<p>Interfacial properties between the fibers and the matrices were analyzed using the optimal contact angle evaluation. The static and dynamic contact angles were evaluated under different epoxy conditions, determine the surface energies of the four types of epoxy. To identify the optimum contact angle method, four types of epoxy resin and glass fiber (GF) were used as specimens. Based on the surface energy results of GF and the matrix, the work of adhesion was calculated to evaluate the interfacial interactions between the matrix and the fibers. Theoretically, the work of adhesion is proportional to the interfacial shear strength (IFSS). The IFSS between the epoxy and GF was evaluated using microdroplet pull-out test to examine its correlation between work of adhesion and IFSS. Ultimately, in the case of static contact angle measurements, the relationship between the work of adhesion and IFSS did not follow the expected trend. In contrast, the dynamic contact angle showed a stronger correlation with IFSS, confirming it as the method that shows better correlation with IFSS trends in surface energy analysis.</p>