Observation and modeling of cone cracks in ceramics

Ceramics undergo a complex failure process when subjected to impact by a projectile. Projectile impacts on thick ceramic targets produce varying levels of comminution, cone cracking, and radial cracking. Sphere impacts result in limited penetration and comminution relative to projectiles with a longer aspect ratio, yet significant radial and cone cracking is produced, and it is similar to Hertzian indentation. Sphere impact is a good way to study ceramics and a good validation problem to study the ability of hydrocodes to predict the formation and extent of radial and cone fractures in ceramic materials. Experimental results from normal and oblique sphere impacts on hot-pressed boron carbide cylinders are reported. Oblique sphere impacts created curved cone cracks, which did not appear oriented perpendicular to the impact surface. Cone angles appear to be the same for normal and oblique impacts for the impact conditions tested. Hydrocode predictions captured some but not all of the experimentally observed features.