Lattice structures have garnered significant attention in industrial applications due to their exceptional mechanical properties and superior energy absorption capabilities. The nonlinear response of these structures under extreme loading conditions can critically influence their mechanical performance and safety. However, existing research mostly focuses on their properties in the elastic range, and only limited studies have been conducted on the large, plastic deformation behavior of lattice structures. This work provides a comprehensive investigation of the complete large plastic deformation process, including the stabilization effects of strain hardening and its influence on collapse mechanisms. In this study, their large, plastic deformation behaviour was studied experimentally and theoretically. Steel BCC lattice structures were fabricated by using selective laser melting (SLM) and tested in compression. Also, an analytical framework was developed based on an idealized deformation mechanism, incorporating two material constitutive models: a rigid-perfectly plastic model and a rigid-linear hardening model. For the linear hardening model, a characteristic length parameter (lambda d) was introduced to represent the extended plastic deformation zone. The analytical model was validated through finite element (FE) analysis and experimental methods. Applicability of the proposed model to lattice structures was thoroughly discussed by considering different geometrical parameters.

A theoretical analysis is conducted on the deformations of the Miura-ori patterned sheet. The sheet deforms within the elastic range of the material Elvaloy in the mechanical tests, which includes the out-of-plane compression, in-plane compression and three-point-bending tests. Among other assumptions, the Miura-ori’s one degree-of-freedom mobility and rigid facets are kept in the theoretical model for the simplicity of the analysis. The global deformations of the patterned sheet are integrated by the elastically deformed portions along the ridgelines. The relationships between reaction forces and displacements are obtained using the principle of virtual work. In energy balance equations, external works are done by reaction forces and internal works are generated by elastic deformations along ridgelines. The theoretical results show good correlation with the experimental data, except in the in-plane X1 compression and three-point-bending X1. The disparities between the theoretical and experimental data indicate a refined model is needed for a better description of the corresponding deformations.

Kresling origami (KO) structures are promising energy absorbers due to their unique coupling of axial and rotational deformation. However, enhancing their energy absorption performance and achieving integrated structural configurations remain challenging. This study proposes three novel tessellated KO designs - linear (KL), array (KA), and circular (KC) - fabricated using 3D-printed thermoplastic polyurethane (TPU). The uniaxial crushing behaviors of these interconnected structures were investigated under quasi-static and dynamic loading. A finite element model validated by experiments, along with an analytical model for predicting mean crushing force, was developed to elucidate the deformation mechanisms. Compared to isolated KO units, the interconnected configurations significantly improved energy absorption, with the KC pattern exhibiting a 1.73-and 1.78-fold increase in SEA under quasi-static and 10 m/s impact conditions, respectively. To eliminate the influence of base material properties, a non-dimensional metric - Effective Energy Absorption (EEA) - was introduced. The proposed KC structure achieved both lower relative density and higher EEA than many representative origami and thin-walled designs, highlighting its superior structural efficiency and potential for lightweight impact protection applications.

This study presents a novel bi-material re-entrant tubular (BRT) metamaterial fabricated via dual-material additive manufacturing, in which a rigid PLA core is encapsulated by a flexible TPU shell. This configuration effectively integrates the high stiffness of PLA with the elasticity of TPU, enabling a stable and controllable collapse process without cracking. The soft-hard coupling ensures efficient stress transfer and coordinated deformation, mitigating stress concentrations and preventing premature failure. Compared with single-material re-entrant tubular (RT) structures, the bi-material BRT metamaterial exhibits substantial mechanical enhancement, with stiffness, total energy absorption, and specific energy absorption increased by 90%, 88%, and 91%, respectively. Parametric analyses reveal that increasing the PLA core thickness significantly improves structural stiffness, plateau stress, and energy absorption capacity, with specific energy absorption enhanced by up to 67%. However, excessive PLA thickness may weaken interfacial adhesion and induce delamination or brittle fracture, highlighting the importance of optimal thickness matching between soft and rigid layers to balance stiffness and ductility. Under cyclic compression, the BRT metamaterial retains over 60% of its initial energy absorption capacity even at 100% strain after four loading cycles, exhibiting pronounced secondary stability and adaptive deformation. The structure recovers 98.9% of its original height, demonstrating excellent geometric stability and recoverability. This research provides an effective design strategy for future multi-material metamaterials with tunable mechanical properties.

As lightweight and high-strength functional-structural integrated materials, cellular structural materials are widely applied in aerospace, automotive manufacturing, and biomedical fields. However, traditional single-configuration cellular materials (e.g., honeycomb structures and point-lattice lattices) gradually exhibit performance limitations under complex conditions such as impact shock waves, multi-directional impacts, or nonlinear deformations. Against this backdrop, heterogeneous cellular structure material (HCSM) have emerged as a research hot pot in impact protection. This paper systematically reviews recent design strategies and impact resistance performance of HCSM. HCSMs are primarily categorized into two types: topological configuration heterogeneity (including complementary and enhanced fusion) and material heterogeneity (e.g., filling with foam materials and shear-thickening materials). Through innovative “functional fusion” approaches, they overcome the performance bottlenecks of single-configuration cellular materials. The study further elucidates the synergistic reinforcement effects and deformation mechanisms of HCSM under impact loads, while analyzing their intrinsic mechanisms for improving energy absorption efficiency, stiffness, and stability. Despite significant progress in HCSM research, challenges remain in connectivity optimization, additive manufacturing process compatibility, complex condition validation, and multifunctional integration. Going forward, the integration of artificial intelligence and machine learning technologies holds promise for achieving end-to-end optimization of HCSMs from design to manufacturing, thereby providing new directions for developing next-generation high-performance impact-resistant structural materials.

Traditional energy absorption structures struggle to balance the demands of lightweight design, high-efficiency blast resistance and acoustic regulation. Integrating honeycomb structures with acoustic metamaterials offers an important solution to this problem. In this paper, the dynamic response of such honeycomb based acoustic metamaterials is investigated, in which Helmholtz resonators are embedded. Three metamaterial configurations and conventional aluminum honeycomb sandwich panels were fabricated. Their performances were examined and compared through impedance-tube measurements and blast tests. Compared with regular honeycomb panels with poor acoustic absorption capacity, all metamaterial panels were designed to have absorption peaks near 100 and 200 Hz, which were demonstrated by acoustic tests. The blast tests showed that the failure modes of metamaterial panels were strongly dependent on stand-off distance and the detonation point offset to the center of panel. Under close-in blast loading, the front face sheet suffered severe localized tearing, whereas at larger stand-off distances the response shifted to global deformation-dominated behavior. The three metamaterial configurations exhibited similar blast-resistant performance within the investigated loading range. At an identical vertical detonation distance, the damage to the metamaterial plate intensifies as the explosive charge approaches the center of the honeycomb cell (the cell opening). Compared with conventional honeycomb panels, this metamaterial panel exhibits superior performance in low-frequency sound absorption. However, its blast resistance is significantly degraded, with the final deflection increasing by up to 27.7%. This is attributed to the weakened structural stiffness caused by the perforated structure on its front surface. These results demonstrate the feasibility of integrating acoustic and mechanical functionalities in a single sandwich structure and provide experimental guidance for future optimization toward a better balance between sound absorption and blast protection.

Topology-optimised porous hip implants have been proposed to reduce stiffness mismatch and improve load transfer after total hip arthroplasty, yet their experimental validation remains limited. This study experimentally evaluates additively manufactured Ti6Al4V-Gr23 porous hip implant prototypes derived from an established modified Floating Projection Topology Optimisation (FPTO) scheme, translating the optimised design from computational development to physical fabrication and standardised mechanical testing. Custom stainless-steel fixtures and dental plaster embedding were developed to reproduce stem and neck loading configurations, with the embedding medium first verified through compression testing. Quasi-static stem compression tests demonstrated consistent force–displacement responses, with maximum displacements of 0.8558–0.9224 mm under 1,500 N and an average stiffness of 1.6846 kN/mm. This stiffness was lower than that reported for solid implant benchmarks while remaining within the range associated with natural femoral behaviour, supporting the intended stiffness-reduction strategy. Fatigue testing based on ISO 7206-4 and ISO 7206-6 loading principles showed that the prototypes withstood the prescribed cyclic regimes without catastrophic failure. These findings provide experimental evidence for the mechanical feasibility of FPTO-derived porous hip implants and establish a foundation for further preclinical validation.

Lattice structures are promising energy-absorbing materials against dynamic impact. However, there is a lack of quantified study of the respective contributions of parent material's strain-rate sensitivity and structural inertia to the dynamic strengthening of lattice structures. Therefore, to assess the contributions of these two mechanisms, BCC lattice structures were fabricated using selective laser melting 316 L stainless steel and tested under quasi-static compression and SHPB impact loading in this study. A finite element (FE) model based on the Johnson-Cook (J-C) constitutive law was developed and validated against experimental results. The influence of strain-rate sensitivity was then quantified by varying the strain-rate parameter in the FE model, and an analytical model incorporating both strain-rate and inertia effects was developed based on shock-wave theory. The results show that the strain-rate contribution can reach approximately 20% of the dynamic plateau stress at low impact velocities and remains about 5% even at 200 m/s. Below the critical velocity, the strain-rate effect dominates the dynamic strengthening, whereas inertia becomes dominant at higher velocities. The proposed model provides a calibrated predictive framework for evaluating the dynamic plateau stress of lattice structures.

BACKGROUND AND OBJECTIVE:Total joint replacement is a cost-effective surgical operation performed in orthopaedics in which a damaged joint is replaced with a medical implant. This can relieve pain, improve motion, and allow patients to return to normal daily activities. However, there are a lot of issues with regard to the conventional solid implantation, such as high potential risk of stress shielding, customised design for different purposes or patients, specific anisotropic and heterogeneous microstructures to restore biological functions. METHODS:A Floating Projection Topology Optimisation (FPTO) algorithm with ersatz material model and multiple constraints is used in this paper for implants design. The algorithm develops with a global volume constraint to control total volume fraction, a local porous infill volume constraint to generate porous infill and the objective of maximising stiffness constrained by lower volume fraction for reducing stress shielding effect. The novel FPTO-finite-element-musculoskeletal modelling and analysing pipeline allows weight factors for considering multiple loading cases in accordance with varieties of postures in gait cycle. Validations and simulation-predicted testing are conduct by finite element analysis (FEA) under varieties of loading cases to investigate the performance of the porous implant design. RESULTS:FPTO is feasible in designing medical implants with lower stiffness for reducing stress shielding effect. Smooth boundary of implants by FPTO can be obtained directly without post-processing, and multiple constraints are allowable. Compared with conventional design, the proposed implant can approximate natural bone structure and load transmission path. Finite-element-based FPTO design provides tailored anisotropic and heterogeneous topology based on host bone and muscle conditions for better biomechanical performance and durable serviceability whilst being lightweight. CONCLUSIONS:This paper proposes a Floating Projection Topology Optimisation (FPTO) algorithm with ersatz material model and multiple constraints for smooth boundary implant design to reduce stress shielding effect. With FPTO technique, it is expected to shed new light on design of porous implant considering tailored biomechanical environment.

It is a big challenge to improve the low and medium-frequency vibration attenuation performance of lattice structures while at the same time maintaining considerably strong mechanical properties. In this paper, a novel body-centered cubic (BCC) truss plate nested hybrid-(TPNH) lattice structure was designed based on the local resonance mechanism and the hybrid design concepts. Experimental samples were prepared by selective laser sintering (SLS) additive manufacturing technique. The vibration attenuation and mechanical properties of the hybrid lattice structure with different geometrical parameters were investigated by the mass-spring equivalent theory, the finite element (FE) numerical simulations and the experimental tests. The results show that the BCC-TPNH lattice structure is more sensitive to the hybrid ratio p. At the angular parameter of 37 degrees and the hybrid ratio p of 0.5, the TPNH lattice structure achieves broadband vibration attenuation at low and medium frequencies, while simultaneously attaining the optimal specific energy absorption (SEA) and densification strain due to the mechanisms of node rotation and truss-plate interaction during the compression. This research paves the pathway for realizing multifunctional lightweight structure design that integrates high energy absorption and excellent vibration attenuation.

Additive manufacturing (AM) has been extensively studied in fabricating metallic components across various industrial sectors, including the automobile and aerospace industries, where the components are usually subjected to dynamic loadings. However, the reported mechanical properties of AM fabricated materials are typically evaluated under quasi-static loading conditions, which cannot satisfy their needs for dynamic applications. In this paper, the dynamic compression properties of stainless steel 316L (SS 316L) manufactured with laser directed energy deposition (L-DED) were studied and their microstructural evolution were revealed. Spilt Hopkinson Pressure Bar (SHPB) technique was utilized in the experiments to achieve various strain rates at 2200, 3300 and 4700 s_1.It was found that the strain rate significantly influences the mechanical properties and microstructural evolution of L-DEDed SS 316L. Under high strain rate loading, twining became the fundamental deformation form, resulting in enhanced strength. However, with further increased strain rate, the rise of adiabatic temperature caused increased stacking fault energy, which then inhibited the twinning behavior. The increase of dislocation density and twinning boundaries (TBs) caused high flow stress through dislocation pileups against the TBs. Adiabatic shear bands (ASBs) appeared at all three strain rates. Subsequently, samples fractured to pieces at 4751 s_ 1 in the ASB areas.

The energy absorption of sandwich tubes impacted between two rigid plates was investigated experimentally and numerically in the paper. Based on the collapse patterns observed in quasi-static experiment, several typical sandwich specimens were made and tested. The specimens were placed on the bottom platen of an Instron machine and gained a constant upwards velocity, followed by the impact with the top rigid platen. Their deformation history and load-compression curves were recorded. The energy absorption of sandwich tubes were then calculated and analyzed. Three different crushing patterns have been identified from previous experiments. The dynamic enhancement of energy absorption of the sandwich tubes were only observed in collapse pattern III under the tested velocity up to 10 m/s. Finite element (FE) models using ABAQUS were developed and validated against experimental results and the strain rate effect of metallic foam was considered. They were used to explore the detailed energy-absorption characteristics beyond the experimental range for impact velocities up to 100 m/s. The dynamic enhancement occurred for each configuration of sandwich tubes when the impact velocities were greater than 20 m/s. It was found that increasing the compression velocity leads to an increase in total plastic energy dissipation. Sandwich tubes with a thicker foam core are proved to be the optimum design.

This study presents a comprehensive investigation into the integration of shear thickening fluid (STF) with closed-cell structures, specifically focusing on sphere-based and tube-based configurations, to develop advanced materials for impact protection applications. A multi-method approach, combining analytical modeling, finite element simulations, and experimental testing, was employed to assess the compressive and bending behaviors of STF-filled structures. Key factors influencing these behaviors, including geometric parameters, loading rates, and the properties of the STF filler, were systematically analyzed. A novel governing equation was developed to predict energy absorption responses, which was validated against both experimental and numerical data. The validated analytical model effectively captures the key factors of geometry, strain rate sensitivity, and STF filling, providing a reliable and effective framework for the design and optimization of STF-filled structures. Experimental results demonstrated that cornstarch-based STF-filled structures outperformed their hollow counterparts in terms of load-bearing capacity. Additionally, the study highlights the beneficial role of entrapped air within hollow structures, which enhances energy absorption across varying loading rates. Furthermore, cornstarchbased STF-filled closed structures exhibited markedly superior load-bearing capacity compared to hollow structures, positioning them as highly promising candidates for applications in low-speed protective equipment, such as footwear, protective shoe soles, as well as other devices requiring effective energy absorption under low loading rates.

This study firstly explores the dynamic compression behavior and energy absorption characteristics of Miura-ori structures enhanced with shear thickening fluid (STF), highlighting the effects of incorporating non-Newtonian fluids into cellular constructs. Employing a combination of experimental and numerical methods, this research elucidates the superior mechanical properties of STF-enhanced Miura-ori structures compared with their unfilled counterparts, particularly under varying dynamic compression speeds. An extensive parametric analysis assesses the impact of geometric configurations of the Miura-ori (including wall thickness and cell count), STF concentration levels (10%, 20%, and 30%), and compression velocities on the energy dissipation processes. This examination reveals the complementary interaction between the fluid's rheological behavior and the structural mechanics, leading to a notable improvement in energy absorption and average crushing force in STF-filled Miura-ori configurations. These variations are systematically analyzed across different conditions such as wall thickness, number of cells, and STF concentration. The study further contrasts the energy absorption capabilities between STF-filled Miura-ori and honeycomb structures filled with STF. It also compares the performance of STF with other filling materials like water and silicone oil, underscoring the distinct benefits of STF attributable to its shear-thickening properties. These properties markedly enhance energy absorption during the plateau phase and modify the commencement of densification. The findings of this study offer valuable perspectives on the application potential of STF in Miura-ori frameworks for scenarios necessitating elevated energy absorption under dynamic loads.

Purpose The paper aims to evaluate the energy absorption properties of optimised strut cross-section AlSi10Mg lattice structures fabricated by laser powder bed fusion (PBF-LB) additive manufacturing (AM). Quasi-static evaluations indicate a transformation in deformation behaviour of lattices with increasing optimisation which supports strong energy absorption capabilities. Design/methodology/approach The paper applies a novel strut element optimisation method using a hybrid continuum-beam finite element model to improve energy absorption in metal lattice structures. Impact testing occurs on laser powder bed fusion (PBF-LB) fabricated aluminium alloy (AlSi10Mg) lattices specimens to validate the approach. Findings The study provides both a qualitative and quantitative understanding on how PBF-LB AlSi10Mg lattices behave at high strain rates and how strut geometry can be manipulated to produce superior as-manufactured structures. Research limitations/implications The qualification of structures produced by AM is dependent on material, structure and process technology. Further evaluation of geometric and topologic derivatives of the presented structures is required. Practical implications The paper demonstrates the refinement of lattice structures for the use as metamaterials with unique properties unattainable through conventional material science. Social implications The efficient distribution of lattice material reduces unnecessary material expenditure. Structural optimisation provides the means to further reduce expenditure for high value applications such as crash safety and biomedicine. Originality/value This study provides a method to elicit different behaviours and properties in metal lattice structures, which may lead to wide reaching applications as they become more common in engineering industry. It also provides a direct evaluation of mechanical properties of optimised metal lattice structures.

This study focuses on dynamic behaviours of short sandwich tubes with honeycomb cores under internal explosive loading. Six types of honeycomb geometries, i.e., Triangle, Square, Diamond, Hexagon, Kagome, and Octagon, are designed as the cores of the sandwich structures. The influence of honeycomb core geometry, wall thickness, and arrangement on the internal blast-resistant performance of sandwich tubes is identified and explored. Experimental data of the authors’ previous work is served as a basis for validation of the finite element (FE) analysis of the sandwich tubes. A comprehensive understanding of deformation modes, damage energy dissipation, and radial velocities are afforded through numerical investigation. The obtained results indicate that geometric designs and axial arrangement of the honeycomb core sandwich tube have significant influence on the deformation mechanism and explosive resistance of sandwich structures. Generally, octagonal and square honeycomb core designs proves to be more efficient in mitigating the damage of the outer shell under explosion than other core geometries. Furthermore, the findings from this research offer valuable benchmark data for the short sandwich tube to enhance the internal blast resistance.

This review addresses the critical safety challenges posed by collisions between over-height vehicles and low-clearance bridge girders, an underexplored topic in impact research. These collisions can lead to significant infrastructure damage, economic losses, and transportation disruptions. This paper synthesises experimental, numerical, and analytical studies on unprotected and protected structural members, focusing on the effectiveness of energy-absorbing protective systems. It highlights the limitations of current design standards that rely on equivalent static forces (ESF) and advocates for a better understanding of dynamic impact behaviour. Further, it also investigates the performance of various energy-absorbing materials that shield structural components from different impact types to identify and implement the most effective cushion systems for the impacts under consideration. The review identifies gaps in the existing literature, particularly in the interaction dynamics between over-height vehicles, cushioning devices, and bridge girders, and suggests future research directions to advance protective systems for infrastructure safety.

In this study, we present the design, fabrication, and investigation of an innovative auxetic tubular reinforced (ATR) metamaterial. The mechanical properties and deformation characteristics of ATR metamaterials were comprehensively analyzed under quasi-static compression in both axial and radial directions. We conducted a comparative analysis between the ATR metamaterials and the original auxetic tubular (AT) metamaterials, employing both experimental and finite element methods. The findings indicate that the ATR structure surpasses the original AT structure in terms of mechanical properties during quasi-static compression in both directional orientations. Subsequently, a meticulous parametric analysis of the rotation angle of the reinforced straight ribs, a pivotal structural parameter, was conducted. The outcomes revealed that the rotation angle of the reinforced straight ribs, serving as a geometric parameter, can effectively influence the Poisson's ratio of the ATR structure. As the rotation angle of the reinforced straight rib increases, the ATR structure demonstrates superior energy absorption. The optimized ATR structure, in comparison to the original AT structure, showcases notable enhancements, exhibiting a 215% improvement in energy absorption (EA), a 62% increase in specific energy absorption (SEA), and a 46% rise in energy absorption efficiency (EAE) under axial quasi-static compression. Moreover, under radial quasi-static compression, the optimized ATR structure displays a remarkable improvement, featuring a 514% increase in EA, a 230% rise in SEA, and a 52% enhancement in EAE.

Heat-treated aluminium thin-walled tubes combine efficient energy absorptive properties with low weight, making them common engineering structures for impact mitigation. Recently, the integration of foam cores within these structures further increases their energy absorption capabilities, however, these foams are stochastic leading to unpredictable failure response and negligible load-bearing enhancements. This study instead integrates a heat-treated aluminium alloy (AlSi10Mg) strut-based lattice structure as the cores for thin-walled tubes through the additive manufacturing process of laser powder bed fusion. Fabricated for lattice relative densities between 10–20