Ply thickness dependence of the intralaminar fracture in thin-ply carbon-epoxy laminates

The effect of ply thickness t in intralaminar fracture of unidirectional thin-ply carbon-epoxy laminates is characterized by testing double cantilever beam (DCB) and compact tension (CT) specimens with different t. While the average intralaminar energy release rate (ERR) at initiation is found equal to the corresponding interlaminar values, the steady-state intralaminar ERRs, only reached in the DCB configuration, are approximately three times higher than the corresponding interlaminar values. Due to changes in the extent of bridging, intralaminar steady-state ERRs are ∼30% higher in thick-ply (t = 0.150 mm) than in thin-ply laminates (t = 0.030 mm). Thin-ply composite laminates exhibit a faster ERR growth with crack length, and for DCB, reach steady-state at a much shorter crack extension than thick-ply composites. Traction profiles, due to bridging, are identified using R-curves and implemented in cohesive element simulations to predict intralaminar fracture of DCB and CT specimens. The experimental and simulated load-displacement responses are in good agreement.