Dynamic fracture toughness of cellular materials with different microstructures

Ultra-lightweight cellular materials have been widely utilized owing to their excellent specific stiffness, strength and fracture resistance ability. However, current understanding of the fracture resistance of cellular materials is mostly limited to quasi-static loading conditions, and their resistance to dynamic fracture is comparatively less understood. In this study, we investigate the dynamic fracture behaviors of the triangular, kagome, and hexagonal honeycomb cellular materials using numerical methods. Both single-edge notched bend and single-edge notched tension specimens under dynamic loading are considered, and the J values of dynamic fracture toughness of the three configurations are determined. Simulation results demonstrate that the fracture resistance of the triangular honeycomb increases with increasing loading velocity, whereas the fracture toughness of the two other structures exhibits slight variation with respect to the loading rates. After examining the fracture response by changing the strain-rate-dependence of the constituent material, we concluded that the microstructure has a more significant effect on the rate-dependence of fracture toughness than the constituent material. A mechanism based on crack deviation is proposed to account for the distinct rate-dependence of fracture toughness in specimens with different microstructures.