To understand the dynamic failure mechanisms of cylindrical lithium-ion battery (LIB) under different impact loadings, the crushing behaviors of 18650 LIBs were experimentally investigated in this work. The drop weight impact tests with different impactor heads were conducted to analyze the crushing responses of the LIBs. By changing the state of charge (SOC) of the battery, impactor types, and impact energy, the force-electric responses of a LIB under multiple impacts were explored. Macro- and micro-deformation of the batteries were further studied including SOC dependency and the failure modes of the separator. Results show that except for impact energy, the mechanical responses and failure behaviors of the LIBs under repeated impacts also depended upon the SOC and impactor types. The relationship between impact velocity and the minimum impact times was established when a hard internal short circuit (ISC) appeared to evaluate the dynamic safety of the LIBs. These results can provide guidance for the crashworthiness design and safety assessment of the batteries under multiple impacts.

In this study, the self-healing properties of mortars mixed with a crystalline admixture (CA) and superabsorbent polymer (SAP) were investigated. By conducting uniaxial compressive strength tests on the mortar samples, the effects of the two admixtures and different admixture ratios on the initial compressive strength and strength repair ability at different curing ages of the mortar after pre-cracking were investigated. To verify the results, optical microscopy, scanning electron microscopy, and X-ray diffraction were used for microscopic observation of the cracks and their healing products. The results of this study show that CA, which generates dense substances through chemical reactions, has obvious advantages in the self-healing of microcracks and has a greater effect on the flexural strength of mortar compared with SAP, which can effectively fill wider cracks, reduce the width of cracks through physical expansion, and has a greater impact on the compressive strength of mortar compared with CA. Compared with ordinary mortar, mortar mixed with CA only, and mortar mixed with SAP only, the appropriate amounts of both CA and SAP can effectively combine the advantageous effects of CA and SAP and optimise the self-healing effect of mortar so that its self-healing rate reaches 103%. The self-healing filler, consisting mainly of calcium silicate and calcium carbonate, is generated in cracks and enhances the repair strength of the mortar so that the strength of the mortar reaches 46 MPa.

The impact mechanical properties of graded hourglass lattice sandwich structures under impact compression were studied using experiments and numerical simulations. The influence of the gradient distribution on the deformation mode, peak load, and energy absorption capacity of the hourglass lattice sandwich structure under the same impact energy level, different impact masses, and different impact velocities is discussed. The results show that the difference in impact mass and velocity has a significant effect on the impact mechanical properties of the graded hourglass lattice sandwich structure under the same impact energy level. The gradient distribution mode is a factor that requires careful consideration in the design. A reasonable gradient distribution design can control the initial and compression peak loads to achieve similarly low values and improve the load consistency of the hourglass lattice sandwich structure. The total energy absorption of the hourglass lattice sandwich structures with different gradient distributions is the same; however, the energy absorption capacity is different at different deformation stages. When the moving distance is 0.005 m, the gradient hourglass lattice sandwich structures with the mass decline distribution can absorb 1 kJ/kg more energy than the gradient hourglass lattice sandwich structures with the mass increment distribution. When the moving distance is 0.037 m, the mass decline distribution gradient hourglass lattice sandwich structures absorb 1 kJ/kg less energy than the mass increment distribution gradient hourglass lattice sandwich structures.

In contrast to the dynamic response characteristics, few propagation characteristics of elastic waves have been described on cellular materials, to date. In view of the development trend of emerging metamaterials on multi-functional, detailed characterization of elastic wave in honeycombs becomes an important task in order to assess their performances. This study investigates the propagation characteristics of elastic wave in square-packed circular honeycombs through combining theoretical analysis and numerical simulation. We also establish a one-dimensional circular chain model to discuss the influence mechanism of impact velocities, material parameters, and structural parameters on the elastic wave propagation characteristics in square-packed circular honeycombs. The influence relations are quantified and a semi-empirical theoretical expression for assessing characterization is presented, which extends theory of elastic wave propagation speed from solid materials to square-packed circular honeycombs. The assessment equation fully describes the elastic wave propagation speed and stress amplitude variation with location during propagation in square-packed circular honeycombs, and the results are consistent with the experimental data from the literature. The findings herein are aimed at providing an assessment equation with simple form for engineering applications easily and providing theoretical basis for elastic wave control and multi-functional combination design of metamaterials.