AbstractThe interface between the fibers and the polymer matrix controls the properties of fiber composites and has been the subject of much study. Recently, special techniques have been developed for single fiber pull‐out experiments on production fibers, which make it possible to obtain data on the frictional forces which govern sliding after the interface has fractured, as well as the adhesion strength of the interface. Tests on glass in polyester and epoxy resins show that the work of fracture of the interface is much smaller than that of the resin, and that the shrinkage pressures of these matrices, when fully postcured, are approximately the same (about 20 MPa). Coefficients of friction at the interface are 0.6 for the polyester and 1.0 to 1.6 for the epoxy. The carbon‐epoxy interface yields at shear stresses as high as 60 MPa, instead of fracturing, and the coefficient of friction during sliding is about
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