EVALUATION OF CYLINDRICAL SHEAR JOINTS FOR COMPOSITE-MATERIALS

The objective of this work was to evaluate the strength of four candidate cylindrical shear joints for composite tubes. The basic design for the joint entails an axial length of one inch with an external 15-degrees tapered cone. The purpose of the joint is to transfer axial load from a cylinder through a steel shear attachment with a matching internal conical seat. The design candidates consisted of a bonded wedge cone, pinned wedge cone, and a bonded and pinned wedge cone attached to a two-inch diameter composite tube and a wedge cone integrally wound into the tube. The actual joint strengths achieved were higher than expected for some designs and were found to be dependent on the amount of hydrostatic or radial compression applied to the joint. The bonded wedge ring and the integral wedge ring both achieved over 96 MPa (14 ksi) of shear strength without failure. Due to the unexpectedly high shear strengths of the joints most of the failures were located in other parts of the test specimen. The bonded wedge cone was probably close to its maximum load carrying capacity while the integral wedge design showed potential for even higher shear strengths. The bonded and pinned joint reached a peak shear strength of 78.9 MPa (11.5 ksi) and the pinned only configuration achieved 70.6 MPa (10.3 ksi). When loaded without any hydrostatic compression the joint strengths were less than 34.3 MPa (5 ksi); however, the failure mode was hoop compression buckling of the tube itself as opposed to a joint shear failure.