Application and finite element implementation of 7-parameter shell element for geometrically nonlinear analysis of layered CFRP composites

This paper presents the extension of the 7-parameter shell element for the analysis of layered CFRP composite structures assuming the Equivalent Single Layer (ESL) approach, and addresses some aspects of its numerical implementation into the package ABAQUS. The theoretical formulation of this element relies on the shell model proposed in Büchter and Ramm (1992) [15], which allows the use of unmodified three-dimensional constitutive laws. In order to remedy locking pathologies of the corresponding finite element implementation, the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) methods are simultaneously employed. A series of benchmark problems assess the applicability of this element for isotropic materials and layered composites. Finally, this element is also used for the analysis of a composite stiffened panel in postbuckling regime subjected to uniform pressure loading. The numerical results are corroborated with experimental data, obtaining a satisfactory agreement along the loading procedure.