Thermomechanical Characterization of Environmentally ConditionedShape Memory Polymer Using Nanoindentation

摘要

Shape memory polymers (SMPs) are an emerging class of active polymers that have dual-shape capability, and aretherefore candidate materials for multifunctional reconfigurable structures (i.e., morphing structures). However, theSMPs have not been fully tested to work in relevant environments (variable activation temperature, fuel and water swell,UV radiation, etc.) required for Air Force missions. In this study, epoxy-based SMPs were conditioned separately insimulated service environments designed to be reflective of anticipated performance requirements, namely, (1) exposureto UV radiation for 125 cycles, (2) immersion in jet-oil at ambient temperature, (3) immersion in jet-oil at 49°C, and (4)immersion in water at 49°C. The novel high-temperature indentation method was used to evaluate the mechanicalproperties and shape recovery ability of the conditioned SMPs. Results show that environmentally conditioned SMPsexhibit higher moduli in comparison to an unconditioned one. During free recovery, the indentation impressions of allSMPs disappeared as temperature reached above Tg, indicating that the material's ability to regain shape remainsrelatively unchanged with conditioning.