POLYMER BASED COMPOSITES FOR STRUCTURAL APPLICATIONS (EFFECT OF ASPECT RATIO OF FUNCTIONALISED CARBON NANOTUBE ON CURING & MECHANICAL PROPERTIES OF EPOXY/CNT COMPOSITES)

Abstract

Epoxy resin is extensively used in structural applications, due to its high modulus and chemical resistance. But epoxy is brittle due to high cross linking density, which reduces its fracture toughness. Incorporation of nano fillers hinders the motion of crack propagation in epoxy and improves the fracture toughness. Therefore Carbon nanotube (CNT) is used extensively as reinforcement in epoxy, leading to enhancement in mechanical, thermal and electrical properties. Epoxy-CNT composites have excellent specific strength, stiffness, chemical resistance, owing to which they find applications in automotives, sporting goods, aerospace, radar absorbing materials etc. But poor dispersion of CNTs in epoxy matrix often forms weak interface leading to inferior mechanical properties. Hence, surface functionalisation of CNT by organic solvents is an effective way of improve dispersion. Functionalization is commonly achieved through carboxyl or amine group attachment to the surface of CNT. Incorporation of CNT also influences the curing of epoxy. Understanding curing kinetics is important as final properties are influenced by it. The curing behavior is affected with changes in aspect ratio of CNT as well. Hence, the present study focuses on studying effect of aspect ratio on curing kinetics and its effect on mechanical properties. Functionalized CNTs, with two different aspect ratios, were used in the study. The effect of curing on mechanical properties of composites was studied using uniaxial tensile & fracture toughness test. Field emission-scanning electron microscopy was used to characterize the strengthening and failure mechanisms prevalent. The maximum increase in fracture toughness was found out to be around 177%, while the maximum increase in tensile strength was found out 91%, both as compared to neat epoxy.