The effect of manufacturing technologies on the flame retardancy of carbon fibre reinforced epoxy resin composites

Abstract

We prepared reference and flame-retarded carbon fibre reinforced composites both by liquid composite moulding, in particular vacuum infusion, and by hand lamination followed by hot pressing (wet compression moulding) in order to study the effect of carbon fibre reinforcement and particle distribution of solid flame retardants (FRs) on fire performance. The flame-retarded matrix had 3% total phosphorus (P) content from ammonium polyphosphate (APP). When the infusion site of the composite produced by vacuum infusion faced the conical heater during the mass loss type cone calorimeter tests, the peak of heat release rate (pHRR) was lower, the time of pHRR became longer and the intumescence increased in comparison to the laminated sample, which supported our hypothesis about the filtration of solid APP during the vacuum infusion process. In order to model the suspected filtration, we prepared a laminated composite sample with an increasing amount of APP equivalent to 1%, 2%, 3%, 4%, 5% P content in each subsequent layer.The HRR curve of the composite produced by vacuum infusion with the infusion site facing the conical heater was basically identical with the curve of the model composite with the 5% P layer facing the conical heater in the early phase of the degradation, while in the main degradation phase, the lower burnable ratio of the composite prepared by vacuum infusion led to a further decrease in pHRR (184 kW/m2) and THR (15.5 MJ/m2), and the consequent best overall fire performance of the composite produced by vacuum infusion. The suspected accumulation of APP in the first layers of the composite caused by the carbon fibre reinforcement was proven by SEM-EDS elemental maps of the whole cross-section of the composite.