Isogeometric analysis of secondary thermal buckling in composite laminates using Reddy’s higher-order shear deformation theory

This study conducts a systematic analysis of the secondary buckling behavior of composite laminated plates under thermal loads based on Reddy’s Higher-Order Shear Deformation Theory (HSDT) and the Isogeometric Analysis (IGA) method. By introducing the von Kármán large-deformation theory and initial geometric imperfections, a mechanical model considering the higher-order shear effects and geometric nonlinearity is established. The Non-Uniform Rational B-Spline (NURBS) basis functions are employed for spatial discretization, effectively achieving the unification of geometrically exact description and high-order continuity. In the model, the in-plane, bending, and initial imperfection stiffness matrices are derived in detail, and the nonlinear equilibrium equations are solved using the Newton-Raphson iterative method. This research proposes a critical load prediction method based on the minimum eigenvalue of the tangent stiffness matrix. By combining the linear interpolation technique, the secondary buckling loads and corresponding modes are accurately captured. Numerical examples verify the effectiveness and accuracy of this method in analyzing the thermal buckling paths, initial imperfection sensitivity, and higher-order mode evolution of composite laminated plates. The results show that initial imperfections significantly reduce the critical buckling load of the structure. Moreover, the combination of IGA and HSDT can accurately characterize the complex deformation behavior of thick plates, providing a theoretical basis for the thermal stability design of composite structures in engineering.