Online characterization of moisture transport in a high-performance carbon fiber-reinforced thermoplastic composite at high temperatures: Identification of diffusion kinetics

Prior to processing, high-performance fiber-reinforced ThermoPlastic matrix Composites (TPC) are usually stored in ambient conditions, thus causing moisture sorption. During processing at high temperature, the stored moisture induces defects that deteriorate the mechanical properties of the produced parts. In order to understand these effects, it is necessary to study water (de)sorption phenomena in TPC, which was only characterized at low temperatures up to now (<100°C). Thus, we characterized online moisture (de)sorption mechanisms at high temperatures (up to 300 °C) on large and representative samples of a high-performance carbon-fiber (CF) reinforced PolyEtherKetoneKetone (PEKK) laminates. This characterization was performed thanks to a new thermogravimetric device named OMICHA (Online Moisture Ingress CHAracterization) that we developed purposely. This new device allows to continuously measure weight variation of large composite samples under controlled and high temperature and/or humid environment. Sorption and desorption tests allowed to determine macroscopic moisture diffusion coefficient of CF/PEKK at several temperatures, highlighting a complex dual stage macroscopic diffusive behavior which is also modeled and discussed.