Free vibration analysis of pretwisted delaminated composite stiffened shallow shells: A finite element approach

TLDR: In this article, the effect of stiffeners on the free vibration response of delaminated composite shallow cylindrical shells employing the finite element method is presented. But, the stiffeners follow the nodal lines of the shell, and the stiffness and mass of the stiffener are lumped at the corresponding nodal points of shell elements considering curvature and eccentricity.

Abstract: This paper presents the effect of stiffeners on the free vibration response of delaminated composite shallow cylindrical shells employing the finite element method. An eight-noded isoparametric shell element based on the first-order shear deformation theory is combined with a three-noded isoparametric curved beam element in the present formulation. The stiffeners follow the nodal lines of the shell wherein the stiffness and mass of the stiffeners are lumped at the corresponding nodal points of the shell elements considering curvature and eccentricity. The generalized dynamic equilibrium equation is derived from Lagrange’s equation of motion, wherein Coriolis effect for moderate rotational speeds is neglected. The multi-point constraint algorithm has been used to model delamination at the desired locations wherein the compatibility of deformation and equilibrium of stress resultants are ensured at the delamination crack front. Numerical results are presented for cantilevered long, intermediate and short cy...