A problem on which the invention is based is explained below with reference to the production of a rudder unit for an aircraft. However, this is not to be considered as a limitation for the method according to the invention which can be used in general for joining stringers to structural components.
The surface of a rudder unit of an aircraft is formed essentially by panel elements. Supporting stringers which impart the necessary rigidity to the rudder unit and which connect the individual panel elements to one another are arranged within the rudder unit. Said stringers are typically formed by “I-shaped stringers”.
For the production of a rudder unit which may be produced entirely from fiber composite materials, in particular the outer panel elements and the inner I-shaped stringers, suitable methods are required to ensure that the I-shaped stringers are joined to the panel elements.
A method known to the applicant makes provision to supply the panel elements in the form of unimpregnated semifinished fiber products. The I-shaped stringers are arranged on the panel elements. The semifinished fiber product of the panel elements is then impregnated by means of an injection method. The stringers resting on the surface of the panel elements are wetted in the process by the resin and are stuck on.
The injection method requires a vacuum film to be arranged with a positive fit on the surface of the panel elements and the T-shaped supports. This requires a considerable, even partially manual effort in order to deposit the vacuum film in a manner such that it follows the contour of the T-shaped stringer, for example on the internal or fillable surfaces in the case of cutouts, recesses, corner regions and edges. In the process, it is to be avoided that the vacuum film is not tensioned (roof effect), since, firstly, the vacuum film could be destroyed by the pressure prevailing in this process, for example in an autoclave, and, secondly, likewise because, of the pressure, a stringer which is not yet cured would be displaced out of its predetermined position and deformed.
In order to join uncured stringers to a structural component and to cure them, complicated supporting elements, for example made of metal, wood and/or pressurized rubber, are currently joined on both sides to the stringer web. This prevents the stringer web from tilting laterally and/or changing its geometry when its matrix is softened by means of raised temperature.