Kinetic modelling of the stabilizing effect of carbon fibres on thermal ageing of thermoset matrix composites

A kinetic analysis has been made on the gravimetric curves obtained for carbon fibre/bismaleimide (T800H/BMI) and carbon fibre/amine crosslinked epoxy (IM7/ACE) composites and the corresponding unreinforced matrices in various O2 partial pressures (between 0 and 1.2 × 105 Pa) at high temperature (between 180 and 240 °C). It has been found that the composite behaviour cannot be predicted using the previously established kinetic model for the unreinforced matrices with a simple correction factor for the matrix mass fraction. The results put in evidence a clear stabilizing effect of carbon fibres on matrix oxidation. This effect was tentatively attributed to the well known radical scavenging property of carbon (Carb) and the kinetic model was modified to take into account this property using the following additional elementary step: PO 2 + Carb → inactive products ( k 8 ) . The stabilizing efficiency can be described satisfyingly by the ratio ϕ8 equal to the number of PO 2 radicals scavenged by carbon per propagation events. ϕ8 ranges between 0.01 and 0.1 for ACE in the 180–200 °C interval and between 0.1 and 0.4 for BMI in the 210–240 °C one.