Composite Periscope Mast

U.S. submarine periscope outer tubes are manufactured from Type 304 or 316 stainless steel. It would be desirable to have configurations that are lighter and with a higher strength to weight ratio. Composite plastic tubes have been studied but these can absorb water and suffer from delamination. This proposal describes a composite tube structure of concentric layers of beryllium (inner layer; 70% of total section), 304 stainless steel (intermediate layer; 15% of total section) and titanium (outer layer; 15% of total section). The tube will be fabricated by co-extrusion of the three principal materials held in an evacuated steel canister. After extrusion over a mandrel, the steel envelope will be removed. 9 to 15 feet of tube at approximately 2 inches O.D. x 1-3/4 inches I.D. will be formed and available for testing. Testing of the finished model tube will include tensile tests, bending tests and optical metallography and SEM inspection of the component material interfaces. Test results will indicate whether this construction has merit and what modifications may be needed to improve the structure.