Robust Approach for the Optimization of Riveted Connections in CFRP Parts and the Effect on Global Structure Optimization
Markus Longeru, Sogeti
Optimization is one of the core competences, in the development of lightweight structures. The project presented in this presentation is about the optimization of a vertical stabilizer (VTP) primary structure, made of CFRP foam sandwich.Generally spoken the VTP skin consists of the foam core, the cover layers, booster areas at the foam runout and monolithic areas where the skin is riveted to the spars.
Due to the fact that the inner and outer geometry of the skin are fixed, the optimization starts with the stacking optimization of the inner and outer cover layers. The second points of interest are the booster regions and finally the riveted area, i.e. the skin to spar flanges. The flanges consist of the inner plus the outer cover layer and thus, the requirements of the riveted regions influence the stacking sequence of the cover layers, even in the sandwich area.
The presentation gives an overview over the optimization process. The Optimization of cover layers and booster areas is performed using Optistruct, while for the optimization of the riveted area a separate tool is developed. For the development of this optimization routine, some pre-studies using Hyperstudy have been performed.Finally the bolt optimization routine offers the possibility to obtain weight optimized rivet connections taking into account the number of rivets, rivet diameter, required sheet thickness and stacking sequence. All these parameters can be optimized under constant strain, constant force or mixed conditions.