Energy absorbing structures made from composite materials are lightweight, fuel economical and environmentally friendly. In spite of these advantages, some issues have to be addressed to ensure more ...efficient energy absorption and crashworthiness performance. Good understanding of the proper material selection, architectural design, fabrication technique as well as repairs and maintenance strategy can guarantee the production, vibration/noise reduction and sustainability of highly efficient energy absorbing composite structures (EACS). In this review, an overview of recent advances of EACS is presented. First, salient explanation of the crashworthiness indices and failure mechanisms during deformation of EACS are given. It then critically examines different composite materials and common manufacturing techniques used for the production of EACS. Different factors affecting the specific energy absorption and energy absorption capacity are detailed. Also, the challenges of EACS with useful proposals and future directions are provided. Moreover, damage assessments as well as composite repairs are also given. Finally, it addresses the need of sensors, green and e-maintenance in EACS for sustainable maintenance.
Periodic driving has emerged as a powerful tool in the quest to engineer new and exotic quantum phases. While driven many-body systems are generically expected to absorb energy indefinitely and reach ...an infinite-temperature state, the rate of heating can be exponentially suppressed when the drive frequency is large compared to the local energy scales of the system—leading to long-lived “prethermal” regimes. In this work, we experimentally study a bosonic cloud of ultracold atoms in a driven optical lattice and identify such a prethermal regime in the Bose-Hubbard model. By measuring the energy absorption of the cloud as the driving frequency is increased, we observe an exponential-in-frequency reduction of the heating rate persisting over more than 2 orders of magnitude. The tunability of the lattice potentials allows us to explore one- and two-dimensional systems in a range of different interacting regimes. Alongside the exponential decrease, the dependence of the heating rate on the frequency displays features characteristic of the phase diagram of the Bose-Hubbard model, whose understanding is additionally supported by numerical simulations in one dimension. Our results show experimental evidence of the phenomenon of Floquet prethermalization and provide insight into the characterization of heating for driven bosonic systems.
Geometric configurations in nature could be mimicked in order to develop novel materials and structures with desirable properties. Lots of bio-inspired configurations had been introduced to tubal ...structures in promoting the energy-absorption performance of thin-walled structures. Nevertheless, these existing studies largely focused on hierarchical hexagonal honeycombs, and the bio-inspired hierarchical circular thin-walled structures under the out-of-plane crushing loads had not been well studied experimentally, numerically and analytically for energy absorption to date. In this study, the bionic honeycomb tubular nested structure (BHTNS) was first inspired by the micro-architecture of bamboo vascular bundles, which could be mimicked by connecting a central circular tube to other six circular tubes in a hexagonal arrangement, regardless of size or choice of materials. The energy-absorption characteristics of BHTNS under axial crushing were systematically studied by drop-weight experiment, numerical simulation, and theoretical analysis. Dynamic drop-weight impact experiments were conducted and the results showed that the specific energy absorption (SEA) of BHTNS was as high as 29.3 J/g. Furthermore, the parametric numerical simulation revealed the influence of diverse mean diameter D of the circular tube and length L of the junction plate on the energy-absorption characteristics. Finally, a theoretical model was also developed to predict the mean crush force Pm, which was in good agreement with the numerical simulation. This work could provide a reference for an energy-absorber design with high efficiency.
An octet truss lattice material is designed for energy absorption purposes featuring an exceptionally high specific energy absorption, a constant plateau stress between initial yield and ...densification, and zero plastic Poisson’s ratio. It is demonstrated through detailed finite element simulations that the meso-structural response of metallic lattice materials under compression changes from an unstable twist mode to a stable buckling free mode at a relative density of about 0.3. Furthermore, it is found that the nature of the macroscopic stress-strain curve changes from mildly-oscillating to monotonically-increasing as the meso-structural deformation mode changes, while a stress-plateau is observed at relative densities above 0.3. Since the specific energy absorption is a monotonically increasing function of the relative density, lattice materials of relative densities around 0.3 feature both a plateau stress and a high specific energy absorption capability. Prototype materials are built from stainless steel 316L using Selective Laser Melting. The basic building element of the micro-lattices are 2.2 mm long beams with a 500 μm diameter cross-sections. Detailed micro- and meso-structural analysis including tomography, microscopy and EBSD analysis revealed substantial local material property variations within the lattice structure. Compression experiments are performed under static and dynamic loading conditions confirming the anticipated exceptional energy absorption material characteristics for strain rates of up to 1000/s.
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In this paper, an innovative bio-inspired multi-layered graded foam-filled structure (MGFS) mimicking the characteristics of the human skeleton was proposed in an attempt to improve the energy ...absorption. The proposed structures consisted of three layers of aluminum foam with different densities filled in three concentric aluminum circular tubes. To find out the optimal foam-filled combination and demonstrate the superior energy absorption performance of the proposed structures, a series of quasi-static compression tests were experimentally and numerically carried out. The results showed the proposed structures had higher energy absorption efficiency than that of both uniform foam-filled structures and the empty tubes, and Model-1 with the foam density increasing from the inner tube to the outer tube was the best combination mode. Furthermore, parametric numerical studies on Model-1 revealed that the diameter and thickness of the aluminum tube and the density of the aluminum foam had significant effects on the energy absorption characteristics. Finally, a theoretical model was developed to predict the mean crushing force of the bioinspired MGFS, which was in good agreement with the experimental results. This study provides an effective guideline for designing a foam-filled energy absorber with high energy absorption efficiency.
•Bionic design inspired by the microstructure of deep-sea glass sponge was introduced to enhance the axial energy absorption for the thin-walled tube.•SEA was improved by 32.2% to 53.1% and 7.7% to ...28.1% when compared to conventional multi-cell tubes and other bio-inspired tubes, respectively.•The performance of energy absorption could be significantly improved by the introduction of hierarchical designs.•A theoretical model was developed based Simplified Super Folding Element (SSFE) theory to predict the mean crushing force of UCGS.
A novel bio-inspired multicell tube (named UCGS), mimicking the unique double-diagonally reinforced configuration in the unit cell of glass sponge (GS), was proposed and fabricated by additive manufacturing. Crashworthiness analysis of UCGS was carried out via ABAQUS/Explicit and validated by quasi-static axial crushing tests. Due to its distinctive double-diagonal reinforcing strategy, the results demonstrated that UCGS had a high specific energy absorption (SEA) of up to 30.7 J/g, which was 32.2% to 53.1% higher than that of conventional multi-cell tubes and 7.7% to 28.1% higher than that of other bio-inspired tubes, respectively. Subsequently, the effects of geometric parameters and hierarchical designs on the energy absorption performance were investigated by numerical simulation. By choosing the proper geometric parameters and hierarchical design, the energy absorption capability of the presented bio-inspired multicell tube could be further increased, and the SEA was 3.3%–39% greater than the original design. Finally, a theoretical model was proposed to predict the mean crushing force, which was in good agreement with the numerical results. This study shed light on a deep understanding of the deformation mechanisms of bio-inspired tubes, and provided inspirations for designing and optimizing of energy absorber with high performance.
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•The deep-sea glass sponge provides a new strategy for energy absorber design.•The proposed lattice simultaneously achieves multiple mechanical advantages.•The topology misalignment of the cell ...vertex hinders the extension of shear bands.•The crashworthiness can be improved by modifying connection of the vertices.
Conventional lattices usually exhibit tradeoff relations between their strength, deformation stability and energy absorption capacity. Here, inspired by the local structure characters of the skeletal system of deep-sea glass sponge, a new structure called vertex modified body-centered cubic (VM-BCC) lattice was proposed. The mechanical properties of the proposed lattices were compared with those of the conventional BCC, Octet and face-centered cubic (FCC) lattices. The results revealed that the BCC, Octet, and FCC lattices correspond to the highest deformation stability, the largest energy absorption and the highest strength among the three conventional lattices investigated, respectively, while the proposed VM-BCC lattice outperforms them all in each of the three properties. Remarkably, the proposed lattice made of stainless-steel possesses strength and energy-absorbing capacity close to that of lattices and foams made of titanium alloy. Moreover, a parametric numerical simulation study was carried out to ascertain the effect of the deviation coefficient, a geometric parameter of VM-BCC lattice on the mechanical properties and the deformation pattern. It indicates that the VM-BCC lattice with an appropriate deviation coefficient can effectively suppress the expansion of shear bands, resulting in high and stable stress response. This work proposes a novel bio-inspired lattice and enriches the design space for lightweight energy absorbers, which have prospective application potential in the fields of national defense, aerospace, navigation, and medical implants.
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