Paul Marks calls aluminium alloy in aircraft "tried-and-trusted." Tried? Yes, and revealed as a treacherous material whose strength can be destroyed by a little crack.
If a crack in a stressed section has grown too long it will race across the alloy, snapping it in two. The more heavily and often aluminium is loaded, the more cracks form. Fortunately, we know (very roughly) how many times and how heavily it can safely be stressed, and we inspect it for cracks. Safe use of aluminium results from our distrust of it.
In fibrous materials, from cables of suspension bridges to carbon-fibre-reinforced composites, little cracks do not become catastrophic ones.
Marks reports problems with the Dreamliner aircraft (9 February, p 28) including concerns over extensive use of composite materials. This reminded me of two serious accidents I witnessed while sailing 20,000 nautical miles. One involved a yacht with titanium fittings. The ...
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