13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- influence on the macroscopic behavior, the toughness and strength of CMCs[20]. Interfaces are very narrow regions between matrix and fibers and are responsible for a variety of key properties, because of its significance role of stress transfer between fibers and matrix[20-23]. Recently, CZM(cohesive zone model) is being increasingly used in describing interfacial debonding and separation[23]. It was first proposed to analyze brittle fracture, and developed to model debonding of inclusions, crack growth processes in elastic-plastic solids, delamination process in composites subjected to low velocity impacts and so on. It is not so easy to simulate the bundle/matrix interface, because the mechanical properties of the interface is very difficult to obtain and the geometry of the interface in woven fabrics is curved surface. The aim of the present contribution is to introduce the interface into the RVE model in terms of CZM, and to analyze the damage evolution in 2D woven C/SiC with the damage behavior of different constituents identified clearly. This paper is organized as follows: firstly, the geometry model and boundary conditions are presented. Next, the meso-model was outlined with the description of material models of matrix, fiber yarns and interface-matrix interface. Then, the damage of different constituents was predicted based on elastic model. In the last but one section, the damage initiation and evolution are described with different damage modes identified. Finally, conclusions are summarized in the final sections. 2. RVE and periodic boundary conditions 2D woven C/SiC is plain weave fabrics, which are formed by weaving of yarns, as shown in Fig. 1. The black yarn are in X(longitudinal) direction and the grey yarn are in Z(transverse) direction. Figure 1. Sketch of 2D plain weave single lamina(left) and its RVE without matrix(right) In order to modeling the fabric-reinforced laminates using FEM, the representative volume elements (RVE) of the respective configurations are chosen. The RVE is the repeated element that can represent the whole composite fabric structure by a periodical array. Then characteristics of the macrostructure composites can be represented by the RVE with a certain proper boundary conditions. And the data points are fit to a sinusoidal function of the form[15]: where, a, the amplitude of the yarn curve is 0.125mm; b=2π/1.8≈3.49, and 1.8 is the pitch of the yarn path curve in millimeters; d, the offset depicted is ±0.125mm; c is the phase adjusting factor. Figure 2. The photomicrograph of the 2D plain weave C/SiC
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