FEM predictions of damage in continous fiber ceramic matrix composites under transverse tension using the crack band method

This paper develops a numerical micromechanics fracture model based on the crack band methodology for the prediction of damage in continuous fiber ceramic matrix composites (CMCs). The energy based crack band formulation offers mesh objective predictions in finite element simulations. Detailed finite element models of CMCs are created based on the actual microstructure and compared with randomly created representative volume elements (RVE). The influence of geometrical inhomogeneities, such as fiber clustering and variations of the fiber coating thickness, on the stress-strain response and the crack development are investigated. Furthermore, FEM models of multi-layer cross-ply laminates are created including thousands of explicitly modeled fibers and fiber coatings. Crack density predictions are compared with well established analytical models by Laws and Dvorak [1] and Nairn [2]. An eight layer FEM model is used to predict damage propagation within each layer. The Numerical prediction of the stress-strain response is compared with experimental results of smooth bar tensile coupons.

Increasing stress in one location of a lamina or laminate automatically leads to a relaxation in another region. Crack closing can be observed as a result and is shown in Fig. 1. Crackclosure at one location can be observed due to increased crack-opening of a nearby crack.Figure optionsDownload high-quality image (372 K)Download as PowerPoint slide