Modelling problems of damage at notches and the fracture stress of carbon-fibre/polymer composites: matrix, temperature and residual stress effects

This paper presents a modelling strategy for analyzing the tensile failure mechanisms and fracture stress of notched carbon-fibre/polymer laminates over a range of elevated temperature. It takes into account changes in the properties of the matrix, the fact that the damage zone may change in shape with increasing stress and temperature, and the possibility of thermal (residual) stresses created when processing the composite. Our approach is to follow a set of steps: (1) identify the physical mechanisms (we do this by X-ray radiography); (2) construct the model (we build upon the previously modelled problems of cracking at notches by Kortschot and Beaumont by applying the tools of fracture mechanics and damage mechanics); (3) test the model (we do this by comparing the model with experimental data of the damage processes and fracture stress for a thermosetting- and thermoplastic-matrix composite over a wide range of temperature); and (4) we tune the model (by lumping together empirical parameters that have to be determined by experiment).