Quantitative and qualitative analyses of mechanical behavior and dimensional stability of styrene-based shape memory composites

The effect of glass fiber reinforcement on the mechanical properties and geometrical shape stability during the thermomechanical cycle of the shape memory polymer composite has been investigated. A substantial improvement in the mechanical properties due to glass fiber reinforcement has been realized. However, unexpected deformation has been observed during heating process, particularly in the first thermomechanical cycle. This unanticipated deformation negatively affects the geometrical shape stability of the composite, and as a consequence the geometry preciseness of the structural parts manufactured with shape memory polymer composites will be reduced. In this article, the unanticipated thermal deformation in the shape memory polymer composites during the heating has been observed experimentally, and constitutive relationships to describe this behavior have been developed. Furthermore, an application of a constant tensile load during the heating process on the shape memory polymer composite part was found to be a reliable solution to reduce the thermal distortion effect and improve the geometric stability of the composite. The results showed that developed constitutive relations have shown a good agreement with the experimental results. Furthermore, the proposed applied tensile load has shown significant improvement in the shape memory polymer composite samples' geometrical shape stability when subjected to a temperature increase.