Novel load-introduction systems for lightweight aircraft components in composite-metal-hybrid design

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Novel load-introduction systems for lightweight aircraft components in composite-metal-hybrid design

Hufenbach, W. / Gude, M. / Helms, O. / Ulbricht, A.

The ever increasing competition forces the aerospace industry to reduce the weight of aircrafts which leads to an increased payload and reduced fuel consumption. Therefore fibre reinforced plastics (FRP) are gradually replacing metals as the material of choice for highlystressed aircraft-structures with well-defined loads. In contrast to that for complex-shaped load-introduction elements with multi-axial stress states isotropic materials like steel are advantageous. Thus, the design process requires a multi-materials construction, in which the single components have to be joined with adequate technologies. Furthermore within multimaterials design the delta alpha-problem due to different thermomechanical properties have to be considered to minimize the resulting residual stresses. On the example of a new lightweight hydraulic actuator, a variety of feasible joining technologies for connecting metallic flanges to FRP-tube components is demonstrated such as loops, threads and bolt-connections. Load introduction systems are dimensioned by using finite element calculation software and new physically based failure criteria. Advantageous solutions for prototypic tube structures made of FRP with integrated load introduction systems are manufactured by specially developed filament-winding and resin-transfer moulding processes and related tools. Furthermore, extensive simulations and tests on the thermomechanical behaviour of hybrid structures are performed to determine the material effort due to residual stresses.