Temperature stress accumulation in polymer composite shells under cyclic temperature impact

The object of research is a polymer composite based on thermosetting epoxy binder and EZ-200 fiberglass fabric. Its behavior in the operating conditions of industrial chimneys, which include high temperatures, long-term operation, cyclic mechanical and temperature impact, and prolonged thermal aging, is yet to be determined. Viscoelasticity of polymer matrix leads to several possible effects. One is the accumulation of temperature stresses due to non-stationary temperature effects. This work aims to evaluate the possibility of such an effect and assess it. It required us to conduct cyclic heating tests and FE shell calculations. Method. Cyclic heating tests were conducted in the specially manufactured testing chamber, which allowed us to prevent specimens from longitudinal deformations, illustrating the work in constrained construction conditions. Specimens were exposed to several heating and cooling cycles, while the longitudinal force was measured during the experiment and converted to stress. To check the adequacy of the equipment and for further calculations, the elastic modulus was calculated through tensile tests. Results. It was observed that the stress amplitudes were not the same during the heating-cooling cycles. There was a shift in the compressive stress direction, meaning the possible accumulation of temperature stresses. Calculations of temperature stresses using The Coefficient of Thermal Expansion (CTE) indirectly proved that. The 3-layered sandwich shell of an industrial chimney was calculated using ANSYS Workbench software to assess the influence of stress accumulation on the stress-strain state of the construction. It showed us that there might be a 5-10% increase in stress. Therefore, it should be considered, and further research on this topic is needed.