Design of a cure monitoring system for composite aircraft repair patches

Aircraft repair patches make use of thermosetting polymers and the quality of the repair depends on proper curing. The design of a cure monitoring system for aircraft repair patches is explored. Cure monitoring was achieved by measuring the signal strength and time of flight of an ultrasonic wave transmitted through the material. Custom transducers, electronics and software was designed for the system.;Preliminary results were encouraging. The present system does not provide accurate measurements of time of flight and thus can not provide a quantitative assessment of the material properties. However, qualitative results based on changes in signal strength provided important information regarding the state of cure of the thermoset. Several cure tests accompanied by mechanical tests demonstrated the usefulness of the present system. Recommendations for creating a commercially viable system are given.;The system was used to evaluate the practicality of Bragg grating fibre optic sensors as cure monitoring devices. Bragg gratings do not appear to produce useful cure related data.