Thermal and kinetic characterization of a toughened epoxy resin reinforced with carbon fibers

Abstract

The oxidation behavior of a composite material (Cycom 977-2/Priform by Cytec), based on a toughened epoxy resin reinforced with carbon fibers, is studied in the kinetic regime and a mixed thermal-diffusive regime. Thermogravimetric measurements for the composite material and the two single components support the existence of three main reaction stages. The first is the oxidative decomposition of the resin taking place at temperatures between 496 and 730 K that can be described by a reaction with an activation energy of 82 kJ/mol. The second and third reaction stages correspond to the oxidation of the resin char, that terminates at about 850 K, and at higher temperatures the oxidation of the carbon fibers, described by global kinetics with activation energies of 105 and 184 kJ/mol, respectively. The thermal history of thick samples burning in a furnace depends on the heating temperature, in nitrogen, and/or the maximum temperature, in air, caused by the reaction exothermicity. After an inert heating stage, when maximum sample heating rates are achieved, the process dynamics again show the existence of three main reaction stages whose characteristic times and temperatures are determined.