Co-molding High Temperature Erosion Coatings for Thermoset Polyimide Composites

High temperature (200-260°C) military composite engine components made of carbon fiber thermoset materials are susceptible to erosion damage. Evidenced by wear seen during operation, erosion protection remains a challenge for composites in the engine air flow path. In this paper, we investigate polyetheretherketone (PEEK), thermoplastic polyimide (TPI), and ceramic fabric (Nextel™) as potential high temperature erosion coatings for thermoset polyimide composite engine components. We evaluate the erosion protection materials for two qualities: (1) co-moldability with thermoset polyimide composite panels, and (2) erosion resistance to a sandblasting test. Autoclave and compression molding were used to test co-moldability with different manufacturing methods. The compression molding process was optimized to reduce surface defects using a pre-imidization step before the erosion protection layer was applied and final cure was completed. Co-molded test panels were cut into small coupons for sandblasting. After 60 s of alumina sandblasting PEEK had negligible mass loss, whereas the TPI and ceramic fabric had roughly the same erosion rate as the uncoated polyimide laminate.