Effect of nano-particles on mechanical properties of epoxy-based composites

A comprehensive experimental investigation has been successfully conducted to characterise effects of a reactive liquid carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber, nanosilica, halloysite nanotubes (HNTs), and hybrid particles of CTBN liquid rubber with nanosilica or halloysite on mechanical properties of the cured epoxies and the fibre-reinforced epoxy composites. Mechanical characterisations on the modified bulk epoxy showed that the hybrid particles, consisting of CTBN rubber and nanosilica or halloysite are effective additives to significantly increase the fracture toughness of the epoxy without considerably sacrificing other properties such as strength, modulus of elasticity and glass transition temperature (Tg). It was also found that nanosilica particles could improve the wear resistance of epoxy only when the content of nano-particles was higher than a critical value (10 wt%), even though the static mechanical properties of the bulk epoxy such as microhardness, modulus, fracture toughness were almost proportionally improved with an increase in the content of nanosilica particles. A transverse fibre bundle (TFB) test method in combination with the finite element analysis (FEA) method was used to identify the effect of the addition of nano-particles. It was found that the addition of nano-particles does not noticeably affect the interfacial bonding behaviour between fibres and matrix. It shows that the improved fracture toughness of bulk epoxy due to the incorporation of the hybrid particles can be transferred to the enhanced interlaminar fracture toughness of the CF/EP composites. CTBN liquid rubber and inorganic particles (nanosilica, or halloysite) were also found to effectively improve the fatigue performance of the CF/EP laminates by noticeably decreasing interlaminar fatigue delamination growth rates.