Enhanced Energy Absorption Research Articles

Enhanced energy absorption and low anisotropy of additively manufactured porous Ti-6Al-4V alloy with disordered trapezo-rhombic dodecahedron structures

Enhanced energy absorption and low anisotropy of additively manufactured porous Ti-6Al-4V alloy with disordered trapezo-rhombic dodecahedron structures

Compression response and optimization design of a novel glass-sponge inspired lattice structure with enhanced energy absorption capacity

Lattice structures have shown tremendous prospects in engineering fields, because of the ultralight, strong and toughness properties. In this paper, a novel configuration of lattice structure (GSIBCC) inspired by the hierarchical skeleton system of glass sponges is proposed. The new configuration of the unit cell is based on modifying the inner cross struts of the body-centered cubic (BCC) lattice, by considering the double diagonal reinforcements and hybridization of unit cells. The compression properties and deformation mechanism of the GSIBCC lattice structure are compared with BCC, OCT (Octet) and other glass sponge inspired lattices. A multi-objective optimization method is established, for maximizing the specific energy absorption (SEA) and simultaneously reducing the compression strength. The novel GSIBCC lattice exhibits superior specific energy absorption than BCC, OCT, and other glass sponge inspired lattices. For example, GSIBCC shows maximum 145.06% improvement (ρ¯=0.124) of SEA with respect to BCC, and maximum 117.4% improvement (ρ¯=0.124) of SEA with respect to OCT. The novel lattice exhibits the whole deformation type and obvious second stress reinforcement effect. Besides, the mechanical properties of GSIBCC are further improved using the multi-objective optimization. The reported biomimicry design strategy, deformation and failure mechanism, and multi-objective optimization method will be beneficial for enriching the lattice system and promoting the multifunctional applications of lattice structures in engineering fields.

Mechanical properties and failure mechanism of 3D printing ultra-high performance concrete

Steel fiber reinforced 3D printing ultra-high performance concrete (3DP-UHPC) is prepared and experimentally studied. The effects of steel fiber content and various interlayer reinforcing materials on compressive, flexural, and splitting tensile properties are investigated, supplemented by Digital Image Correlation (DIC) technique for crack propagation analysis. Fabricated 3DP-UHPC specimens exhibited compressive strengths exceeding 160 MPa, with a peak at 205.2 MPa. Incremental increases in steel fiber content slightly enhanced compressive strength, whereas the addition of interlayer reinforcing materials, textile/steel wire mesh (SWM), reduced it due to altered interlayer bonding characteristics. The incorporation of textile/SWM significantly improved the flexural performance, enhancing energy absorption capacity and toughness. Specimens reinforced with SWM exhibited excellent flexural performance, with their flexural strength and ultimate deflection reaching 110.9 % and 192.5 % respectively of those before reinforcement. The splitting test revealed typical fractures along the interfaces between printed layers, with higher splitting strength obtained in the bottom layers. In specimens reinforced with carbon textile, glass textile, and SWM, the splitting strengths were more than double those of the subsequent layers. These insights contribute to a deeper understanding of 3DP-UHPC, paving the way for optimized use of reinforcing materials to improve structural integrity and performance.

Enhancing energy absorption of the sandwich beams with a synergetic strategy of flexible/rigid materials in re-entrant auxetic cores under flexural loading

Enhancing energy absorption of the sandwich beams with a synergetic strategy of flexible/rigid materials in re-entrant auxetic cores under flexural loading

Impact Resistance Performance and Damage Characteristics of Mortise-and-Tenon Joint Prefabricated Bridge Piers

The mortise-and-tenon joint prefabricated connection combines the assembly form of mortise-and-tenon joints and cast-in-place wet joints. It achieves reliable joint connections through small joint depths and lap-spliced reinforcement lengths. To study the impact resistance and damage characteristics of the assembled pier, a nonlinear finite element analysis was performed on the assembled and monolithic pier model piers to study the effects of mortise-and-tenon joint depths, lap reinforcement, and grout on the response of the piers to vehicle impact. The results showed that, after impact, the damage to the prefabricated pier was similar to that of the monolithic one. The failure mode involved opening of the seam at the impact face-pier bottom junction and localized concrete compression at the back-impact face pier bottom, and damage accumulated from the column base towards the column centerline. The mortise-and-tenon joint provided substantial horizontal constraint for the pier, imparting excellent resistance to lateral stiffness. Consequently, both piers showed nearly identical peak impact forces, yet the prefabricated pier exhibited a lesser degree of bending deformation compared to the monolithic one. The depth of the mortise-and-tenon joints was a critical factor affecting the impact response of the prefabricated bridge pier. When the depth reached 0.4D or more, it ensured good impact resistance and joint connection, enhancing energy absorption capability and reducing pier damage. The length of lap-spliced reinforcement significantly affected the overall integrity of prefabricated component connections. Lap lengths of 10d or more greatly reduced the probability of failure in the connection between pier columns and cap beams, lowering damage to the pier columns, joints, and pier cap beams, thus ensuring good impact resistance. The diameter of the lap-spliced reinforcement and the elastic modulus of the grouting material affected the local stiffness near the joints. Increasing the diameter of the lap-spliced reinforcement appropriately prevented excessive local damage, while altering the elastic modulus had minimal impact on improving pier damage.

Numerical and experimental study of energy absorption in multilayer tubes manufactured through spinning forming process under quasi-static axial loading

Currently, dual-layer tubes play a pivotal role in sectors like nuclear, oil, gas, and steam generation. Recent research focuses on enhancing energy absorption in these tubes using the spinning forming process. This thin-walled nature benefits their application as efficient energy absorbers in transportation like trains and aircraft. A novel approach integrates coarse and fine-threaded ridges between steel and aluminum layers to create a mechanical interlock using the spinning forming technique. This interlock enhances the bond through flow forming, resulting in robust dual-layer tubes. Interlayer connection strength is rigorously tested through shear tests, pre and post flow forming, indicating a significant post-flow forming enhancement. This process substantially bolsters the overall structural integrity of dual-layer tubes. In crush tests, both single-layer and dual-layer steel and aluminum tubes undergo pressing through flow forming. Comparative analysis of energy absorption parameters—specific energy and crushing percentage—reveals notable performance differences. An annealed version of the tube with an aluminum layer is also included due to prior aluminum layer failures. Among dual-layer samples, the flow formed variant with fine-threaded ribs exhibits superior energy absorption and bonding. Finite element simulation of the pressed dual-layer sample demonstrates an 8.42 % deviation between simulated and experimental energy absorption outcomes. The study highlights that tightly bonded layers result in enhanced bonding characteristics.

Design and additive manufacturing of novel hybrid lattice metamaterial for enhanced energy absorption and structural stability

In this work, a novel dual-phase metamaterial, named as “hybrid lattice metamaterial (HLM),” are designed and fabricated by combining reentrant and sea-urchin (SU) based surface-lattice (SL) structure with polyamide12 (PA12) material via material extrusion (MEX) process. Four different designs with varying reentrant truss thicknesses of 0.8 mm (H1), 1.0 mm (H2), 1.2 mm (H3), and 1.5 mm (H4) have been modified to assemble seamlessly with the empty spaces within the SL structure. Quasistatic compression tests were conducted to evaluate the deformation modes and compression characteristics. The findings from quasistatic experiments were subsequently validated using numerical simulations. The H4 metamaterial exhibited superior structural properties, with 42 % increase in stiffness and 35 % enhancement in specific energy absorption compared to only SL structure. Additionally, dynamic sinusoidal compression tests were conducted to evaluate the dynamic elastic ratio (DER), hysteresis work and viscoelastic properties using the tan δ. The H4 metamaterial outperformed the SL in all dynamic properties, with a 50 % increase in elastic modulus and 36 % increase in hysteresis work. This study shows metamaterial properties can be tailored for specific requirements. SL structure facilitate elastic recovery, while H4 metamaterials offer superior energy absorption and stability, making it well-suited for protective equipment and impact-resistant components.

Mechanical properties and fracture phenomena in 3D-printed helical cementitious architected materials under compression

The mechanical response and fracture behavior of two architected 3D-printed hardened cement paste (hcp) elements, ‘lamellar’ and ‘Bouligand’, were investigated under uniaxial compression. A lab-based X-ray microscope was used to characterize the post-fracture crack pattern. The mechanical properties and crack patterns were analyzed and compared to cast hcp. The role of materials architecture and 3D-printing-induced weak interfaces on the mechanical properties and fracture behavior are discussed. The pore architecture that inadvertently forms in the design of solid architected materials dictated the overall mechanical response and fracture behaviors in both 3D-printed architected materials. While no specific crack pattern or microcracking was observed in the cast element, lamellar architecture demonstrated a crack pattern following weak vertical interfaces. Bouligand architectures, on the other hand, exhibited a helical crack pattern with distributed interfacial microcracking aligned with the helical orientation of filaments. As a result, the bouligand architected elements showed a significant 40% increase in work-of-failure compared to cast counterparts. The enhanced energy absorption was obtained without sacrificing the strength and was attributed to higher fractured surface and microcracking, both of which follow the weak helical interfaces.

Mechanical properties and ductility improvement mechanisms of fiber-reinforced biomimetic mineralized composites using sea sand

Biomimetic mineralized composites (BMC) is an emerging green cementing material. However, the application of BMC is limited by brittle failure. This study proposes novel fiber-reinforced biomimetic mineralized composites (FRBMC) with excellent ductility based on the coupling method of fiber reinforcement and biomimetic chemically induced calcium carbonate precipitation (BCICP). Three typical fibers, including polymer fibers (polypropylene fiber, PF), mineral fibers (basalt fiber, BF), and plant fibers (coir fiber, CF), were used to explore the feasibility of application in FRBMC. Accordingly, mechanical properties, pore structures, and microscopic characteristics were assessed through unconfined compressive strength (UCS) test, mercury intrusion porosimetry (MIP) tests, and scanning electron microscopy (SEM). The results show that fiber induces a transition from brittle to ductile failure modes in BMC. PF exhibits the most notable enhancement in residual strength and peak strain, while BF leads to the highest compressive strength. CF can effectively enhance energy absorption after reaching peak stress. Moreover, FRBMC with CF contains a higher quantity of minute pores, while BF can reduce the porosity of FRBMC. The calcium carbonate crystals effectively cement fibers and sand particles, enhancing the ductility of FRBMC through forming various cementing structures. This study investigates the synergistic effect of BCICP and fiber reinforcement, providing valuable guidance for potential practical applications of FRBMC.

Enhanced strength and toughness of carbon fiber reinforced aluminum matrix composite prepared via novel indirect extrusion method

The fabrication of large-sized, high-performance CF/Al composites presents significant challenges for the aerospace industry. This study introduces a novel indirect extrusion (IE) method for the high-quality production of CF/Al composites. The study investigates the infiltration mechanism of the alloy liquid during the IE process, highlights the technique's advantages, and systematically analyzes the mechanical properties and failure mechanisms of CF/Al composites. Results show that the aluminum liquid initially fills the interlayers and subsequently penetrates the fiber bundles, effectively shortening the infiltration distance. At a casting temperature of 800°C and an infiltration pressure of 40 MPa, the composite exhibits excellent forming quality and microstructural integrity. Compared to direct extrusion (DE) CF/Al composites, IE-CF/Al composites show significant improvements in compressive strength (16.72 %), flexural strength (16.87 %), fracture toughness (43.18 %), and work of fracture (90.61 %). The interlayer alloy and increased fiber spacing in IE-CF/Al composites enhance energy absorption capacity and reduce the risk of brittle fracture. This process lays a solid foundation for the high-quality production and application of CF/Al composites.

A novel windmill-shaped auxetic structure with energy absorption enhancement

The traditional anti-tetra-missing rib structure often suffers from uneven stress deformation and poor energy absorption, which limits its engineering applications. To address these limitations, this paper proposed a novel windmill-shaped auxetic structure by incorporating reinforcing ligaments into the traditional anti-tetra-missing rib structure. The incorporation of these reinforcing ligaments ensures that both the outer and inner ligaments of the windmill-shaped auxetic structure are adequately supported, leading to more uniform structural deformation and enhanced energy absorption capabilities. Further modifications, such as reducing the length of the outer and inner ligaments and increasing their thickness within a reasonable range, significantly enhance the energy absorption capacity. These findings provide a theoretical basis for the design and practical application of auxetic metamaterials.

Coupling Chiral Cuboids with Wholly Auxetic Response.

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

Investigating the Mechanical Behavior and Energy Absorption Characteristics of Empty and Foam-Filled Glass/Epoxy Composite Sections under Lateral Indentation.

In this study, the crashworthiness behavior and energy absorption capacity of composite tubes under lateral indentation by steel rods aligned parallel to the specimen axis are investigated using experimental methods. Key parameters such as tube diameter, length, wall thickness, and indenter diameter are systematically examined and compared. Additionally, the influence of polyurethane foam fillers on damage modes and energy absorption capacity is rigorously analyzed. Contrary to conventional findings, smaller diameter specimens filled with foam demonstrate superior energy absorption compared to their larger counterparts, primarily due to enhanced compression of the foam volume. Experimental results reveal a complex interplay of damage mechanisms in composite specimens, including matrix cracking, fiber breakage, foam crushing, foam densification, foam fracture, and debonding of composite layers, all contributing to enhanced energy absorption. Increased tube thickness, length, and indenter diameter, alongside decreased tube diameter, are correlated with higher contact forces and improved energy absorption. Smoother shell fractures are promoted, and overall energy absorption capabilities are enhanced by the presence of foam fillers. This investigation provides valuable insights into the structural response and crashworthiness of composite tubes, which is essential for optimizing their design across various engineering applications.

Enhanced energy absorption of a novel skeletal-united tubular metamaterial exhibiting negative Poisson’s ratio

The study introduces a novel approach to balancing energy absorption (EA) and negative Poisson’s ratio (NPR) in metamaterial design, which typically present desired properties and conflicting objectives. This is achieved by developing a skeletal-united tubular metamaterial (SUTM), created by splitting and reconstituting a central in-line skeleton within the unit structure of a traditional re-entrant tubular metamaterial (RETM). The innovation design from unit to tubular structure enables SUTM to achieve a compromise between high EA and improved NPR by leveraging the generated re-entrant skeleton. Experimental and numerical comparisons demonstrate that the SUTM outperforms the RETM in both EA and auxetic properties. Additionally, the tube adopts an uncommon out-plane configuration of metamaterials, so the study investigates the effects of various tubular geometric parameters, including tube thickness, diameter, and height, on EA and NPR. Furthermore, a series of SUTM variants are proposed and examined, highlighting the advantageous role of the skeleton generated from the corner of the unit cell in enhancing EA.

Microstructure, mechanical and tribological properties of AA5083-TiO2 nanocomposite by multi-pass friction stir processing

This study examines the impact of Friction Stir Processing (FSP) with TiO2 nanoparticle incorporation on the microstructural, mechanical, and tribological properties of AA5083 Metal Matrix Composites (MMCs). It offers a detailed analysis of the alterations in the alloy’s characteristics due to FSP. Microstructural examination was conducted using optical microscopy (OM) and scanning electron microscopy (SEM). Significant findings include the microstructural refinement where TiO2 nanoparticle addition during FSP shrank the grain size from 20 to 3 µm after one pass, which then rose to 7 µm following four passes. Mechanical properties, specifically microhardness and tensile strength, were assessed. Results indicated that after four FSP passes, the material can reach a yield strength of 192 MPa and an ultimate tensile strength (UTS) of 359 MPa, alongside a consistent microhardness of 103 HV0.1. Furthermore, it was observed that increasing FSP passes enhances energy absorption, although it remains lower than that of the base material. Analysis of fracture and wear mechanisms has led to the conclusion that with more passes, fracture mechanisms transition to a mix of ductile and brittle behaviors, and the friction coefficient decreases by up to 22.95%.

Crashworthiness analysis and optimization design of special-shaped thin-walled tubes by experiments and numerical simulation

Thin-walled structures are widely used as typical high-efficiency energy-absorbing structures in crash safety protection. This paper aims to combine the characteristic of the square tube which concentrates energy dissipation through angle elements with the stable fold deformation of the circular tube, and innovatively propose a special-shaped thin-walled tube that contains both angle elements and arc elements. The failure behavior and energy absorption characteristics of the special-shaped tube were investigated by compression test and numerical simulation. The simulation results showed that the special-shaped thin-walled tubes have a significant advantage in energy absorption, and the specific energy absorption of the special-shaped tubes is 31.57% and 75.2% higher than that of the equal-mass circular and square tubes, respectively. Next, through finite element analysis, the effects of various parameters and initial imperfections on the crashworthiness of the special-shaped tubes were compared. The results indicated that adjustments to geometrical parameters significantly impact the energy absorption properties and crushing behavior of thin-walled tubes. Moreover, the tube with induced circular holes exhibited an optimal deformation mode. Further, a multi-objective optimal design of the metal special-shaped tube was carried out to obtain the best parameter configuration of the metal special-shaped tube. Finally, the special-shaped structure was extended to CFRP/AL hybrid thin-walled tubes. The failure behavior and energy absorption enhancement mechanism of the hybrid special-shaped tubes were investigated with experiments, and the absorbed energy of the hybrid tube was about 20% higher than the sum of the absorbed energy of the single constituent tubes. The effect of the CFRP lay-up pattern on the crashworthiness of the hybrid tube was investigated by numerical simulation, and it was found that the energy absorption capacity of the hybrid tube could be improved by appropriately increasing the number of layers and the proportion of axial fibers.

Design and mechanical properties analysis of bionic tube based on cattle horn structure

Composite tubes are widely adopted in engineering protections owning to desirable passive energy absorption. With the aim of enhancing energy absorption and making full use of structural materials, a novel tube inspired by the structure of cattle horn has been designed. It consisted of a shell composed of nested tubes and a core composed of evenly distributed tubes, which are connected by beams. The energy absorption properties of bionic tube, six-cell tube, four-cell tube and circular tube were compared by numerical models verified by axial compression. The factors affecting mechanical responses and energy absorption capacities of bionic tube were analysed. Compared to the six-cell tube, the bionic tube exhibited a 104.91% increase in peak load, a 239.51% increase in mean load and an 83.39% increase in specific energy absorption. Under the premise of ensuring the energy absorption, mean load and crushing force efficiency, the mass and peak load can be controlled by limiting the wall thickness and height of core. The proposed bionic tube had the potential to be applied in the automobile and aerospace industry.

Adjustable Ultra-Light Mechanical Negative Poisson's Ratio Metamaterials with Multi-Level Dynamic Crushing Effects.

Mechanical metamaterials with multi-level dynamic crushing effects (MM-MLs) are designed in this study through coordinate transformation and mirror arrays. The mechanical effects of the diameter and length ratio of the struts and connecting rods, the Euler angles, and the cell numbers on the mechanical properties are investigated separately. MM-ML can exhibit significant two-level platform stress, and the local cells in the first platform stress stage undergo rotational motion, while the second platform stress stage mainly involves collapse compression and bending. Although increasing the length of the connecting rods can increase the range of Poisson's ratio, it will reduce the level of platform stress and energy absorption. Increasing the Euler angle will reduce the strain interval of the first platform stress and can improve the energy absorption capacity. In addition, increasing the cell number while maintaining a constant relative density can effectively enhance energy absorption. MM-ML has significant parameter controllability, can achieve different platform stress regions, different ranges of Poisson's ratios, and energy absorption requirements according to the application scenario, and can demonstrate functional diversity compared to existing research. The design scheme can provide ideas for adaptive crushing protection requirements.

Using a Negative Poisson's Ratio to Mitigate Stress Concentrations in Perforated Composite Plates

Stress concentrations pose a significant challenge in designing and optimizing composite components, often resulting in structural alterations and crack formation. This study delves into a detailed numerical and analytical analysis of stress concentration factors in composite materials, with a specific focus on the influence of negative Poisson's ratio and out‐of‐plane modulus. By exploring the interaction of these material properties, the objective is to devise effective strategies for alleviating stress concentrations in composite structures. Through analytical and numerical simulations, a robust correlation between the customized Poisson's ratio and modulus and the mitigation of stress concentration factors, particularly in epoxy/graphite‐reinforced composites are established. This tailored approach has the potential to enhance energy absorption capabilities and consequently reduce the risk of crack propagation in perforated laminated composite plates. This research findings offer valuable insights into composite material design, presenting innovative solutions for enhancing structural integrity and reducing susceptibility to stress‐related issues.

Bionic design of thin-walled bilinear tubes with excellent crashworthiness inspired by glass sponge structures

In order to enhance energy absorption, this study draws inspiration from the diagonal bilinear robust square lattice structure found in deep-sea glass sponges, proposing a design for thin-walled structures with superior folding capabilities and high strength-to-weight ratio. Firstly, the crashworthiness of bionic glass sponge tube (BGSTO) is compared with that of equal-wall-thickness equal-mass four-X tube through both experiments and simulations, and it is obtained that the specific energy absorption of BGSTO is increased by 78.64%. And the crashworthiness of BGSTO is also most significant compared to that of multicellular tubes with the similar number of crystalline cells. Additionally, we found that the double-line spacing of the glass sponge can be freely adjusted without changing the material amount. Therefore, based on BGSTO, we designed two other double-line structures, BGSTA and BGSTB. Then with equal wall thickness and mass as a prerequisite, this study proceeds to design and compare the energy absorption properties of three bilinear thin-walled tubes in both axial and lateral cases. The deformation modes and crashworthiness of the three types of tubes with variable bilinear spacing (βO/A/B ) are comparatively analysed. The improved complex proportional assessment (COPRAS) synthesis decision is used to obtain that BGSTO exhibits superior crashworthiness over the remaining two kinds of tubes. Finally, a surrogate model is established to perform multi-objective optimization on the optimal bilinear configuration BGSTO selected by the COPRAS method.