Intelligent masts that warn sailing crews when they are about to snap have been created by a team of British scientists and engineers.
The carbon composite mast has optical fibre sensors and microprocessors embedded that tell the crew how much stress and strain the mast is experiencing.
The project, led by Ian Bennion of Aston University with collaborators from British Aerospace, mast builder Carbospars and the Pendennis Shipyard, was part of the government's Link photonics programme funded by the Engineering and Physical Sciences Research Council.
The key to the system lies in creating tiny periodic physical perturbations, Bragg gratings, in the core of the optical fibres with high-intensity ultraviolet lasers. Each one acts as an obstacle to light of a specific wavelength. Normally, light passes down the whole length of the fibre and emerges intact at the other end. However, when light of the appropriate wavelength encounters a Bragg grating it is reflected back towards the source.
When the configuration of the fibre is stretched or compressed, the grating is disturbed and so reflects light of a different wavelength.
"This provides us with a means of measuring strain," Professor Bennion said. "The shift in the reflected wavelength gives a direct measure of the amount of strain in the mast."
To measure strain at many different points along the length of the mast, several gratings are inscribed at intervals into the fibre, corresponding to different wavelengths.
"So you inject a fairly broad spectrum of light and constantly scan what comes back at the receiving end. As the mast moves, the wavelengths change," Professor Bennion said.
The system incorporates a microprocessor to analyse the pattern and to provide a colour-coded visual representation of the strain profile in the mast on a video
"The person steering the boat can look at the monitor displaying the information and can make use of information about the strain profile in the mast to influence how they sail the boat," Professor Bennion said. "This is particularly important in modern, high-performance craft."
The system has been used successfully on a super-yacht called New Dawn, which has the largest unstayed mast in the world, manufactured by Carbospars.
The technology is now being developed to monitor the integrity of a variety of structures, from bridges to aircraft and is being commercialised by a new Southampton-based company, Smart Fibres Limited.