This work describes the mechanical stress behavior of composite materials made up of a polymer matrix of epoxy resin or polyester resin and reinforcements of: nylon fiber and combinations between fiberglass and nylon fiber. The composite material was evaluated regarding its mechanical stress behavior and its microstructure; results indicate that the highest tensile strength is achieved in the combination using epoxy resin as matrix and nylon fiber as reinforcement. The presence of fiberglass in the material diminishes tensile strength; given that the fiber-matrix interface does not prevail, as evidenced in the microstructural analysis and argued with the chemical bond taking place among the epoxy resin, nylon fiber, and the fiberglass silane. It is, likewise, established that upon increasing the epoxy resin content, mechanical stress strength increases and that said behavior is related with the hydrophilic nature of the fiber and the porosity in the material. Regarding ductility, it was noted that nylon favors slightly the increase of this property in the composite material.