Reversible plasticity shape memory effect in carbon nanotubes reinforced epoxy nanocomposites

Reversible plasticity shape memory (RPSM) property of multi-walled-carbon-nanotube (MWCNT) reinforced epoxy nanocomposites is investigated as an alternative to conventional shape memory programming and for possible applications in self-healing systems. A commercially available structural grade epoxy resin is tailored to realize RPSM effect and the material properties are further enhanced with the addition of MWCNT in the polymer matrix. The samples are characterized for their mechanical, thermal, morphological and crystallographic properties. This paper systematically investigates the effect of MWCNT addition on the properties of the epoxy matrix. To study the RPSM effect, the nanocomposites are programmed by cold drawing and stress relaxation below the glass transition temperature (Tg) and recovered by reheating above Tg. A comprehensive study on the effect of programming conditions like strain rate, strain level and stress relaxation time on the RPSM property is presented. Results reveal that all samples show excellent shape recovery property under various programming conditions. The addition of MWCNT resulted in a significant increase in modulus and strength, decrease in failure strain, increase in Tg and an improvement in RPSM properties like shape fixity, response temperature and recovery speed. As a result, this study shows that by controlling the parameters like glass transition temperature, filler content and the programming conditions, the material can be effectively designed for application in smart structures with shape memory and/or self healing capabilities.