Investigation of carbon fiber composite stiffened skin with vacuum assisted resin infusion/prepreg co-curing process

Co-cured vacuum assisted resin infusion process (co-VARI process), which combined vacuum assisted resin infusion (VARI) with prepreg vacuum bag only process (VBO), was adopted to fabricate T-shaped stiffened skin with non-crimp fabric (NCF) stiffener and prepreg skin. During compaction stage of co-VARI process, prepreg resin impregnated fiber fabric under elevated temperature and vacuum pressure. This phenomenon was characterized by fluorescent micrographs with different holding temperature and time. Its influences on processing quality and mechanical performance for co-VARI stiffened skin with different filler materials at triangular region were further analyzed by optical micrographs and pull-off test, respectively. The results show that increasing holding temperature and prolonging holding time can promote prepreg resin impregnation in fiber fabric. Moderate prepreg resin impregnation is favorable to reduce resin rich region and increase fiber volume fraction at prepreg-fabric interface. Moreover, prepreg resin impregnation effect plays significant roles on pull-off performance for co-VARI stiffened skin with fabric filler but has negligible influences on specimens with prepreg filler. In addition, compared with stiffened skin with fabric filler, superior processing quality and pull-off performances are achieved for co-VARI stiffened skin with prepreg core filler. These results are helpful to optimize processing procedures and fabricate composite structure by co-VARI process.