Characterization of unconstraint and constraint shape recoveries of an epoxy based shape memory polymer

Shape memory polymers (SMPs) are an emerging class of active polymers that can be used on a wide range of reconfigurable structures and actuation devices. The present study comprehensively examines the shape recovery abilities of an epoxy-based SMP under unconstraint and constraint conditions. Results show that the present SMP exhibits excellent shape recovery under unconstraint conditions, regardless of the levels of fixing strain and fixing temperature. The SMPs are also able to recover fully under load and to generate high levels of stress during recovery. When activated under a programed thermomechanical cycle, the material has demonstrated excellent shape fixity and reached full recovery on re-heating. The shape recovery process of the SMP has been analyzed by using Chen and Lagoudas' model. Each step of the thermomechanical cycle (deforming, cooling, fixing, and recovering) has been successfully predicted. The simulated results are found to be consistent with the experimental observations.