Rapid evaluation of long-term thermal degradation of carbon fibre epoxy composites

Two commercially available carbon fibre reinforced composites (8552/IM7 and M18-1/G939) were exposed to heat above maximum operational temperature at various durations. Mass loss and mechanical properties were measured over time. A chemical analysis was also performed on these composites. The two primary components of each matrix, the epoxy resin and the thermoplastic, were observed to degrade at different rates under various thermal loading conditions. The epoxy resins degrade predominantly as measured by IR spectroscopy and thermal desorption/gas chromatography mass spectrometry. By using mass loss, strength, and IR spectroscopic data, a correlation was made between strength characteristics of each composite and the relative amount of the two primary matrix components. The developed relationship can be used to estimate rapidly the mechanical properties from the intensity ratio of IR bands characteristic of the two components.