Hypervelocity impact on brittle materials of semi-infinite thickness: Fracture morphology related to projectile diameter

Hypervelocity impact on brittle materials produces features not observed on ductile targets. Low fracture toughness and high yield strength produce a range of fracture morphologies including cracking, spallation and shatter. For sub-mm diameter projectiles, impact features are characterised by petaloid spallation separated by radial cracks. The conchoidal or spallation diameter is a parameter in current cratering equations. An alternative method for interpreting hypervelocity impacts on glass targets of semi-infinite thickness is tested against impact data produced using the Light Gas Gun (LGG) facility at the University of Rent at Canterbury (UKC), U.K. Spherical projectiles of glass and other materials with diameters 30-300 mu m were fired at similar to 5 km s(-1) at a glass target of semi-infinite thickness. The data is used to test a power law relationship between projectile diameter and crack length. The results of this work are compared with published cratering/spallation equations for brittle materials. (C) 1997 COSPAR.