1. Field of the Invention
The present invention relates to a shaft for transmitting rotational movements and/or forces, also commonly called a “torque shaft”.
2. Brief Description of the Related Art
The invention relates in particular to what are known as “composite” shafts, i.e. shafts of which the main body consists of a tube made of a composite material having a plastic matrix, in other words made of a material composed of a thermoplastic or thermosetting resin and of an, in particular fibrous, mechanical strength reinforcement.
This type of shaft is used, in particular in the field of aeronautics, to carry various functional mechanical assemblies, particularly mechanisms, which are actuated or stressed as the shaft is being rotated about itself. Thus, this type of shaft is used to deploy flaps on the leading edge and trailing edge of airplane wings in order thereby to improve lift, or to orient the airplane door latches so that these doors can be opened and closed. In the automotive field, this type of shaft can be used as a steering column.
In practice, to prevent deterioration of the tube of composite material, the abovementioned mechanisms are not directly supported by the tube but rather by metallic tubular inserts which are arranged fixedly around the tube and which ensure a good mechanical link between the tube and the mechanisms. However, as the tube twists and therefore as forces are transmitted by the insert between the tube and the mechanisms, the interface region, of circular section, between each insert and the tube is subjected to high shear stresses which, in particular eventually, can destroy the plastic resin surrounded by the insert. In other words, the performance of currently available shafts, in terms of torsional strength, is limited.