Processing of poly(ethersulfone)/graphite fiber composites: Thermooxidation, rheology, and consolidation

Abstract This study relates the formability of thermoplastic poly(ethersulfone) HTA composites to thermooxidative history and rehological behavior. HTA/IM8 graphite fiber performs were prepared under various temperature, time, and environmental (unbagged and vacuum‐bagged) conditions, then consolidated into finished laminates under identical conditions. X‐ray photoelectron spectroscopy and pyrolysis/gas chromatography/mass spectrometry were used to assess chemical degradation, and dynamic mechanical analysis (DMA) was used to evaluate T_g and rheological behavior in the finished laminates. All performing conditions resulted in some degradation of the HTA matrix, the presence of air being especially detrimental. The nature of this degradation is discussed and related to changes in T_g., melt viscosity of the matrix resin, and the extent of consolidation. A new DMA approach to evaluating degree of consolidation is developed and shown to offer considerable promise for quantitative assessment and ranking of composites.