STRUCTURAL MECHANIC AND AEROELASTIC APPROACH FOR DESIGN AND SIMULATION OF CFRP FAN BLADES

Kurzfassung

Since the development of CRISP, a counter rotating integrated shrouded propfan, within a MTU-DLR cooperative project between 1985 and 2000, major advances have been made in various areas of engine development and fan technology. Therefore DLR launched a successive project CRISPmulti in 2010, redesigning the existing blades to increase the level of aerodynamic efficiency, lower the noise emissions and reduce the overall weight. The improvements are made possible by using the method of multidisciplinary optimization involving the DLR Institutes of Propulsion Technology, Aeroelastics and Structures and Design, together with the DLR facility Systemhaus Technik. This paper focuses on the structural mechanics and aeroelastic aspects in design and simulation for a counter rotating fan stage with blades made from carbon fiber reinforced PEEK. With the use of the thermoplastic resin PEEK, a new approach for the manufacturing of fan blades was used. Different from the so called “onion skin configuration” of CRISP the layers of the CRISPmulti blades are stacked up to a flat plate and are reshaped using a hot press. Afterwards the final blade geometry is obtained through a milling process. The material testing program to identify the important material parameters for this approach is specified and adjusted to suit the highly sophisticated simulation techniques. Based on the material properties, the structural mechanic approach for the calculation of the static and dynamic behavior is presented. The aeroelastic simulation validates the forced response and flutter behavior of the CFRP fan blades. The presented design strategy has been successfully completed and undergone a critical design review to prove mechanical and aeroelastic feasibility regarding a planned rig test.