Design and Testing of Advanced Composite Load Introduction Structure for Aircraft High Lift Devices

This paper focuses on innovative composite load introduction structures for high lift devices and their design philosophy. In a joint project between different EADS Business Units, a new composite flap support system is developed for which design principles are investigated. The load introduction of these composite high lift elements is of most interest. The design of single pin load introduction can be divided into composite lugs and load introduction loops. Both designs are analyzed in detail with finite elements using non-linear boundary conditions (e.g. gap elements, deformable body contact definitions) and afterwards are verified by static and dynamic tests. It is shown that force introduction loops have advantages at in-plane tensile loads, but lead to poor performance at out of plane loads in comparison to composite lugs. Therefore load introduction loops can be used for limited design space and in-plane tensile loads. For multiple loadings in various directions composite lugs should be used instead. The investigations further show that friction within the bearing leads to a major load increase. Advanced composite linkage structures of the flap support system are designed and verified by full scale fatigue tests.