Composites proved for submarine hulls

Pressure testing of an experimental composite submarine hull at the University of Portsmouth has validated finite element analysis (FEA) models it had created

The results mean that accurate simulation can be made for larger hull structures to assess feasibility of using composite as the main material instead of steel. Paul Smith is a lecturer with the Royal Navy, working in collaboration with Dr Andrew Little and Professor Carl Ross, who had a major hand in designing the hulls for Britain's nuclear submarine, high pressure tests of carbon-glass reinforced composite tubes, 50mm in diameter and up to 240mm long, made with three layers of glass fibre reinforced composite and two layers of carbon fibre reinforced composite. Smith ran simulations through a commercial FEA package as well as proprietary software written by Professor Ross developed at the University. The results were then compared with the physical tests on tubes that were tested to destruction in a tank capable of reproducing pressures down to the deepest depths of the oceans. The University of Portsmouth software was able to reliably predict the results of the tests, while the commercial alternative was less successful. Professor Ross told us that this was because of a 'Plastic KnockDown' factor in the University's software that represented knowledge based on practical experience. Failure modes were either axi-symmetric or resulted from shell instability. While it is unlikely that composites will immediately replace the steel hulls of larger submarine structures, they are already being used in the design of smaller unmanned underwater systems such as BAE Systems Talisman.