Modelling and simulation of the mechanical behavior of ceramic matrix composites as shown by the example of SiC/SiC

Modelling of the mechanical behavior of unidirectionally fiber-reinforced ceramic matrix composites (CMC) is presented by the example of SiC/SiC. The starting point of the modelling is a substructure (elementary cell) which includes on a micromechanical scale the statistical properties of the fiber, matrix and fiber-matrix interface and their interactions. The substructure is chosen in such a way that a macrostructure rc:presentative of the whole structure can be modelled from a suitable number of substructures, The typical damage behavior of ceramic composites is modelled by taking fiber and matrix cracks into account. Cracks are inserted into the substructure by reducing the elastic coefficients of the material. The fracture criterion used is a surface represented by a spheroid in the principal stress space. The crack direction is determined by the criterion of the energy release rate. Interfacial behavior is simulated by consideration of fiber-matrix debonding and frictional sliding. The numerical evaluation of the model is accomplished by means of the finite element method (FEM). The effect of important parameters such as the fiber volume fraction or the fiber Weibull-shape parameter on the nonlinear behavior of the substructure is examined. Finally, a macrostructure is modelled to show the effects of these important parameters on the mechanical behavior of the whole structure. (C) 1999 Elsevier Science B.V. All rights reserved.