LOAD INTRODUCTION IN TUBULAR COMPOSITE SPECIMENS

A study of load transfer at the ends of tubular composite laminates has been performed such that in-plane loads, singly or in any combination, can be passed between end tabs and the tubular structure in a way that will minimize stress concentrations at geometric discontinuities. Axisymmetric anisotropic finite element analyses were performed to determine the stress concentrations through an evolution of end tab materials and configurations. Tapered end tabs that utilize multiple materials of increasing rigidity from the tubular specimen to the point of gripping were shown to be the most effective means of minimizing stress concentrations. The study shows the criticality of end design in transferring loads to tubular composite specimens and suggests several tapered end tab configurations that can substantially reduce stress concentrations.