When the pin rubs against the epoxy during pin-on-disc test in
dry air condition, the adhesion of epoxy to the pin will occur to raise the
friction, which consequently increases the friction coefficient. On the other hand, much fluctuation is observed in the coefficient curve for
composite material (Fig. 8b). When the counter face contacted to the
composite material, the adhesion occurred at the contact areas since
the presence of the epoxy and raised the friction force and the friction
coefficient consequently, however, at some time points the tangential
forces were sufficient to overcome the adhesive bonds at the interface,
fracture accrued, and the friction force dropped [24].