Failure model for phenolic and polyester pultrusions under load in fire

The failure of polyester and phenolic pultrusions under tensile and compressive load and a one sided heat flux of 50 kW m-2 has been studied. A thermal/mechanical model, based on the Henderson equation and laminate theory, has been used to model their behaviour. In tension, significant load bearing capacity was retained over a period of 800 s, due to the residual strength of the glass fibres. However, pultruded composites are susceptible to compressive failure in fire, due to the loss of properties when the resin Tg is reached. The fire reaction properties reported here showed the phenolic pultrusions to perform better than polyesters in all fire reaction properties (time to ignition, heat release, smoke and toxic product generation). The measurements under load in fire showed that the phenolic system decayed at a slower rate than the polyester, due mainly to the very shallow glass transition of the phenolic, but also the char forming characteristic of the phenolic. The behaviour described here for phenolic pultrusions is superior to that reported for some phenolic laminates, the main reason probably being their lower water content.