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 ceramic-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 mechanisms, 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 their influence on the elastic moduli. Subsequent evaluation is made by using constituent properties, particularly the interface debonding and sliding resistances in the presence of matrix cracks. This is achieved by analyses of hysteresis loops, using a matrix cracking model. This model provides a representation of the influence of load direction on the interface responses and the inelastic strains. The ultimate strength is controlled by two mechanisms, It is fiber-controlled in 0/90 tension but becomes matrix controlled in +/-45 degrees tension. A model characterizing this mechanism change has yet to be devised.