Impact of Fabrication Process Variations on Epoxy Shape Memory Polymer Mechanical Properties Across Temperature Gradients

Abstract Shape Memory Polymers (SMPs) are versatile polymeric materials that are able to undergo reversible shape changes triggered by external stimuli like temperature, electric current, UV light, and magnetic fields. Epoxy Shape Memory Polymers (ESMPs), a subset of SMPs, are notably influenced by compositional changes. While previous studies focused on the response of thermal and mechanical properties based on composition changes, understanding how the fabrication process affects mechanical performance remains limited. This research addresses the mentioned gap, by systematically evaluating the mechanical properties at different temperatures, and particularly considering variations in time and temperature during the curing process of the ESMP. Using the Taguchi method, an L9 orthogonal array design was employed with a signal-to-noise quality characteristic analysis. Ninety ESMP samples with consistent composition but varying curing and post-curing parameters were produced. ESMP molar ratio was chosen for a glass transition temperature of 36°C, enabling sample programming by body temperature. Tensile testing at different environmental conditions revealed significant impacts of fabrication process on the ESMP mechanical behavior. Longer curing and post-curing times and higher temperatures increased stiffness and strength, while shorter processing times at lower temperatures decreased these properties. Maintaining the manufacturing parameters and testing the samples at higher temperature reduced the stiffness, strength, and strain at failure. These findings facilitate customized fabrication for applications requiring variable properties, particularly in active mechanical interfaces responding to external stimuli.