Stress wave propagation characteristics of functionally graded cellular sacrificial layers under impact load

Abstract

To explore interface effects between the soft and hard layers of cellular solids, the shock wave propagation of the functionally graded cellular sacrificial layers (FGCSLs) under impact load was investigated in this paper. Firstly, a theoretical model of stress wave propagation in FGCSLs was developed based on the rigid-perfectly plastic-lock (R-PP-L) and the rigid-plastic hardening (R-PH) constitutive models by changing the yield strength of the matrix material. The propagation characteristics of shock waves in positive and negative FGCSLs were analyzed. An explicit dynamic finite element (FE) model of two-dimensional FGCSL was established based on Voronoi technique. The reliability of the theoretical model was verified by the corresponding FE results. Two models mentioned above have been proven to effectively describe the dynamic responses of double-layer FGCSLs under impact load. The transmission and reflection process of stress waves at the enhancement of material properties can be predicted by the R-PH model, and the variation trends of impact velocity and end stress can be more accurately reflected. It is found that shock waves possess different propagation modes in sacrificial layers with different gradient arrangements, and the enhancement of end stress is mainly caused by wave reflection at interlayer interfaces or ends. The magnitude of the end load of the sacrificial layer can be effectively controlled, and the stress distribution of the structure layer can be changed by the yield stress gradient design. Our work will provide a pathway to design optimal cellular sacrificial layers for damage protection.