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Bubbling over with ideas

Metallic foams are just one of the areas being investigated by the team of researchers working under the umbrella of the Cambridge Centre for Micromechanics, which was set up under the Directorship of Professor Norman Fleck in March 1996. The Centre, which is inter-disciplinary and inter-departmental, is enhanced by the talents of researchers from the Departments of Materials Science, Physics, and Applied Maths and Theoretical Physics, as well as Engineering. 'Micromechanics is a way of quantifying the properties of materials from a knowledge of their microstructure,' explains Professor Fleck. 'The concept of the Centre is quite unusual in that it is not driven by a single funding agency but rather by a group of senior academics who get together, brainstorming to define problems and produce ideas. We are addressing basic research problems on a five- to ten-year timescale, with funding from worldwide sources, rather than the short-term goals often set for research today. In the case of metallic foams, the relationship between the properties and the microstructure (that is, the 'architecture' of the bubbles) has yet to be established.

The toughness of metal/ceramic laminated materials is the subject of a current programme in the Micromechanics Centre. At higher ratios of metal-to-ceramic thickness, the ceramic layers undergo multiple cracking, raising the toughness considerably.

Properties and applications

These materials, which are manufactured by a number of companies, mimic natural structures with a porous core, such as wood or bone, and have a number of unique properties. Their density is only 20% of that of the parent metal, they possess a high energy-absorption capacity and excellent heat-transfer characteristics, and they can be cast directly into sandwich structures of final shape. Potential application areas include bumpers and firewalls for cars, heat exchangers for microcircuits, pre-heaters for jet engines, lifts, tunnels, and blast-proof doors for buildings such as foreign embassies. It is hoped to extend the technology of current aluminium metallic foams to steel and nickel-based alloys. By determining the underlying theory behind these types of materials, the Micromechanics Centre will provide the knowledge needed for industrial exploitation.

Enquiries to Professor Norman Fleck Tel: (01223) 332650, e-mail: naf1@eng.cam.ac.uk