Experimental fracture investigation of CNT/epoxy nanocomposite under mixed mode II/III loading conditions

For the first time, the brittle fracture of epoxy-based nanocomposite reinforced with MWCNTs (multi-walled carbon nanotubes) and subjected to mixed mode II/III loading conditions is investigated. This experimental investigation is carried out using a newly developed test configuration. Araldite LY 5052 epoxy, which is a resin frequently used in aerospace industry, is utilized to fabricate pure epoxy and nanocomposite test specimens with two different MWCNTs contents of 0.1 and 0.5 wt%. The obtained experimental results reveal that adding MWCNTs to epoxy resin up to 0.5 wt% improves the fracture toughness under pure mode II and pure mode III loading with an increasing trend. This is while the improvement under mixed mode II/III loading is reduced by adding nanotubes more than 0.1 wt%. To justify the variations of fracture toughness in terms of nanoparticles content, SEM (scanning electron microscopy) photographs of the fracture surfaces of the specimens in the vicinity of the initial crack front are prepared. Additional fracture mechanisms caused by adding carbon nanotubes are discussed in detail based on the provided SEM images.