COMPOSITE MATERIALS

1,193,493. Extruding; making turbine blades or wire. WHITTAKER CORP. 27 June, 1967 [27 June, 1966], No. 29687/67. Headings B3A and B3P. [Also in Division F1] A composite structure is formed by assembling a set of cladded filaments 10 into a bundle, heating the bundle and extending it through a die to form a cellular matrix. The bundle is placed in a canister 16 and the canister is evacuated to 10-3 torr. before heating. The core of each filament may be molybdenum, titanium, tungsten, nickel, cobalt or alloys thereof. The shell may be nickel-chrome, iron-chromealuminium, hafnium based tantalum alloys, refractory oxides or organic material such as plastics. The shell may be applied as a tube around the core or by plasma-jet spraying. The canister 16 may be of the same material as the shell or it may be expendable. The surfaces of the filaments and the canister which are to be bonded together are preferably cleaned with ethyl alcohol. The surfaces may be cleaned by machining and the parts assembled in a protective atmosphere. A solid copper guide 26 is welded to the front of the canister 16 to guide the canister and also act as a lubricant. During the extrusion the cores of the filaments are deformed into polygonal cross-section. If the core and shell materials do not readily bond a diffusion layer (36), Fig. 6 (not shown), is interposed between them, for example, a layer of aluminium or magnesium oxide between a molybdenum alloy core and an ironchrome-aluminium-yttrium shell. Each filament may be multi-cored. The composite billet may be extruded to form composite wire or through a shaped die with the cross-section of a turbine blade. Alternatively the billet may be made up of a turbine cross-section shaped canister 44 surrounded by a filler 46. The filler is removed by acid after extrusion. When the extruded product has to be cut into shorter lengths the ends of the cores are protected from contamination by spacers (58), Fig. 9 (not shown), of shell material.