FATIGUE PERFORMANCE OF CARBON-FIBER VINYL-ESTER COMPOSITES - THE EFFECT OF 2 DISSIMILAR POLYMERIC SIZING AGENTS

Carbon fibre/vinyl eater composites were made from sized carbon fibres . The carbon fibres were sized with an in-house sizing process and the n formed into a unidirectional fabric. This fabric was processed into composite panels by a resin film infusion (RFI) technique. The effects of two dissimilar sizing agents--a brittle thermoplastic K-17 poly(vi nyl pyrrolidone) (PVP) and a ductile thermoplastic polyhydroxyether (p henoxy resin)--on notched fatigue, short-beam shear, transverse flexur e properties and compression properties were studied. The fatigue prop erties of carbon fibre/vinyl eater composites were influenced drastica lly by the type of sizing agent used. A 20-fold increase in lifetime w as demonstrated at a loading level of 207 MPa for the ductile phenoxy sized composite compared with the unsized composite. The brittle PVP s ized composite panel showed a sixfold increase in lifetime compared wi th the unisized case. The phenoxy-sized composite panel showed a 40% i ncrease in flexural modulus and the PVP-sized panel showed a 20% incre ase compared with the unsized composite panels. Negligible differences in the shear strength, flexural strength and static compressive stren gth were observed for the different interphase agents. The implication s of these results for tailoring polymeric interphases in vinyl-ester- matrix composites are discussed. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.