Instability characteristics of variable stiffness composite panels under thermomechanical loadings

Variable stiffness laminated composite (VSLC) structures offer significant advantages for tailoring mechanical properties. However, their stability under non-uniform thermomechanical loadings, particularly for shell panels using semi-analytical approach, remains underexplored. Most research has focused on constant stiffness laminates, leaving a gap in understanding how varying fiber orientations affect VSLC buckling behavior. Thus, the present study develops a semi-analytical model to investigate the instability characteristics of VSLC plates and shallow cylindrical shell panels under non-uniform thermomechanical loads. Initially, the pre-buckling stress distributions within the panels are evaluated by minimizing the membrane strain energy. Subsequently, a displacement-based Ritz method is employed to obtain the matrix representation of the governing equations for instability problems. Finite element calculations are also conducted using ABAQUS to verify the obtained semi-analytical results. Additionally, the study examines the effects of fiber orientation, ply sequence, geometry, and boundary conditions, showing that fiber center angle significantly enhances buckling strength.