Behavior of Thermoset Shape Memory Polymer-Based Syntactic Foam Sealant Trained by Hybrid Two-Stage Programming

Recently, a shape memory polymer-based self-healing syntactic foam was proposed and tested as a sealant for expansion joints. The key for success is to train the foam by using a two-dimensional (2D) stress condition (compression in the horizontal or traffic direction and tension in the vertical direction) at a temperature above the glass transition temperature (Tg). However, for practical applications, programming a full-size slab of sealant with a 2D stress condition and under temperature control is not a trivial task. This study demonstrated that the programming with a one-stage 2D stress condition can be replaced by a sequential two-stage one-dimensional (1D) stress condition. To further simplify the programming process, 1D tension programming was conducted at a temperature above the Tg, followed by 1D compression programming at a temperature below the Tg (cold compression). The test results show that the hybrid programming leads to similar shape memory behavior as long as the prestrain level i...