Highly Efficient Induction Heating Process to Cure and Health Monitor the Bonding of Composite Patches on Aircraft Structures (INHEATPRO)
More aircraft structures than ever before are now manufactured from lightweight composite materials, requiring a different approaches to repairs, particularly temporary repairs carried out in-field. Bonded composite patches are used to repair corrosion, fatigue and impact damage to airframes due to their superior mechanical integrity characteristics compared with mechanically fastened repairs. Such repairs also reduce aircraft down-time, maintenance labour costs and enable useful life extension. Success of a bonded repair is critically dependent on achieving suitable surface preparation and cure under difficult field conditions. As the scope of bonded composites patch repairs expands to include primary structures, an added level of assurance needs to be demonstrated that an adequate adhesion and cure has been achieved over the entire patch area.
This £1.3m three year three-year ATI-supported project was led by Stirling Design Dynamics in partnership with Hitex (UK), TWI, Argon Design and McWade Associates. The objective was to develop a “smart patch” system with a reliable, low cost, integrated sensor network that will act as part of a feedback control system for active cure control to optimise both adhesive mechanical properties and minimise residual stress. It was also proposed that the sensors be used as active transducer elements to enable non-destructive inspection of the patch to a high probability of detection for voids and disbands that are equal to or larger than the critical size.