Composite to Metal Joints for the ARPA Man-Rated Demonstration Article

The design, analysis and testing of composite-to-metal joints for the ARPA Man-Rated Demonstration Article are discussed. The first is a composite-to-titanium sphere joint designed to react sphere membrane stress with block compression loading. A series of uniaxial compression tests to simulate this joint assembly was conducted. Test results successfully demonstrated the ability of the joint to withstand block compression loading even in the presence of assembly fitup gaps. A polymer shimming material (Hysol EA9394) was also evaluated as a means to fill potential fitup gaps and was found to effectively reduce stress concentrations resulting from the gaps. The second joint discussed is one between 120-degree segments that make up a stiffener ring for a ringstiffened composite cylinder. Joint design includes Hysol EA9394, boltedon titanium splice plates, and bondedon thermoset flange straps. 2D joint tests, single stiffener tests, and sub-scale ring-stiffened cylinder hydrostatic tests to validate the joint design are described.