Abstracts of Patents

Abstracts of US patents prepared by Dr R. J. Hand, Department of Engineering Materials, University of Sheffield, UK

Orthopaedic device of biocompntible polymer with orientated fibre reinforcement Chang, F.-K., Reifsnider, K., Davidson, J.A. and Georgette, F.S. (Richards Medical Company, Memphis, TN, USA) f/S Put 5064439 (I2 November 1991) A number of prepregs comprising continuous parallel fibres and a biocompatible thermoplastic polymer are stacked onto a receiving surface that defines a curve parallel to the prepreg fibre direction. Heat and pressure are applied to form a composite blank which is subsequently shaped into a prosthetic device.

Method of producing a composite article Gutowski, T.G., Sentovich, M.F. and Okine, R.K. (MIT, Cambridge, MA, USA and E.I. Du Pont de Nemours & Co., Wilmington, DE, USA) US Pat 5066442 (I9 November 1991) A laminate of fibres in a thermoplastic resin is rough-formed in a first die which has surface protrusions that make a preselected array of holes in the laminate. The formation is completed in a second die which does not have the protrusions and in which the holes are healed whilst the desired shape is formed.

Method for providing a silicon carbide matrix in carbon-fibre reinforced composites Streckert, H.H., Sheehan, J.E. and Mazdiyasni, K. (General Atomics, San Diego, CA, USA) US Put 5067999 (26 November 1991) A soluble boron compound is applied to the surface of carbon-based fibres in an amount sufficient for bonding. The fibres are formed into a preform and impregnated with a polysilane. The whole is then heated to a temperature sufficient to cure and/or crosslink the polysilane, after which it is heated to a temperature sufficient to form a carbon fibre-reinforced silicon carbide matrix from the carbon-based fibre cloth embedded therein.

Molybdenum disilicide alloy matrix composite Petrovic, J.J., Honnell, R.E. and Gibbs, W.S. (University of California, Alameda, CA, USA) US Pat 5069841 (3 December 1991) SO-90 mol% molybdenum disilicide powder is mixed with at least one refractory silicide and IO-30~01% silicon carbide and the resulting mixture is heated to 19OO”C, 30 MPa pressure is then applied for any time between 5 min and 1 h, after which the pressure is released and the resulting composite cooled. The refractory silicide may be tungsten di- or trisilicide, niobium di- or trisilicide, tantalum di- or trisilicide, molybdenum trisilicide, titanium di- or trisihcide, chromium disilicide, zirconium disilicide, yttrium disihcide or vanadium disilicide. The silicon carbide is present as one or a mixture of submicron particles, VS whiskers or VLS whiskers.

0956-7143 /94/03/0197-02 @ 1994 Butterworth-Heinemann Ltd

Tool for forming complex composite articles Dublinski, A.C., Evans, D.A., Goldberg, J., Davis, G.C.R., Sharp, W. and Kornitzky, M.A. (United Technologies Corporation, Hartford, CT, USA) US Pat 5071338 (IO December 1991) The tool comprises an elastomer layer which is sufficiently flexible to provide uniform compaction to a set of laminate plies and has a shape which essentially matches the shape of the article and which forms a cavity about each detail structure. There is also a reinforced elastomer layer which increases the rigidity of the elastomer layer in detail cavities without eliminating the elasticity of the elastomer layer.

Method and apparatus for wetting fibre reinforcements with matrix materials in the pultrusion process using continuous in-line degassing Koppernaes, C., Nolet, S.G. and Fanucci, J.P. (American Composite Technology, Inc., Boston, MA, USA) US Pat 5073 413 (I7 December 1991) Fibre reinforcements are formed into a tow and passed through a pultrusion die via inlet and outlet ports which are pneumatically sealed by the tow passing through them. Whilst the tow is in the die, it is simultaneously impregnated with matrix material at a first port in the cavity and degassed at a second port by reducing the pressure at this port below the pressure at the impregnation port.

Method for producing a fibre-reinforced ceramic honeycomb panel Han, J.H. and Hegedus, A.G. (Hexcel Corpor- ation, Dublin, CA, USA) US Par 5078818 (7 .hnuar~ I992) Sheets of a fabric made with fibres that remain stable at temperatures exceeding 1OOOC are impregnated with a liquid which can be converted on heating to a solid ceramic. The impregnated sheets are formed into corrugated sections and then heated to at least partially convert the liquid to a ceramic before they are bonded togetherintoa honeycombstructure.

Process for reinforced polymeric composites Staneluis, J.M. and Rodenbeck, D.L. (Centrite Corp., Bowling Green, OH, USA) US Par 5 089 I89 (I8 February 1992) A pair of cojointly moving upper and lower mould sections (which define in cross-section an open-ended cacity) and flexible means (which are non-adherent to the mould sections) are provided. A coating of a first thermoset reactant is applied to the flexible means, followed by continuous strands of a high modulus material such that the strands are at least partially wetted with the coating. Chopped strands are then deposited over the

continuous strands, followed by a foamable thermoset reactant. The whole (including the flexible means) is transferred into the mould; the thermosets are allowed to react and to wet and embed the strands. Finally, the whole is cured to produce the finished composite material.

Method to make fibre/polymer composite with nonuniformly distributed polymer matrix Li, H.L., Harpell, G.A. and Prevorsek, DC. (Allied-Signal Inc., Morris Township, Morris County, NJ, USA) US Paf 5093 I58 (3 March 1992) A polymer composition is fed into contact with a unidirectional fibrous web between two rollers. At least one of the rollers has a pattern which distributes the polymer non-uniformly into thin and thick regions as matrix for the fibrous web. The amount of matrix varies between 2 ~01% in the thin regions and 15 ~01% in the thick regions.

Flexible multiply towpreg and method of production therefor Muzzy, J.D. and Varughese, B. (Georgia Tech Research Corporation, Atlanta, GA, USA) US Pat 5 094 883 (IO March 1992) Reinforcing filaments are spread in a columnated manner and coated with a matrix-forming material which adheres to the filaments. Towpreg plies are formed by heating the matrix until it liquifies; these are then cooled and only allowed to contact neighbouring plies once the matrix has solidified.

Method of making postformable fibre reinforced composite articles Breitigam, W.V., Ubrich, W.P., Hunter, G.A. and Viola, G.G. (Shell Oil Company, Houston, TX, USA) US Pat 5098496 (24 March 1992) Reinforcing fibres are continuously introduced into a liquid, thermosetting, polymerizable composition. The mixture is then continuously pulled through a die with a non-trivial cross-section and which has at least one heating section and at least one cooling section. The rate of pull and the temperature are controlled such that the composition gels sufficiently to retain its shape. The article is then cooled to such an extent that no further curing takes place until it is postfonned into some other shape, after which it is fully cured.

Polymer-reinforced metal-matrix composite London, G.J., Frazier, W.E. and Williams, J.G. (Secretary of the Navy, Washington, DC, USA) US Pat 5 IO0 736 (31 March 1992) Metal particles and thermoplastic polymer particles are blended homogeneously and consolidated to form a unitary mass. This

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