A new mixed node-based solid-like finite element method (MNS-FEM) for laminated shell structures

A new solid-shell finite element formulation is investigated in this paper. Departing from the S-FEM concept of node-based stress smoothing scheme, a new pattern that introduces new stress variables linked with an extra smoothing region inside the element is proposed. This finding preserves all the advantageous features of the standard NS-FEM but it makes approximate solutions much more accurate. The assumed natural strain (ANS) and the Discrete shear gap (DSG) techniques are employed to alleviate trapezoidal and shear locking. The simple assumptions made allow the analytical computation of the discrete operators based on the node based backgrounds making the model particularly efficient. Popular benchmark tests are successfully solved for structured and unstructured triangular meshes in linear and buckling analysis. Numerical results show that the proposed method avoids cross-diagonal meshes, which reduces the generality of three-node degenerated shell elements proposed in the literature. This aspect makes the present formulation much more appealing than the published methods available in the literature. Moreover, in the context of the S-FEMs it is the first time in which geometric nonlinear contributions are presented.