Experimental analysis of high-temperature shape memory polymers for deployable structures

Abstract

Shape memory polymers (SMPs) continue to capture interest in the aerospace industry due to their unique properties. In general, the focus has been on SMPs with low transformation temperatures below 100 °C. However, certain aerospace applications require shape memory polymers with higher transformation temperatures to prevent undesirable actuation upon heat exposure. Moreover, and despite significant work on characterizing mechanical and recovery properties of shape memory polymers, the literature lacks full-field characterization of recovery properties, in particular at elevated temperatures. In this work, a high-temperature thermoset epoxy SMP (Tg ≈ 130 °C), named EPON SMP, is thoroughly investigated. This study provides a comprehensive experimental analysis of the mechanical and shape memory properties of the aforementioned high-temperature epoxy SMP. In addition, this study uses a full-field characterization technique, Digital Image Correlation (DIC), to provide further insight on localization, heterogeneity, and local recovery of shape memory strains. Furthermore, the study evaluates the recovery properties of the EPON SMP at different loading conditions (i.e., bending and tensile) and proposes shape-recovery evaluation methods that can be later implemented on other SMPs. • An epoxy-based shape memory polymer with high switching temperature (Tg ≈ 130 °C) was considered in this work. • The temperature dependant mechanical properties were evaluated across a wide temperature range around Tg. • The shape recovery properties were studied under simple tensile and complex bending conditions. • The heterogeneities in the accumulated and recovery strains were evaluated using full-field deformation measurements. • A deep insight into the local accumulation of programmed, thermal, mechanical, and recovery strains is provided.