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Plate-based lattice structures are an emerging category of mechanical metamaterials with exceptional mechanical performance. In this work, plate-based SCFCC metamaterials of AlSi10Mg with various relative densities are fabricated by laser powder bed fusion (LPBF). Circular holes are strategically designed and placed at the center of each non-load-bearing face for residual powder removal. Quasi-static compression experiments and numerical simulations are performed to investigate their mechanical performance and deformation mechanisms. Results indicate that the elastic modulus of SCFCC metamaterials decreases by 3.5% with the presence of 0.9 mm diameter holes, while increasing the hole size shows negligible impact on the elastic modulus. The novel plate-based SCFCC structure exhibits superior mechanical properties and enhanced energy absorption capacity concerning conventional high-stiffness truss-based and shell-based counterparts. The improvement, at the relative density of 0.2, can be observed in terms of elastic modulus (around 50%), peak compressive strength (around 300%), energy absorption capacity (around 400% or 200%). When increasing the relative density from 0.2 to 0.5, plate-based SCFCC metamaterial still maintains superior mechanical performance while the gaps between SCFCC and its counterparts narrow down gradually owing to the loss of structural features. Moreover, mechanical characteristics and coefficients of three Gibson and Ashby analytical equations are determined. This work proposes a novel type of plate-based structure with both exceptional mechanical performance and good additive manufacturability, which opens a new avenue for the design of lightweight mechanical metamaterials.

In this article, the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes. 3D printing technology was utilized to create the hollow centers of the tapering tubes, with and without corrugations. The results demonstrate that the energy absorption (EA) and specific energy absorption (SEA) of the single corrugated tapered tube sandwich are 51.6% and 19.8% higher, respectively, than those of the conical tube sandwich. Furthermore, the results demonstrate that energy absorbers can benefit from corrugation in order to increase their efficiency. Additionally, the tapered corrugated tubes’ resistance to oblique impacts was studied. Compared to a straight tube, the tapered tube is more resistant to oblique loads and has a lower initial peak crushing force (PCF), according to numerical simulations. After conducting a parametric study, it was discovered that the energy absorption performance of the sandwich construction is significantly affected by the amplitude, number of corrugations, and wall thickness. EA and SEA of DTS with corrugation number of 8 increased by 17.4% and 29.6%, respectively, while PCF decreased by 9.2% compared to DTS with corrugation number of 10.

Defense mechanisms remain important and indispensable due to the different types of pistols and ordnance besides many guns. Hybrid composite sandwich panels are an attractive focus because of their ingrained characteristics, such as high stuffiness and high energy absorption. Hybrid composite sandwich panels are among the most important in armoring various structures. Despite the high density of these panels, they have significant qualities that qualify them to be the first selection for use in armored vehicles or body armor. Recently, there have been several types of structures, and selecting the appropriate structure as armor against the projectiles is very important. The study subjected three samples to the ballistic impact test using a 7.62 × 39 mm bullet. The first sample, S1, consists of ultra high molecular weight polyethylene (UHMWPE)/epoxy, unfilled honeycomb core, Kevlar/epoxy, unfilled honeycomb core, Kevlar/epoxy, and UHMWPE/epoxy; the second sample, S2, comprises Kevlar/epoxy, unfilled honeycomb core, Kevlar/epoxy, unfilled honeycomb core, and UHMWPE/epoxy, and the third sample, S3, comprises Al2O3, Kevlar/epoxy, unfilled honeycomb core, carbon/epoxy, unfilled honeycomb core, and carbon/epoxy. ABAQUS software was used to evaluate the ballistic impact numerically, and after that, the study examined the same armor samples experimentally. The results manifested that only the armor S3 succeeded in stopping the bullet. This is attributed to the structure of the cores, which helps compress and accumulate the cells under the projectile. The speeds of the bullet after penetration (residual velocity; VR) were 748.5 and 715.3 m/s for S1 and S2 armors, respectively, where the back face signature for S3 was 1.5 mm, which is optimum and within the allowed range. The total energy absorption of these armors S1, S2, and S3 is 344.65, 539.04, and 2585.66 J. Furthermore, the highest deviation between numerical and experimental approaches is about 2.04% in the VR.

Developing a reliable and robust finite element model of a carbon fiber-reinforced plastic (CFRP) composite structure is investigated by using the LS-DYNA solver and Python. This study tries to provide a systematic numerical approach to cover the principal impediment to adaptation of composite energy absorbers, that is the lack of a reliable predictive method. The proposed procedure aims to further the understanding of advanced composite structures' behavior during the crash phenomenon by developing an accurate finite element model. To do so, the mechanical properties of the material were extracted from American Society for Testing and Materials (ASTM) standard test methods, followed by experimental investigation of circular CFRP tubes undergoing quasi-static loading. A numerical simulation framework was then utilized to scrutinize the effectiveness of simulation parameters on the crushing mechanism. Finally, a systematic approach based on machine learning techniques was performed to adjust non-physical modeling parameters for further calibration and validation. In this regard, a versatile Python code was developed to automate pre-processing, processing, and post-processing steps. The code also provides a groundwork to perform machine learning techniques. Interestingly, the numerical and experimental results were highly correlated with a correlation coefficient of almost 90%. Additionally, several non-physical numerical parameters were found to be inactive, while some else were identified as effective parameters, and their corresponding effectiveness was quantitatively extracted and discussed for the first time in the literature. [ABSTRACT FROM AUTHOR]

The objective of the study is to evaluate the performance of solid cellular structures in Polylactic Acid (PLA) by extrusion of material. The structures studied are Strut-Based, Triply Periodic Minimal Surfaces (TPMS) and Spinoidal. Impact tests allowed the identification of three categories of energy absorption (low, medium, high). The structures with lower deformation were subsequently subjected to cyclic impact tests, while the others were discarded from the analysis. Once the structures were deformed, they were immersed in a thermostat bath at 70 ºC, a temperature higher than the glass transition of PLA, necessary for the recovery of shape. TPMS structures display the best performance for high and medium impact energies, thanks to the presence of few internal defects. Spinoidal structures perform well at low impact energies but are less suitable for cyclic testing due to their geometric characteristics. Despite featuring the same density of TPMS structures, the strut based ones are not suitable for cyclic testing due to poor mechanical strength. The experimental findings are very promising as the best performing structures can be suitable for the fabrication of products with an increased life cycle, especially in the ever growing and flourishing market of technical items for impacts protection. [ABSTRACT FROM AUTHOR]

In this study, oil palm empty fruit bunch (OPEFB)-reinforced composites were subjected to a low-velocity impact test to study their energy absorption characteristics. Two sets of OPEFB-reinforced composite specimens were used, comprising 30:70 and 40:60 fiber/epoxy fractions. One set of specimens was treated with a 3% NaOH solution. The drop impact responses, fragmentation characteristics, energy absorptions, and residual strengths of both sets of specimens were analyzed. Drop impact tests were performed using three different energy levels, namely, 10, 13, and 16 J. In general, the results indicated that all the untreated specimens absorbed higher energy than that of the treated specimens, thus suffering severe surface and structural damage. This result is attributed to the treated specimens providing a better interlocking mechanism between the matrix and fibers and dissipating the impact energy through the impactor. Regarding fiber loading, all the 30:70 fiber/epoxy composites exhibited slightly less energy absorption than the 40:60 fiber/epoxy composites. [ABSTRACT FROM AUTHOR]

The honeycomb sandwich panel presents a highly promising solution for enhancing ballistic behavior owing to its excellent strength-to-weight ratio and impact resistance. This study focuses on investigating the shock mitigation properties of honeycomb sandwich panels through experimentation and numerical simulation of high-velocity impact tests. Single-scale and double-scale hierarchical honeycomb cores are manufactured using selective laser melting with AlSi10Mg powder, combined with a pair of stainless steel (SS 316) sheets. High-velocity impact experiments were conducted within a velocity ranging from 100 to 270 m/s to examine the effects of different cores and projectile nose shapes on the dynamic response of the panels. Numerical simulations using ABAQUS/Explicit software were performed and validated against the experimental results. The sandwich panel with a double-scale hierarchical honeycomb core exhibited 7.8% and 6.1% more energy absorption compared to the single-scale hierarchical honeycomb core against conical and hemispherical nose projectiles, respectively. Additionally, the ballistic limit for the hemispherical projectile was found to be 8.9% higher than the conical-nose projectile under the same impact velocity and panel thickness. Moreover, an increase in panel thickness from 12 mm to 25 mm prompted a significant improvement of approximately 39% in specific energy absorption and a 44% increase in ballistic limit velocity. These findings highlight the considerable potential of single-scale and double-scale hierarchical honeycomb sandwich panels for the development of threat-resistant structures in critical dynamic loading applications. [ABSTRACT FROM AUTHOR]

Aluminum foam sandwich (AFS) are widely used in energy absorption because of their light weight and excellent energy dissipation capabilities. In this study, energy absorption, deformation modes, and dynamic response of AFS under low-velocity impact are investigated using experimental and numerical approaches. Dynamic impact tests are performed utilizing a drop hammer impact test on AFS with different core densities, face sheet thicknesses, and impact energy. Based on the 3D Voronoi foam model, a full-scale finite element model (FEM) is developed to simulate the mechanical response of AFS under low-velocity impact, and verified by experimental results. The contributions of different AFS components to energy absorption at various impact velocities are further analyzed, along with the effects of face sheet thickness distribution. The results indicate that the performance of the face sheet and core and the impact energy have a remarkable influence on the low-velocity impact response and damage modes of the AFS. The type of structure configuration, "thin top and thick bottom," enables the AFS better play its energy absorption while ensuring the overall light weight. This study provides a reference for the design and optimization of the face sheet thickness of AFS when it is used as an energy-absorbing member and improves their design efficiency. [ABSTRACT FROM AUTHOR]

This study aimed to improve the energy absorption capabilities of auxetic structures, which are used in sandwich structures in engineering. To achieve this, the study used a combination of CFRP and aluminum materials in a hybrid double arrow-head auxetic (DAHA) structure. This paper conducted experiments and simulations to analyze the mechanical properties of the hybrid DAHA structures and found that the mixture ratio of hybrid material, ply angles of CFRP laminates, and inclination angles of beams significantly influenced the energy absorption performance of the structures. Additionally, the proposed hybrid DAHA structures outperformed other control groups when the thickness ratio of CFRP was 75%. The inclination angles of beams also affected the energy absorption capacity by changing the structural void of DAHA structures. These findings offer new insights into enhancing the energy absorption capacity of hybrid auxetic structures. The proposed hybrid structures can absorb more energy by 56.4% with a lower peak crushing force comparing with the traditional metal auxetic structure. Therefore, the CFRP/Aluminum hybrid auxetic structure has a bright future in the energy absorption fields. [ABSTRACT FROM AUTHOR]

Highlights Additive manufacturing (AM) involves the development of complex, lightweight sandwich structures for the automotive and aerospace industries. These structures are essential for load bearing and impact resistance. Nevertheless, there is a significant obstacle of failure under compressive loading, e.g. through brittle fractures and crushing. To address this issue, this study evaluates the compressive properties, energy absorption and failure damage in quasi‐static tests (flatwise, in‐plane, and flexural) of sandwich composites with 3D‐printed hexagonal honeycomb cores of different unit cells (6, 8 and 10 mm) and materials (polylactic acid (PLA), PLA‐Carbon and PLA‐Wood). The results show that increasing the core density enhances compressive strength, modulus, and energy absorption. An 8 mm unit cell absorbs energy optimally for lightweight structures. In PLA flatwise testing, the 8 mm unit cell absorbed 419.49 J more energy than the 10 mm unit cell. Additionally, PLA‐Wood has better mechanical performance than PLA‐Carbon due to the better filler with the PLA‐ matrix. In flatwise testing with an 8 mm unit, PLA‐Wood absorbs 214.01 J, while PLA‐Carbon absorbs 122.49 J. The failure modes vary depending on tests performed. The study highlights the potential of 3D‐printed honeycomb core structures for load‐bearing applications in various industries, including aerospace and automotive. Quasi‐static loading behavior of 3D‐printed hexagonal honeycomb cores. Increased core density improves compressive stress, modulus, and absorbed energy. An optimal unit cell size for lightweight 3D printed core structures is 8 mm. PLA‐Wood performs better in energy absorption due to filler compatibility. The failure modes are related to the type of quasi‐static loads applied. [ABSTRACT FROM AUTHOR]

AbstractTo improve energy absorption and efficiency and develop a structure with outstanding energy absorption capability, this study proposed designing multi-cell tubes filled with triply periodic minimal surface (TPMS) lattices. Based on experimental and simulation methods, the crashworthiness of multi-cell tubes filled with three types of TPMS lattices (Diamond, Gyroid, and Primitive) was investigated. Five multi-cell tube structures were fabricated by increasing the thin-walled tube corner units, improving the energy absorption efficiency by 67.98%. The results show that due to the coupling between TPMS lattices and thin-walled tubes, multi-cell tubes filled with TPMS lattices exhibited better crashworthiness performance. The energy absorption of multi-cell tubes filled with Diamond, Gyroid, and Primitive lattices increased sequentially. The energy absorption per unit mass and energy absorption capability were most notably enhanced for the multi-cell tubes filled with Diamond lattice, with energy absorption efficiency 17.24% higher and energy absorption 104.26% greater than empty multi-cell tubes. This inspires crash designs of rail vehicles and automotive fronts. [ABSTRACT FROM AUTHOR]

Nowadays, hybrid structures, which combine low‐density composites with low‐cost thin‐walled metals, have shown great effect in enhancing the performance of automotive body structures, especially the energy absorber components. This study focuses on the experimental and numerical investigation of the bending energy absorption behavior of CFRP/aluminum hybrid double hat‐section beams used in the side part of the car body. In the experimental section, two types of double hat‐section beams were fabricated: aluminum and Al/CFRP. These beams were then subjected to quasi‐static three‐point bending tests. The results demonstrated that the hybrid beam exhibited superior energy absorption capabilities compared to the single beam. Subsequently, a finite element model was developed using LS‐Dyna software and was validated by comparing the experimental and numerical load–displacement results. In‐depth numerical analyses were conducted to investigate the influence of various design parameters, including CFRP‐reinforcement configuration, numbers of CFRP layers, CFRP ply‐angle, CFRP reinforced length, and aluminum/CFRP mass, on crashworthiness indicators. The numerical findings indicate that the hybrid beam with 04, 45/−45s ply‐angles exhibited better crash force efficiency (CFE) and specific energy absorption (SEA) compared to other ply‐angles, respectively. Furthermore, increasing the number of CFRP layers within the total beam's mass improved its energy absorption capacity. It was also revealed that the CFRP length on the upper and lower hats could be considered as 42.5% of the total aluminum beam length, as opposed to the full CFRP length, providing enhanced energy absorption capabilities. Highlights: Bending behavior of the Al and Al/CFRP double hat section beams.Effects of variable thickness and identical mass on the double hat section beam.Effects of variable ply angle and number of CFRP layers on the hybrid beams.Discrete effect of CFRP reinforcement configurations and inner CFRP lengths. [ABSTRACT FROM AUTHOR]

Manufacturing and investigating metallic‐glass‐fiber‐reinforced epoxies is an important new attempt to present their potential to contribute to the aviation industry. In order to explore the energy absorption in novel CoFeSiB metallic‐glass‐fiber/epoxy resin composites, CoFeSiB/epoxy resin composite cylinders with different fiber volume fractions were prepared by a hot‐pressing method. The amorphism of the metal fibers was analyzed using x‐ray diffraction. The quasi‐static compression tests were performed on different fiber oriented samples with a diameter of 3.6 mm and a height of 7.2 mm. The sample with the fiber orientation [0°/90°] has a higher energy absorption capacity, compared to the one with the fiber orientation [0°/0°]. The dynamic‐ compression tests were performed on the [0°/0°] samples with a diameter of 3 mm and height of 6 mm at different air pressures. The compression fracture surfaces were examined by scanning electron microscope. Then the energy absorption mechanism of the composites was investigated. This study is of great significance for the energy absorption in amorphous metal fiber/epoxy composites. [ABSTRACT FROM AUTHOR]

In this research, a new series of bioinspired multicell tubes was designed based on the cross-sectional patterns of square bamboo and optimized to enhance energy absorption under multiple loads. A data-driven model was proposed to efficiently design and optimize structures with improved energy absorption performance under axial and oblique crushing scenarios simultaneously. Furthermore, the influence of design parameters on energy absorption performance was extensively investigated. Results demonstrated that the energy absorption performance of the optimized structures under axial and oblique loads was considerably improved compared with the performance of the original and reference tubes. Under axial load, the highest enhancements in specific energy absorption (SEA) and crush force efficiency (CFE) were 133.58 % and 20.21 %, respectively. Under oblique load, the improvements in SEA and CFE were 108.78 % and 23.65 %, respectively. This study introduced an efficient data-driven model for designing and optimizing energy absorption structures under multiple loads. This optimized structure shows great potential for use in energy absorption devices. [ABSTRACT FROM AUTHOR]

This paper investigates the energy absorption capacities of selected cellular topologies under quasi-static loading conditions. Twenty topologies with nearly identical relative densities belonging to 4 groups were examined: honeycomb, re-entrant, bioinspired and chiral. The topologies were modeled using an experimentally validated numerical ABSplus model and subsequently subjected to in-plane uniaxial compression tests. The findings revealed the topologies with the most favorable energy absorption parameters and the main deformation mechanisms. The topologies were classified by mechanism, and a parametric study of basic material properties, namely modulus of elasticity, yield stress, and ductility, was performed for a representative topology from each mechanism. The results indicated that the honeycomb group topologies were characterized by the largest average absorbed energy, and yield stress was found to have the greatest impact on energy absorption efficiency regardless of the main deformation mechanism. [ABSTRACT FROM AUTHOR]

Although there are constant improvements in wave energy converter (WEC) technology, it is crucial to investigate site-specific sea conditions for optimal power absorption and efficiency. This study compares the efficiency of a floating buoy-type WEC device, with three differently shaped floats: a semi-sphere, a cylinder considered suitable for a location near Ensenada, on the Baja California peninsula, and a novel, rounded, semi-rectangular float. A statistical analysis of the wave climate of the last 42 years was performed to define the conditions to which the device is subjected. The WEC location was chosen for shallow waters, using a computational model that solves the modified mild slope equation. The hydrodynamic response of the three float designs was then analyzed in the frequency and time domains, using the software ANSYS AQWA 19.2, to assess the dynamics of the floating body, the forces exerted, and the power absorbed, as well as the suitability of the proposed power take-off (PTO) system. The findings show that the proposed float design absorbs the most energy, with an annual power of 135.11 MW, and that the PTO mechanism is appropriate. [ABSTRACT FROM AUTHOR]

To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static compression, low-speed impact, high-speed impact, and non-destructive tests. The mechanical properties and energy absorption capacities of the impact-resistant panels, featuring ceramic/ultra-high molecular-weight polyethylene (UHMWPE) and carbon fiber/PMI foam structures, were evaluated and compared, and the feasibility of using the latter as a raw material for personal impact-resistant equipment was also evaluated. For the PMI sandwich panel with a constant total thickness, increasing the core layer density and face/back layer thickness enhanced the energy absorption capacity, and increased the peak stress of the face layer. Under a constant strain, the energy absorption value of all specimens increased with increasing impact speed. When a 10 kg hammer impacted the specimen surface at a speed of 1.5 m/s, the foam sandwich panels retained better integrity than the ceramic/UHMWPE panel. The results showed that the carbon fiber/PMI foam sandwich panels were suitable for applications that require the flexible movement of the wearer under shock waves, and provide an experimental basis for designing impact-resistant equipment with low weight, high strength, and high energy absorption capacities. [ABSTRACT FROM AUTHOR]

Periodic truss-based lattice materials, a particular subset of cellular solids that generally have superior specific properties as compared to monolithic materials, offer regularity and predictability that irregular foams do not. Significant advancements in alternative technologies—such as additive manufacturing—have allowed for the fabrication of these uniquely complex materials, thus boosting their research and development within industries and scientific communities. However, there have been limitations in the comparison of results for these materials between different studies reported in the literature due to differences in analysis approaches, parent materials, and boundary and initial conditions considered. Further hindering the comparison ability was that the literature generally only focused on one or a select few topologies. With a particular focus on the crashworthiness of lattice topologies, this paper presents a comprehensive study of the impact performance of 24 topologies under dynamic impact loading. Using steel alloy parent material (manufactured using Selective Laser Melting), a numerical study of the impact performance was conducted with 16 different impact energy–speed pairs. It was possible to observe the overarching trends in crashworthiness parameters, including plateau stress, densification strain, impact efficiency, and absorbed energy for a wide range of 3D lattice topologies at three relative densities. While there was no observed distinct division between the results of bending and stretching topologies, the presence of struts aligned in the impact direction did have a significant effect on the energy absorption efficiency of the lattice; topologies with struts aligned in that direction had lower efficiencies as compared to topologies without. [ABSTRACT FROM AUTHOR]

Due to their high load-bearing capacity and excellent energy dissipation properties, metal honeycomb lightweight sandwich panels are commonly utilized as highly efficient weight-saving components in the automotive, aerospace, and military industries. Especially the auxetic honeycomb sandwich panels have higher yield strength, more robust shear modulus, fracture toughness, less fatigue expansion, and higher vibration and energy absorption. In this paper, the ballistic resistance and energy absorption mechanisms of a novel re-entrant auxetic honeycomb (RSH) sandwich panel are investigated. The ballistic limits and energy absorption of the re-entrant star-shaped honeycomb (RSH), star-shaped honeycomb (SSH), and re-entrant star-shaped honeycomb (RH) sandwich panels are compared and analyzed, as well as the deformation mechanism during projectile penetration. The results show that the RSH sandwich panel has the best in-plane ballistic performance among the three types of honeycomb sandwich panels. For the same relative density, the ballistic limit of the RSH sandwich panel is 17.4% and 7.1% higher than that of the SSH and RH sandwich panels respectively. In addition, the effects of different design parameters on the ballistic resistance of RSH sandwich panels are investigated by changing the panel thickness, the relative density of the core layer, the cell angle and the cell size. It can be concluded that increasing the thickness of the face sheet is more effective in improving the ballistic limit (perforation energy) of the RSH with a thinner core layer. However, increasing the relative density of the core layer is more effective in enhancing the ballistic limit (perforation energy) for thicker core layers. Cell size has a significant effect on the ballistic resistance of RSH sandwich panels compared to cell angle, especially at impact velocities close to the ballistic limit. [ABSTRACT FROM AUTHOR]

Cellular approaches facilitate the flexible design of materials with desirable properties that may be manufactured from single polymers, metals, and, recently, fiber-reinforced composites. This paper describes cellular materials with metal and carbon fiber-reinforced plastic (CFRP) struts. Composite lattice tubular structures were automatically braided, and the effects of axial CFRP yarns on the compressive behaviors of braided lattices were studied. Metal wire-reinforced plastic and metal rods served as axial yarns when preparing hybrid triaxially braided metal-CFRP lattices. The effects of the axial yarns in polyurethane (PU) foam-filled samples were also assessed. Ten braided structures were manufactured, and their compressive behavior and energy absorption were evaluated by axial compression tests. Finite element (FE) simulations were used to investigate deformation, buckling, and damage. Addition of axial CFRP yarns improved the compressive properties; the specific absorbed energy (SAE) increased by 16%. Hybridization further enhanced the SAE by 62%. [ABSTRACT FROM AUTHOR]

This study explores the design and performance of axisymmetric hexachiral honeycombs, utilizing the hexachiral honeycomb framework and axisymmetric design method. Four axisymmetric hexachiral honeycombs with distinct arrangements were developed: left–right symmetry hexachiral honeycomb (LSHH), up–down symmetry hexachiral honeycomb (USHH), central symmetry hexachiral honeycomb (CSHH), and subunits symmetry hexachiral honeycomb (SSHH). The deformation patterns and compression behaviors of these honeycombs were comprehensively examined through experimental and numerical simulations, and comparisons were made with a non-symmetric hexachiral honeycomb (NHH). The results indicate that symmetrically designed honeycombs exhibit a larger mean plateau stress than the asymmetrically designed the NHH during low-velocity impacts. The study further discusses deformation patterns, specific energy absorption, and the negative Poisson's ratio effect across the five honeycombs under different parameters. Notably, symmetrically designed honeycombs demonstrate superior specific energy absorption, and the negative Poisson's ratio effect becomes evident at an impact velocity of 10 m/s. However, the advantages of axisymmetric honeycombs diminish at higher impact velocities of 50 m/s and 100 m/s. The Poisson's ratio effects of symmetric honeycombs weaken with an increase in the circular ligament r of the honeycomb. Additionally, the study identifies that platform stress and SEA increase for honeycombs with horizontal cell numbers greater than 6. [ABSTRACT FROM AUTHOR]

Auxetic structures possess high energy absorption, especially under impact loads that are influenced by their negative Poisson's ratio (NPR). This negative ratio is due to their specific microstructural designs. In this article, newly modified designs for an existing chiral auxetic structure have been proposed and their mechanical and energy absorption performances have been investigated. In the proposed designs, the geometry of slots in an available peanut-shaped auxetic structure has been modified and some extra masses have been removed to introduce innovative auxetic structures with higher NPRs, higher energy absorption, and lower structural weight. By performing finite element simulations in ABAQUS software, it has been found that the proposed modifications in the design of the available auxetic structure result in up to 7.3% and 76.6% increases in Poisson's ratio and energy absorption respectively. The accuracy of simulations has also been confirmed by performing a comparison study with some available results of experimental tests. [ABSTRACT FROM AUTHOR]

As the backing plate conditions significantly affect the ballistic performance of ceramic/metal composite armor, we have conducted impact experiments using 12.7 mm API projectiles (brittle-hard) to examine the influence of different material characteristics of metal backing plates on the ballistic impact performance of ceramic/metal composite armor. By weighing multilevel sieved fragments and employing the Rosin-Rammler fragment distribution model, we analyzed the influence of backing plate material parameters on the fragment size distribution patterns of the penetrator and ceramic panel. Further, we utilized numerical simulations to explore the impact of backing plate density, Young's modulus, and yield strength on ceramic fracture and energy absorption during penetration. Overall, a high-density backing plate provides better inertial support. Backing materials with a high Young's modulus can enhance the ballistic performance of the ceramic composite target, but there is a limit to this effect. The yield strength of the backing plate is not necessarily better when higher; instead, there is an optimal value. Either too high or too low yield strength can reduce the energy absorption efficiency of the ceramic. [ABSTRACT FROM AUTHOR]

Highlights 3D woven tubular composites (3D‐WTC), known for their lightweight and high‐strength characteristics, are widely used in various energy‐absorbing components. To enhance the energy absorption capacity of 3D‐WTC, this study conducted a mechanical analysis of bamboo tube structures and proposed concentric circular nested biomimetic structures with “single tube + double ribs” and “double tubes + double ribs.” 3D woven tubular composites with bamboo‐structures (3DWTC‐Bamboo) were fabricated using the vacuum‐assisted resin transfer molding (VARTM) process. Axial compression tests were conducted using a universal testing machine to reveal and discuss the energy absorption capacity and failure modes of 3DWTC‐Bamboo. The results showed that 3DWTC‐Bamboo with a “double tube + double ribs” concentric circular nested biomimetic structures performed exceptionally, with a peak load of 28.93KN and specific energy absorption of 7.74 J·g−1. The failure mode was a hybrid of “rib folding + tube wall buckling.” Finally, finite element analysis of the stress distribution during the compression of 3DWTC‐Bamboo was conducted using ABAQUS, which validated the experimental results. In summary, this work provides a reference for structural innovation in 3D‐WTC and further expands its application in the field of energy absorption. Propose “single tube + double ribs” and “double tubes + double ribs” structures. Introducing the “rib” structures to enhance the local strength/stiffness. Test results show that 3DWTC‐Bamboo has great potential in energy absorption. The “ribs” can increase the local strength/stiffness of the tube structures. [ABSTRACT FROM AUTHOR]

AbstractBionic gradient hierarchy design as a design method that can effectively improve the structural crashworthiness, but its current research only focuses on the symmetric fractal method related to the discussion. In view of this, this article carries out the innovative design and research of asymmetric tree-like fractal gradient hierarchy structure (ATFGHS). The results show that the crashworthiness of the structure can be greatly improved by using the asymmetric tree-like fractal gradient hierarchy design method. Specifically, the ATFGHS-P3 showed a 98% increase in energy absorption (EA), a 98% increase in specific energy absorption (SEA), and an 84% increase in crush force efficiency (CFE) compared to a conventional hexagonal multicellular tube. The completion of this study provides valuable insights into the design and optimization of novel lightweight thin-walled energy-absorbing structures. [ABSTRACT FROM AUTHOR]

This paper introduces a biomimetic gradient hierarchical multicellular structure consisting of two tree-like fractal variants: one based on vertex connections (HCV) and the other based on wall connections (HCW). We investigate their mechanical behavior and deformation through numerical simulations. Our findings reveal that, irrespective of whether they have the same wall thickness or mass, second-order and third-order structures exhibit superior energy absorption capacity (EA) and crushing force efficiency (CFE) compared to first-order structures, resulting in significantly enhanced crashworthiness performance. In the case of HCV structures with identical wall thickness, the third-order structure outperforms the first-order structure by 79.73% in specific energy absorption (SEA) and by 38.51% in CFE. Similarly, for HCW structures, the third-order variant surpasses the first-order one by 45.57% in SEA and 28.39% in CFE. We also conduct a parametric study, exploring the influence of inner circle diameter, fractal coefficient, and fractal angle on the crashworthiness of biomimetic gradient hierarchical multicellular structures. We identify the optimal fractal coefficient and inner diameter distribution range for HCV when the fractal angle is 60°. Lastly, we compare these structures with traditional multicellular tubes, demonstrating that biomimetic gradient hierarchical multicellular tubes achieve up to 50.34% higher SEA and 55.13% higher CFE. The results of this study offer valuable design insights for developing lightweight and efficient energy-absorbing structures. [ABSTRACT FROM AUTHOR]

Recent progress in additive manufacturing, also known as 3D printing, has offered several benefits, including high geometrical freedom and the ability to create bioinspired structures with intricate details. Mantis shrimp can scrape the shells of prey molluscs with its hammer-shaped stick, while beetles have highly adapted forewings that are lightweight, tough, and strong. This paper introduces a design approach for bioinspired lattice structures by mimicking the internal microstructures of a beetle's forewing, a mantis shrimp's shell, and a mantis shrimp's dactyl club, with improved mechanical properties. Finite element analysis (FEA) and experimental characterisation of 3D printed polylactic acid (PLA) samples with bioinspired structures were performed to determine their compression and impact properties. The results showed that designing a bioinspired lattice with unit cells parallel to the load direction improved quasi-static compressive performance, among other lattice structures. The gyroid honeycomb lattice design of the insect forewings and mantis shrimp dactyl clubs outperformed the gyroid honeycomb design of the mantis shrimp shell, with improvements in ultimate mechanical strength, Young's modulus, and drop weight impact. On the other hand, hybrid designs created by merging two different designs reduced bending deformation to control collapse during drop weight impact. This work holds promise for the development of bioinspired lattices employing designs with improved properties, which can have potential implications for lightweight high-performance applications. [ABSTRACT FROM AUTHOR]

In this study, a new structure is proposed based on the body-centered cubic (BCC) lattice structure by adding a cubic truss in the center of the BCC structure and denoting it TLC (truss–lattice–cube). The different dimensions of the central cube can notably affect the mechanical properties of the lattice structure. With a fixed length (15 mm) of a unit cell, the optimal size for the central cube is determined to be 5 mm. Quasi-static compressive tests are performed on specimens made of polylactic acid (PLA) using additive manufacturing technology. The deformation characteristics of the new structure are analyzed in detail by experiments and numerical simulations. Compared to the BCC structure, the mechanical properties of the TLC structure were significantly improved. The initial flow stress of the TLC increased by 122% at a strain of 0.1; the specific strength enhanced by 293% at a strain of 0.5; and the specific energy absorption improved by 312% at a strain of 0.6. Printing defects in the lattice structure may remarkably damage its mechanical properties. In this work, incorporation of microcracks into the finite element model allows the simulation to capture the influence of printing defects and significantly improve the predictive accuracy of the simulation. [ABSTRACT FROM AUTHOR]

AbstractTo further improve the load-bearing capability and anti-impact properties of the auxetic structure, a novel enhanced auxetic honeycomb core (NEH) was introduced, and the bending resistance and crashworthiness of this sandwich beam (NEH-SWB) were analyzed through numerical simulation. First, bending tests on sandwich beams under different loading situations revealed that NEH-SWB was more susceptible to impact damage in three-point bending situations than those under four-point bending, and the influence of structural parameters were more pronounced. In addition, the impact of load position and structural parameters on the bending response and deformation pattern of NEH-SWB were investigated. NEH-SWB exhibited superior bending resistance when the punch was located in the S position. Furthermore, increasing the panel thickness and altering the panel thickness configuration both contributed to improving the flexural resistance of NEH-SWBs. At a certain mass, the configuration with Tf/Tb>1 exhibited better bending resistance. Meanwhile, increasing both the cell angle (θ) and wall thickness-to-length ratio (t/l) enhanced load-carrying capability and energy absorption of NEH-SWB. Subsequently, further analysis showed that NEH had better bending performance compared to cell structures with reentrant (RH), star-shaped (SSH), and reentrant-star (RSH) honeycombs. Finally, the complex proportion assessment method was employed to examine the significance of structural parameters regarding the flexural behavior of the NEH-SWB. It was concluded that increasing the t/l value could be the best solution to enhance the bending performance of the NEH-SWB. [ABSTRACT FROM AUTHOR]

AbstractThis experimental study delves into the vibration response and energy absorption characteristics of three distinct auxetic tubular structures under quasi-static compression: the Reentrant, Double-V, and Anti-Trichiral designs. Notably characterized by their negative Poisson’s ratio, these structures exhibit superior mechanical properties in comparison to conventional tubular structures with a positive Poisson’s ratio. For consistency, all samples were standardized in terms of diameter and height, while variations due to unit cell geometry were parameterized based on the structure’s weight. The samples were fabricated using Fused Deposition Modeling (FDM) with both PLA and PLA-Carbon filaments. Modal testing was conducted to evaluate structural damping, providing insights through time domain plots and frequency response functions. Subsequent compression testing facilitated the assessment of force-displacement relationships, thereby enabling the quantification of energy absorbed, specific energy absorption, and peak crushing force metrics. The analysis revealed that Reentrant unit cells constructed from PLA exhibited a 5% higher damping efficiency compared to Double-V and 4% higher than Anti-Trichiral units. Similarly, Reentrant units in PLA-Carbon demonstrated an 8 and 30% increase in damping relative to Double-V and Anti-Trichiral, respectively. During quasi-static compression, Double-V units in PLA showcased a 66 and 13% superior energy absorption capacity over Reentrant and Anti-Trichiral units, respectively. With PLA-Carbon, Double-V units exhibited a 28 and 116% enhanced energy absorption capacity compared to Reentrant and Anti-Trichiral units, respectively. This comprehensive evaluation offers insightful revelations into the damping and energy absorption capabilities of varying auxetic cell structures when composed of different materials, highlighting their potential in engineering applications. [ABSTRACT FROM AUTHOR]

In this article, the crashworthiness performance of 3D printed origami tubes with variable thickness and different printing angles are investigated. First, experimental results showed that, compared with the traditional equal thickness origami tubes, the initial peak crushing force of variable thickness origami tubes (VTOT) was reduced by 41% and the specific energy absorption (SEA) had an improvement of 22%. Then, the energy absorption (EA) capacity of 3D printed origami tubes at different printing angles was measured and analyzed experimentally. It can be concluded that smaller print angles provide better EA, and the larger print angles result in a significant increase in layer-to-layer shear under quasi-static axial loads, which makes the component more susceptible to buckling and cracking. Finally, the finite element method was constructed through Abaqus/Explicit to study the crashworthiness of VTOT under different mean thickness and the thickness difference in detail. As the mean thickness increases, the load-carrying capacity and EA capacity increase during the crushing process, but the VTOT with a mean thickness of 1.2 mm has the highest SEA and CLE. The larger thickness differences can significantly improve the EA properties of the VTOT through the changing of the deformation mode. Highlights • Both experimental and numerical methods were used to study origami tubes with varying thicknesses. • Origami tubes printed at 0 have a higher energy absorption capacity. • Variable thickness origami tubes improve the crashworthiness of traditional origami tubes. [ABSTRACT FROM AUTHOR]

AbstractThis research explores the use of Double Arrowhead (DAH) structures, known for their light weight, high compressive stiffness, and energy absorption. A novel truss-supported DAH structure with a circular node was investigated under compression loads. Samples were fabricated using FDM additive manufacturing with both reinforced and non-reinforced PLA filaments. The truss supported DAH structure with a circular node, made from Carbon Fiber reinforced PLA, demonstrated superior performance with a compression strength of 19.3780 MPa, a strength to weight ratio of 0.3561 MPa/g, and a total specific energy absorption of 13903.3367 J/kg. [ABSTRACT FROM AUTHOR]

AbstractA new square hierarchical multicellular tube design is introduced, and the crashworthiness of various square hierarchical multicellular tubes with identical wall thickness and mass is systematically analyzed using validated numerical models. The study explores the impact of parameters such as layer level, wall thickness, and impact load angle on the structure’s impact resistance. Additionally, the impact resistance of square hierarchical multicellular tubes is compared to that of conventional square multicellular tubes with the same wall thickness. The findings reveal that the proposed square hierarchical multicellular tube effectively mitigates peak crushing forces and enhances crushing force efficiency under the same mass. Specifically, the third-order square hierarchical multicellular (SHMT-3) tube exhibits a 48.23% increase in specific energy absorption and a 75.14% improvement in crushing force efficiency. Notably, the peak crushing force decreases by 15.40% compared to that of the square tube. Under identical wall thickness, the crush force efficiency of SHMT-3 reaches 89.51%, marking a 125.21% improvement compared to square tube. Overall, the comprehensive crashworthiness of square hierarchical multicellular tubes surpasses that of traditional square multicellular tubes. These results contribute valuable insights for innovatively designing new hierarchical multicellular tube structures. [ABSTRACT FROM AUTHOR]