GB661108A - Improvements in or relating to composite structures of sheet form - Google Patents

Abstract

661,108. Making compound plates. KING, E. P. July 14, 1949 [July 14, 1948], No. 18956/48. Classes 83 (ii) and 83 (iv). [Also in Groups VIII, X and XXXIII] A composite sheet structure, e.g. for use as skin material for aircraft wings and fuselages, comprises a core fabricated from metal strips to form a honeycomb mesh and two facing sheets, the strips being formed or provided with metal sub-facing members of substantial surface area, lying in face-to-face relation with the facing sheets and secured thereto by adhesive, e.g. a thermosetting synthetic resin. As shown in Figs. 2, 3, the core comprises dimpled channel strips 37 having slots 39 or slits and cut-away flange portions 41 to permit interlocking to form a mesh, two metal facing sheets 31 being secured by adhesive to the flanges 36 forming, the sub-facing members. Alternatively, the core may be formed of slotted parallel channel strips interconnected to form a mesh by short strips having pairs of end lugs which engage the slots and are bent over in opposite directions. In a further example, the core is formed of interlocking channel strips 51, Fig. 10, cut and bent as shown in Figs. 11, 12, portions of the flanges 36 being cut away whilst,other portions 52 are slit and bent over the web of an adjacent strip at its cut-away flange portion. As shown in Fig. 13, a core of aluminium alloy comprises zig-zag strips 61 with intervening flat strips 63, a surrounding strip 64 and two flat perforated sub-facing sheets 65 to which are secured by adhesive the facing sheets. Instead of using the strips 63, the zig-zag strips may be aligned by forming small channels in the strips to receive and locate the peaks of adjacent strips. In a further modification, the core may be formed of straight intersecting flat strips with subfacing sheets brazed to the edges of strips. Sub-facing sheets 65, Figs. 19, 20, 21 (not shown) may be brazed to the edge of strips bent and arranged in various forms. The core parts may be secured together by the aluminium brazing process in which the assembled parts are coated with aluminium silicate and are then heated to a temperature of about 600 ‹ C. in a salt bath or in a furnace by a hot-air process so that the parts are fused together. Aluminium silicide material may alternatively be employed for cores made by this process and to restore the strength of the material the brazing may be followed by quenching the assembled parts from 540‹ C. and then re-heating them for 18 hours at 165‹ C. High-strength facing-sheets of steel, aluminium, aluminium or magnesium alloy may be used, or materials known under the Registered Trade Marks " Alclad " or " Duralumin." Alternatively the facing-sheets may be of fibrous material, e.g. plywood, asbestos or glass fabric and may be of composite structure, e.g. two or more superposed sheets of different characteristics. Adhesives used may be those known under the Registered Trade Marks " Redux," " Araldite " and " Cycleweld." The core may comprise strips of ferrous or non-ferrous alloy coated with fusible tin or copper alloy to cause adhesion and resist corrosion of the parts and the strips themselves may be secured together by adhesive or by welding or soldering. The core may be curved and may comprise a number of units of decreasing, thickness and the subfacing sheets may be slit to provide flexibility. Metal facing sheets may be provided with a layer of fine fabric secured to the faces adjacent the core to enable them to be secured to the sub - facing members with a cold - setting, adhesive. The compound sheet structure may be fabricated in bent or curved form by placing the facing-sheets and core in or on a mould with a thermosetting synthetic resin adhesive between the facing-sheets and sub-facing members and subjecting the assembly to heat and pressure, e.g. in an autoclave. The core alone or the core already secured to one facing-sheet may be first bent to the desired shape and then the facing-sheets or sheet bonded to the core under pressure in a mould. Specifications 528,062, 577,705 and 604,752, [all in Group VIII], are referred to.