MITC9 Shell elements based on RMVT and CUF for the analysis of laminated composite plates and shells

In this paper, we present some advanced shell models for the analysis of orthotropic multilayered structures in which the mechanical and physical properties may change in the thickness direction. The finite element method showed successful performances to approximate the solutions of the advanced structures. In this regard, two variational formulations are available to reach the stiffness matrices, the principle of virtual displacement (PVD) and the Reissner mixed variational theorem (RMVT). Here we introduce a strategy similar to MITC (Mixed Interpolated of Tensorial Components) approach, in the RMVT formulation, in order to construct an advanced locking-free finite element. Moreover, assuming the transverse stresses as independent variables, the continuity at the interfaces between layers is easily imposed. We show that in the RMVT context, the element exhibits both properties of convergence and robustness when comparing the numerical results with benchmark solutions from literature, even for higher span to thickness ratios, and both interlayer continuity conditions and boundary conditions are fully satisfied.