Low-velocity impact of a novel CFRP-faced sandwich structure with multi-level negative Poisson's ratio cores

Honeycomb sandwich structures with carbon fiber-reinforced polymer (CFRP) face sheets have found widespread application in aerospace, ship engineering, and automotive industries. This research introduces a novel sandwich structure featuring CFRP face sheets and a multi-level negative Poisson's ratio honeycomb core. Experimental and finite element analysis were conducted to assess the impact resistance of both CFRP laminates and the proposed sandwich structure. A damage model incorporating elastic-plastic behaviour was developed and integrated into the ABAQUS software via VUMAT. Experimental validation confirmed the accuracy of the finite element method (FEM). The study shows that matrix tensile damage is the primary damage mode under low-velocity impacts, with the damage extent and damage pattern being significantly influenced by impactor. Laminate stacking sequences have a minor impact on overall mechanical behaviour but can influence the damage response. Crucially, the honeycomb core configuration significantly enhances energy absorption. For example, the double-arrow multi-level honeycomb structure consisting of only two layers exhibits a 21.4% increase in energy absorption compared to the hexagonal honeycomb structure. These insights offer valuable guidance for optimizing composite structures to achieve superior impact resistance and energy absorption.