High Specific Energy Absorption Research Articles

Dynamic compressive behavior of functionally graded triply periodic minimal surface cellular structures

The Triply Periodic Minimal Surface (TPMS) structure is regarded as a porous structure used for impact protection due to its lightweight, high strength, and high specific energy absorption (SEA). This paper investigates the dynamic mechanical properties of the TPMS structure by Split Hopkinson Bar (SHPB) experiments and finite element analysis (FEA). We compare stress peak, SEA, strain rate effect, and deformation pattern for functionally graded Primitive (P), uniform P, and uniform Gyroid (G) structures. It is found that the increasing magnitude of peak stress in the TPMS structures becomes more evident under high-impact loads. As the relative density increases, the strain rate effect becomes more prominent. The uniform G structures exhibit higher plateau stress and SEA than uniform P structures. Besides, graded P structures exhibit a climbing phenomenon compared to uniform P structures in the platform section. The FEA results also demonstrate that higher SEA and plateau stresses are exhibited in the graded P structure. The graded design minimizes the strain rate effect compared to the corresponding uniform structures. It is essential to set a properly graded index to enhance the dynamic energy absorption capacity of the TPMS structure, as more fluctuations occur when the graded index increases.

The mechanical characteristics of an aluminum foam winding CFRP composite structure under axial compression

To enhance the energy absorption properties of the energy-absorbing structure, carbon fiber-reinforced polymer (CFRPs) with higher specific energy absorption and porous material aluminum foam with better compressive characteristics were organically combined, and a lighter aluminum foam winding carbon fiber-reinforced polymer structure (CFRP-FA-FW) was designed. Through quasi-static compression testing, the deformation mode and energy absorption properties of CFRP-FA-FW under axial load were examined. The energy absorption and specific energy absorption of CFRP-FA-FW are both increased by 113.55 % and 60.73 %, respectively, compared to the simple composite structure CFRP-FA. Finite element simulation was used for the parametric analysis of the CFRP-FA-FW structure to assess the effects of the relative density of the aluminum foam, the fiber lay-up angle, and the thickness. The results reveal that the change in the relative density of aluminum foam has little impact on the failure deformation mode of CFRP-FA-FW under axial load; the structure has a higher energy absorption capacity and a smoother energy absorption process when the fiber lay-up angle is [0°/90°]ns and [45°]ns; the energy absorption capacity of CFRP-FA-FW is significantly improved by increasing the thickness of the carbon fiber lay-up, and the procedure is also more efficient.

Temperature and Strain Rate Related Deformation Behavior of UHMWPE Fiber-Reinforced Composites.

As they possess the qualities of high specific strength, high specific modulus, high specific energy absorption, and excellent designability, ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced composites have gradually replaced traditional materials such as ceramics and steel plates as the main ballistic protection materials. Using an improved test method, the uniaxial tensile tests of UHMWPE fiber-reinforced composites at two strain rates of 10-4 s-1 and 10-2 s-1 and a temperature range from -20 °C to 80 °C are carried out to study the effects of strain rate and temperature on the tensile behavior of UHMWPE fiber-reinforced composites. The experimental results indicate that the tensile responses exhibit nonlinear characteristics and the sensitivity of strain rate and temperature. The yield strength and modulus decrease with increasing temperature and increase with the increase in strain rate. A phenomenological viscoelastic constitutive model composed of a nonlinear spring and a nonlinear Maxwell element is proposed to characterize the temperature and strain rate dependent deformation behavior of UHMWPE fiber-reinforced composites before yielding. The results show that the model can accurately predict the tensile nonlinear viscoelastic responses of UHMWPE fiber-reinforced composites before yielding over a wide temperature range under quasi-static loading.

Heterogeneous hexagonal honeycombs with nature-inspired defect channels under in-plane crushing

Taking inspiration from geometric defects in hexagonal lattices existing in nature (beehive and graphene), this work explains how defects in the form of channels can improve the effective Young’s modulus and specific energy absorption properties of hybrid-lattice hexagonal honeycombs under compression due to non-uniform collapse band behavior and strain delocalization. The results reveal that in terms of effective Young’s modulus, honeycombs with octagon-pentagon and pentagon-trigon defected cells outperform the benchmark structure by roughly 13% and 20%, respectively. In terms of specific energy absorption (SEA), all composite-lattice honeycombs show superior behavior to the benchmark honeycomb, especially the pentagon-trigon defective honeycomb with about 56.5% higher SEA. The novel structures show promising design prospects for applications in various industries, especially automotive and construction with cost-effective advantage in customized or low-volume production cases.

Large deformation response of a novel triply periodic minimal surface skeletal-based lattice metamaterial with high stiffness and energy absorption

Triply periodic minimal surface (TPMS) lattice metamaterials present superior mechanical performance over traditional strut-based lattice metamaterials due to their unique structural characteristics. However, the high stiffness–stable plastic response trade-off dilemma is still the major challenge for skeletal-based metamaterials. Herein, a novel TPMS skeletal lattice metamaterial is proposed. Finite element simulations are conducted to reveal its elastic properties and plastic response under compression. Afterwards, validation experiments are performed on the lattice specimens fabricated by the most common Fused Deposition Modeling (FDM) process. The nominal stress–strain curves and collapse mode of the lattice materials are obtained accordingly. Both the numerical simulations and experiments demonstrate that the proposed TPMS lattice metamaterial exhibits high specific modulus, strength and energy absorption, together with a smooth and elongated stress plateau, thereby overcoming the strength-efficiency trade-off. Different from the rigid nodal region in traditional strut-based lattices, the strut connection parts in the novel TPMS lattices experience shear and twisting, which avoids the catastrophic failure of the struts and enhances the loading efficiency of the structure under compression. Meanwhile, the numerical results indicate that the stable plastic response of the designed architecture is insensitive to the plastic flow behavior of the bulk material, which is also supported by the experimental results. It is also demonstrated that the novel TPMS lattice metamaterial presents several times higher stiffness as well as energy absorption simultaneously than the current strut-based lattice materials, which can be potentially applied as load-bearing components and impact energy absorbers.

Study on the Deformation Mode and Energy Absorption Characteristics of Protective Honeycomb Sandwich Structures Based on the Combined Design of Lotus Root Nodes and Leaf Stem Veins

Sandwich structures are often used as protective structures on ships. To further improve the energy-absorbing characteristics of traditional honeycomb sandwich structures, an energy-absorbing mechanism is proposed based on the gradient folding deformation of lotus root nodes and a leafy stem vein homogenizing load mechanism. A honeycomb sandwich structure is then designed that combines lotus root nodes and leafy stem veins. Four types of peak-nest structures, traditional cellular structure (TCS), lotus root honeycomb structure (LRHS), leaf vein honeycomb structure (LVHS), and lotus root vein combined honeycomb structure (LRVHS), were prepared using 3D printing technology. The deformation modes and energy absorption characteristics of the four honeycomb structures under quasistatic action were investigated using a combination of experimental and simulation methods. It was found that the coupling design improved the energy absorption in the structural platform region of the LRHS by 51.4% compared to that of the TCS due to its mechanical mechanism of helical twisting and deformation. The leaf vein design was found to enhance the peak stress of the structure, resulting in a 4.84% increase in the peak stress of the LVHS compared to that of the TCS. The effects of the number, thickness, and position of the leaf vein plates on the honeycomb structure were further explored. The greatest structural SEA effect of 1.28 J/g was observed when the number of leaf vein plates was four. The highest SEA of 1.36 J/g was achieved with a leaf vein plate thickness of 0.6 mm, representing a 7.3% improvement compared to that of the 0.2 mm thickness. These findings may provide valuable insights into the design of lightweight honeycomb sandwich structures with high specific energy absorption.

On the crashworthiness analysis of bio-inspired DNA tubes

This study presents a thorough numerical evaluation of the crashworthiness properties of a new bio-inspired DNA tubes (BIDNATs) with circular, elliptical, and rectangular cross-sections. Deformation and crashworthiness behaviors are evaluated using axial quasi-static crushing simulations by ABAQUS/Explicit (Abaqus 6.14, https://www.3ds.com/products-services/simulia/products/abaqus/). The study compares the performance of conventional tubes with rectangular and elliptical cross-sections to DNA-inspired tubes. Increasing the rotation angle leads to more helices and a pronounced helix angle, resulting in lower initial peak force (IPF). However, lower cross-section aspect ratios generally have higher IPF and specific energy absorption (SEA) values. BIDNATs with rectangular cross-sections and a 540° rotation angle have the lowest SEA and IPF values across all aspect ratios. Notably, for the 110/100 aspect ratio, the SEA of E110/100 is 71% higher than the conventional tube. Overall, BIDNATs with elliptical cross-sections and a 360° rotation angle exhibit higher SEA values and lower IPF values, particularly for a width (W) of 100 mm. Conventional circular and elliptical tubes generally have SEA values exceeding 6 J/g, with only E110/100 surpassing this among DNA-inspired tubes. The NE110/100 tube has the highest SEA, surpassing E110/100 by 54%, while its IPF is 10% greater than DNA-inspired E110/100. It's worth noting that conventional circular and elliptical tubes have higher IPF values compared to their DNA-inspired counterparts. These findings offer valuable insights for engineers and researchers in the design of crash tubes to improve overall vehicle safety for both occupants and pedestrians.

Mechanical behavior of interpenetrating phase composite structures based on triply periodic minimal surface lattices

The triple periodic minimal surface (TPMS) structures have received widespread attention due to their excellent mechanical properties, such as high specific strength and energy absorption. However, these structures are prone to suffering catastrophic damage due to stress concentration and shear deformation in actual loading environments, affecting their load-bearing performance. In this work, interpenetrating phase composite (IPC) structures were fabricated by filling thermoplastic polyurethane (TPU) as a soft material into the diamond minimal surface structure using the multi-material fused deposition modeling technique, and their mechanical behavior was investigated numerically and experimentally. The effects of topological types and volume fractions on the performance of IPC structures were investigated. It is shown that the IPC structure undergoes stretching-dominated deformation, and its strength and toughness are significantly improved compared to the TPMS structure. Due to the addition of a complementary phase structure made of TPU, stress concentration and shear failure are reduced. The global deformation of the IPC structure and stress distribution of the TPMS phase are more uniform, effectively protecting the entire structure from catastrophic failure.

Energy Absorption Characteristic of Biomimetic Gradient Hierarchical Multicellular Tubes Under Axial Impact

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.

Preparation of bi-continuous interpenetrated AF/ZAlSi9Cu2Mg with excellent energy absorption capacity via in situ method

Integrating the high strength of ordered structures and the plateau stage of aluminum foam is an effective mean to enhance porous composite metal materials. In this work, bi-continuous interpenetrated porous composite (BIPC) was fabricated by a combinational way of melt foaming and infiltration casting. The mechanical properties of BIPC under quasi-static compression have been investigated. With the highest compressive strength and plateau stress, BIPC exhibits excellent energy absorption which is 130% higher than the sum of single structures. The desired mechanical performance of BIPC is attributed to the synergy of structural and interfacial effects during the compression process. Compared to the conventional counterparts, BIPC combines high specific energy absorption and specific compressive strength.

Comparative study of the mechanical properties of glass and Kevlar fiber-reinforced honeycomb composite

Honeycomb sandwich structures have wide range of applications in the aircraft, automobile, and satellite sectors due to their superior properties such as high specific strength, stiffness, energy absorption, and high impact strength. In this study, mechanical characteristics such as compression, three-point bending, and in-plane impact properties of 3D woven honeycomb composites produced from Kevlar and glass fiber were investigated. The focus of this research is to compare the mechanical performance of woven honeycomb composites developed from these two fibers with similar cell structures. The results revealed that Kevlar fiber honeycomb composite shows higher peak load and energy absorption for flatwise and edgewise compression while in three-point bending and in-plane impact, glass fiber honeycomb composite shows higher peak load, and impact energy absorption. The deformations shown in all the mechanical properties give the ductile behavior for Kevlar fiber and brittle behavior for glass fiber composite. The findings of the study suggest that the failure modes are mostly determined by the nature of the material itself.

4D printed zero Poisson’s ratio metamaterials with vibration isolation properties for magnetic response

Although mechanical metamaterials possess high specific energy absorption, they suffer from drawbacks such as irreversible deformations and non-adjustable mechanical properties. Magnetic excitation is considered to be one of the most promising methods for special working environments; for which uniform incorporation of UV-cured four-dimensional (4D) printed resin is considered to be an effective approach to achieving fine structural features. Our study investigated the impact of soft magnetic particle content on the mechanical and dynamic mechanical properties of a shape memory polymer matrix material. This paper presents a 4D printed metamaterial with a zero Poisson’s ratio that can sense magnetic field intensity and alter its mechanical properties. Its rapid shape recovery, achieved through magnetic excitation, enables multiple energy absorption within a short timeframe. By increasing the curvature radius, the stress concentration in the hexagonal honeycomb structure is reduced, ensuring the metamaterial maintains its zero Poisson’s ratio even under in-plane loading. The study investigates the energy absorption performance and force–displacement curve of metamaterials with different layers and cell sizes, focusing on a four-layer metamaterial for the analysis. Furthermore, the paper explores the tunable energy absorption characteristics of the four-layer metamaterial under time-varying electromagnetic fields, aiming to enhance the stability of a lander’s center of gravity while landing on uneven terrain.

Investigation on quasi-static axial crushing of Al/PVC foam-filled Al6063-T5 tubes

Abstract This study experimentally investigated the energy-absorbing capability of foam-filled 6063-T5 aluminum tubes. Thus, different sample combinations were created with two different foams, PVC (80 kg m−3) and aluminum (200, 350 kg m−3), which were used as filling materials. The first group of samples consisted of uniform foam-filled aluminum tubes. In contrast, tubes were filled with radially graded foams in the second group, which included a ring PVC foam and a cylindrical aluminum foam in the center. Empty tube absorbed 329 J, while it reached the values of 384, 488, and 606 J by using PVC and low- and high-density aluminum foams, respectively. The specific energy absorption value of the empty tube was obtained as 23.2 J g−1. In comparison, it was 19.3 J g−1 in the high-density aluminum foam-filled sample, although it absorbed the highest energy value. This shows that high-density aluminum foam was inefficient in terms of the crashworthiness of the structure. Finally, the best sample regarding the specific energy absorption and crush force efficiency was obtained in the sample where the PVC foam ring and high-density aluminum tube were used together. This sample had 7 % higher specific energy absorption and 34 % higher crush force efficiency than the empty tube.

Modified re-entrant auxetic metamaterials with energy absorption enhancement

The re-entrant auxetic topology was one of the first unit-cells proposed to build cellular auxetic structures. This unit cell (UC) is still widely used in energy-absorbing systems, but there is considerable scope for enhancing its design. This paper describes a series of experimental tests and finite element (FE) models used to evaluate the energy absorption capabilities of novel auxetic structures based on replacing straight struts of the re-entrant unit cell with curved-shaped ones. Three structures have been first designed and manufactured using fused deposition modeling (FDM) 3D printing techniques. The samples have then been subjected to quasi-static compressive testing. The results have been compared with those of a traditional re-entrant structure having similar relative densities and showed that the modified metamaterial topologies demonstrate significantly improved energy absorption and specific energy absorption (SEA) capabilities. In addition, all the proposed new topologies exhibit negative Poisson’s ratio (NPR). After selecting the structure with the highest SEA, a geometrical parametric analysis has been performed to investigate the design space to enhance overall SEA and NPR values. The proposed work provides an overview of the state-of-the-art in re-entrant auxetic structures and introduces a new class of modified re-entrant metamaterials with remarkable energy absorption capability.

Impact resistance of a double re-entrant negative poisson’s ratio honeycomb structure

Auxetic metamaterials, usually consisting of cellular solids or honeycombs, exhibit the advantages of high designability and tunability. In particular, the negative Poisson’s ratio (NPR) property endows them with innovative mechanical properties and makes them promising for a wide range of applications. This paper proposes a modified double re-entrant honeycomb (MDRH) structure and explores its Young’s modulus and Poisson’s ratio through theoretical derivation and finite element analysis. Additionally, it discusses the relationship between these parameters and the concave angle. Furthermore, the deformation mode, nominal stress–strain curve, and specific energy absorption of this MDRH are investigated for different impact velocities and compared with traditional re-entrant honeycomb (TRH) materials. The results show that the MDRH honeycomb structure greatly widens the range of effective modulus and NPR values. At different impact velocities, the MDRH exhibits high plateau stress and specific energy absorption, indicating good impact resistance. These results provide a theoretical foundation for the design and implementation of new energy-absorbing structures.

Lateral compression behavior of expanded polypropylene foam-filled carbon fiber reinforced polymer and aluminum/carbon fiber reinforced polymer composite tubes: An experimental study

This study investigates the energy-absorbing capability of the circular cross-section carbon fiber reinforced polymer (CFRP) and Aluminum/CFRP (Al/CFRP) composite tubular structures under quasi-static lateral compression. The CFRP composite tubes were manufactured with the 6, 8, and 10 layers to observe the thickness effect. A specially designed and manufactured polymer mold was used to manufacture identical CFRP composite tubes. Expanded polypropylene (EPP) foam with densities of 30 kg/m3, 60 kg/m3, and 75 kg/m3 was chosen as a filler material to enhance the energy absorption and efficiency because of its superior properties of high strength-to-weight ratio. The experiments revealed that the carbon fiber layer number directly affected CFRP and Al/CFRP composite tubes' force and the absorbed energy values. The increase in the maximum and average force values is more evident than in the Al/CFRP tubes due to using aluminum tubes constraining the effect of the carbon woven part. Additionally, EPP foam filling significantly contributes to the tubes' absorbed energy. The absorbed energy increased proportional to the foam density, and the 10-layer Al/CFRP tube filled with 75 kg/m3 sample absorbed the highest energy value as 257 J. However, considering the crashworthiness parameters (i.e., specific energy absorption, crush force efficiency, and work effectiveness), the best sample combination did not absorb the highest energy. Although the 6-layer CFRP composite tube absorbed the lowest energy, it has higher specific energy absorption and work effectiveness. According to the crashworthiness parameters, the best efficiency was obtained in the 10-layer composite tubes filled with 75 kg/m3.

Optimizing functionally graded hexagonal crash boxes with honeycomb filler for enhanced crashworthiness

A crash box is typically designed to enhance crashworthiness by absorbing impact energy and reducing the crushing force that can cause injury or fatality to passengers. However, the structural integrity of conventional crash boxes is often compromised due to buckling deformations during collisions. This study introduces a novel approach utilizing functionally graded thickness (FGT) in hexagonal crash box design with honeycomb fillers to improve crashworthiness through multi-objective optimization. Finite element analysis using LS-DYNA was performed for axial and oblique impacts. Mesh sensitivity study indicated that constructing the FGT crash box with 41 layers yielded favourable outcomes, with simulation results differing by a mere 2.5% compared to experimental data. A surrogate model based on response surface methodology was employed to mathematically formulate the objective functions, which aimed to maximize specific energy absorption (SEA) and minimize initial peak crash force (IPF). Subsequently, a multi-objective particle swarm optimization was used to determine the optimal grading exponent of both outer and filler structures. The optimized FGT crash box demonstrated superior control over progressive deformation, exhibiting high SEA and reducing IPF compared to the uniform thickness crash box. Particularly, under oblique impact loads, using two grading exponents in optimizing the FGT crash box potentially achieved significant improvements in crashworthiness within the design procedure.

Auxetic mechanical metamaterials with symmetry-broken Re-entrant units

Three innovative auxetic metamaterials with symmetry-broken unit cells and possible applicability in the construction and automotive industries are presented by breaking the mirror symmetries of the conventional re-entrant unit cell. The single symmetry-broken re-entrant (SBR), double symmetry-broken re-entrant (DBR), and hybrid symmetry-broken re-entrant (HBR) structures are fabricated via 3D printing and examined by experimental compression tests and finite element analysis (FEA). The proposed metamaterials exhibit remarkable specific energy absorption (SEA) properties in comparison to the benchmark symmetric-unit honeycomb, with the SBR model showing 103.9 % higher SEA. The novel structures also show superior stability under large compressive deformation, exhibiting excellent auxeticity in comparison to the symmetric-unit model. Parametric investigations reveal that the level of asymmetricity of the unit cells plays a key role in the stability and superior mechanical properties of the proposed metamaterials under compression. One set of parametric studies discovers an HBR structure with a special combination of SBR and DBR units which outperforms the parent structures under compression. Finally, parametric investigation of transverse and inclined compression of the structures indicated superiority of the DBR metamaterial to other structures due to having a deformation mechanism with organized self-contact regions. The DBR metamaterial owns 314 % and 86 % higher SEA rather than the benchmark honeycomb under transverse and inclined compression, respectively.

Experimental and numerical crashworthiness investigation of 3D printing carbon fiber reinforced nylon origami tubes

AbstractIn 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.

Enhancing the compressive properties of re-entrant honeycombs by line defects with insight from nature

Three novel heterogenous re-entrant honeycombs with possible applicability in the construction and automotive industries are designed with insight from geometric defects in cellular structures of nature (beehives and graphene). The honeycombs that are composed of geometric defect channels and the geometrically perfect honeycomb are produced via fused deposition modeling 3D printing method. The structures are tested via experimental and numerical methods and their behavior is assessed in terms of specific energy absorption (SEA), effective Young’s modulus (Ee), and deformation mechanism under compression. Each innovative structure outperforms the benchmark model in terms of Ee, owning a stiffer response to loading. Two of the defective honeycombs exhibit superior performance to the benchmark in terms of SEA, with about 100% and 157% higher specific energy absorption, due to having better stability and different lateral buckling modes under compression. Unlike the benchmark model, the defective honeycombs’ auxeticity is maintained under compression. Also, one of the parametric studies proves that the novel honeycombs have promising potential in applications where structures are subjected to inclined loads, due to having roughly 148% higher SEA than the benchmark under inclined compression.