Composite materials

Underwater structures are often coated with a layer of tiles consisting of a rubber substrate combined with a random distribution of gas-filled microspheres. The purpose of this layer is to match with the acoustic impedance of water so as to hinder the detection of the structures by sonar or by unintentional transmission of noise.

Uniaxial pressure tests on this material highlight a marked softening of the material as the increased stress causes the microspheres to buckle. An analysis of the buckling problem of a thin spherical shell embedded in an elastic substrate subject to uniaxial compression will give us great insight into the mechanics of the micro-processes of the material, which would then enable a homogenisation process to calculate the macro-scale deformation of the material.

People working in this area within OCIAM are

• Prof. John Chapman

• Dr David Allwright