Journal of Polymer Science and Engineering 2026, 9(1), 11929; https://doi.org/10.24294/jpse11929

Under thermo-mechanical stress via a bulge test (BT), composite circular diaphragms (CCD) exhibit temperature-dependent mechanical behavior, including changes in Young’s modulus, yield strength, and residual stress. The application of a differential pressure and temperature causes the membrane to deform, allowing researchers to characterize composite material properties, particularly for materials used in microelectromechanical sensors (MEMS) operating in harsh environments. This paper aims to explore how CCD made from basalt fiber reinforced polymer (BFRP) behaves under thermal and mechanical stress, particularly in various engineering and bioengineering sensor applications, using a technique known as the BT. To start, the diaphragm is pre-stressed and clamped between two plates. When applying differential pressure, it causes the diaphragm to deform. An analytical approach is developed for utilizing the BT to describe the thermo-mechanical properties of these diaphragms. This method is well-suited for examining how diaphragms behave mechanically in both elastic and plastic states. A finite element model (FEM) is extended to analyze the BT outcomes and look into how pre-stress influences the pressure testing, comparing results from the FEM with those derived from analytical calculations. The variations in thickness and material type are also taken into account to better understand how they affect the diaphragm’s mechanical behavior under stress. Additionally, this work considers how temperature impacts the material properties of the diaphragm, which is crucial for analyzing its thermo-mechanical response. The relative () for maximum deflection the analytical and numerical results is less than 0.3%. The simulations are done using ANSYS, MATLAB and its PDE toolbox to get the results.