Thanks Genghis, and Joe, Don't wish to steal the OPs thread but more on composites. I am currently working in crash testing. We undertook a project recently with some EU funding looking into embedding sensors in composite wind turbine blades for early failure detection. I also had a bit of a dabble into acoustic emissions with a group up in Aberdeen (Composite pressure vessels) our longer term aspirations was to embed the transducers into the windings. I don't think this happened on this project before I moved on. I do wonder if this has been applied to composite aircraft structures. We were imposing significant damage to these vessels before testing to ultimate to ensure the sensors were able to detect early fibre failure. The Design Authority had applied factors way over the top but I did understand the caution. A fine example of multiple load paths on a different level working in your favour.