1. Introduction
Epoxy resins (EPs) are considered as one of the most important classes of thermosetting polymers. They have been used extensively as high performance adhesive composite materials, due to their outstanding mechanical and thermal properties such as high modulus, tensile strength, low creep, high glass transition temperature, high thermal stability, and moisture resistance [1]. In the cured state, EPs are brittle materials that have fracture energies some two orders of magnitude lower than modern thermoplastics and