Co-Continuous Metal-Ceramic Interpenetrating Composites (IPCs) for Light Armour Applications

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Light weight armour materials are becoming increasingly important due to the need for increased personnel protection and also the move towards light, faster, more fuel efficient vehicles. Current armour usually consists of a number of individual materials sandwiched together. This can lead to heavy sections that are complex to manufacture, replace or repair. Metal Matrix Composities (MMCs) have been shown to display improved strength, stiffness, hardness, wear and abrasion resistance, lower thermal expansion coefficients and better resistance to elevated temperatures and creep compared to the matrix metal, whilst retaining adequate electrical and thermal conductivity, ductility, impact and oxidation resistance and may be an ideal material for armour applications. Traditional approaches to making MMCs, result in materials with microstructures consisting of discrete particles, whiskers or fibres dispersed in an otherwise homogeneous matrix metal. These approaches yield problems with obtaining a high enough reinforcement phase content which limits potential applications as a result of the increased costs and, more importantly, the development of anisotropic properties.Recent work at Loughborough University under EPSRC grant GR/S15471 has demonstrated that it is possible to infiltrate ceramic foams with densities in the range 5-50% of theoretical with a range of aluminium-based molten metals to form interpenetrating composites (IPCs). The foams, developed by the same research team, have fully dense pore walls and struts, which provide high strength, whilst the pores are fully connected by windows making them suitable for a range of applications, including infiltration. The composites produced have both the ceramic and metal phases fully connected in all three dimensions, yielding a material that not only has isotropic properties but a true mix of the ceramic and metal properties. These properties can be modified by varying the composition, density and pore sizes of the foams, by varying the foam density across a section and infiltrating different metal alloys.Recent preliminary has shown that these IPCs have the potential to fulfil the need for an armour material. Not only have they been shown to have useful ballistic properties but are also lightweight and easy to manufacture in a range of shapes. Work is now needed to:-Scale up the processing of the composites to allow full sized test pieces to be manufactured. These will have a range of cell sizes and ceramic contents and will be infiltrated with two different aluminium alloys.-As many armour solutions are made up of a multi-layered system, this technology is ideal for adaptation to producing a fully integrated layered structure. By varying the ceramic preform density from fully dense to semi-solid followed by metal infiltration it will be possible to manufacture two layer (IPC-metal) and three layer (ceramic-IPC-metal) materials. This type of structure negates the need to glue separate materials together, improving the overall properties of the structure.-For full realisation of these materials for ballistic applications extensive testing is needed. In the first instance, laboratory based tests will be used to optimise the material properties followed by full scale ballistic testing by both ADML and Permali. Analysis of the material following testing will be carried out to determine the damage mechanism, area (spread) of damage and the influence of IPC makeup. Two and three layer armour solutions will be developed and tested.-Finally, as we near the point where we can exploit this material commercially, we need to develop a better understanding of end users requirements. Considerable interest is being shown by a number of companies in the area, as demonstrated by the support for this project, who will assist in realising the full potential of these materials. Work is needed fully to realise the use of IPCs which will be addressed in the final task.