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

摘要

In this study, the influence of stacking sequence on mode / delamination resistance (R-curve) behavior of E-glass/epoxy laminated composites with an initial delamination between 0°//0° interface is experimentally investigated. To this end, symmetric double cantilever beam (DCB) specimens of stacking sequences; [0°_12]_s, [(0°/90o)_3]2s and [0°/90°/ ±45°/90°/0°]_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 (UD) one reveals the significant effect of the non-dimensional coupling parameter, D_c= D_12~2/D_11D_22, on the R-curves. Thus, three main outputs of R-curves could be summarized as; (a) the initiation delamination toughness (G_1c-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.