Cyclic compression behavior of epoxy shape memory polymer foam

Shape memory polymer foams have significant potential in aerospace and biomedical applications, however their thermomechanical behavior and damage response under cyclic deformation are not well understood. This paper investigates effects of pre-strain and hold period between compressive cycles on cyclic behavior of epoxy shape memory polymer foam with relative densities of 20%, 30%, or 40%. For each relative density, foams were cyclically deformed under conditions of strain control with periodic hold times (0, 40, and 300 s). During the hold time the sample was completely unconstrained; neither stress nor a strain was applied. A 17% relative density foam was periodically imaged at 12 μm resolution using micro-computed tomography scans to determine the mesostructural response to cyclic deformation of 40%, 60%, or 80% engineering strain. These scans provided global quantitative data as well as qualitative regional information on cyclic deformation mechanisms. Individual struts were isolated and tracked across the scans to qualitatively show local response to cyclic conditions. The experimental data are discussed in light of finite element modeling of the foam (published in another article) to better understand the cyclic deformation behavior.