Parametric Study on the First Ply Failure Load of Delaminated Shallow Pretwisted Conical Shells – A Finite Element Approach

Abstract

The present study deals with the effect of offset length on the first ply failure load of undelaminated and mid plane delaminated composite shallow conical shells. Numerical results were obtained using finite element codes for the failure loads of undelaminated and mid plane delaminated composite conical shell for different offset length considering twisted and untwisted instance. From Lagrange’s equation generalized dynamic equations have been derived for moderate rotational speed ignoring the Coriolis Effect. Based on Mindlin’s theory the theoretical formulation has been carried out and it has been implemented by using an isoparametric plate bending element having eight nodes. Multi-point constraint algorithm has been used to ensure the equilibrium of resultant forces, moments and compatibility of deformation at delamination crack front. The standard Eigen value problem has been solved based on standard QR iteration algorithms. Convergence studies are carried out considering mesh sizes, and results are validated with open literature to verify the correctness of the present finite element formulation. The first ply failure load considering different failure criteria namely Max stress (independent), Tsai Hill, Tsai Wu Hahn and Tsai Hill Hoffman are evaluated. The variation of the failure loads for different offset length and twist angle are illustrated and presented.