The mechanical properties of composites made of six different non-asbestos fibers (mineral, phosphate, wollastonite, wollastokup, glass and carbon) and two resins (phenol-formaldehyde and cashew-modified phenolic) have been studied, in order to determine the binary interactions between the fiber and resin. The Young's modulus, ultimate tensile strength and flexural strength have been determined. The Young's modulus values have been compared with a theoretical model designed for random short fiber composites based on the Halpin-Tsai model with an empirical coefficient of 1/10. Scanning electron micrographs (SEM) of the fiber and fractured composite surface have been taken in order to determine the failure mode of the composites.