Underwater structure repairs under investigation
15 Jan 2000
In recent years the use of carbon fibre composites has become increasingly popular for the repair and/or strengthening of all manner of industrial structures. Although most applications take place in air, there are many instances where repair/strengthening is needed in wet conditions and in underwater environments.
To address these specific problems, a joint industry project has been set up between Devonport Royal Dockyard and MSL Engineering. The principal issue under investigation is how best to identify appropriate materials and procedures to obtain high quality bonds between composites and substrates.
Project sponsors include Amoco, BG, Elf Exploration UK, Enterprise Oil, Mobil, the MoD and Rockwater. Repairs are carried out by attaching a carbon fibre preform to the defective structure and then enclosing the area in a watertight bag. Differential pressure is used to force water out of the bag, with the aid of a dewatering agent, and then force resin through the carbon fibre preform. This forms the composite reinforcement and, simultaneously, the adhesive bond between composite and structure.
Following an initial screening programme to identify appropriate materials, lab trials have demonstrated the strength and durability of the composite and adhesive bond. Subsequent trials in a dive tank have proved the practicality of the technique and helped to refine the implementation procedures.
The partners in the project are currently preparing full scale repairs underwater of tubular joints. These will then be subject to ultimate load tests (static and fatigue) to validate the repair/strengthening procedures.
