70 A. Tessema et al. Fig. 9.3 Full-field axial and shear strain contour for (a, b) 0/ 45/90/C45, (c, d) 0/ 45/C45/90 and (e, f) 0/90/C45/ 45 respectively In the (0/ 45/C45/90)s laminates, as seen in the Fig. 9.3c, the axial strain localization seems to occurr at early stage of the loading. The large matrix crack/localization appeared in the two 90ı-plies that found at the middle of the laminate. These cracks are oriented vertically straight and have shown an interesting gradual growth and formation. It looks like that newly coming matrix cracks appeared in between two preexisting cracks, the new crack emerge near exactly at the middle of the two craks. Shear strain localizations have been observed at the interface of 45/C45 plies. As discussed earlier, these two plies have oppositely oriented fibers and during loading the two plies will have opposite inplane shear. Thus, there will be a higher relative displacement at the interface that leads to higher interlaminar shear at the interface. In addition, more shear strain localization are seen at the site where matrix crack reached the interfaces. Following, a delaminating crack has initiated at one of the location where the matrix cracks reached the interface and propagated through the interface of 90/C45 plies. Similarly, for the (0/90/C45/ 45) laminate, a number of axial strain localizations/matrix cracks appeared in the 90ı-plies at higher stress. These matrix cracks have slant angles but it is not as large as the one in the (0/ 45/90/C45) laminate. There was no sign matrix crack or strain localization appeared in the other plies and the matrix cracks remained in the 90ıplies. On the other hand, shear strain localizations appeared at the interfaces of 45/C45 plies. Moreover, small shear strain localization are noticed at the interface where the matrix cracks reached the interface. Summing up, matrix cracking appeared in all of the laminates and it occurred in the 90ı-plies. The stress at which the matrix cracks initiated varied for each laminate. It seems like, in the laminates where the 90ı-ply is far from the mid plane the matrix cracks appeared at the higher loading than in the laminates where it is located at the mid-plane.
RkJQdWJsaXNoZXIy MTMzNzEzMQ==