Delamination analysis of composite laminates

grantor: University of TorontoA combined theoretical and experimental study has been conducted on the delamination of fibre reinforced polymeric composites. The main objectives were to gain a better understanding of the physical origin of delamination fracture toughness and to develop theoretical models to predict the critical strain energy release rates of delamination in composite materials. Of the many energy dissipation mechanisms present in the delamination process, crack tip plastic deformation was determined to be the most critical one. Two analytical beam models, based on the double cantilever beam (DCB) specimen and the end notched flexure (ENF) specimen, were developed. A fracture criterion, based on the size of the crack tip plastic zone, was incorporated into these beam models so that the mode I and mode II critical strain energy release rates of composites can be predicted using the corresponding resin and fibre properties as well as composite structural parameters. A complete set of mechanical tests were performed on five polymeric composite systems, including both thermoset and thermoplastic systems, and on their corresponding neat polymer resins. The theoretical predictions for delamination fracture toughness from the present analytical models agreed very well with the data obtained in the present experiments and those in the literature over a wide range of composite laminates.Ph.D