A stress analysis of a mechanical joint for carbon composite rods

The high axial tensile strength and the low transverse strength of pultruded composite rods present some unique problems in testing with conventional grips. The high transverse compressive forces required in the conventional method of gripping tent to crush the rod, thereby causing premature failure. Design guidelines for an end tab grip adapter used in tensile testing of pultruded composite rods can be found in ASTM standard D3916-84. Although this standard is applicable to glass fiber reinforced rods, it is inadequate for high-strength composites because of slip. It is therefore necessary to develop and characterize a new tension jig for high-strength fiber composite rods such as graphite fiber composites. The present paper presents results from a two-dimensional nonlinear finite element analysis to characterize the contact pressure and stress distributions at the interfaces and maximum axial load available in the jig developed.