Effect of stacking sequence on R-curve behavior of glass/epoxy DCB laminates with 0°//0° crack interface

In this study, the influence of stacking sequence on mode 1 delamination resistance (R-curve) behavior of E-glass/epoxy laminated composites with an initial delamination between 0 degrees//0 degrees interface is experimentally investigated. To this end, symmetric double cantilever beam (DCB) specimens of stacking sequences; [0 degrees(12)](s), [(0 degrees/90 degrees)(3)](2s) and [0 degrees/90 degrees/+/- 45 degrees/90 degrees/0 degrees](2s) with two initial crack lengths are used. A pronounced R-curve behavior is observed on all stacking sequences due to locating delamination between two similar layers. Comparison of R-curve behavior of cross-ply and quasi-isotropic DCB specimens with unidirectional CUD) one reveals the significant effect of the non-dimensional coupling parameter, D-c = D-12(2)/D11D22, on the R-curves. Thus, three main outputs of R-curves could be summarized as; (a) the initiation delamination toughness (G(Ic-init)) of multidirectional (MD) laminates are much lower than that of UD one, (b) stacking sequence has no effect on the fiber bridging length in DCB specimens, and (c) the greater the D-c value of a laminate, the higher the steady-state propagation toughness (G(Ic-prop)) is. (C) 2011 Elsevier B.V. All rights reserved.