Fracture Toughness of Laminated Composites – A Non-Linear Analysis

Abstract

Non-linear fracture behaviour of laminated composite materials under mode I (crack opening) loading conditions was studied experimentally and theoretically. For this purpose, single edge notched tension (SENT) tests were carried-out using displacement-controlled loading under room temperature dry conditions. It was found that the load-displacement diagram had non-linear character prior to onset of macroscopic crack propagation. Thus, the main objective of this paper was to study the fracture properties using non-linear fracture mechanics. A two-dimensional finite element model was set-up in order to analyze the non-linear response of the SENT test specimen. Non-linear deformation due to damage was simulated using the Tsai-Hill failure criterion. The failure analysis revealed that the damage was localized in the vicinity of the crack tip. The fracture response was characterized using a J-integral. It was shown that a realistic appraisal of the potential for crack growth should include the effects of non-linear material deformation. It was found that taking into account the non-linear deformation increased the fracture resistance. This finding was attributed to the increased strain energy dissipation due to the damage induced non-linear behaviour of the SENT test specimen.