On Cohesive Modelling ofCarbon/Epoxy Composites : Delamination and Fibre Compressive Failure

Abstract: Carbon Fibre Reinforced Polymers are widely used in engineering applications where weight saving and high mechanical performance are a key factors. However, an inheren tweakness of laminated CFRP:s is there relatively low resistance to delamination. Therst part of this thesis is devoted to extract cohesive laws associated with delamination.The method is based on fracture mechanical tests and measurement of the displacementeld close to the crack tip. The second part of the thesis is concerned with mixed modecohesive modelling under small scale yielding conditions. Under such loading conditions,a robust cohesive model should conform to Linear Elastic Fracture Mechanics (LEFM). Itis shown that two design rules for mixed mode cohesive laws are sucient to achieve thisproperty. The third part focuses a failure mode entirely dierent from delamination. Theobjective is to determine cohesive laws associated with longitudinal compressive failure.Equilibrium of congurational forces is used for this purpose. Identied congurationalforces are continuously measured by monitoring the displacements eld on the specimen'slateral surface. This allows for identication of the cohesive law.