A mixed isostatic 24 dof element for static and buckling analysis of laminated folded plates

A mixed, quadrilateral, 3D plate element is proposed for static linear and buckling analysis of folded laminated composite structures. Numerical results show accuracy, comparing to analytical and numerical references, and convergence rate h2h2 measured using an s-norm. These characteristics are due to the self-equilibrated, isostatic state of stress in the element, and to the element kinematics leading to element compliance and compatibility matrix calculations based solely on the interpolation along the element edges. For folded plates, the drilling rotations do not require penalty functions or non-symmetric formulations, thus avoiding spurious energy modes. Buckling analysis is achieved by a corotational formulation, which is possible thanks to the accuracy of rotation approximations. Benchmarking for laminated composite plates includes convergence of displacements and stress-resultants, global error measures, and comparison with literature results.