Post-fire flexural properties of fibre-reinforced polyester, epoxy and phenolic composites

The effect of fire damage on the flexural properties of fibre-reinforced polymer (FRP) composites is investigated. The FRP composites studied contained glass, carbon or Kevlar fibres with a polyester, epoxy or phenolic resin matrix. Artificial fire tests were performed on the composites using a cone calorimeter. The residual flexural modulus and strength of the burnt composites were determined at room temperature after the fire tests. The post-fire flexural properties of all the composites decreased rapidly with increasing heating time. Even the properties of the fibre-reinforced phenolic materials were severely degraded despite their low flammability and excellent fire resistance. The flexural properties of the phenolic-based composites were reduced due to thermal degradation and cracking of the resin matrix. In comparison, the properties of the polyester- and epoxy-based composites were reduced by combustion of the resin and formation of delamination cracks. A model is presented for determining the post-fire flexural properties of FRP composites with good accuracy.