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 02 partial pressures (between 0 and 1.2 x 10(5) Pa) at high temperature (between 180 and 240 degreesC). 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: PO2. + Carb --> inactive products (k(8)). The stabilizing efficiency can be described satisfyingly by the ratio phi(8) equal to the number of PO2. radicals scavenged by carbon per propagation events. phi(8) ranges between 0.01 and 0.1 for ACE in the 180-200 degreesC interval and between 0.1 and 0.4 for BMI in the 210-240 degreesC one. (C) 2004 Elsevier Ltd. All rights reserved.