The Analysis and Design of Tee-Joints for Composite Hull Structures

The design of polymer matrix composite joints is strongly influenced by the presence of out-of-plane or through-the-thickness stresses. These stresses can be critical, since out-of-plane interlaminar tension and shear strengths, as well as moduli, are strongly influenced by the low strength and stiffness of the polymer matrix constituents, as well as the fiber matrix interface. To aid in the design of these structures, this research develops a methodology for predicting structural adequacy of composites in the presence of through-the-thickness loadings. Specifically, this work details guidelines for the design of resin fillet tee-joints for use in marine applications. A combination of finite element analyses and approximate analytical formulations are used to create these practically oriented design guidelines. A parametric study, using finite element models, was conducted examining the effects of changing various material and geometric variables on the stresses and failure modes of the tee-joint structure. The tee-joint structure was sectioned in order to facilitate the creation of analytical approximations to predict the failure stresses in the various sections. This approach offers the added benefit of developing insight that guides the designer towards the most appropriate joint configuration for a specific application.