Flexible Conductive Composite Repair Heaters
An appropriate curing of the patch resin and adhesive layer is essential to secure the proper integrity of a bonded composite repair for aeronautical application with promising benefits in terms of increased aircraft reliability in operations, improved availability in terms of less time spent on ground and to contribute to further accelerate the use of composites in aerospace structures with obvious advantages in terms of fuel consumption and emissions reduction.
The project, assigned to a consortium made up of an SME (GMI Aero) specialising in composite repairs and a university (NTUA), was developed in the frame of the Eco design for airframe project dealing with long life structures and with the topic manager Airbus requiring some new solutions in the field.
The base applied technology was the so called ‘Conductive Skin Heating’ providing a high quality, efficient and cost-effective repair curing through newly-developed heating blankets provided with a mesh of NiCr coated and encapsulated wires between two silicon sheets to ensure electrical insulation. Power wires installed regularly provide an easy connection to electricity supply. The technique has been further enhanced to ensure better repairs in order to optimise the process, i.e. the temperature distribution during bonding and other parameters through simulation.
The novelty resides in the fact the airframer could easily use blankets, in the form of procured pre-manufactured sheets, to apply to its repairs and operate inside the maintenance line, completely suppressing the lead time to fabricate or order heating elements on purpose.
Moreover the versatility of the process to also use a combination of blankets (multi-zone heating) to cover wide surfaces with more complex geometries is certainly an important element worth investigating further in view of a market application.