Development of Ejector Interfaces for Air Launch Composite Motor Cases,
MORTON THIOKOL INC BRIGHAM CITY UT WASATCH DIV
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A significant challenge in the development of composite cases for air launch applications is the integration of the missileejector interface fittings into the composite cylindrical section of the case. The feasibility of one concept, which utilizes an external metal lug fitting bolted through the reinforced carbonepoxy cylinder into an internal reaction plate, was demonstrated by subjecting a full-scale 18-in diameter cylinder to radial loads representative of ejector interface loads during air carry or missile ejection. A radial tension lug load of 67,374 1bf was achieved without catastrophic failure. Radial compression loading representative of sway brace or ejector piston loading resulted in localized delamination of the cylinder wall directly under the load site and demonstrated that radial compression, rather than lug tension, is the primary design driver for air carry loading on a composite case and that interlaminar shear strength is the material property most significant to this design situation. A pressure vessel incorporating a lug was hydroburst. Burst initiated in the free membrane region away from the lug, thus demonstrating that the bolt-through design could be incorporated into a composite case without degrading pressure chamber integrity.