GB1173740A - A Composite Structure and a Method of Forming it - Google Patents

Abstract

1,173,740. Casting composite articles. FMC CORP. 20 Sept., 1966, No. 1520/69. Divided out of 1,155,292. Addition to 1,064,271. Heading B3F. A composite structure comprises at least two layers of metal and an intermediate fibrous structure bonded between the metal layers, the fibrous structure being formed of filaments made by adding to, and incorporating in a cellulosic spinning solution at least one glassforming compound, shaping the spinning solution into the structure throughout which the cellulosic material and glass-forming compound(s) are uniformly distributed, converting the glass-forming compound(s) to glass-forming oxide(s) when the glass-forming compound(s) do(es) not comprise oxide(s), and removing the solvent from the structure, the amount of the said glass-forming compound(s) added to the cellulosic spinning solution being sufficient to provide a a ratio of glass-forming oxide(s) to the cellulosic material of between 0À2 : 1 to 2 : 1. The fibrous structure may be made according to the method of Specification 1,064,271, and the filaments may be sintered. Such a composite structure may be made by supporting the fibrous structure within a mould cavity, filling the mould cavity with molten metal, maintaining the molten metal at an elevated temperature until the cellulosic material has been decomposed and - carbonized, and cooling the molten metal to room temperature. Alternatively, the said fibrous structure may be sintered, the sintered fibrous structure being supported within a mould cavity, the mould cavity filled with molten metal, the metal being maintained in a molten condition until gases occluded by the fibrous structure have been released and the molten metal cooled to room temperature. Suitably the structure or fabric of Specification 1,064,271 is used as a reinforcement for a metal in such a composite structure. The glass-forming compound, or one of the glass-forming compounds may be a zirconium compound, as disclosed in Specification 1,155,292. Example 1 describes the production of regenerated cellulose filaments containing silica and zirconia as glass formers. In Example 2, a composite structure is made comprising two layers of aluminium and an intermediate fibrous structure comprising a woven cloth made of filaments according to Specification 1,064,271, the fabric being clamped between the two sections of a rectangular mould and molten aluminium being poured into both sides of the mould cavity at a temperature about 800‹ C., so that the regenerated cellulose is carbonized but as the fabric is protected from the atmosphere, the carbon is not burnt off. In a modification, the unfired woven fabric is replaced by a fabric woven from filaments as described in Example 1. Alternatively, the fabric is subjected to the heat treatment necessary to convert the filaments to the sintered form and such treated fabric utilized as a reinforcing means for metal in the same manner as fabric is used in moulded resinous products. This is illustrated by Example 3 in which woven sintered fabric as described in Specification 1,064,271 is clamped between the two sections of a mould, and molten lead at about 400‹ C. is poured into both sides of the mould cavity. The mould and molten lead are maintained at the elevated temperature until all gassing has ceased. The fabric is found to be securely bonded between the two layers of lead. In a modification, the woven sintered fabric is replaced by a woven sintered fabric comprising filaments as described in Example 1. For the production of ablative structures, a further increase in resistance to high temperature conditions is obtained by incorporating in the cellulosic matrix a high temperature resistant synthetic resin, e.g. an epoxy resin, phenolic resin or urea-formaldehyde resin. Such resins may be incorporated in the spinning solutions by conventional injections spinning methods or by impregnating the shaped article during processing with a solution or dispersion of the resin. The resin is preferably in the precondensate form and polymerizes and becomes a thermoset resinous material during processing of the filaments. The presence of such resinous materials distributed throughout the structure improves the strength of the ablative structures and provides another organic constituent which will dissipate considerable energy when it decomposes at high temperatures. Such resins are not necessary when it is desired to form a sintered ceramic body, as the structures have sufficient strength to permit the necessary heat treatments.