The present invention relates to the repair of composite-material aircraft parts. The expression “composite material” is understood as meaning a fibre-reinforced cured thermosetting resin which is widely used to produce the so-called “outer skin” of the aircraft, in particular the fuselage, the wings and the tail units. More generally, the invention is applicable to the repair of panels, beams, nose-cones (or radomes) and tail-cones.
Hitherto, in most cases, manufacturing defects such as discontinuous gluing lines or zones with excessively high porosity are repaired by applying exclusively a vacuum inside a vacuum bag. During these repair operations, a resin-impregnated patch made of carbon fibre (or glass fibre or some other fibre, depending on the type of composite material to be repaired) is applied first of all onto the defective part of the panel, arranging an adhesive sheet in between. A thermal covering layer and a vacuum bag are placed on top so as to compact the patch against the panel and evacuate the air which would prevent correct compaction. Repairs carried out using only a (low pressure) vacuum are the cause of high porosity (resulting in poorer mechanical properties) and a gluing line of unsatisfactory quality.
It has been proposed to repair composite bodies using a portable autoclave so as to obtain, owing to the pressure exerted by the autoclave, better quality repairs; the use of these autoclaves is limited because they cannot be applied directly on an aircraft or on other large composite structures. These autoclaves require in fact the introduction inside them of the part to be repaired and therefore cannot be used to repair large-size panels. Autoclaves are moreover very costly.
In the past pressurized boxes have been designed, but these required an external fixing system in order to remain attached to the panel; the boxes are sealed onto a vacuum bag, but fixing to the panel, in addition to not being easy to adapt to different situations, results in an unacceptable load on the parts. Therefore these boxes have never found a practical application.