Fig. 3.

Crack morphology in glass/sapphire/polycarbonate trilayers with bottom-surface abraded sapphire, showing subsidiary modes after failure by core radial cracking. (a) Reinitiation of the radial crack in an adjacent underabraded veneer layer. Indentation at P_m = 375 N, after n = 4129 cycles. (b) Delamination at the interface, indicated by a fringe pattern. Note how the delamination pattern is constrained by foregoing radials. Indentation at P_m = 375 N, after n = 3261 cycles.