Development of Virtual Micro-Models for Prediction of Macroscopic Properties of Ceramic Matrix Composites (CMCs) and Optimization of Manufacturing Process

Kurzfassung

The Finite Element Method (FEM) is used to obtain the stress distribution in the material as a reaction to the thermal load which is applied. A Cohesive Zone Model (CZM) approach is used to implement fracture behavior of the material. Material specific input parameters for the simulations are determined by experiments and taken from literature. Scanning Electron Microscope (SEM) images show that the developed models represent the behavior of the physical material in an excellent way. According to this study, the presence of initial defects prior to the pyrolysis and a homogeneous distribution of these defects in the matrix are crucial for the formation of an ordered crack pattern. A homogeneous defect distribution leads to defined growth of segmentation cracks. Defect types which mainly govern the crack development are stress induced microcracks which appear during curing of a thermosetting resin to CFRP. The influence of the interface strength and the interface area are also studied. A strong interface and a low interface area support the growth of segmentation cracks. The courses of the porosity and crack density increase fit well to other findings in literature. The porosity increases in a linear fashion. The crack density increases linearly before approaching a constant value. This study shows that a weak fiber/matrix Interface leads to a higher porosity and crack density increase during pyrolysis.