DSTO is working with project collaborators, the US Naval Surface Warfare Centre, US Naval Academy and CRC for Advanced Composite Structures, to advance a system of rapid, non-destructive inspection of large composite structures.

Composites are increasingly used in construction of new Australian Defence Force air and maritime structures, for their strength-to-weight ratio and corrosion resistance.

However, excessive pounding from high seas and underwater explosions and impacts with submerged objects, can cause sub-surface structural damage, requiring the platform be withdrawn from service for inspection.

"The current system, known as SIDER, was developed for the US Navy and relies on procedures applied when the vessel is docked. We are adapting the technique so it can be performed at sea, reducing platform downtime," DSTO research scientist, Dr Claire Davis says.

As part of the new system, sensory networking using state of the art Bragg gratings in optical fibres, will replace SIDER excitation grids. Sensors will record structural responses to environmental excitation, caused by the vessel's movement through the sea. Using modal analysis, the operational curvature shape of the vibrating structure can be determined. Curvature discontinuity indicates a change in the composite structure's stiffness, implying damage or a structural anomaly.

The sensory network's optical fibres, about the dimensions of human hair, are immune to electromagnetic interference, light weight and corrosion resistant. Consequently, the new system can be surface mounted or embedded within the vessel's structure with minimal intrusion.

DSTO researchers in Melbourne aim to validate the new system soon. Successful validation could mean the system is fitted to an in-service naval composite structure.

The program is funded by the US Office of Naval Research Global, via the Naval Cooperative Opportunities in Science and Technology Program.

The Defence Science and Technology Organisation (DSTO) is part of Australia's Department of Defence. DSTO's role is to ensure the expert, impartial and innovative application of science and technology to the defence of Australia and its national interests.

Source: http://www.dsto.defence.gov.au/news/5971/