Strain history of 3D printed bilayer structure with flexible elastomer and shape memory polymer filaments during thermal tensile test

This study aimed to investigate the strain history of a 3D-printed shape-memory polymer (SMP) and elastomer bilayer specimen under thermal tensile load. First, printing conditions for producing single-layer and bilayer specimens using a fused deposition modeling 3D printer were determined. Tensile tests under thermal effects were then conducted on both specimens. A 1 kg weight was used as a constant tensile load, and temperature cycles ranging from 25 to 65 °C were implemented to determine the thermal effects. The strain history was measured using a strain gauge attached to the specimen during the tests. An initial bending deformation caused by the shrinkage of the elastomer layer was observed in the bilayer specimen immediately after printing. This initial bending was then removed from the bilayer specimen via uniform heating. Strain relaxation was observed in the strain history of the single-layer SMP specimen. Mismatch strain between the two layers of the bilayer specimens was also confirmed from the thermal tensile test results. Analyses and discussions on the strain history data are provided in this paper. In general, this study determined the empirical deformation characteristics of a 3D-printed SMP–elastomer bilayer structure under combined thermal and tensile loading conditions. The results can be used to comprehend the deformation of bilayer SMP–elastomer structures and will be useful for designing a bilayer structure made of 3D-printed SMP material.