Anisotropic crack extension in aligned glass ceramic

Abstract Crack systems created by a Vickers indentation in longitudinally aligned glass–ceramic did not follow the direction of indenter diagonals. Their deflection depends strongly on the orientation of the indenter with respect to the aligned crystals. Unlike crack deflection by second phase particles which toughen ceramics, crack paths were deflected into the extrusion direction. Anisotropic behavior of crack propagation in extruded glass as well as an oriented crystallized glass–ceramic of the lithium disilicate system were examined and orientation-dependent fracture toughness and microhardness are presented.