Interlaminar and intralaminar fracture characterization of composites under mode I loading

The interlaminar and intralaminar fracture of laminated composites under mode I loading was studied using the double cantilever beam test. The effect of bridging on the measured fracture energy was assessed by cutting fibres during crack propagation. The fracture energy was evaluated considering a previously developed data reduction scheme based on the beam theory and crack equivalent concept. The model only requires the applied load–displacement data and provides a complete R-curve allowing the definition of the critical energy from the plateau value. A cohesive damage model was used to validate the procedure. It was verified experimentally that bridging phenomenon is pronounced, being more important in intralaminar tests. However, a detailed observation of the intralaminar R-curves showed that the intrinsic toughness, without fibre bridging effects, is similar to the interlaminar one.