Brittle materials (such as a lot of ceramics and glass) fail by a cone crack when locally impressed. In static loading a typical Herzian cone crack is formed; a ring crack starts in the tensile zone surrounding the interaction zone and from this stress intensifier a conical crack propagates into the bulk of the materials.

Upon projectile impact (a dynamic loading condition) multiple ring cracks are formed and also a cone crack occurs, but these cracks seem to be less related. Also the cone angles differ with impact velocity.

So, what is the relation between the impact conditions, the material (intrinsic) properties and the cone crack angle?