Mechanical properties of GRP composites with localised thermal damage

The effect of thermal damage on the mechanical properties of glass-reinforced polyester (GRP) composites is investigated. GRP panels underwent surface heating to high temperature (750-800° C) in a cone calorimeter to create localised regions of thermal damage having a circular, oval, square, diamond or irregular shape. The size of the heat-affected region ranged from 10% to 100% of the panel width. The heat damage consisted mostly of char from combustion of the polyester matrix and delamination cracks. After heating in the cone calorimeter, the GRP was cooled to room temperature and then the residual tension and compression properties were determined. Increasing the size and depth of the fire damage zone caused reductions to the stiffness and strength of the GRP. It was found that the shape of the heat-damaged region did not affect the mechanical properties. A model is presented for accurately determining the tension and compression properties of composites with localised heat damage of any shape.