Fracture behavior of alumina/monazite multilayer laminates

Monazite (LaPO4) has been proposed as an interphase to promote debonding be tween the reinforcement and the matrix during the fracture of oxide-based c omposites. The correlation between fracture behavior and micromechanical pr operties in model alumina/monazite (Al2O3/LaPO4) multilayer laminates has b een investigated in this study. The delamination fracture energy (Gamma(i)) was dependent on crack length, which is consistent with previous results; the initial value of Gamma(i) was similar to 10 J/m(2). The interfacial fri ctional sliding resistance increased as the normal stress on the interface increased. Using a Coulombic Friction model, the coefficient of static fric tion between the Al2O3 and LaPO4 layers was determined to be 0.63. The infl uence of Gamma(i) and flaw size in the Al2O3 layers on fracture path has be en predicted, using an existing model, and confirmed experimentally. The re sults indicate that, in addition to satisfying energy-based fracture criter ia, several other factors affect whether LaPO4 is a suitable interphase for oxide composites.