Critical composite maintenance

A group of non-destructive evaluation specialists are set to investigate an advanced ultrasonic evaluation technique that monitors the structural integrity of composite aircraft parts.

The team from Bristol and Nottingham universities are working with Airbus and Rolls-Royce on a new technique that would place an array of nearly 100 transducers on large composite structures to build up 3D pictures of their internal structure.

Anthony Croxford, a mechanical engineer at Bristol, said large arrays are currently used to study the internal structures of metal but they are not used with much reliability on composite structures because their internal structure is not uniform.

‘The problem is when you put ultrasonic energy into this structure, it will have different velocity in different directions because of all the fibres being aligned differently,’ he added.

These issues can be avoided when studying thin sections of composites by using higher frequencies. It remains a problem when trying to study thick sections - sizeable enough for use as a safety-critical component - because high-frequency waves become absorbed in the structure.