Variable-angle tow (VAT) composites have gained significant attention due to their tunable stiffness and strength properties. The instability issues of variable stiffness thin-walled structures under thermal environments cannot be ignored. This paper investigates the thermal buckling performance and geometric imperfection sensitivity of plate and cylindrical shell structures with straight layups and manufacturable optimal curved fiber layups under different thermal conditions. First, the optimal layup angles considering the minimum radius of curvature are obtained using an optimization algorithm based on a variable-fidelity Kriging surrogate model. Second, the thermal buckling problems of variable stiffness plate and cylindrical shells are studied through linear and nonlinear buckling analysis considering thermal environments and initial imperfections. Comparisons are made between VS and straight fiber plate and cylindrical shells considering their imperfection sensitivities. The results show that the linear buckling loads of the optimized variable stiffness structures are all greater than those of the straight layups. Thermal stress leads to a reduction in the total instability load of variable stiffness plates, while having a smaller impact on conventional straight layups; for VS cylindrical shell structures, the total buckling load value increases slightly under thermal stress. Temperature has a minor effect on the imperfection sensitivity of laminated plates, while for cylindrical shell structures, temperature increases their compressive imperfection sensitivity.
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