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Thin-walled tubes have been predominantly utilized in passive vehicle safety systems as crash energy absorbers. With the increasing popularity of additive manufacturing technique, it is feasible to fabricate novel internal reinforcement structures to further reinforce the crashworthy performances of thin-walled tubes. In the present work, a novel nonuniform Lattice-reinforced multi-cell tube based on topology optimization was put forward to explore the crashworthy performances under axial loading and lateral bending. Numeric models validated against the experiments were established to reveal the crashworthy performances of lattice material infilled multi-cell tubes (MCTs). It is observed that the optimized nonuniform lattice structure absorbs more energy than the uniform counterpart. In addition, the hybrid multi-cell filled tubes exhibit remarkable improvements in terms of energy absorption and crushing force efficiency in contrast to the corresponding empty tubes. Furthermore, the specific energy absorption of the three-layer hybrid multi-cell tube is improved by 38.2% and 20.0% under two loading conditions respectively relative to the sum of individual components on account of interplay effect. Collectively, the hybrid nonuniform lattice reinforcement tube provides a promising method for the crashworthy design of MCTs, which can be recommended as an underlying candidate for passive safety protection applications. [ABSTRACT FROM AUTHOR]

Intricate lattice structures can be fabricated by the selective laser melting method, which decreases the production limitations effectively and significantly provides more design freedom. In the present work, additive manufacturing and topological optimization are integrated to develop a novel body- and edge-centered 12 vertices lattice structure with modified triangular prismatic strut pattern (MTP-lattice). Finite element models of MTP-lattice were first established in PAM-CRASH and then experimentally verified via compressive test. The validated finite element models were then employed to investigate the novel MTP-lattice's energy absorption and mechanical behavior under axial and offset loading. The results show that topology-optimized MTP-lattice has a superior energy absorption performance compared with competing unit cells. Besides, its mechanical performance is greatly influenced by the strut pattern and shape parameters. Furthermore, the deformation evolution from the overall structure to the strut level during the entire compression process was analyzed. The observations illustrate that the MTP-lattice exhibits a steady deformation mode with optimal shape parameters, which appears to have a promising prospect for the application of crashworthy components. The research results provide excellent guidance for the application of novel lightweight energy-absorbing lattice. [ABSTRACT FROM AUTHOR]

• Novel design strategy with cost-efficiency of multi-cell structure for energy absorption. • Shape of node-locked cell can be expanded for NMH. • Various bending shape selected for on-demand design of the node-locked effect. • Irregular localized deformation is beneficial to energy absorption of NMH. Material reconfiguration at node positions is currently a prominent method for enhancing the energy absorption capability of honeycomb structures. However, the complexity of cellar configuration poses challenges in the manufacture with cost-efficiency due to intricate preparation processes, which limits its widespread application. In this work, an innovative approach was proposed to fabricate the multi-cell honeycomb structure by nesting and assembling node-locked components with a specific shape. The stable energy absorption of multi-cell structure with node-locked design strategy was preliminarily validated by the numerical and experimental results. Additionally, the effect of the bent panels number and the cell size ratio were investigated numerically and theoretically to reveal the energy absorption mechanism of node-locked multi-cell honeycomb (NMH). It is demonstrated that the strategy by assembling node-locked components can significantly simplify preparation processes of multi-cell structure while maintaining excellent energy absorption capabilities, this offers a better balance between the cost-efficiency and superb energy absorption for multi-cell structures. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A hierarchical multifunctional chiral metamaterial (HMCM) is proposed for both excellent energy dissipation and low-frequency broadband sound absorption. • The distance ratio and wall thickness distribution of HMCM have vital effects on energy absorption performance. • The quasi-perfect absorption of the HMCM is attributed to the coherent coupling effect and hierarchical scale effect. • The multifunctional performance of the HMCM was investigated systematically through experimental, numerical, and theoretical methods. Traditional materials or advanced artificially engineered metamaterials are incapable of effectively addressing the simultaneous challenges of impact energy hazards and low-frequency noise. There is an urgent need for multifunctional materials that can address this multi-physics field coupling problem. Herein, a hierarchical multifunctional chiral metamaterial (HMCM) is proposed for damage-resistance and low-frequency broadband sound-absorption capabilities fabricated by means of laser powder bed fusion technology. Cavity resonators with internally extended tubes with hierarchical chiral configuration were selected as primary units. The damage-resistance performance of the HMCM was investigated systematically through experimental, numerical, and theoretical methods. Crashworthiness design and optimization on the multifunctional chiral metamaterial were implemented to explore the effect of geometrical parameters including distance ratio and wall thickness distribution on crushing resistance. It was determined that specific configurations in these parameters significantly enhance mechanism for dissipating energy of the HMCM. Furthermore, the designed metamaterial has been experimentally, numerically, and theoretically proven to possess quasi-perfect broadband sound absorption in the target range of 425 Hz to 553 Hz with an average sound absorption coefficient exceeding 0.9. Overall, this work not only offers a promising solution for designing multifunctional metamaterials but also highlights the potential of additive manufacturing techniques in the development of such sophisticated materials. [ABSTRACT FROM AUTHOR]

A layered-hybrid metamaterial structure (LHMS) composed of a bio-inspired lattice cell and a dodecagon body-centered lattice cell is proposed, for the purpose of combining the advantages of the bending-dominated and stretching-dominated structures. For the sake of investigating the mechanical performance and deformation evolution of the LHMS, compressive experiments of the specimens fabricated by laser powder bed fusion were performed via electronic universal machine, drop hammer, and Split Hopkinson Pressure Bar system. The deformation modes of the LHMS were captured by a digital camera. The experimental observations reveal that the LHMS exhibits a stable deformation mode under a large range of loading speeds. The outcomes demonstrate that the LHMS exhibits a controllable deformation mode, which has a potential serving as safety protective components. Meanwhile, numerical simulations were carried out to disclose the deformation details. Subsequently, parametric analysis was performed on the basis of the validated finite element results, aiming to discuss the mechanical performance advantage, the effect of component ratio of each sub-cell, and the effect of loading angle on the mechanical properties of the LHMS. The results indicate that the layered-hybrid design possesses superior energy absorption ability and the specific energy absorption is 25.0% and 84.7% higher compared with each individual component with the same mass. Also, the LHMS with component ratio 1.0 possesses the highest specific energy absorption of 10.64 kJ/kg, which is 32.7% and 25.9% higher than that of the LHMS with component ratio 0.7 and 1.5, respectively. • A layered-hybrid metamaterial structure (LHMS) is proposed and tested dynamically. • The layered-hybrid design strategy can effectively control deformation sequence. • The coupling of different cells leads to the superiority of LHMS over single cells. • The component ratio in LHMS has a vital effect on energy absorption performance. [ABSTRACT FROM AUTHOR]

Self-similar structures with hierarchy become novel configuration by presenting higher energy absorption efficiency and better crashworthiness performance, however, its performance is hard to increase continually via expanding hierarchy. In this work, a novel multi-cell hierarchical hexagon honeycomb structure (HHHS) was obtained by changing the topological connection, of which structure is ruled by a length coefficient defined as the ratio of 1st and 2nd hexagon honeycomb. The effect of wall thickness and length coefficient on structural energy performance was numerically investigated using finite element model validated by experiments. The optimization problem was established via surrogate model and solved using Non-dominated Sorting Genetic Algorithm (NSGA-II) to increase specific energy absorption (SEA) and decrease peak crushing force (PCF) of the HHHS for seeking superior crashworthiness. It is indicated that there is an optimal ratio between two level sub-structure, which is beneficial to enhance the crashworthy performance due to the interaction effect of adjacent folded element. The HHHS with optimal geometrical parameters presents remarkable enhancement and energy absorbing potential, which can be selected for energy absorption in consideration of a balance between better crashworthiness and preparation cost. • Crashworthy performance was effected by diameters of sub-hexagon honeycomb. • Relation between SEA and equivalent ratio was revealed for hierarchy structure. • Interaction effect of adjacent folded element can enhance crashworthy performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel lattice structure inspired from the beetle's front wing and the arrangement pattern of honeycomb cells is proposed. • The deformation mechanisms of the bio-inspired lattice structure under static and dynamic loading are unveiled. • The specific energy absorption of the bio-inspired lattice structure exhibits certain sensitiveness to the strain rate. • Numerical simulations using Johnson-Cook constitutive model of heat-treated AlSi10Mg material are in good agreement with experimental results. The progress of additive manufacturing (AM) technique broadens the conceivement and adoption of new types of lattice structures effectively. A new lattice structure, drawing on inspiration from nature, was developed and manufactured via selective laser melting (SLM) to explore the effects of printing parameters on densification and mechanical performance. Compressive experiments were conducted by universal testing machine and Split Hopkinson Pressure Bar (SHPB) system to assess energy absorption and collapse behaviour of bio-inspired structures subjected to static and dynamic load. Each deformation evolution was captured and the digital image correlation (DIC) method was adopted to analyze the strain distribution in the compressive process. The observations reveal that the bio-inspired structure possesses a steady deformation mode under static and dynamic loading, which exhibits a promising prospect for impact resistant applications. Furthermore, energy absorption of this bio-inspired structure displayed some sensitiveness to the rate of strain. Finally, finite element analysis based on Johnson-Cook constitutive model was performed as well to simulate the static and dynamic response of the bio-inspired structure. The finite element outcomes remarkably coincide with the outcomes of experiments. [ABSTRACT FROM AUTHOR]

Multi-cell design and graded thickness are two efficient strategies for improving the mechanical behaviors of metallic thin-walled tubes. This paper combines these two strategies to present a novel multi-cell structure with a double surface gradient (DSG) and to address the energy absorption characteristics of the new tube subjected to axial compression. A mathematical formulation for the mean load was derived through theoretical analysis of the multi-cell structure's folding mechanism, and two vital parameters were proposed. Afterwards, comprehensive numerical simulations were conducted to validate the formulation and to investigate effects of the DSG on the mechanical properties. The results demonstrated that the combination of the DSG strategy and the multi-cell structure led to a greater energy absorption capacity. Finally, the key factor of the DSG design in promoting the energy absorption efficiency was analyzed. To achieve a higher promotion, an approach of rationalizing the sectional material distribution of the DSG tube was attempted and proven valid. All these achievements shed a light on the multi-cell and graded thickness effects on mechanical properties. • We theoretically predicted the mean load of a graded thickness multi-cell tube. • Effects of key parameters on the energy absorbing performance are investigated. • Material distribution laws affecting the specific energy absorption are studied. • A material distribution type that is efficient in energy absorption is presented. [ABSTRACT FROM AUTHOR]