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The adhesion of bisphenol-A polycarbonate, an amorphous thermoplastic, to carbon fiber was studied by varying both the intrinsic and the extrinsic properties such as the molecular weight, processing conditions, and test temperature. It was seen that processing methods and conditions had a significant effect on adhesion as measured by the interfacial shear strength. Commercial grade Lexan 141 solvent deposited onto carbon fibers showed poor adhesion when processed below the glass transition temperature and reached a limiting value at a higher temperature. Melt consolidated pure polycarbonate specimens showed increases in adhesion both with increasing processing temperature and with time. Pure polycarbonate having a molecular weight above the critical molecular weight exhibited a higher adhesion at different processing conditions, while for polycarbonate below the critical molecular weight adhesion was poor and unaffected by the processing temperature. Increases in temperature lowered the adhesion as a result of the dependence of adhesion on the matrix modulus, which decreases with increasing temperature.

A method for determining the fiber volume fraction in continuous fiber composites by automatically counting the fiber ends per unit area in digitized microscope images of representative cross sections has been developed. Since fiber counts are digital variables, the accuracy of the method is essentially independent of small variations in microscope focus and specimen surface preparation. In addition to producing averaged data, the method enables the construction of volume fraction variation profiles ranging from the finest possible scales up to full size components. Results are in agreement with values obtained by acid digestion tests.

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