Novel joining method for smooth-bore composite pressure hulls

Filament wound smooth-bore composite pressure hulls offer the potential for increasing the displacement-to-weight ratios of externally loaded, hydrostatic pressure hulls well beyond those achievable with conventional metal alloys. Increasing the displacement-to-weight ratio affords the ability to extend the operational pressure without a corresponding weight penalty. However, for viable hydrostatic pressure hull designs, reliable attachment methods for interfacing the composite structure with existing metallic components must be developed. While significant work has been done in composite-to-metal joining, developmental thrusts have not focused on problems specific to the design and fabrication of circular joints. The present paper discusses a novel circular composite-to-metal bonded joint developed for smooth-bore composite pressure hulls. Details of the concurrent engineering approach, fabrication method, and validation testing of the cylindrical joint are presented. Validation test results demonstrate that the novel circular joint is a viable alternative to more complex and costly composite-to-metal circular bonded joints.