Bright IDEAS Award: The Clay Aeroplane - Step One

Carbon fibre composites have finally made their way into structural components of civil aircraft; the Airbus A380 has 25% composites and the Boeing 787 will have 50%. Anything that flies or accelerates needs to have high strength and stiffness to weight ratios. So also, the Volkswagon prototype 250 mpg car has a carbon fibre composite body. But carbon fibre is complicated, expensive and energy intensive to make. Will the cost ever come down to meet the margins of the motor industry? There is another, humbler putative reinforcement waiting to be dug out of the ground. Smectite clays exfoliate into silicate layers that are 1 nm thick, have aspect ratios greater than 200 (necessary to defeat composite fatigue) and Young's modulus in the 200 GPa region (compared with carbon fibre; 200-500 GPa and glass 70-80 GPa). Nylon-montmorillonite composites have already found their way into vehicle components but with very low reinforcement volume fractions (less than 5 vol.%). The next stage is to increase the volume fraction, which can only be done by orientation effects, but it must be done by a method that can be scaled up. This will lead first to the 'clay car' and as confidence in clay nanocomposite engineering grows, subsequently to the 'clay aeroplane'. Indeed there are many intermediate engineering applications for this new class of material with its light touch on the climate.

The ultimate impact is that high volume fraction nanoscale clay reinforced composites will replace carbon and glass fibre throughout all regimes of engineering up to and including aircraft engineering because it will be cheaper and have a lower energy footprint. It is unlikely that the costs of carbon fibre composites will come down sufficinetly to meet the tight margins of the automobilie industry and therefore a new generation of car bodies with high strength/weight ratio will use high volume fraction clay nanocomposites after a short dalliance with glass fibre reinforcement. Once experience is gained and confidence established with clay reinformcent it will move up into civil aviation, initially in non-structural applications and then structural members, following a path taken by carbon fibre composites.