Reversible plasticity shape memory effect in carbon nanotube/epoxy nanocomposites: Shape recovery studies for torsional and bending deformations

Thermally activated shape memory polymers (SMP) are typically programmed by initially heating the material above the glass transition temperature (T-g), deforming to the desired shape, cooling below T-g and unloading to fix the temporary shape. Though this approach is employed in small-scale applications, the process of deforming at high temperatures becomes a time, labor, and energy expensive process while applying to large structures (e.g. deployable space structures). The reversible plasticity shape memory (RPSM) property provides an alternate programming approach wherein the material is plastically deformed to a temporary shape at temperatures well below the transition temperature, preferably at room temperature. This paper aims to study the advantages of RPSM programming under bending and torsional deformations in multi-walled carbon-nanotube (MWCNT) reinforced epoxy nanocomposites. The samples are characterized for their thermal, morphological, and mechanical properties. The shape recovery behavior under various deformation modes is studied in detail. The effect of deformation level, relaxation time, and thermo-mechanical cycles are also studied. All samples show excellent shape memory properties under all deformation modes and programming conditions. As a result, it is demonstrated that the RPSM programming can be used as an effective and a simplified alternative to conventional shape memory programming. POLYM. ENG. SCI., 58:E189-E198, 2018. (c) 2018 Society of Plastics Engineers