INPLANE MECHANICAL-PROPERTIES OF SEVERAL CERAMIC-MATRIX COMPOSITES

An attempt has been made to assess the generalized in-plane inelastic deformation and rupture properties of typical laminated or woven ceram ic-matrix composites. The assessment is made by first identifying two principal classes of behavior. These classes are distinguished by the ratio of the elastic properties of the fibers to those of the matrix, which determines the mechanisms of deformation and rupture. These mech anisms, in turn, control the magnitude and orientation sensitivity of the stress/strain curves, Assessment of the inelastic deformations is achieved by first establishing the evolution of matrix cracks and thei r influence on the elastic moduli. Subsequent evaluation is made by us ing constituent properties, particularly the interface debonding and s liding resistances in the presence of matrix cracks. This is achieved by analyses of hysteresis loops, using a matrix cracking model. This m odel provides a representation of the influence of load direction on t he interface responses and the inelastic strains. The ultimate strengt h is controlled by two mechanisms, It is fiber-controlled in 0/90 tens ion but becomes matrix controlled in +/-45 degrees tension. A model ch aracterizing this mechanism change has yet to be devised.