<p>This study models and analyzes the thermomechanical vibration behavior of doubly curved sandwich shallow shells using a novel high-order sinusoidal shear stress theorem. The equations of motion are derived from Hamilton's principle and solved with the Navier method. The doubly curved sandwich shell comprises a functionally graded core layer and a hybrid surface layer made of metal and ceramic. The analysis extensively examines the effects of the FGM core layer, hybrid surface layers, radii of curvature, and thickness ratios on the thermomechanical vibration behavior of the doubly curved sandwich shell, with results presented accordingly. The surface layers consist of pure metal, pure ceramic, and a hybrid of metal and ceramic, whereas the core layer is functionally graded, featuring metal on the bottom surface and ceramic on the top surface, with variations in composition throughout the thickness based on the Power-law. This study's results are anticipated to advance the fields of aviation, space, and construction, particularly in thermal and vibration barrier applications, the design of specialized structures for safeguarding critical equipment, and the development of submarine vehicle hulls and protective structures. A review of the literature reveals that no previous study of this kind has been conducted, and this study is expected to make a significant contribution to the literature.</p>