R-curve behavior and flexural strength of zirconia-toughened alumina and partially stabilized zirconia composite laminates

A composite-laminate formed by thick layers (similar to 320 mu m) of zirconia-toughened alumina (ZTA) with thin (similar to 50 mu m) interlayers of zirconia partially stabilized (Y-PSZ) has been fabricated by tape casting and pressureless sintering. Fracture behavior and strength has been investigated and compared to a "monolithic" reference, e.g. a stack of zirconia-toughened alumina (ZTA) without interlayers. The fracture behavior has been analysed using stable crack growth in V-notched specimens loaded in 3-point bending. The ZTA + Y-PSZ composite laminate presented a rising crack resistance with maximum values between 6 and 14 MPa m(1/2). In contrast, the "monolithic" ZTA laminate shows a plateau 11-curve behavior at 2.7 MPa m(1/2). Several toughening mechanisms were identified in the ZTA + Y-PSZ composite laminate, such as, crack arrest/slow down, micro cracking and bifurcation. These toughening mechanisms are most likely caused by high tensile residual stresses that were estimated theoretically.