Fracture behaviours of epoxy nanocomposites with nano-silica at low and elevated temperatures

An investigation was conducted to characterize fracture behaviours of nano-silica modified epoxies at low and elevated temperatures. A nano-silica dispersed epoxy (Nanopox XP 22/0516, Hanse-Chemie, Germany) with 40 wt% silica nano-particles was used as modifier to toughen an epoxy resin, Araldite F (Bisphenol A based, Ciba-Geigy). Fracture toughness and other mechanical properties were measured using standard compact tension (CT), tensile and flexural specimens to elaborate the effects of nano-silica particles on fracture behaviours of epoxy nanocomposites at different temperatures, −50, 0, 23, 50 and 70 °C. Dynamic mechanical analysis (DMA) was utilized to define the glass transition temperature (Tg) upon the addition of different amounts of nano-silica particles. Fracture toughness of the nano-silica modified epoxies was clearly increased at 23 °C and 50 °C, but the role of nano-silica particles in enhancing the fracture toughness became less pronounced at 0 °C and −50 °C and disappeared at 70 °C.