Damage-fragmentation transition: Size effect and scaling behavior for impact fragmentation of slender projectiles

The focus of the present article is on the size effect of a transition region from the damaged to the fragmented phase in impact-induced breakup of a slender projectile. Molecular dynamics simulations of the classic ballistic Taylor test are performed with a simple generic model to explore an extended low-energy range. In the simulation setup, flat-ended, monocrystalline, nanoscale projectiles, with a fixed aspect ratio but 10 different diameters, collide perpendicularly with a rough rigid wall. With gradually increasing impact energy, a non-negligible projectile disintegration eventually takes place and is identified with the damage-fragmentation phase transition. These atomistic simulations offer an indispensable tool to gain an insight into damage evolution in the neighborhood of the damage-fragmentation transition resulting in the occurrence of fragmentation at the critical point. A finite size scaling analysis of the average fragment mass is carried out to determine critical exponents and dependence of the critical striking velocity upon the slender projectile’s diameter.