics of the new cellular configurations. This work further explores the potential design space of BEP cellular metamaterials by altering the geometry of the trabeculae and facilitates further investigation into the mechanical properties of these new BEP topologies with wave-shaped units. Although – and as expected - the specific nondimensional out-of-plane tensile modulus has values here close to unity, BEP topologies with out-of-plane wave-shaped cylinders show enhanced in-plane moduli values than classical straight cylinder configurations, except for the Young's modulus of MBEP cores with only one semi-wave. The same trend is observed for the nondimensional Young's modulus of EBEP configurations, whereas the situation is opposite for the MBEP topologies. The nondimensional out-of-plane shear modulus decreases for both EBEP and MBEP configurations compared to the straight cylinder cores.

Out-of-plane engineering constants of beetle elytra inspired sandwich cores

The Beetle Elytron Plate (BEP) is a new type of biomimetic sandwich core developed as a potential replacement of classical honeycomb cores in sandwich panels. This work investigates the out-of-plane engineering elastic constants, including Young's and pure shear moduli of parametric BEP cellular topologies. The BEP core configurations are simulated using Finite Element models, with both full-scale and representative unit cells for asymptotic homogenization. The numerical models are also validated by flatwise compression and out-of-plane pure shear loading experiments performed according to ASTM standards. The benchmarked models are then used to perform a parametric analysis of the beetle elytra cellular cores against their geometry characteristics. Results show that the out-of-plane Young's modulus E3/Esand the transverse pure shear modulus G31/Es of both BEP configurations are larger than those of the classic hexagonal honeycombs and increase when the size of the unit cell cylinders, or rib thickness become large. The specific shear moduli of the beetle-elytra inspired honeycombs are however lower than those of classical pure hexagonal honeycomb configurations, although the added presence of cylinders within the cell configuration offers opportunities for tailoring the design of multifunctional cores.

A novel bionic straw-filled concrete block: compression and heat-transfer performance

To develop economical, environmentally friendly and lightweight building materials, a novel straw-filled bionic concrete hollow block (BCHB) was designed. Compression tests were conducted to determine the compressive strength of the BCHB. Furthermore, the compressive and heat-transfer properties of these blocks were investigated with finite-element analysis, and the following results were observed. (a) The BCHB model did not easily experience local collapse. Instead, it mainly exhibited thin cracks due to shear failure, providing great cracking and collapse resistance, thereby resulting in excellent compressive performance. (b) By reducing the thickness of the short edges of the BCHB models, they exhibited great compressive and thermal insulation performance, making these the preferred BCHBs. (c) The BCHB presented herein was the simplest model of the beetle elytron plate. In contrast to a traditional hollow brick, the BCHB was proven to be a lightweight, fully enclosed brick (block) with a high hollow ratio and could be used as a new non-bearing wall material replacing the traditional type in building construction.

Experimental and theoretical study on out-of-plane compression buckling properties of grid beetle elytron plate

Experimental and theoretical study on out-of-plane compression buckling properties of grid beetle elytron plate

Free vibration properties of beetle elytron plate: Composite material, stacked structure and boundary conditions

Beetle elytron plate (BEP), which is derived from the bionics of Trypoxylus dichotomus's elytra, is a typical lightweight and high-strength structure with superior and comprehensive mechanical properties. To promote the engineering application of BEPs, this paper explores the vibration characteristics of foam-filled fiber composite BEPs. Through the finite element method (FEM), structural parameters such as the length-to-width ratio, core height-to-thickness ratio, skin thickness and foam density influence the natural frequency and mode. Furthermore, the influence pattern of parameters (such as boundary conditions and the number of stacked layers) toward the first two orders of natural frequencies and modes of the BEP were investigated under controlled total height and controlled single layer height. The results indicate that 1) the ranking of structural parameters on the 1st order frequency from a strong to weak sequence is as follows: length-to-width ratio, core height-to-thickness ratio, foam density and skin thickness; for the 2nd order natural frequency: length-to-width ratio, skin thickness, foam density and core height-to-thickness ratio. 2) Generally, an increase in the length-to-width ratio will reduce the frequency of the BEP, and increases in the core height-to-thickness ratio and skin thickness will raise its frequency. Additionally, foam filling plays a decisive role in local deformation. 3) When the total height of the sandwich plate is controlled, the improvement of the boundary conditions can effectively boost its 2nd-order frequency (approximately 200%), but the 1st-order frequency can be significantly increased (approximately 140%) only when all four sides are improved. 4) In the case of controlling the height of the single layer of the sandwich plate, its frequency gradually increases with the increase in the number of stacked layers. However, when the constraints are weak or there are few stacked layers, increasing the number of stacked layers can effectively boost the vibration frequency. This paper provides references and suggestions for the design and application of sandwich structures, enriching the research on the mechanical properties of BEPs and establishing groundwork for promoting BEPs in engineering practices.

Compressive properties of aluminum middle-trabecular beetle elytron plates with a large height-to-thickness ratio core

To develop lightweight and high-strength biomimetic structural materials, the compression characteristics of aluminum middle-trabecular beetle elytron plates (MBEPa) with a large height-to-thickness ratio (β) core were investigated by flat compression tests and finite element simulations, and the results are as follows. 1) Compared with aluminum honeycomb plates (HPa), the core compressive strength and energy absorption of MBEPa with two trabeculae per honeycomb can increase by 12.4 % and 28.6 %, respectively, with an increase of about 1.8 % in the total volume; and for the first time, the MBEPa core structure with a large β was found to have a triple interval deformation morphology with a small C or S shape deformation in the central part. 2) Compared with HPa, MBEPa with six trabeculae has a 9.3 % increase in total volume, 106.7 % increase in compressive strength and 147.3 % increase in energy absorption core. 3) Compared with the BEPs with a small β, with the increase of trabeculae, the compressive property increase of the large-β ones reflects the characteristic of "small in the early stage and large in the later stage". And the strengthening and influence mechanism of trabecula on the compressive properties and deformation was revealed from the perspectives of the aforementioned core deformation characteristics and the constraining effect of skins.

Research and Optimization of Lateral Compressive Performance of the 3-D Printed Beetle Elytron Plate

In this paper, two types of beetle elytron plates (end-trabecular beetle elytron plate (EBEP) and middle-trabecular beetle elytron plate (MBEP)) and honeycomb plate (HP) were manufactured by 3-D printed and applied to large-span spatial structure. The lateral compressive performance of the 3-D printed beetle elytron plate was investigated by lateral compression bearing capacity test and numerical analysis. The influence of number of cylinders, ratio of the radius of the cylinder to the side length of the hexagonal honeycomb core (ratio of radius-length), thickness of core layer and configuration of beetle elytron plate on the lateral compressive performance of the beetle elytron plates were studied and the optimization method for lateral compressive performance of the beetle elytron plates was proposed. The result shows that the lateral compression bearing capacity of EBEP is greater than that of MBEP, and both are greater than of HP. The lateral compression bearing capacity of the beetle elytron plate with six cylinders is about 25% higher than that of the HP without cylinders. The lateral compression bearing capacity of beetle elytron plate can be improved by increasing the thickness of plates. The results of the study will promote the application of beetle elytron plates in large-span spatial structures.

Compressive performance of a foam-filled fiber-reinforced grid beetle elytron plate

Compressive performance of a foam-filled fiber-reinforced grid beetle elytron plate

Transcriptomic exploration of the Coleopteran wings reveals insight into the evolution of novel structures associated with the beetle elytron.

The acquisition of novel traits is central to organismal evolution, yet the molecular mechanisms underlying this process are elusive. The beetle forewings (elytra) are evolutionarily modified to serve as a protective shield, providing a unique opportunity to study these mechanisms. In the past, the orthologs of genes within the wing gene network from Drosophila studies served as the starting point when studying the evolution of elytra (candidate genes). Although effective, candidate gene lists are finite and only explore genes conserved across species. To go beyond candidate genes, we used RNA sequencing and explored the wing transcriptomes of two Coleopteran species, the red flour beetle (Tribolium castaneum) and the Japanese stag beetle (Dorcus hopei). Our analysis revealed sets of genes enriched in Tribolium elytra (57 genes) and genes unique to the hindwings, which possess more "typical" insect wing morphologies (29 genes). Over a third of the hindwing-enriched genes were "candidate genes" whose functions were previously analyzed in Tribolium, demonstrating the robustness of our sequencing. Although the overlap was limited, transcriptomic comparison between the beetle species found a common set of genes, including key wing genes, enriched in either elytra or hindwings. Our RNA interference analysis for elytron-enriched genes in Tribolium uncovered novel genes with roles in forming various aspects of morphology that are unique to elytra, such as pigmentation, hardening, sensory development, and vein formation. Our analyses deepen our understanding of how gene network evolution facilitated the emergence of the elytron, a unique structure critical to the evolutionary success of beetles.

Experimental, numerical and analytical study to develop a design method for bending and shear resistances of 3D printed beetle elytron inspired sandwich plate (beetle elytron plate)

Beetle elytron plate (BEP) is a new type of sandwich structure inspired by the internal architecture of beetle elytra and characterized by trabeculae in the core to achieve better mechanical resistance compared to conventional honeycomb sandwich plate under lateral loads. To take advantage of this improved performance in design, this paper presents, for the first time, a series of static four-point bending and shear tests for buckling and post-buckling behaviour of small-scale 3D printed BEPs until failure. Tensile coupon tests were also carried out on the 3D printed material. The experimental results are then used to validate ABAQUS numerical modelling that previously could only be partially carried out due to a lack of experimental data. The test results confirm large increases in BEP resistances compared to conventional honeycomb sandwich plates of the same dimensions. The observed BEP failure mode under bending is post-buckling of the compressive skin. Assuming that the post-buckling stress of BEP can be calculated in the same way as conventional sandwich plate, and making use of the elastic–plastic buckling stress solution for BEP that had previously been proposed by the authors, this paper proposes a simple method to calculate the post-buckling stress of BEP for design purpose. For shear resistance, the shear buckling stress of the trabecular core of BEP can be calculated in the same way as for conventional honeycomb sandwich plate except for using the web width between the near edges of the two adjacent trabeculae. The proposed calculation methods give results in good agreement with experimental results, with the maximum difference being 8%. The difference would be even lower if the smooth 3D printed surface is under compression.

The compressive mechanical properties of honeycomb plates and beetle elytron plates with different foam densities and height-to-thickness ratios

To investigate a new type of bionic energy-saving sandwich plate—the beetle elytron plate (BEP), the compressive mechanical properties of short basalt fiber reinforced epoxy resin composite BEPs and honeycomb plates with different polyvinyl chloride foam densities and height-to-thickness ratios were investigated. The mechanism of the coupling effect of the core structure, foam density and height-to-thickness ratio was revealed by observing the failure mode of the outer and inner ring honeycomb walls. This study can provide useful instruction for designing lightweight sandwich structures and accelerate the application of BEPs in engineering.

Vibrational Characteristics of a Foam-Filled Short Basalt Fiber Reinforced Epoxy Resin Composite Beetle Elytron Plate.

The vibrational properties and mechanism of a foam-filling short basalt fiber reinforced epoxy resin composite beetle elytron plate (EBEPfc) were studied by experiments and the finite element (FE) method in this paper. The experimental results showed that the natural frequencies of the first two modes of the EBEPfc were very close to those of a foam-filling short basalt fiber reinforced epoxy resin composite honeycomb plate (HPfc), while the vibrational response of the EBEPfc was weaker than that of the HPfc, and the damping ratio was improved; the improvement of the second mode was significant. Therefore, the EBEPfc had a better vibration reduction performance and could directly replace the HPfc in engineering applications. The FE results showed that foam filling enhanced the shear stiffness of the whole core structure, and had a more obvious effect on the shear stiffness of the HPfc. Meanwhile, it particularly reduced the shear force proportions and contributed to the protection of the skin and core skeleton. The mechanisms of the vibrational characteristics of these two types of sandwich plates were explored from the perspective of the equivalent cross-sectional area, shear stiffness, shear strain energy per unit volume and friction. These results provide a valuable reference for the promotion and application of EBEPfc in the fields of vibration reduction and seismic resistance.

Free vibration and sound transmission properties of beetle elytron plate: structural parametric analysis

Honeycomb plate (HP), which is a high-strength and lightweight structure, has good vibration characteristics, while beetle elytron plate (BEP) has better mechanical properties. To promote the engineering application of BEPs, the vibration and sound transmission characteristics of aluminium BEPs were investigated in this paper with HP as the comparison object. This paper investigated the effects of the number of trabeculae, the ratio of length and width, skin thickness, core height and core thickness on the first 4 frequencies using finite element method. The results show that (1) the vibration characteristic of BEP is optimal when the number of trabeculae is 6, and its 3rd and 4th modes show mixed mode, i.e., torsion-bending or bending-torsion mode. (2) The frequencies of BEPs are generally lower than those of HPs. Compared with HPs, the ratio of length and width and core thickness have a smaller influence on the mode shapes of BEPs, and the core height has a smaller influence on BEPs’ frequencies. When the skin thickness is small, increasing the thickness can effectively change the natural frequencies of BEPs and HPs. (3) Considering the common frequencies of four applications (aircrafts, unmanned aerial vehicles, high-speed trains and automobiles) of sandwich plates, the effects of the abovementioned parameters including the ratio of length and width, skin thickness, core height and core thickness are analysed. (4) Combined with the theoretical calculation formula, the effect of the above structural parameters on the sound transmission characteristic is explored using the index of sound transmission loss, and targeted recommendations are given. This paper progresses the application in engineering.

Shear properties of 3D-printed grid beetle elytron plates

Shear properties of 3D-printed grid beetle elytron plates

In-plane elasticity of beetle elytra inspired sandwich cores

The Beetle Elytron Plate (BEP) is a new class of biomimetic sandwich core that features excellent compressive strength, energy absorption capacity and flexural properties. These characteristics make BEPs suitable as potential replacements of classical honeycomb cores in sandwich panels. This work describes the behaviour of the in-plane engineering elastic constants of parametric BEP topologies for the first time. The beetle elytron cores configurations are simulated using Finite Element models, including full-scale models and representative unit cells with periodic boundary conditions for asymptotic homogenization. The models are also benchmarked against experimental results obtained from ASTM tensile tests related to the in-plane Young’s modulus, Poisson’s ratio and shear modulus. The benchmarked models are then used to perform a parametric analysis against the geometry characteristics of the cellular configurations. Results obtained from this work will provide a solid foundation for further research on BEP structures and expand their applications into wider engineering fields.

Elastic–plastic buckling behaviour of beetle elytron plate with simple, fixed and flexible core supports

Beetle elytron plate (BEP) is a new type of sandwich structure inspired by the internal architecture of beetle elytra and characterised by trabeculae in the core to achieve higher load bearing capacity compared to the basic conventional honeycomb sandwich plate. This paper investigates elastic–plastic buckling behaviour of the compressive skin of BEP with flexible core. The development is based on adapting existing solutions for relevant structures through the following three transformation steps: (1) obtaining the elastic–plastic buckling stresses of BEP with simple and fixed supports by extending respective solutions for conventional sandwich plate; (2) modifying the elastic buckling stress solution for conventional sandwich plate with flexible core to BEP with flexible core through replacement of deformation shape functions; (3) assuming that the interpolation function between simple and fixed supports for BEP with flexible core for elastic buckling stresses is applicable to elastic–plastic buckling stresses. Despite complexity of the problem and simplification in the above mentioned transformation steps, the proposed analytical method is shown to be quite accurate by comparison against numerical simulation results using a validated ABAQUS model for a variety of BEP geometries (such as trabecular diameter, slenderness values of the compressive skin and the core layer) and different material properties as represented by Ramberg–Osgood model covering the entire spectrum of elastic buckling to plastic behaviour, with the maximum difference between the proposed analytical model and numerical simulation results being 7%.

Structural and thermal performance of a novel form of cladding panel: the I-beam beetle elytron plate

To develop a non-bearing prefabricated straw sandwich concrete wallboard (I-beam beetle elytron plate: IBEPsc), the effect of certain structural parameters (e.g. panel thickness, T, number of I-cores, N, and core height, h) on mechanical and thermal insulation performance was investigated using the finite-element method, with the following results. (a) Bearing capacity of the IBEPsc is controlled by the maximum principal tensile stress; the optimal structural parameters of the IBEPsc for a self-insulated wall with a large safety margin are presented. (b) The consideration of strips as opposed to whole plates and the selected upper bearing constraint type have little influence on the mechanical properties. In practical applications, the strips and whole plates can be reasonably selected according to engineering needs, and these components can be connected with the main structure by conventional mortar. (c) According to qualitative analysis and comparison with common I-shaped thermal insulation walls, the IBEPsc requires the least material and weight while ensuring a sufficient safety margin in terms of mechanical and thermal insulation performance. Hence, biomimetic techniques can play a key role in breaking through the limitations of traditional structures. This paper can help direct the application of beetle elytron plates in prefabricated wallboards.

Unveiling characteristic proteins for the structural development of beetle elytra

Beetles possess a set of highly modified and tanned forewings, elytra, which are lightweight yet rigid and tough. Immediately after eclosion, the elytra are initially thin, pale and soft. However, they rapidly expand and subsequently become hardened and often dark, resulting from both pigmentation and sclerotization. Here, we identified changes in protein composition during the developmental processes of the elytra in the Japanese rhinoceros beetle, Trypoxylus dichotomus. Using mass spectrometry, a total of 414 proteins were identified from both untanned and tanned elytra, including 31 cuticular proteins (CPs), which constitute one of the major components of insect cuticles. Moreover, CPs containing Rebers and Riddiford motifs (CPR), the most abundant CP family, were separated into two groups based on their expression and amino acid sequences, such as a Gly-rich sequence region and Ala-Ala-Pro repeats. These protein groups may play crucial roles in elytra formation at different time points, likely including self-assembly of chitin nanofibers that control elytral macro and microstructures and dictate changes in other properties (i.e., mechanical property). Clarification of the protein functions will enhance the understanding of elytra formation and potentially benefit the development of lightweight materials for industrial and biomedical applications. Statement of significanceThe beetle elytron is a light-weight natural bio-composite which displays high stiffness and toughness. This structure is composed of chitin fibrils and proteins, some of which are responsible for architectural development and hardening. This work, which involves insights from molecular biology and materials science, investigated changes in proteomic, architectural, and localized mechanical characteristics of elytra from the Japanese rhinoceros beetle to understand molecular mechanisms driving elytra development. In the present study, we identified a set of new protein groups which are likely related to the structural development of elytra and has potential for new pathways for processing green materials.

The effect of trabecular chamfers on the compressive ductility of beetle elytron plates

Beetle elytron plates (BEPs) are a type of sandwich structure inspired by the internal architecture of beetle elytra and characterized by trabeculae (tube structure) in the core. BEPs are categorized into two types, end- and middle-trabecular BEPs (EBEPs and MBEPs, respectively), according to the trabecular position. Both have been shown to possess superior compressive strength relative to conventional sandwich plates. To further improve the compressive ductility of the BEP, the mechanical effect of the trabecular chamfer inspired by the Allomyrina dichotoma beetle elytron is experimentally investigated. The results are as follows: 1) Only the EBEP stress-strain curve can form a plateau, which means better compressive ductility. 2) Various buckling modes are produced in BEPs with different β (ratio of core height to wall thickness) and ξt (ratio of chamfering radius to trabecular radius); however, the compressive ductility is significantly improved only when full global buckling deformation is generated in the core of the EBEP. 3) In the present condition, only when ξt is not less than 1.5, global buckling can be generated in EBEPs with a larger range of β, and the ductility improvement effect can also be better utilized. These results reveal the mechanism of the chamfering effect and parameter range previously found in Allomyrina dichotoma elytra, which facilitates further optimization of the compressive property of the BEP.