Reversible Plasticity Shape-Memory Effect in Epoxy Nanocomposites: Experiments, Modeling and Predictions

Abstract

Conventionally, shape memory programming involves deforming the material at a temperature higher than the glass transition ($T_\mathrm {g}$) and subsequently cooling the material below $T_\mathrm {g}$ while holding the deformation to fix the temporary shape. Alternatively materials with reversible plasticity shape memory (RPSM) property can be programmed at temperatures well below the glass transition temperature which offers several advantages over conventional programing. Here, the RPSM property of multi-walled-carbon-nanotube (MWCNT) reinforced epoxy nanocomposites is investigated. A commercially available epoxy resin is tailored to realize RPSM effect and the properties are enhanced with the addition of nano-fillers in the epoxy matrix. This report systematically investigates the effect of MWCNT addition on the mechanical, thermal and RPSM properties of the epoxy matrix. The RPSM performance under different programming conditions like strain rate, strain level and stress relaxation time is studied. Results reveal that all samples show excellent shape memory properties under various programming conditions. The addition of MWCNT resulted in a significant improvement in mechanical and shape memory properties. Further the RPSM mechanism is explained using a thermo-viscoelastic-viscoplastic model and the model is used to predict the RPSM behavior of the nanocomposite under different programming conditions. As a result, this study shows that by varying the parameters like glass transition temperature, filler content and programming conditions the material can be designed for applications in self-healing systems and smart structures.