Characterization of the translaminar fracture Cohesive Law

Quasi-brittle materials such as fibre-reinforced composite materials develop a relatively large Fracture Process Zone where material toughening mechanisms such as matrix cracking, fibre-bridging and fibre pull-outs take place. The damage onset and damage propagation are well defined from a cohesive model point of view, although no standard procedure has been yet developed to characterize the translaminar Cohesive Law. The present work proposes an objective inverse method for obtaining the Cohesive Law with the use of an analytic model capable of predicting the load-displacement curve of a Compact Tension specimen for any arbitrary Cohesive Law shape. The softening law has been obtained for two laminates, providing an excellent agreement with the experimental results. With the obtained softening function, the nominal strengths of a Center Cracked Specimen and an Open Hole specimen have been predicted for a wide range of specimen sizes.