Metallic foam material

Abstract

The invention provides a metallic foam material with better mechanical properties than known foamed materials, and a method of making such a material. Although known foamed metals are light in weight, and sandwich structures formed of such materials can be formed into structural components, the tendency for the structure to crush and fracture under compressive loading, with consequent crack propagation, limits their use in applications in which the integrity of the component is important. The invention addresses this problem by providing a fibre-reinforced foam that combines the tensile strength of a high strength fibre such as carbon fibres with the impact resistance (through crushing and deformation) of metallic foam. The metal foam imparts a greater strength to the carbon-fibre-reinforced plastics (CFRP) part of the structure than it would have by itself. Under tensile loads, the fibre reinforcement gives the metallic foam enhanced strength and low creep.

1 - 18 . (canceled) 
     
     
         19 . A metallic foam material in which at least part of the foam is reinforced by fibres embedded within it. 
     
     
         20 . A material as claimed in  claim 19 , in which the foam comprises cells. 
     
     
         21 . A material as claimed in  claim 20 , in which the cells are of uniform size and are arranged in a hexagonal close-packed array. 
     
     
         22 . A material as claimed in  claim 20 , in which the cells are not of uniform size and are arranged in a pseudo-random manner. 
     
     
         23 . A material as claimed in  claim 19 , in which the fibres are carbon. 
     
     
         24 . A method of making a reinforced metallic foam material, comprising the steps of:
 a) constructing a precursor comprising a plurality of beads secured to a fibre;   b) arranging a plurality of the precursors in a processing vessel;   c) modifying the beads to form a cellular structure reinforced by the fibres.   
     
     
         25 . A method as claimed in  claim 24 , in which step a) comprises forming the beads by moulding them around the fibre. 
     
     
         26 . A method as claimed in  claim 25 , in which the moulding step comprises coating the fibre with the bead material and then actuating the mould to form the beads around the fibre. 
     
     
         27 . A method as claimed in  claim 24 , in which step a) comprises curing the beads. 
     
     
         28 . A method as claimed in  claim 24 , in which step a) comprises coating the beads in carbon. 
     
     
         29 . A method as claimed in  claim 24 , in which step b) comprises arranging the precursors so that the beads form a hexagonal close-packed array. 
     
     
         30 . A method as claimed in  claim 24 , which comprises before step c) the step of arranging in the processing vessel additional beads that are not secured to a fibre. 
     
     
         31 . A method as claimed in  claim 30 , in which the additional beads form in step c) a cellular structure that is integral with or attached to the cellular structure formed by the precursors. 
     
     
         32 . A method as claimed in  claim 24 , in which step c) comprises an electroforming process. 
     
     
         33 . A method as claimed in  claim 32 , in which the electroforming process is preceded by a heating process to carbonise the beads.