Design Optimization of a CFRP Wing Cover for the AFP Process

Kurzfassung

The economic application of carbon fiber reinforced plastics in large-scale aerospace structures demands cost-efficient production technologies. In recent years, much progress was achieved in automation engineering, like automated fiber placement (AFP) and automated tape laying (ATL) technologies. In the design process, new methods have been established to incorporate boundary conditions of the production process. Henceforth the optimization process is not only focused on weight-reduction, but on an improved cost/weight ratio. Most research on this topic has been done in the field of conceptual design, as the highest percentage of the later arising manufacturing cost is defined by decisions made in the early design phase. But there is also a potential for reducing production cost in the detailed design phase. In the Composite Design department of the DLR Institute of Composite Structures and Adaptive Systems the detailed design of a wing cover skin section was optimized for the AFP-process. Ply shapes and ramp geometries have been modified to reduce the number of courses needed for ply-layup, and thus to reduce production time. Uncomplete courses with less than all of the available tows, as well as repeated stops and acceleration of the fiber-placement head due to unnecessary tow-cutting processes have been avoided. With these approaches the total layup time was reduced by 3,4% whereas the on-surface time of the fibre placement heads decreased by even 5% compared to the reference design, while structural weight remained constant. The optimization strategies, originally developed for the AFP-process, are also applicable to the ATL-process. The optimized design was analyzed in 3 sections and compared to the reference design for 408 combinations of longitudinal, transversal and shear loads, showing only minor differences in strength and stability.