Impact response characteristics and meso-evolution mechanism of functionally gradient brittle materials with pore hole damage

摘要

Functionally graded brittle materials will inevitably produce defects such as micropores in the preparation process, which will significantly affect its impact response. Understanding its mesoscopic evolution mechanism and macro-response law will make micropores favorable for the engineering application of functionally graded brittle materials. By establishing a lattice-spring model that can accurately represent the elastic properties and fracture evolution of materials, this paper reveals the influence of pore evolution on functionally graded brittle materials. Collapse deformation caused by impacted holes and slip deformation caused by shear cracks emitted from holes produce significant stress relaxation and modulate the propagation of shock waves. In porous functionally graded brittle materials, shock waves are gradually broadened into elastic waves and deformation waves. The deformation wave is macroscopically similar to the plastic wave of ductile metal material, and corresponds to the collapse deformation and slip deformation process on the micro-level. Porosity in the sample determines the elastic limit of functionally graded brittle materials. Porosity, material parameters, and impact velocity jointly affect the propagation speed of the deformation wave and the stress amplitude in the final state of impact. Functionally graded brittle materials with micropores have potential application value in shock wave complex loading experiments, failure prevention of functional materials, building protection, etc. The obtained impact response laws are helpful to optimize the design of impact response and dynamic mechanical properties of functionally graded brittle materials for specific applications.