Showing the strain

Too much sail plus a strong wind equals a broken mast. So Smart Fibres of
Southampton makes masts from a carbon-fibre composite laced with optical fibres,
which act as strain gauges to warn the crew of a yacht when it’s time to ease
off. As the mast bends it modifies light signals passing through the fibres,
giving a measure of the strain the mast is under. A warning signal is given when
high winds create dangerously high stress levels in the mast, the maker reveals
in Materials World (vol 7, p 406).