GEOMETRICALLY NONLINEAR ANALYSIS USING A COROTATIONAL TRIANGULAR THICK AND THIN SHELL ELEMENT

A simple and efficient 3-node triangular planar shell element for the geometrical nonlinear analysis of laminated composite structures is developed based on corotational formulation (CR). The shell element is constructed by combining the generalized conforming membrane element GT9 with the drilling degree of freedom and the generalized conforming thick/thin plate element TMT with assumed rotation and transverse shear strain fields. In order to avoid membrane locking, one-point reduced integration scheme is employed for calculating the terms related to membrane strains, and a stabilization matrix is added to eliminate zero energy modes. Based on the first-order shear deformation theory (FSDT) for laminated composite plates, the correctional transverse shear stiffness is calculated, considering the real ply stacking sequence of the laminate, such that the shell can be applicable to modeling moderately thick laminated composite structures. The geometrically linear stiffness matrix in the core of CR formula can be calculated only once and can be saved to be used throughout the whole procedure for the nonlinear analysis. Numerical examples show that the present shell element is accurate and efficient for thin and thick shell structures, including laminated composite structures.