Simple models for determining the mechanical properties of burnt FRP composites

Simple-to-use models based on the rule-of-mixtures are presented for predicting the post-fire tension, compression and flexure properties of burnt fibre-reinforced thermoset polymer (FRP) composites. The accuracy of the models is tested against experimental mechanical property data for a variety of FRP composites after having been burnt in an artificial fire using a cone calorimeter. The composites consisted of E-glass, carbon or Kevlar-49 fibres within a thermoset polymer matrix of polyester, vinyl ester, epoxy or phenolic resin. The mechanical properties of the composites dropped with increasing burning time and heat flux due mainly to thermal degradation and combustion of the polymer matrix. The degradation to the mechanical properties was accurately predicted using the models, and in most cases the agreement between the theoretical and measured post-fire mechanical properties was within 10%.