Structural sizing of rotorcraft composite airframe using the open-source based design environment PANDORA

During the last years, the design environment PANDORA has been developed at DLR in order to assess airand rotorcraft airframes. As part of this design environment structural sizing routines have been implemented. The airframe models are numerically solved using commercial Finite Elements solvers and the results are passed to the sizing algorithm using in-house developed converters. This paper introduces the sizing routine that was implemented into PANDORA to assess orthotropic structures using a two-step approach: Gradientbased optimization is conducted using lamination parameters and subsequently an evolutionary algorithm is executed to get a discrete ply lay-up. The theory behind the implemented methods is described and the evaluation of the implemented strength and stability criteria is illustrated. Exemplary sizing runs of rotorcraft main frames are shown and isotropic and orthotropic main frames designs are compared