13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- longitudinal at the strain of 6000. 5700 5800 5900 6000 6500 10000 y+ y- Figure 10. The damage process of the fiber bundle 4.4. The yarn/matrix interface damage evolution The CZM was introduced to the RVE by cohesive element in Abaqus, which aims at investigating the possible damage process of yarn/matrix interface. 500 1000 2000 4000 6000 8000 10000 Figure 11. The damage process of the interface Fig. 11 shows the damage initiation and propagation process of the interface in terms of MAXSCRT(0.0 means no damage occurs, shown in white grey; and 1.0 corresponding to failure, shown in black grey). It is found that the damage initiates at the weaving edge of the interface around the yarns in longitudinal direction as shown in the MAXSCRT contour of 6000, then it spread to the weaving point of the RVE in longitudinal(X) direction, marked with circles and arrows. The interface around yarns in transverse(Z) direction get damaged at the strain of 10000, later than it in longitudinal direction. 4.6. The effect of the void in matrix The porosity in C/SiC may have great influence on the damage initiation, evolution. So, the RVE with void in matrix is investigated. From the photomicrograph of the 2D plain weave C/SiC, it can be found that the void in matrix is mainly around the weaving gap between yarns, so the mechanical properties of the matrix in this region, showing as four small rectangles in the matrix (the volume is about 6% of the whole volume of the RVE) is reduced to 10%. The result of the matrix damage evolution is shown below in Fig. 12. The damage of the matrix initiates around the void, which differs from the damage evolution in matrix without void compared with Fig. 8. And it is also found that the through damage in the model with void comes earlier than that without void. So the void in
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