DEVELOPMENT AND EVALUATION OF SURFACE TREATMENTS TO ENHANCE THE FIBER-MATRIX ADHESION IN PAN-BASED CARBON-FIBER LIQUID-CRYSTAL POLYMER COMPOSITES .1. COUPLING AGENT AND AMINE SURFACE TREATMENTS

Several surface treatments, using both commercially available coupling agents and reagents containing multiple amines, were applied to commi ngled continuous as-received AS4 carbon reinforcing fiber/liquid cryst al polymer (LCP) matrix fibers. Unidirectional composites (nominally 6 0 vol% carbon fiber) were prepared from as-received and treated commin gled fibers and characterized. To estimate the effect of the treatment s on flber-matrix adhesion, short beam shear (SBS) tests were conducte d, the failure surfaces were examined, and spectroscopic studies were performed. The mean SBS strength of the as-received unidirectional AS4 carbon fiber/LCP matrix composite system was 49 MPa. The best couplin g agent and amine treatments yielded increases in composite shear stre ngth of approximately 10 to 20%, relative to the as-received AS4/LCP s ystem. For the amine treatments, ESCA and FTIR analyses suggested that chemical interactions with functional groups on the sur-faces of both the carbon and LCP fibers may have caused the increased adhesion. Mor eover, SEM analysis of the failure surfaces of SBS specimens from comp osites prepared with the treated fibers (both with coupling agents and amines) showed that strong fiber-matrix adhesion was present. That is , failure occurred in the LCP matrix material.