Measurement of the compressive crack resistance curve of composites using the size effect law

This paper presents a new methodology to measure the compressive crack resistance curve of the longitudinal plies of carbon–epoxy laminates. The methodology is based on three main steps: the first one corresponds to the determination of the energy release rate of cross-ply laminates with two edge cracks using a parametric finite element model. The energy release rate is used in the definition of a relation between the crack resistance curve and the size effect. Finally, experimental tests are performed in scaled double-edge notched specimens to quantify the size effect law, thus proving the last piece of information required to define the crack resistance curve. The full crack resistance curve is obtained for the IM7-8552 carbon epoxy composite material. The methodology proposed in this paper overcomes the inherent limitations of the existing test methods, and it serves as the basis for the identification of cohesive laws used in some analysis models.