Instrumented impact properties and fracture behaviour of epoxy/modified halloysite nanocomposites

Surface modification of halloysite nanotubes (HNTs) by gamma-aminopropyltriethoxysilane (APTES) and bisphenol-A-diglycidyl-ether (DGEBA) was explored through NaOH pretreatment and found to be effective in improving their toughening effect in epoxy nanocomposites. The impact performance and fracture mechanism of epoxy/modified-HNTs nanocomposites were studied by instrumented impact testing and electron microscopy observations. The quality of modification had a significant effect on the impact properties of epoxy/HNTs nanocomposites. Whilst the crack initiation stage was not affected by incorporation of modified or unmodified HNTs, the crack propagation energy was dramatically increased by the incorporation of HNTs and their modification. The force required for crack propagation was considerably increased in epoxy/modified-HNTs nanocomposites to even higher than those of crack initiation force, which is important to maintain the structural integrity of the nanocomposites after crack initiation. This study helps to explain how the modified and unmodified natural nanotubes can positively contribute to the fracture mechanism of nanocomposites, throughout the whole fracture process. (C) 2014 Elsevier Ltd. All rights reserved.