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AbstractChiral honeycomb structures, renowned for their superior mechanical properties, find extensive application in passive safety protection and beyond. However, existing research predominantly centers on chiral honeycomb structures, neglecting discussions on the energy absorption capabilities of anti-chiral honeycomb structures subjected to out-of-plane impacts. In view of this, an innovative design method is proposed in this paper to construct a series of anti-tri-chiral honeycomb structures (MATCH-θ) with missing rib-plate and excellent crashworthiness by skillfully designing and replacing the nodal elements of the anti-tri-chiral structures. Subsequently, the effects of the constitutive angle θ and the wall thickness t of the cellular elements were investigated using a validated finite element model, revealing the energy absorption mechanism of MATCH-θ. It is shown that this type of structure has better crashworthiness performance compared to the conventional anti-tri-chiral honeycomb structure ATCH-90°. In particular, the MATCH-110° structure with t = 0.1 mm showed a 36% increase in specific energy absorption, a 36% increase in mean crush force, and a 35% increase in crush force efficiency compared to the conventional anti-tri-chiral honeycomb structure ATCH-90° with the same mass. The completion of this study provides valuable insights into the design and optimization of future honeycomb structures for crashworthiness. [ABSTRACT FROM AUTHOR]

The continuous increase in the operating speed of rail vehicles demands higher requirements for passive safety protection and lightweight design. This paper focuses on an energy-absorbing component (circular tubes) at the end of a train. Thin-walled carbon fiber-reinforced polymer (CFRP) tubes were prepared using the filament winding process. Through a combination of sled impact tests and finite element simulations, the effects of a chamfered trigger (Tube I) and embedded trigger (Tube II) on the impact response and crashworthiness of the structure were investigated. The results showed that both triggering methods led to the progressive end failure of the tubes. Tube I exhibited a mean crush force (MCF) of 891.89 kN and specific energy absorption (SEA) of 38.69 kJ/kg. In comparison, the MCF and SEA of Tube II decreased by 21.2% and 21.9%, respectively. The reason for this reduction is that the presence of the embedded trigger in Tube II restricts the expansion of the inner plies (plies 4 to 6), thereby affecting the overall energy absorption mechanism. Based on the validated finite element model, a modeling strategy study was conducted, including the failure parameters (DFAILT/DFAILC), the friction coefficient, and the interfacial strength. It was found that the prediction results are significantly influenced by modeling methods. Specifically, as the interfacial strength decreases, the tube wall is more prone to circumferential cracking or overall buckling under axial impact. [ABSTRACT FROM AUTHOR]

Based on the conventional star-shaped tube, a star-shaped multicellular tube was proposed and designed; finite element modeling was carried out using Abaqus/Explicit software, and the accuracy of the finite element model was verified under axial impact, the crashworthiness study shows that the star-shaped multicellular tube is significantly improved compared to the conventional star-shaped tube for the same wall thickness and same mass conditions. Namely, for the same wall thickness conditions, the energy absorption of the star-shaped quadrangular multicellular tube (SSMT-4-140°) is 1.77 times that of the star-shaped quadrangular tube (SST-4-140°), and the crush force efficiency is 1.24 times that of SST-4-140°; at the same mass, the energy absorption of SSMT-4-140° is 1.17 times that of SST-4-140°, and the crush force efficiency is 1.14 times that of SST-4-140°. Subsequently, the parametric study of the number of corners N, angle between two adjacent corners θ°, and wall thickness on the star-shaped multicellular tube was systematically carried out. The results of this paper can provide valuable information toward the innovative design of multicell tube structures. [ABSTRACT FROM AUTHOR]

Recently, auxetic honeycombs have attracted widespread attention with characteristics of lightweight, excellent energy absorption capacity and high shear stiffness. The present paper proposes the hybrid star-shaped tetra-chiral honeycomb (STCH) by embedding the tetra-chiral honeycomb (TCH) into the star-shaped honeycomb (SSH). The deformation mode and compression behavior of the STCH were studied numerically and compared with that of the SSH and TCH. Particularly, under the impact velocity of 2 m/s, the specific energy absorption (SEA) of the STCH increases by 80 and 179% than that of the SSH and TCH, respectively. Through investigating the effect of impact velocity and relative density on the crushing behavior of the STCH, the deformation modes map was summarized, and the empirical formula of the plateau stress was presented. Subsequently, the detailed parameter analysis of the STCH revealed that in a certain range, the SEA and stability of the STCH increase with the increase of N x , θ , and R , and with the decrease of L 2 and L 1. Finally, the improved STCH (ISTCH) with stable deformation and better crashworthiness was further proposed, and the crashworthiness of it was comprehensively compared with other structures. The result shows the excellent crashworthiness of the ISTCH. Particularly, the SEA of ISTCH can be nearly 8 times higher than that of the TCH. The novel star-shaped tetra-chiral honeycomb (STCH) can absorb more energy due to the increase of plastic hinges and the complex coupling deformation. The deformation modes map of the STCH was summarized and the plateau stress was fitted. The change of radius and cell wall angle can greatly change the Poisson's ratio from positive to negative. The STCH and improved STCH have excellent crashworthiness. [ABSTRACT FROM AUTHOR]

In order to improve the crashworthiness of traditional Thin-Walled Struct, a new method for designing multicellular tubes is presented in this paper. In this work, multicellular columns based on origami centripetal folding method (MCOCFM) are proposed. The cross section of MCOCFM is designed in the way of origami. The mechanical properties of MCOCFM under uniaxial compression are analyzed by numerical simulation. Studies have shown that increased levels and wall thickness facilitate energy absorption. In addition, the theoretical prediction of MCF is in good agreement with the simulation results. Compared with some existing structures, MCOCFM has better crashworthiness. [ABSTRACT FROM AUTHOR]

In contrast to single‐phase materials the manufacturing process of composites creates multiscale interfaces among constituent materials and between laminar multilayers. Targeting the interfaces in these composite structures, this paper presents a perspective study on the impact safety of potential future composite rail vehicles. The aim is to conceptually explore the key role of interfacial discontinuities of composite material structures as they are a critical issue affecting the impact performance of future composite rail vehicles. Following a theoretical description, the issues are addressed in two parts. First, composite materials are characteristically analyzed from the perspective of their interfacial discontinuities within the materials and between the laminate multilayers to identify their influence. Second, the structural conditions required for crashworthiness are determined in relation to the dual requirements of global stability and local deformability for efficient energy absorption. The key findings are: (1) The interfacial discontinuities of the material phases and the designed structural assemblies need to be tailored for crashworthiness performance and (2) Global stability and locally deformability are the key dual requirements for the energy absorbing progressive deformations that are essential for application of composite for crashworthiness of rail vehicles. The research conceptually explores a key issue of the impact mechanics of composite structures from the perspective of impact safety of composite rail vehicles. [ABSTRACT FROM AUTHOR]

Hierarchical design and gradient design have been shown to improve the crashworthiness of structures. However, fewer studies combine the two. Therefore, this study combines the two to design a novel double-gradient hierarchical hexagonal tube (DGHHT) based on a hexagonal tube (HT). According to the different axial gradients, they are divided into DGHHT-1 and DGHHT-2. The crashworthiness under multiple loads was studied by finite element simulation. Firstly, the reliability of the finite element model is validated by experimental results. Secondly, compared with single-gradient hierarchical hexagonal tubes (SGHHT), DGHHT have better resistance to global bending under multiple loads. When studying mass effects, it was found that both HT and DGHHT had increased peak force and SEA. When HT is designed as DGHHT-2, specific energy absorption (SEA) can be increased by up to 82.74%. Studying the effects of impact angle found that DGHHT-2 has better resistance to global bending than HT as the angle increases. Studying the effect of DGHHT-2 axial gradient distribution found that reasonable distribution of its axial gradient can further improve its ability to resist global bending. Finally, compared with the structures proposed in other studies, DGHHT-2 also has better resistance to global bending at an impact angle of 30°. The double-gradient hierarchical design in this study can provide new design ideas for crashworthiness design. [ABSTRACT FROM AUTHOR]

Inspired by brain corals and cuttlebone, this study employed 3D printing technology to fabricate a novel bio-inspired multilayer sandwich structure based on the Hilbert space-filling curve (named BHSS). The mechanical behavior and deformation process of the BHSS were compared through quasi-static axial crushing experiments and finite element (FE) simulations. The energy absorbing characteristics of the BHSS with different layers were compared through FE simulations, and the results indicated that the 4-layer BHSS displayed superior crashworthiness. Then, parametric studies were conducted to investigate the influence of layer-height gradient and wall-thickness gradient on the energy absorption performance and deformation modes of the BHSS. It was confirmed that the double gradient designs significantly reduced the initial peak force and improved the specific energy absorption of the BHSS. Finally, the multi-objectives optimization based on response surface method and the non-dominated sorting genetic algorithm (NSGA-II) was employed to optimize the geometric parameters of the BHSS, aiming at the optimal configuration for better crashworthiness. Compared to the original design structure, the SEA of the optimized knee point structure was increased by 21.8% and the IPF was reduced by 72.6%. These findings provided valuable guidelines for the brain-coral-inspired design of multilayer sandwich structures with superior energy-absorbing performance. [ABSTRACT FROM AUTHOR]

This article examines the compressive behavior of re-entrant auxetic structures to optimize its energy absorption. The unique properties of auxetic structures have made them popular in various industries, especially for sports equipment. This study aims to create different types of structures using an FDM 3D printer. First, an appropriate raster angle for 3D printing of tensile test samples is examined for PLA and PLA+ materials. Next, three types of structures are constructed using brittle PLA and ductile PLA+ materials, and their energy absorption is compared. These structures are homogeneous auxetic re-entrant (HAR), unilateral graded thickness (UGT), and bilateral graded thickness (BGT). Changing from brittle (PLA) to soft material (PLA+) increases energy absorption in all structures. Likewise, grading the thickness of the structure, especially on BGT, increases energy absorption. Simulation results are validated by modeling the structures in two ways for brittle and ductile materials using Abaqus software. Finally, based on the simulation results, the most appropriate step of the bilateral graded thickness is recognized as 0.8-1-1.2. [ABSTRACT FROM AUTHOR]

In this paper, a sinusoidal corrugated filled tube (SCFT) is proposed by filling aluminum foam into a sinusoidal corrugated tube, the finite element model is established using the finite element software Pro/Engineer and Abaqus/Explicit, and the accuracy of the finite element model is verified. Crashworthiness studies under axial impact show that SCFT has better energy absorption (EA) performance than a circular filled tube (CFT) under the same outer tube wall thickness conditions, and the EA and specific EA of SCFT are 1.16 times and 1.12 times that of CFT, respectively; in addition, SCFT has a better interaction effect than CFT under the same outer tube wall thickness. Subsequently, a parametric study of SCFT by amplitude, wavenumber, outer tube wall thickness and aluminum foam density was systematically carried out. The structure studied in this paper can provide a reference for the innovative structural design of filled tubes. [ABSTRACT FROM AUTHOR]

In this paper, a novel bioinspired hexagonal honeycomb (NBHH) is proposed. Different from the conventional honeycomb (CH), the core wall of the NBHH has a saw-tooth corrugated shape. Firstly, LS-DYNA R11.0 is used to construct a finite element model and conduct experimental verification; then, a comparative analysis is carried out with the CH and the bionic honeycomb sandwich panel (BHSP) with sinusoidal curves, and the proposed NBHH exhibits excellent energy absorption capability under dynamic impact. In particular, compared with the CH and the BHSP with the same wall thickness, the specific energy absorption of the NBHH is 58.60% higher than that of the CH. Compared with the BHSP, the specific energy absorption of the NBHH has increased by 7.23%. Finally, parametric research is carried out on the NBHH. [ABSTRACT FROM AUTHOR]

To enhance the out-of-plane mechanical performance, a novel honeycomb with arc-curved edge is proposed. The numerical model is built based on the elastoplastic failure criterion. The impact performance of proposed honeycomb is investigated and revealed. The influence of central angle and thickness on the crashworthiness is researched. The results show that the numerical result is in agreement with that of experimental test. The central angle has great influence on the deformation mode. The global buckling of edge tube is exhibited for the small central angle, and the consistent deformation mode is demonstrated for the central area. With the increasing of central angle, the energy absorption ability is enhanced for the plastic hinge could absorb more impact energy. The more stable deformation mode is exhibited for the larger central angle. The honeycomb with relatively large central angle has the best crashworthiness performance for the balance of energy absorption and structural mass. Compared with traditional honeycomb, the proposed honeycomb could improve the out-of-plane energy absorption characteristics. [ABSTRACT FROM AUTHOR]

This study extensively characterizes the out‐of‐plane stiffness and energy harvesting capabilities of a newly proposed anti‐trichiral hierarchical auxetic honeycomb structure, both mechanically and deformationally. By introducing a design concept based on the anti‐trichiral honeycomb (ATCH), a structure with superior out‐of‐plane load‐carrying capacity and excellent auxeticity is achieved. To validate the finite element model, compression simulations are conducted. Comparative investigations into the morphing characteristics and energy harvesting performance between the novel structure and the ATCH are performed. Additionally, the influence of various parameters on the comprehensive performance of the novel auxetic structure is explored. It has been found that the angle φ is most sensitive to the auxetic properties, while the ratio k significantly impacts energy absorption. This research advances the design of novel auxetic structures for potential applications in protective engineering. [ABSTRACT FROM AUTHOR]

AbstractDrawing inspiration from nature’s hierarchical organization, we propose a novel bio-inspired hierarchical multi-cellular circular tubes (BHMC) with a fractal structure. Using an experimentally validated LS-DYNA finite element model, we investigated the impact resistance of this structure under axial loading. Numerical analysis was conducted to explore the energy absorption performance of BHMC tubes with varying numbers of branches, fractal orders, and tube masses. The numerical findings indicate that specific energy absorption (SEA) increases with higher numbers of fractal orders. Specifically, the SEA of 2nd order BHMC tubes surpasses that of conventional multicellular circular and single-layer tubes by approximately 35.07% and 17.10%, respectively. Optimal performance is achieved with the proposed structure featuring tree branching (N = 6) and 2nd order fractal characteristics, yielding the highest specific absorption energy across different parameters. These results offer valuable insights for designing multicellular bilayer tubes with superior energy absorption efficiency, providing an effective guideline for structural optimization. [ABSTRACT FROM AUTHOR]

In order to improve the crashworthiness of the novel circular-vein branched nested tube (CVBNT) proposed in recent research work, the crashworthiness design is optimised in this paper. Based on numerical simulation technology, the finite element model under transverse quasi-static compression of CVBNT is first established and effectively verified. Then, the energy absorption characteristics of CVBNT and different nested tubes were compared and analysed to reveal the excellent energy absorption performance of CVBNT. Finally, the structural design and the cross-sectional thickness optimisation of CVBNT are carried out. The results show that CVBNT has better energy absorption capacity than other nested tubes. The parameters N and γ have an important influence on the crashworthiness of CVBNT, and when N = 6, γ = 0.5 is the best choice in favour of its crashworthiness. At the same time, the optimisation of cross-section thickness effectively improves the crashworthiness of CVBNT. [ABSTRACT FROM AUTHOR]

AbstractHierarchical tubes have been proved to be excellent energy absorbers under axial compression. However, there are limited studies exploring their oblique crushing performance. Therefore, the oblique crushing characteristics of hierarchical tubes, bio-inspired hierarchical multi-cell square tubes (BHMS), hierarchical multi-cell square tubes (HMSA and HMSB), have been numerically studied. The influencing factors of loading angle and hierarchical order on deformation modes, force-displacement curves, and energy absorption (EA) behaviors were explored. It is found that BHMS tubes present the superior crushing performance among these hierarchical square tubes. Moreover, BHMS tubes display the excellent crushing characteristics in comparison with single square tubes. Specifically, the specific EA of BHMS-3 tubes is 213%, 212%, 66%, and 42% greater than that of single square tubes at loading angles of 0°, 10°, 20°, and 30°. The findings demonstrate the priority of hierarchical square tubes under oblique crushing, and provide the reference and insight for the design of energy absorbers. [ABSTRACT FROM AUTHOR]

In this study, thin-walled tubes were circumferentially strengthened by plasticity ball burnishing of critical locations determined from buckling mode analysis. Axial crush test results revealed that the surface-treated (ST) tubes increased localized yield strength, attained superior crashworthiness performance, and triggered predictable deformation modes according to the buckling modes of the tubes. Numerical analysis was performed and successfully validated with the experiment at 90% prediction accuracy. The treated tube ST-4 with the 12th buckling mode outperformed a conventional tube with an increase in specific energy absorption (SEA) and crush force efficiency (CFE) by up to 70% while sustaining a low increase in initial peak force (IPF). Furthermore, the tube demonstrated a greater rate of energy dissipation compared to tubes with conventional surface-treated patterns at the same level of surface-treated area. The crashworthiness performance improved as the surface-treated area ratio increased. A theoretical model was developed for the surface-treated tube based on fundamental deformation kinematics, predicting mean crushing force and total energy absorption with acceptable accuracy. The findings strongly suggest that the proposed surface-enhanced tubes have great potential to be used as energy-absorbing structures in crashworthiness applications. [ABSTRACT FROM AUTHOR]

To enhance the crashworthiness of thin-walled structures, this study proposes a self-similar nested hierarchical hexagonal tube. This innovative design incorporates the hierarchical technique into the structural configuration of hexagonal thin-walled tubes. Numerical analysis, conducted using a validated finite element model, reveals that the proposed self-similar nested hierarchical hexagonal tube (SNHHT) significantly enhances energy absorption compared to traditional hexagonal tubes, maintaining consistent wall thickness and mass conditions. Particularly noteworthy is the improvement in energy absorption indexes under the same mass condition, with SNHHT-4 demonstrating enhancements of up to 76.45% and 86.84% in energy absorption and crushing force efficiency, respectively, while concurrently achieving a 4.11% reduction in initial peak crash force. Subsequently, a parametric study exploring wall thickness, shape factor, and various rib thicknesses was performed to investigate structural crashworthiness. Finally, employing the simplified super-folded element method, the theoretical formulation of mean crushing force was derived, and its accuracy was validated through numerical simulations. [ABSTRACT FROM AUTHOR]

AbstractTo achieve a thin-walled structure with enhanced crashworthiness, inspired by tree fractals, a new right-angle fractal of gradient hierarchical multi-cellular square bi-tubular tube (RFGHMBT) was proposed. Its energy absorption characteristics under axial impact were systematically studied using numerical simulation methods. The results show that, for both the same wall thickness and the same mass, the high-level hierarchical multicellular bi-tubular tube has a higher energy absorption capacity and crushing force efficiency compared to the low-level hierarchical multicellular bi-tubular tube. This substantially improves crashworthiness performance. Under the condition of the same wall thickness, the specific energy absorption (SEA) and crushing force efficiency (CFE) of the third-order RFGHMBT improved by 270% and 244.13%, respectively, compared to the 0th-order. The energy absorption (EA) and CFE under the same mass condition are 1.96 times and 2.20 times higher than those of the 0th-order RFGHMBT, respectively. Further geometric parameter analysis revealed that structural parameters (inner measured square tube side length 2 l, shape scale factors γ1, γ2, wall thickness t) significantly affect the crashworthiness of the square gradient-layered multicellular bi-tubular tubes. Additionally, a comparative study with other multicellular tubes demonstrated the superiority of the proposed square gradient-layered multicellular bi-tubular tubes. The findings of this study offer an effective design concept for developing lightweight and efficient energy absorbers. [ABSTRACT FROM AUTHOR]

In the pursuit of global energy conservation and emissions reductions, utilizing beverage cans as energy-absorbing components offers potential for a sustainable economy. This study examines the impact of foam filling on the crushing behaviors and energy absorption of various types of beverage cans. Quasi-static compression tests were conducted on five geometrically sized cans filled with three densities of polyurethane foam to study their deformation modes and calculate crashworthiness parameters within the effective stroke. Results show that empty beverage cans have lower energy absorption capacities, and deformation modes become less consistent as can size increases. Higher foam density leads to increased total energy absorption, a slight reduction in the effective compression stroke, and a tendency for specific energy absorption to initially increase and then decrease. Regarding crush behavior, smaller cans transition from a diamond mode to a concertina mode, while larger cans exhibit a columnar bending mode. Next, the coupling effect of energy absorption between foam and cans was analyzed so as to reveal the design method of energy-absorbing components. The specific energy absorption of smaller cans filled with polyurethane foam is superior to that of similar empty cans. These findings provide valuable insights for selecting next-generation sustainable energy absorption structures. [ABSTRACT FROM AUTHOR]

A novel structure resembling plant stems, termed bio-inspired fractal plant stems multi-cellular circular tubes (BFPMC), was developed by incorporating fractal plant stem characteristics into smaller circular tubes within larger ones. The crashworthiness of this structure under axial impact was investigated using a validated LS-DYNA finite element model. The energy absorption performance of BFPMC tubes, varying in the number of branches, fractal orders, and inner circular diameters, was numerically studied. The numerical findings reveal a 19.27% increase in specific energy absorption (SEA) for BFPMC with Di = 30mm compared to Di = 0mm, indicating that filling a single circular tube can enhance the structure’s impact resistance. Subsequently, structural parameters conducive to excellent energy absorption characteristics were determined for various combinations of a number of branches, fractal order, and inner circle diameter parameters. These results offer valuable insights for designing multi-cellular double tubes with high energy absorption efficiency. [ABSTRACT FROM AUTHOR]

Abstract In contrast to single‐phase materials the manufacturing process of composites creates multiscale interfaces among constituent materials and between laminar multilayers. Targeting the interfaces in these composite structures, this paper presents a perspective study on the impact safety of potential future composite rail vehicles. The aim is to conceptually explore the key role of interfacial discontinuities of composite material structures as they are a critical issue affecting the impact performance of future composite rail vehicles. Following a theoretical description, the issues are addressed in two parts. First, composite materials are characteristically analyzed from the perspective of their interfacial discontinuities within the materials and between the laminate multilayers to identify their influence. Second, the structural conditions required for crashworthiness are determined in relation to the dual requirements of global stability and local deformability for efficient energy absorption. The key findings are: (1) The interfacial discontinuities of the material phases and the designed structural assemblies need to be tailored for crashworthiness performance and (2) Global stability and locally deformability are the key dual requirements for the energy absorbing progressive deformations that are essential for application of composite for crashworthiness of rail vehicles. The research conceptually explores a key issue of the impact mechanics of composite structures from the perspective of impact safety of composite rail vehicles.

This study conducts a comparative analysis of glass fiber (GF) and jute fiber (JF) as energy-absorbing filament wound eco-friendly structures under quasi-static axial crushing with varying wall thickness, starting with a 2-layer configuration and progressing to 4 and 6 layers. Three primary failure modes, fiber-matrix fracturing, local buckling, and delamination were observed. Both JF and GF 2-layer configurations showed less progressive failure due to their lightweight nature, with crush force efficiency (CFE) of 0.44–0.46 and specific energy absorption (SEA) of 4.4–5.1 J/g, raising considerations for crash scenarios involving human safety. The 4-layer JF configuration demonstrated a significant increase in IPF to 3496 N, effectively restricting buckling and brittle fracture and leading to a higher SEA of 12.61 J/g. In comparison, the GF 4-layer configuration exhibits lower initial peak force (IPF) and SEA values but a higher CFE value of 0.64 at a lower weight of 58 g. The 6-layer JF configuration attains increased stability in load-bearing capacity with a CFE of 0.84 but at the cost of a high weight of 128 g. On the other hand, the 6-layer GF configuration showcases a higher SEA of 10.5 J/g with a moderate CFE of 0.75 and slightly lower weight, suggesting a delicate balance between performance and weight. Visual examination revealed dominant failure modes as local buckling in GF and brittle fracturing in JF configurations. Overall, the 4-layer configurations of JF and the 6-layer configuration of GF composite tubes demonstrate exceptional energy absorption efficiency, suggesting the potential for exploring hybrid configurations to achieve a balanced crashworthiness performance.

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]

Creating lightweight and impact-resistant box structures has been an enduring pursuit among researchers. A new energy-absorbing structure consisting of a bionic gradient lattice-enhanced thin-walled tube is presented in this article. The gradient lattice and thin-walled tube were prepared using selective laser melting (SLM) and wire-cutting techniques, respectively. To analyze the effects of gradient pattern, mass ratio, diameter range and impact speed on structural crashworthiness, low-speed impact at 4 m/s and finite element simulation experiments were conducted. The study demonstrates that the design of inward radial gradient lattice-reinforced thin-walled tubes can effectively enhance structure's energy-absorption efficiency and provide a more stable mode of deformation. It also shows a 17.44% specific energy-absorption advantage over the uniformly lattice-reinforced thin-walled tubes, with no significant overall gain in peak crushing force. A complex scale evaluation method was used to determine the optimum structure and the structure type with the best crashworthiness was found to be a gradient lattice-filled tube with a thickness of 0.9 mm and a slope index of 10. The gradient lattice-reinforced thin-walled tube suggested in this investigation offers guidance for designing a more efficient thin-walled energy-absorption structure. [ABSTRACT FROM AUTHOR]

AbstractDrawing inspiration from the branching structure of trees, a novel Tree-like Hierarchical Multi-cellular Bi-tube (THMBT) has been devised. This design merges the hierarchical distribution traits of tree branches with the superior crashworthiness of double square tube structures. Utilizing a validated finite element model, this study investigates the crashworthiness of THMBT, examining the impacts of wall thickness, bifurcation angle, and bifurcation length on its performance. The Simplified Super Folding Element theory is employed for theoretical analysis, facilitating the calculation of the mean crushing force of THMBT. Findings reveal that wall thickness exerts the most pronounced influence on crashworthiness. As wall thickness increases, THMBT-3 demonstrates a substantial 88.07% enhancement in specific energy absorption, accompanied by a notable increase in peak crushing force. Particularly noteworthy is the exceptional crashworthiness of THMBT-3 with a bifurcation angle (θ) of 60°. For instance, the crushing force efficiency of THMBT-3 with a wall thickness of 0.5 mm reaches 92.08%. Furthermore, when considering different bifurcation lengths under the same wall thickness and bifurcation coefficients (c) set to 1/3, both THMBT-2 and THMBT-3 exhibit superior impact resistance within their respective structures. This study marks a significant advancement by integrating biomimetic design with double square tubes, resulting in a substantial improvement in structural crashworthiness. The findings offer valuable insights for the further development of biomimetic and double square tubes. [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]

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]

Bio-inspired design is an impressive design method that improves a structure's crashworthiness performance and mechanical features. A cellular structure bio-inspired by a 6-legged starfish shape has been developed. Accordingly, this study examines the in-plane crushing behavior and crashworthiness of the 6-legged starfish-inspired structure (6LSIS). Analytical solutions were built based on the principle of energy balance to estimate the plateau stress in low-impact velocity conditions. Plateau stresses are related to high-impact velocities using a curve fitting method for a given wall's thickness. The predictions matched the numerical results. The crashworthiness performance of the 6LSISs mainly depends on wall thickness, impact velocity, and loading direction. It has been observed that an increase in wall thickness and impact velocity results in an enhancement in plateau stress (σ pl), specific energy absorption (SEA), and peak load (PL) in both directions. However, if the wall thickness is >0.3 mm, SEA decreases due to an increase in the structure's mass. The in-plane crushing direction (X or Y) determines the crushing strength and deformation mode of the structure. This study illustrates that the crashworthiness of the structure in the X -direction is superior to that in the Y -direction. [ABSTRACT FROM AUTHOR]

Tubular structures are common in vehicles in the form of crash energy absorbers. Inevitably, these tubes contain holes for assembling fasteners and heating sources. Though the introduction of holes in the surface of the tube minimizes the initial peak crushing force (IPF), their structural stability also gets affected, which leads to a reduction in energy absorption capacity (EA). Therefore, the shape, dimension, and patterns of the holes in the tubular structure are to be scrutinized to minimize its unstable response during the crash event. This paper addresses the hole's position, shape, and dimensional effects on the performance characteristics of aluminum square tubes subjected to axial quasi-static compression experimentally. Numerical models were initially created using ABAQUS/CAE® code for simulating the quasi-static structural response of square tubes (without holes) and validated against experiments. Further, numerical analysis was explored to investigate the hole's position, shape, and dimensional effects on IPF and EA. The performance characteristics of all the examined specimens were quantified based on the best performance with the help of the TOPSIS method. Finally, Response Surface Methodology (RSM) was carried out to determine the best optimal square tube with holes. It was observed that, with an increase in the hole size, the IPF gets minimized. Among all the specimens, the diamond-shaped hole exhibits the best performance characteristics. The study also reveals that the EA varied greatly with the arrangement of holes (patterns). The research findings can provide ample guidance when designing crash tubes in the automotive protective system. [ABSTRACT FROM AUTHOR]

Thin-walled structures are widely used in cars due to their lightweight construction and energy-absorbing properties. However, issues such as high initial stress and lowenergy-absorbing efficiency arise. This study proposes a novel energy-absorbing structure inwhich a straight tube is combinedwith a conical tube and a bamboo-inspired bulkhead structure is introduced. This configuration allows the conical tube to flip outward first and then fold together with the straight tube. This deformation mode absorbs more energy and less peak force than the conical tube sinking and flipping inward. Through finite element numerical simulation, the specific energy absorption capacity of the structure is increased by 26% compared to that of a regular circular cross-section tube. Finally, the impact resistance of the bionic straight tapered tube structure is further improved through multi-objective optimization, promoting the engineering application and lightweight design of hybrid cross-section tubes. [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]

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]

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]

The research focus has shifted towards lightweight structures with high energy absorption capabilities due to advancements in automotive safety technology. This study specifically investigates the impact of cross-sectional area on the energy absorption characteristics of hemispherical composite shells. The experimental phase involves characterizing a glass fiber epoxy composite, followed by the manufacture of hemispherical composite shell specimens with varying cross-sectional areas. These specimens undergo quasi-static axial compressive loading, and the energy absorption parameters are analyzed. The results indicate a significant influence of the composite cross-sectional area on the crushing behavior of hemispherical shells, with a observed decrease in specific energy absorption as the cross-sectional area increases. Additionally, a 3D Finite Element (FE) model is created using ABAQUS FE code to numerically simulate the crushing process. The model’s predictions are compared and validated against experimentally measured values, demonstrating a satisfactory correlation.

Reducing vehicle weight is crucial for enhancing fuel efficiency and reducing emissions in transportation. Traditional composite materials offer improved energy absorption over metals yet are limited by brittleness. This study introduces an innovative approach, inspired by the mantis shrimp's natural defense mechanisms, to enhance the crashworthiness and energy absorption of composite structures, optimizing safety and performance. Utilizing a bio-inspired design, we developed corrugated Carbon Fiber Reinforced Polymer (CFRP) crash box structures, aiming to optimize their energy absorption capabilities and crash force efficiency (CFE) for potential applications in transportation safety. Through a series of quasi-static axial compression tests, the corrugated structures' performance was evaluated against traditional crash box designs. The experimental results demonstrate that the bio-inspired configurations improved crashworthiness characteristics. Strategic manipulation of layer numbers and corrugations led to superior CFE values, indicative of safer, more controlled collision behavior. The “7N-6L” configuration featuring seven corrugations with six layers of CFRP demonstrated the highest efficacy, achieving an optimal CFE of 1.08. This configuration demonstrated a Specific Energy Absorption (SEA) of 1.56 J/g and an Energy Absorption (Ea) of 42.56 J. Furthermore, compared to conventional steel crash boxes, the CFRP crash box with 7N-6L corrugated structure showcased competitive energy absorption capabilities with significantly reduced mass, absorbing 2850 J with a CFE of 0.91, nearly matching the ideal CFE and highlighting its superior lightweight performance. These results underline the potential of integrating bio-inspired designs to develop robust, lightweight structures for improved crashworthiness, paving the way for safer and more sustainable transportation solutions.

The continuous increase in the operating speed of rail vehicles demands higher requirements for passive safety protection and lightweight design. This paper focuses on an energy-absorbing component (circular tubes) at the end of a train. Thin-walled carbon fiber-reinforced polymer (CFRP) tubes were prepared using the filament winding process. Through a combination of sled impact tests and finite element simulations, the effects of a chamfered trigger (Tube I) and embedded trigger (Tube II) on the impact response and crashworthiness of the structure were investigated. The results showed that both triggering methods led to the progressive end failure of the tubes. Tube I exhibited a mean crush force (MCF) of 891.89 kN and specific energy absorption (SEA) of 38.69 kJ/kg. In comparison, the MCF and SEA of Tube II decreased by 21.2% and 21.9%, respectively. The reason for this reduction is that the presence of the embedded trigger in Tube II restricts the expansion of the inner plies (plies 4 to 6), thereby affecting the overall energy absorption mechanism. Based on the validated finite element model, a modeling strategy study was conducted, including the failure parameters (DFAILT/DFAILC), the friction coefficient, and the interfacial strength. It was found that the prediction results are significantly influenced by modeling methods. Specifically, as the interfacial strength decreases, the tube wall is more prone to circumferential cracking or overall buckling under axial impact.

AbstractThis article proposes a soft/hard dual-material honeycomb structure. The quasi-static and dynamic crush modes and crashworthiness of six groups of honeycombs were studied by using universal testing machine and multi-purpose impact gun system. Experimental results indicate that under quasi-static conditions, dual-material honeycombs exhibit similar crush modes, while single-material honeycombs have regular and progressive folding modes. Under dynamic impact, single-material honeycombs will collapse overall along cracks, while dual-material honeycombs exhibit layer-by-layer collapse and negative Poisson’s ratio phenomena. The dual-material structures exhibit the best crashworthiness. The bionic corrugation and dual-material design show excellent synergy in enhancing the energy-absorbing performance of the structure. [ABSTRACT FROM AUTHOR]

In order to further improve the crashworthiness, this paper introduces hierarchies and gradients into thin-walled structures, and designs a new type of rhombic hierarchical gradient multicellular hexagonal tube (RHGMHT), which has the characteristics of hierarchies and gradients in structure. Experimental analysis showed that the mean crashing force (MCF) of 2nd order RHGMHT is greatly improved, and its crushing force efficiency (CFE) is increased by 104.91% compared with 0th order hexagonal tube (HT). The finite element model validated by the experiment is simulated to analyze its deformation mechanism and crashworthiness. Compared with other structures at the same mass, RHGMHT has higher specific energy absorption (SEA) and no increase in initial peak force (IPF). The parametric analysis shows that the SEA of 2nd order RHGMHT is 57.89% higher than that of the 0th order HT. In addition, increasing the mass of the structure can further improve the plateau force, but the IPF also increases with the mass. By comparing the thickness ratios of different rib plates, the analysis shows that different rib plate thicknesses significantly affect the deformation mode and thus the crashworthiness of the structure. Finally, according to the simplified super folded element (SSFE) theory, the MCF theoretical prediction model is established. The results show that the MCF predicted by theory is in good agreement with the MCF obtained by numerical simulation. The hierarchical gradient design proposed in this paper provides a certain guiding significance for the design of new energy absorbers. [ABSTRACT FROM AUTHOR]

The energy absorption (EA) capacity of the thin-walled structures with variable cross-section shape (VCS) under axial impact loading is investigated in this work, which plays an important role in the field of vehicle lightweight and crashworthiness designs. The accuracy of numerical models is validated by the experiments of corresponding VCS specimens. We investigate the influence of structural parameters (i.e. scaling of cross-section, ratio of width to height, thickness and cross-section shape) on the deformation mode and EA capacity of the VCS structures. A good agreement is observed by the comparison between simulation results and experimental ones, which proves the effectiveness of numerical models. Finally, we find that the permutation of appropriate parameters can significantly improve the collision EA capacity of the thin-walled structures. This work will have wild engineering applications in the field of crashworthiness design of car body structures. [ABSTRACT FROM AUTHOR]

AbstractInspired by tree fractals, a novel square gradient hierarchical multicellular tube (SGHMT) is proposed, and a finite element (FE) model of the structure is constructed using Abaqus/Explicit. The accuracy of the FE numerical model was verified using experiments, and the energy absorption characteristics of the structure under axial impact were analyzed. The results show that the high-level SGHMTs have higher energy absorption capacity and impact force efficiency (CFE) compared with the low-level SGHMTs for both the same wall thickness and the same mass, and crashworthiness is greatly improved. The energy absorption (EA) and CFE of SGHMT-3 are 11.39 and 4.47 times higher than those of SGHMT-0 under the same wall thickness condition, respectively. The EA and CFE of SGHMT-3 are 2.15 and 2.28 times higher than those of SGHMT-0, respectively, under the same mass condition. On this basis, further geometrical parameter analysis was carried out, and it was found that the structural parameters (wall thickness, hierarchy, and shape scale factor γ1, γ2) had a significant effect on the crashworthiness of the square gradient hierarchical multicellular tubes. Finally, a comparative study with other multicellular tubes was carried out to demonstrate the superiority of the proposed square gradient hierarchical multicellular tubes compared with other multicellular tubes. [ABSTRACT FROM AUTHOR]

Crashworthiness is a passive device that has an important function as an absorbing component of the impact energy resulting from an accidental event. The main problem in the crashworthy design is the dimensional limitation on the front end of the vehicle with the driver so that most of the energy absorption is limited. Besides, the complexity of crashworthiness design is difficult to make conventionally. This research aims to find out the effectiveness of crashworthiness design in energy absorption and the resulting deformation patterns. Crashwortines are made in a multi-cell shape using PLA material and printed using a 3D printing raise machine. Crashworthiness is produced with four variation shapes of a Multi-cell circle (MCC), Multi-Cell square (MCS), Multicell pentagonal (MCP), and Multi-Cell pentagonal circles (MCPC) with a side thickness of 2 mm and a length of 150 mm. Experimental quasi-static testing is carried out in the frontal direction using a UTM machine at an operating speed of 2mm/s. The results of the study show that the design of the crash box of the pentagon circle has a significant increase in the energy absorption value of 62.49%, which can be recommended in future impact resistance tube designs. The characteristics of the deformation pattern and the failure resulting from the crashworthiness tend to form the pattern of the bending lamina failure. Failures can occur due to plastic fold, elastic bend, and pressure deformation mechanisms followed by new folding formations (lobes). [ABSTRACT FROM AUTHOR]

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