Thermal Buckling Behaviour of Thin and Thick Variable-Stiffness Panels

The possibility of designing composite panels with non-uniform stiffness properties offers a chance for achieving highly-efficient configurations. This is particularly true for buckling-prone structures, whose response can be shaped through a proper distribution of the membrane and bending stiffnesses. The thermal buckling behaviour of composite panels is among the aspects that could largely benefit from the adoption of a variable-stiffness design, but, in spite of that, it has rarely been addressed. The paper illustrates a semi-analytical approach for evaluating the thermal buckling response of variable-stiffness plates (VSP) by considering different boundary conditions. The formulation relies upon the method of Ritz and a variable-kinematic approach, leading to a computationally efficient implementation, which is particularly useful for exploring the larger design spaces, typical of variable-stiffness configurations. Due to the possibility of choosing the underlying kinematic approach as an input of the analysis, the formulation is not restricted to thin plates, but is suitable for analyzing the response of thick plates as well. Novel results are derived, which can be useful for benchmarking purposes and for gathering insight into the mechanical behaviour of variable-stiffness plates. Furthermore, the importance of transverse shear flexibility is illustrated with respect to the boundary conditions as well as the degree of steering of the fibers.