Thermal Properties of Magnetite Nanoparticle and Carbon Fiber Doped Epoxy Shape Memory Polymer

Abstract

Presented are the results of an experimental investigation into the effects of particle and carbon fiber (CF) doping in epoxy shape memory polymer (SMP). Motivation for the work originates from the need to increase the thermal performance, and thus decrease the time required to transition the polymer given a finite amount of thermal energy, of a SMP link in a bi-stable linkage. Such a multi-functional link is responsible for structural support, mechanism reconfigurability, as well as system damping. Thus any improvement in thermal properties must be weighed against increases in brittleness and weight as well as altered mechanical properties as a result of the chosen method. Two part epoxy SMP by CRG Industries is doped with Fe3O4 (magnetite) nanoparticles (20–30nm spheres) at a weight fraction of 10% as well as 3mm and 10mm carbon fibers at a weight fraction of 5.4%; resulting in all dopants having a volume fraction of approximately 2.5%. The thermal conductivity, specific heat, and diffusivity are experimentally measured by a Hot Disk Thermal Constants Analyser from ambient through transition and the results compared with several thermal composite models. Changes in the thermal properties of the composites and neat polymers with respect to temperature are presented and the effects these changes have on the predictions of thermal models discussed, specifically the effect of changes in thermal properties near the transition temperature and the resulting change in predicted energy required for transition. The effects of adhesion between the particles and the matrix and particle dispersion on conductive paths and material thermal properties are also discussed.