Research on plastic structural wave behavior and crashworthiness of continuous gradient mesoscopic foam structures under high speed impact

Abstract

Under high speed impact, the macro and mesoscopic mechanical behavior, the stress wave propagation mechanism, and the relationship between density gradient and crashworthiness of continuous density gradient foam are the key issues to improve and optimize the protection capability of support structures. The numerical simulation of various density gradient foams is carried out, and the meso-discontinuity of foams is overcome by using the local gradient tensor method of least square error, and the plastic structure wavefronts with clear interfaces are obtained. The plastic structure wave propagation mechanism of foam with different density configurations was analyzed and the relationship between density gradient and crashworthiness was further revealed. The results show that inertia effect is the dominant factor of collapse in the early stage of impact. In the middle and late stage of impact, the dominant factor of collapse changes to the microscopic density of foam. The distribution of continuous density gradient significantly affects the impact resistance. Compared with low-high density configuration foam (LH), high-low density configuration gradient foam (HL) has a 140% increase in impact end force, a 24% decrease in support end force, a 3% decrease in maximum compression, and a 41% longer response time.