The resin is comparatively brittle and can crack or fail when force is applied across the fiber orientation, which is why a fiberglass object can be dented or shattered by a localized blow despite its overall strength. Hybrid Rod Construction: Many high-end rods use a hybrid of fiberglass and carbon fiber. Resin Systems: Epoxy resins used to bind the fibers together help. Fiberglass is a composite material composed of fine glass fibers embedded within a polymer resin matrix, often polyester or epoxy resin. The. One of the key aspects of fiberglass rod properties is their impressive tensile strength, which allows them to withstand heavy loads and high-stress conditions without breaking. Tempering increases hardness and makes it less prone to breakage when under stress or pressure.