Effect of interface fiber angle on the R-curve behavior of E-glass/epoxy DCB specimens

In this study, the effect of interface fiber angle on the R-curve behavior of double cantilever beam (DCB) specimens made of E-glass/epoxy under mode I loading is investigated experimentally. For this purpose, DCB specimens with stacking sequences of [0 11 /θ//0 12 ] and θ = 0, 30, 45, 90 are manufactured by hand lay-up method. These stacking sequences are chosen to eliminate the effect of remote ply orientation on the R-curve behavior of DCB specimens during the delamination propagation. In order to obtain the critical strain energy release rate, fracture tests are conducted on these specimens. Results show that DCB specimens with 0°//0° interface have the lowest initiation interlaminar fracture toughness and the greatest bridging zone length due to good penetration of two adjacent layers of the delamination interface. Moreover, results indicate that the interface fiber angle has significant effect on the steady-state interlaminar fracture toughness as well as the bridging zone length.