Effects of Particle Shape, Size and Interfacial Adhesion on the Fracture Strength of Silica-Filled Epoxy Resin

The effects of particle shape, size and interfacial adhesion on the fracture strength of a particle-filled epoxy resin were investigated. For this purpose, various types of spherical and irregular-shaped silica particles having different mean sizes in the range from 2 to 30 pm were used. The particle content was 50% by weight. In order to prepare well and poorly adhered interfaces, surface treatment of the particles was carried out using silane coupling and decoupling agents. Surface treated particle-filled resins were compared with untreated particle-filled resin. The flexural strength increased with a decrease in particle size in both the untreated and the well adhered systems, whereas it was independent of size in the poorly adhered system. The flexural strength was higher in the order: well adhered > poorly adhered > untreated systems for spherical particles, but, well adhered > the untreated > poorly adhered systems for the irregular-shaped ones. According to a scanning electron microscopic observation of fractured surfaces, the fracture strength of particle-filled brittle polymers was affected by the number, size and sharpness of the defects in the material derived from particle fracture or interfacial debonding.