Composite method allows fine-tuning of material properties

The key feature of the new composites is that they have a co-continuous structure comprised of two different materials with very different properties, creating a material combining the aspects of both.

In their experiments, the MIT researchers combined two polymer materials: one that was glass-like — strong but brittle; and another that was rubber-like — not so strong, but tough and resilient. The result was a material that was stiff, strong and tough.

Some existing composite materials, such as carbon-carbon composites that use fibres embedded in another material, can have great strength in the direction parallel to the fibres, but not much strength in other directions. Because of the continuous 3D structure of the new composites, their strength is nearly equal in all dimensions.

Edwin Thomas, materials science and engineering professor at MIT, said: ‘In most existing composite materials, the fibres form disordered mass with zero continuity, while the other material — typically a resin that fills the space and then hardens — is continuous and connected in three dimensions.