Flow and void characterization of stitched structural composites using resin film infusion process (RFIP)

Abstract

AbstractThe resin film infusion process (RFIP), which is similar to resin transfer molding (RTM), was applied to investigate the possibility of manufacturing high performance stitched composites. With the objective of understanding the resin flow mechanisms and void formation in stitched fibrous perform, two recent technological developments in homogeneous tough resin and bendable stitching fibers were incorporated in producing stituched composites with RFIP. These included new lightly crosslinked thermosets (LXT) that were phenolic or amine based. Second, bendable carbon stitching reinforcement (T‐900) was utilized as a stitching fiber. Flow characteristics were inferred by ultrasonic C‐scan analysis of cured panels. Microscopic studies indicated that voids were distrubuted along the stitching fiber because of low consolidation pressure in the resin‐rich area (stitching fiber region) where the fiber volume content was lower. In contrast to stitched composites, non‐sitiched composites contained lower void content and irregular void distribution because of uniform fiber compaction. Microscopic studies of partially resin infused quasi‐istropic stitched composites demonstrated that the resin flows along the stitching fiber region and then infuses into the fibrous preform. These infusion phebnomena were the result of anistropic permeability in the preform. Consequently, anisotropic resin flow in the stitched fibrous preform was found to be related to the heterogenous textile structure caused by the stitching process.