J. Am. Ceram. Soc., 83 [4] 802–808 (2000)

Fracture Behavior of Alumina/Monazite Multilayer Laminates

Jennifer R. Mawdsley,*^,† Desiderio Kovar,*^,‡ and John W. Halloran*

Materials Science and Engineering Department, University of Michigan, Ann Arbor, Michigan 48019–2136

Monazite (LaPO₄) has been proposed as an interphase to promote debonding between the reinforcement and the matrix during the fracture of oxide-based composites. The correlation between fracture behavior and micromechanical properties in model alumina/monazite (Al₂O₃/LaPO₄) multilayer laminates has been investigated in this study. The delamination fracture energy (G_i) was dependent on crack length, which is consistent with previous results; the initial value of G_i was ;10 J/m². The interfacial frictional sliding resistance increased as the normal stress on the interface increased. Using a Coulombic friction model, the coefficient of static friction between the Al₂O₃ and LaPO₄ layers was determined to be 0.63. The influence of G_i and flaw size in the Al₂O₃ layers on fracture path has been predicted, using an existing model, and confirmed experimentally. The results indicate that, in addition to satisfying energy-based fracture criteria, several other factors affect whether LaPO₄ is a suitable interphase for oxide composites.