Impact Energy Absorption Research Articles

Numerical study of composite structures behavior under ballistic impacts

The aim of this paper is to introduce a finite element study of the behavior of composite plates subjected to ballistic impacts. The work studies different configurations of laminated composite structures, with and without reinforcements, subjected to high-speed projectile impacts (400-1000 m/s). The investigation focuses on the response of different composite materials' stacking sequences, as well as the impact of epoxy carbon reinforced with carbon nanotubes and the behavior of hybrid sandwich structures made of Kevlar epoxy and glass epoxy. The purpose is to develop a strategy of composite material damage modelling, identify the effects of multi material hybridization, and the influence of reinforcement by carbon nanotubes, on the structures' resistance to ballistic impacts. Numerical simulation provides a detailed description of plate damage. Results show that composite plates with 2% carbon nanotubes (CNT) displays a better impact energy absorption compared to 1% CNT and plates without CNT. The study also revealed the hybridization sequences offering the greatest energy absorption.

Characterization and optimization of TIG welding parameters for AISI 304 and AISI 316 stainless steel dissimilar joints

This study explores the impact of tungsten inert gas (TIG) welding parameters on the mechanical properties and microstructure of dissimilar welds between AISI 304 and AISI 316 austenitic stainless steels. Given the growing industrial demand for these materials, the research focuses on optimizing welding current, shielding gas flow rate, and voltage to enhance tensile strength, hardness, and impact toughness. Using the L9 orthogonal array based on Taguchi’s methodology, the experiments revealed that Relatively highs currents and voltages significantly improved the ultimate tensile strength (up to 673.67 MPa) and impact energy absorption (up to 36.5 J). Microstructural analysis indicated refined grain structures in the heat-affected zones, with pronounced grain growth in AISI 316 due to its thermal sensitivity. The micro-hardness analysis revealed that the highest hardness occurred in the HAZ of AISI 304, with samples 5 and 6 exhibiting the optimal hardness profile, reflecting the most favorable welding parameters. The study concludes that a current range of 80-90 A and a voltage range of 10-11 V and a shielding gas flow rate of 12-16 L/min provide optimal welding conditions, offering robust guidelines for industrial applications requiring high-performance dissimilar welds.

Dynamic damage behavior of auxetic textile reinforced concrete under impact loading

To investigate the dynamic compression behavior of Textile-reinforced concrete (TRC) under impact load, low speed and high speed impact tests were performed using a ball drop test and a split Hopkinson pressure bar (SHPB) with ϕ50mm, respectively. In view of the advantages of auxetic materials in impact resistance and energy absorption, the auxetic fiber preforms with negative Poisson's ratio effect were woven into meshes and added to the cement-based materials to obtain the auxetic textile-reinforced concrete. Thus, the auxetic textile reinforced cement-based material is obtained. In this paper, TRC with different textile types, laying layers and surface treatments were prepared, and impact tests with different impact speeds were carried out to evaluate the impact resistance of TRC. The impact damage behavior of TRC was analyzed through the method of digital scattering analysis, and then the impact damage mechanism of TRC was investigated. The results show that the auxetic effect of auxetic textiles can still be stabilized under impact loads of different velocities, which provides better control of deformation and energy consumption in the matrix material. Under different impact heights of falling balls, the impact fracture energy of cementitious materials reinforced with auxetic textiles was increased by up to 22.5 and 20 times, respectively, compared with that of blank samples.

Crushing responses and energy absorption characteristics of the dynamic stiffening porous material subjected to different strain rates

Porous material (PM) has excellent energy absorption performance and is widely used as an impact-energy absorber. However, the PM may provide little utility when the impact conditions change. Shear stiffening gel (SSG) with an extremely strong viscosity effect can be as a dynamic responding fortifier to overcome the limitation of PMs. In this paper, a rate-dependent, smart energy-absorbing material (SSG/PM) is fabricated by incorporating SSG that is reinforced with CaCO3 particles onto the PM. Aided by the dynamic compression experiments at the strain rate range of 0.001 to 100 s−1, both SSG/PM and neat PM are assessed and compared for crushing performance. Results reveal that the SSG/PM exhibits a pronounced dynamic stiffening characteristic in response to various strain rates owing to the rate-dependent phase transition of embedded SSG, thereby contributing to enhancing the PM skeleton's ability to withstand deformation. The SSG/PM displays a noteworthy boost in energy absorption (up to 831.98 %). Moreover, the influence of loading rate, particle mass fraction, and PM aperture size are also examined. The findings indicate that its crushing resistance and energy absorption capability are enhanced with the increase in strain rate, demonstrating the ability to adapt to various dynamic scenarios. The use of a higher particle mass fraction and smaller aperture size helps to improve the energy absorption capability of the SSG/PM. Additionally, quantitative energy analysis is implemented in which the energy dissipation mechanisms of the SSG/PM are attributed to the synergistic interaction of skeleton deformation, shear stiffening effects, and particle enhancement. It is ascertained that as the loading rate increases, the shear stiffening effect continues to strengthen; the particle content effect exhibits a rising-falling trend; while the skeleton deformation shows a rate-independent feature. This study sheds light on the crushing behaviors and corresponding energy dissipation mechanisms of SSG-based composites, thereby providing valuable insights for the design of SSG-based composites.

Low-velocity impact response and energy absorption of Menger sponge-inspired fractal structures fabricated by selective laser melting

An innovative cellular structure, the Menger Fractal Cube (MFC), is introduced and studied systematically for the first time for low-velocity energy absorption applications. Formed through a recursive process of removing smaller cubes from a larger one, the MFC exhibits a hierarchically repeating pattern of cubical voids, resulting in a lightweight and highly complex structure. MFCs of three orders were fabricated using Selective Laser Melting (SLM) with highly ductile AlSi7Mg material. These structures were subjected to dynamic compression tests at impact velocities of 5.7 ms−1, 8 ms−1 and 10 ms−1 corresponding to input energies of 100 J, 200 J and 300 J respectively, both experimentally and numerically. Results reveal a unique failure mode involving buckling, shearing, shear band localisation and tensile yielding, resulting in a smooth force response in the plateau region. In contrast to conventional cellular structures, MFC structures exhibit multi-stage yield platforms without force drops. Notably, higher-order MFCs demonstrate extensively improved load bearing, crashworthiness, and energy-absorbing properties under dynamic loading conditions. This study provides crucial insights for optimising Additive Manufacturing (AM) cellular structures for dynamic energy absorption scenarios, with implications for automotive, sports, aerospace, and defence applications.

Soft Magnetoelastic Tactile Multi-Sensors with Energy-Absorbing Properties for Self-Powered Human-Machine Interfaces.

Tactile sensors play a key role in human-machine interfaces (HMIs) for augmented and virtual reality, point-of-care devices, and human-robot collaboration, which show the promise of revolutionizing our ways of life. Here, we present a sensor (EMTS) that utilizes the magnetoelastic effect in a soft metamaterial to convert mechanical pressure into electrical signals. With this unique mechanism, the proposed EMTS simultaneously possesses self-powering, waterproof, and compliant features. The soft metamaterial is essentially a porous magnetoelastomer structure designed based on the Fourier series expansion, which allows for programmable mechanical response and sensing performance of the EMTS. Fabricated by simple 3D-printed molds, the EMTS also holds potential for low-cost production. Particularly, the porous magnetoelastomer structure comes with selectable buckling instabilities that can significantly enhance biomechanical-to-electrical energy conversion. Also, with the embedded magnetic microparticles, the energy-absorbing performance of the sensor is greatly improved, which is highly beneficial to HMIs. To pursue practical applications, the EMTSs are further integrated with two systems as control and perception modules. It is demonstrated that the EMTS is able to identify different hand gestures to control a lighting system even in a high-humidity environment. Also, the EMTS stands out for its superior capability of simultaneous impact perception and energy absorption in drop tests. Overall, with its compelling array of features, the presented EMTS gives impetus to multi-sensing technology and practically enables a variety of HMI applications.

Preparation, characterisation, physical, and compression testing of sucrose based closed-cell aluminium foam

ABSTRACT Aluminium foam can be used as a porous and lightweight material having comparatively high impact energy absorption. To reduce the death rate caused by collisions of vehicles, there is a need of analysing the crash-worthiness properties of materials. In this present work, the Aluminium foam was prepared using the powder metallurgy method for the crash-worthiness analysis. The Al6061 powder as a matrix material having particle sizes ranging from 5 to 30 µm and Sucrose particles as a space-holding material were mixed. The compaction process was done up to a pressure of 450 MPa to make the green compact and was further subjected to sintering up to a temperature of 500 °C for 1 hour resulting into the Aluminium foam. The compressive strength significantly decreased by 26.56%, 51.39%, 72.49%, and 64.34% approximately while volume fractions of sucrose particles varied as 20%, 30%, 40%, and 50%. On the other hand, the measured maximum porosity was found as 51.8% approximately in the Aluminium foam corresponding to the addition of 50% sucrose particles by volume. Out of all the examined samples, the foam developed by containing 20% (vol.) sucrose has exhibited the maximum strain energy absorption, specific energy absorption (SEA), and crushing force efficiency (CFE).

In-plane mechanical behavior design of triangular gradient rib honeycombs

Two types of triangular gradient rib honeycombs (Triangular gradient rib honeycomb-Type Z-AXBYs) were designed and proposed in this paper. A finite element numerical model was constructed using Abaqus/Explicit, with model accuracy verified, and a series of studies were conducted. Firstly, the mechanical properties of TCH, TGH, and two types of TGRH-Type Z-AXBYs under axial impact were analyzed. Results showed that the specific energy absorption (SEA) of TGH improved by 101.27 % compared to TCH; TGRH-Type I-170°-AXBYs SEA improved by up to 77.21 % compared to TGH; TGRH-Type II-180°-AXBYs SEA improved by up to 63.84 % compared to TGH. Adding a layer with a larger angle at the bottom of the honeycomb effectively improved the impact resistance and energy absorption of the structure. The mechanical properties of two types of TGRH-Type Z-θ-AXBYs with different layers were studied, showing that TGRH-Type I-θ-AXBYs had the best mechanical properties. TGRH-Type I-θ-AXBYs SEA improved by a maximum of 23.57 % compared to TGRH-Type II-θ-AXBYs and by a minimum of 13.71 %. TGRH-Type I-θ-AXBYs SEA improved by a maximum of 74.95 % and a minimum of 12.88 % compared to TGRH-Type I-θ-6X. Finally, the effects of wall thickness and velocity on the two types of TGRH-Type Z-AXBYs were analyzed. Properly increasing the wall thickness effectively improved the impact resistance of the structure. This paper provides a feasible reference for introducing a gradient ribbed plate design into triangular honeycombs to enhance their in-plane mechanical properties.

Mesoscopic finite-element prediction method for impact-energy absorption mechanism of multiphase STF/Kevlar composite fabric

Shear-thickening fluids (STFs) effectively enhance the impact-energy absorption of Kevlar fabrics and offer an extensive range of applications for human-safety protection. To precisely depict the impact-energy absorption mechanism and stress transfer behavior of multiphase STF/Kevlar composite fabrics under high strain rates, this study introduces a yarn-interface-friction constitutive model that accounts for the strain rate-thickening effect of STFs. The model is incorporated into a mesoscale numerical simulation to enhance computational accuracy. Theoretical models (impact-pit morphology, yarn-strain, and fabric-strain energy models) are employed to evaluate the off-plane displacement, strain distribution, and impact-energy absorption during impact imprint tests. The established simulation model shows high similarity (0.99) to the impact imprint profile curve and reveals that the strain energy and interfacial friction energy of the composite fabrics contribute primarily to energy dissipation during the impact process. Furthermore, in all specimens, C-STF/Kevlar (CNTs reinforced STF/Kevlar) exhibits reduced off-plane displacement, increased primary-yarn stress, and a higher capacity for impact kinetic-energy absorption. The proposed interface-friction constitutive model can accurately predict the deformation and energy absorption levels of the composite fabrics at various strain rates, thereby offering effective simulation guidance for the preliminary design of composite fabrics.

Effect of Low-Temperature Tempering Temperature on the Mechanical Properties of NM500 Wear-Resistant Steel

Abstract In order to explore the effect of low temperature tempering heat treatment temperatures on Brinell hardness (HB), impact absorption energy (KV2) and tensile mechanical properties of NM500 wear-resistant steel, isothermal tempering heat treatment of NM500 wear-resistant steel sheets after quenching were carried out at 200~260 °C. The microstructures, Brinell hardness, -20 °C impact energies and tensile mechanical properties of NM500 wear-resistant steel after tempered were analyzed by optical microscope, Brinell hardness tester, pendulum impact testing machine and tensile testing machine respectively. The results show that when the tempering temperature increases from 200 °C to 260 °C, the Brinell hardness of NM500 wear-resistant steel decreases from 490 HBW to 460 HBW, the offset yield strength (Rp0.2) decreases from 1396.3MPa to 1351.0MPa, and the tensile strength (Rm) decreases from 1708.5 MPa to 1615.0 MPa. However, the low temperature tempering temperature has no significant effect on the microstructure and elongation after fracture. According to GB/T 24186-2022, 200~220 °C is the suitable low temperature tempering temperature range for NM500 wear-resistant steel.

Effect of wood varnish coating on the water absorption and mechanical properties of jute fiber reinforced epoxy composites

Natural fiber-reinforced composites are becoming popular day by day because of their low cost and renewable nature. However, a major concern of these composites is water absorption. To minimize the water absorption in natural fiber-reinforced composites, wood varnish coating was used in this paper to investigate the effect of this coating on water absorption and mechanical properties of jute fiber-reinforced composites. Four types of composites were fabricated using the hand lay-up technique, among them on Type 1 no coating was used, Type 2 was surface coated, Type 3 was fiber coated and Type 4 was both fiber and composite surface coated. Water absorption, tensile, bending, short beam shear, and impact tests were performed on the composite specimens according to their respective ASTM standards to see the effect of coating. Both fiber and fracture surface morphology were observed using Scanning Electron Microscope. It was found that the water absorption was significantly reduced for Type 2 (50.31 %) and Type 4 (56.01 %) specimens. However, the tensile strength and bending strength were reduced by 74.17 %, and 72.71 % for Type 3 and 77.07 % and 84.24 % for Type 4 composites while for Type 2, they were slightly increased (7.26 % and 1.13 %). The ILSS of Type 3 and Type 4 were reduced by 69.34 % and 58.07 % respectively while it was reduced by only 4.49 % for Type 2 composite. On the other hand, the impact energy absorption was increased by 85.32 % for Type 4 composite. The findings of this study suggest that Type 2 composite (only composite surface coating) has the overall best performance and wood varnish coating has the potential to reduce the water absorption on natural fiber-reinforced composites.

Impact characteristics of S2-glass fibre/FM94-epoxy composites under high and cryogenic temperatures: Experimental and numerical investigation

The aerospace industry uses glass fibre reinforced polymer (GFRP) composites to manufacture structural and non-structural parts of an aircraft as they possess superior strength to weight ratio and exceptional corrosion resistance. Commercial aircraft operate in a very wide temperature ranges from −54 to 55 °C. Potential GFRP laminates are susceptible to impact during aircraft operation, and the temperature at impact governs the nature of damage and failure mechanisms. As a result, the current study focuses on examining how aeronautical GFRP composites behave in various temperature environments that are encountered during high- and low-altitude operations. Using S2-glass fibre/FM94-epoxy unidirectional prepreg, GFRP plates were created. Drop weight impact tests were conducted at ambient (25 °C), high (50, 75, 100 °C), and low (−25, −55 °C) temperatures, as well as at various impact energies (75, 150, 225 J). The damages were assessed visually, along with their sizes. Each testing scenario's impact parameters, including the impact load, deflection, and energy absorption, were also examined. In Abaqus/Explicit, a coupled temperature-displacement numerical model was created to predict the onset of stress and damage. According to experimental findings, GFRP plates are stiffer and show less apparent damage at cryogenic temperatures (∼15−34 % lower displacement) than they do at other temperatures. Furthermore, it was observed that the matrix softens at high temperatures, showing larger damaged area at entry but with less obvious damage and increasing energy absorption, while semi-perforation occurred under cryogenic temperatures at entry with smaller damaged area. A strong correlation is shown between the experimental and FE data, confirming the capability of FE models to predict impact damage and deflections at different temperatures in the future.

Impact resistance and energy absorption characteristics of nickel-based alloy ring at elevated temperatures

To evaluate the high-temperature containment capability of a turbine casing, the impact resistance of half-ring specimens and full circular casings made of GH4169 nickel-based alloy was investigated. Ballistic impact tests were first conducted on GH4169 half-ring specimens using blade-shaped projectiles of DZ125 material fired from a single-stage gas gun. Meanwhile, explicit finite element simulations of the half-ring impact tests were performed with LS-DYNA. Comparing experimental and simulation results validated the accuracy of the model and revealed the effects of impact angle and ambient temperature. Then the process of a turbine casing containing a blade at 500 °C was simulated using the validated FE model. The results showed that the impact angle and the ambient temperature significantly affect the impact resistance of GH4169 half-ring specimen. Furthermore, the interaction mechanism between the turbine blade and casing differs across the three stages of the containment process.

Comprehensive performance evaluation of HGM hybrid modified resins: Excellent high resistivity terahertz shielding and impact energy absorption properties

AbstractThe development of electronic fuze has placed higher demands on encapsulation resins, which are required to provide not only insulation and protection, but also higher impact resistance and good electromagnetic shielding performance. A new composite material consisting of hollow glass microspheres (HGM) and modified epoxy resin was developed. This material exhibits significant electromagnetic shielding capabilities for terahertz (THz) waves, as well as superior impact energy absorption properties. Bisphenol A‐type epoxy resin (E‐44) was modified using Al(OH)3, red phosphorus, carbon black, and SiO2, and the material properties were optimized by adjusting the HGM content. The electromagnetic shielding effectiveness and impact energy absorption of the composite material in the THz band were comprehensively tested using THz time‐domain spectroscopy and split Hopkinson pressure bar testing systems. Additionally, a comprehensive evaluation of the mechanical and dielectric properties, thermal conductivity, and thermal stability of the material was conducted. The results showed that the electromagnetic shielding effect of 60 vol.% HGM hybrid‐modified resins was the best, reaching 43.78 dB. The 20 vol.% HGM hybrid‐modified resins not only has a specific absorption energy of 18.51 J/cm3, but also has the best overall performance. This work has advanced the design and development of multifunctional and impact‐resistant potting epoxy resins.

Optimizing an auxetic metamaterial structure for enhanced mechanical energy absorption: Design and performance evaluation under compressive and impact loading

Auxetic metamaterials, characterized by their negative Poisson’s ratio, offer promising prospects for utilization in absorbing energy during quasi-static compressive loading as well as in applications requiring impact energy absorption. The optimization of auxetic structures’ geometrical parameters can improve their performance. This research aims to optimize the design of an auxetic structure for maximum specific energy absorption and investigate its behavior under quasi-static compressive and high-velocity impact loading. The geometrical parameters of the cross-petal auxetic structure are optimized using genetic algorithm and a neural network surrogate model. The behavior of the optimized auxetic structure is examined in quasi-static compressive loading and compared with that of the basic auxetic structure using finite element simulations. The optimized auxetic structure is then evaluated in high-velocity impact loading as the core of a sandwich panel, with two plates placed in the front and rear. Simulations of projectile impacts at velocities ranging from 100 to 250 m/s reveal the sandwich panel’s behavior. Results indicate a 69.82% increase in specific energy absorption capacity for the optimized auxetic structure as compared to the basic structure in quasi-static compressive loading. In high-velocity impact, the sandwich panel with the optimal auxetic core outperforms the one with the basic core. At velocities more than the minimum perforation velocity, the core contributes about 64%–67% of the total absorbed energy by the sandwich panel.

Effects of Diamond Content on the Morphology and Compressive Properties of Porous Aluminum Composites.

Porous aluminum (Al) is popular due to its lightweight properties and impact energy absorption. However, it often has a lower mechanical strength than solid Al. To improve the performance, diamond reinforcement was introduced into the matrix. Further, addressing the challenge of interfacial bonding between Al and diamond, coated diamond with varying contents of 5, 10, 15, and 20 wt % was added to the porous Al alloy matrix via the powder metallurgy technique. The porosities were formed by using poly(methyl methacrylate) (30 wt %) as a space holder. The densities of the resultant porous composites ranged from 2.20 to 2.37 g/cm3 and porosities ranged from 33 to 38% for 5-20 wt % diamond contents. Furthermore, the yield strength and plateau stress increased from 21.47 to 29.46 MPa and 14 to 20 MPa, respectively, up to 10 wt % diamond content but declined upon further addition. Similarly, the energy absorption capacity increased from 2.15 to 2.95 MJ/m3 up to 10 wt % diamond content and thereafter decreased. Thus, the addition of coated diamond and alloying elements in Al strengthened the porous Al composites, making it suitable for applications requiring good compressive strength and energy absorption capacity.

Effects of Rubber Core on the Mechanical Behaviour of the Carbon-Aramid Composite Materials Subjected to Low-Velocity Impact Loading Considering Water Absorption.

The large-scale use of composite materials reinforced with carbon-aramid hybrid fabric in various outdoor applications, which ensures increased mechanical resistance including in impact loadings, led to the need to investigate the effects of aggressive environmental factors (moisture absorption, temperature, thermal cycles, ultra-violet rays) on the variation of their mechanical properties. Since the literature is still lacking in research on this topic, this article aims to compare the low-velocity impact behaviour of two carbon-aramid hybrid composite materials (with and without rubber core) and to investigate the effects of water absorption on impact properties. The main objectives of this research were as follows: (i) the investigation of the mechanical behavior in tests for two impact energies of 25 J and 50 J; (ii) comparison of the results obtained in terms of the force, displacement, velocity, and energy related to the time; (iii) analysis of the water absorption data; (iii) low-velocity impact testing of wet specimens after saturation; (iv) comparison between the impact behaviour of the wet specimens with that of the dried ones. One of the main findings was that for the wet specimens without rubber core, absorbed impact energy was 16% less than the one recorded for dried specimens at an impact energy of 50 J. The failure modes of the dried specimens without rubber core are breakage for both carbon and aramid fibres, matrix cracks, and delamination at matrix-fibre interfaces. The degradation for the wet specimens with rubber core is much more pronounced because the decrease in the absorbed impact energy was 53.26% after 10,513 h of immersion in water and all the layers were broken.

Impact resistance of polyurethane elastomer enhanced by organic montmorillonite with interlayer anchored polymer chains

AbstractThe development of materials with excellent impact resistance is essential for safety protection. Polyurethane elastomer (PUE) is widely used in impact protection; however, it has low dynamic compressive strength and poor energy absorption efficiency under high‐speed impact, limiting its in‐depth application in the protection field. Herein, an organic montmorillonite (MMT) with interlayer anchored polymer chains, named M@NH3+, was synthesized via the dual modification of MMT involving surface grafting and cation intercalation by macromolecular amino silane, which was used to enhance the impact resistance of PUE. Based on the uniform dispersion of M@NH3+ within the PUE matrix, the strong bonding at the polymer‐filler interface and the synergistic action between M@NH3+ lamellae, PUE‐M@NH3+ composite exhibited excellent mechanical properties and energy absorption capacity. Compared with pure PUE, the elastic modulus (+98.3%), static compressive strength (+37.0%), dynamic compressive strength (+35.4%) and impact energy absorption (+50.8%) of PUE‐2wt%M@NH3+ were significantly improved, which shows that it has potential applications in the field of high‐speed impact protection.Highlights Organic MMT with interlayer anchored polymer chains was prepared. The large interlayer spacing of M@NH3+ facilitates its dispersion within the matrix. The interconnected M@NH3+ lamellae can collaboratively disperse impact stress. The impact energy absorption of PUE composite has been remarkably improved.

Cushioning property and structure optimization of double-arrow sandwich composite based on modified genetic algorithm

Owing to the ability of negative Poisson’s ratio (NPR) structures in enhancing the stiffening effectof shear stiffening gels (SSG), combining the two in cushioning applications has attracted much attention. This paper presents the design of NPR flexible cushioning sandwich composites featuring a double-arrow structure (DAS). The DAS is optimized using a modified genetic algorithm, and the cohesive property is leveraged to reinforce the stiffening effect of SSG, thereby improving the material’s cushioning efficiency. The synergistic effect of the DAS and SSG and the law of SSG arrangement on the energy absorption efficiency of cushioning were revealed using the finite element method and experiment. It can be found that the size effect of the DAS significantly contributed to the enhancement of the energy-absorption efficiency of the SSG stiffening. In double-arrow sandwich composite (DASC), the larger reversed-triangle deformation and the increased number of reversed-triangle configurations, amplified the shear stiffening of the SSG, improving the impact load dissipation and energy absorption efficiency of sandwich composite. The energy absorption efficiency of the DASC was improved owing to the synergistic effect of the DAS cohesive effect and the SSG stiffening properties, with the energy absorption ratio and mass specific energy absorption increased by 83.02% and 136% compared to neat polyurethane. The DASC optimized in this study has good flexibility and energy absorption capacity and is promising for application in the field of flexible protection.

Coupling Chiral Cuboids with Wholly Auxetic Response.

Auxetic materials have been extensively studied for their design, fabrication and mechanical properties. These material systems exhibit unique mechanical characteristics such as high impact resistance, shear strength, and energy absorption capacity. Most existing auxetic materials are two-dimensional (2D) and demonstrate half-auxetic behavior, characterized by a negative Poisson's ratio when subjected to either tensile or compressive forces. Here, we present novel three-dimensional (3D) auxetic mechanical metamaterials, termed coupling chiral cuboids, capable of achieving negative Poisson's ratio under both tension and compression. We perform experiments, theoretical analysis, and numerical simulations to validate the wholly auxetic response of the proposed coupling chiral cuboids. Parametric studies are carried out to investigate the effects of structural parameters on the elastic modulus and Poisson's ratio of the coupling chiral cuboids. The results imply that the Poisson's ratio sign-switching from negative to positive can be implemented by manipulating the thickness of Z-shaped ligaments. Finally, the potential application of the coupling chiral cuboids as inner cores for impact-resistant sandwich panels is envisioned and validated. Test results demonstrate a remarkable 49.3% enhancement in energy absorption compared to conventional solid materials.