Aeroelastic Tailoring Framework of Pazy Wing With Variable Stiffness of Composites Spar

Abstract

Top speed of an aircraft is limited by the stiffness and damping of a structure which are contributing to aeroelastic response such as divergence and flutter, respectively. This study explores stiffness tailoring of Carbon Fiber Reinforced Polymer (CFRP) spars using a proposed bi-level framework. Frequency-based aeroelastic approaches are fast but less accurate for highly flexible structures, while time-based methods utilizing Fluid-Structure Interaction offer high accuracy but at a significant computational cost. This work addresses the computational challenge by proposing a bi-level framework for efficient and accurate aeroelastic analysis. This framework employs a two-step process: Initially, a frequency-based approach in MSC NASTRAN provides an initial prediction of critical velocities. However, this method can be over-conservative for flexible structures due to limitations in capturing non-linear aerodynamics such as wake, viscous effects and induced drag. Subsequently, the framework utilizes ANSYS for more detailed analysis beyond the earlier predicted velocities. Essentially, this bi-level approach can reduce the computational cost upto 60% compared to a full-time-based analysis depending upon flight envelope, while maintaining an acceptable error margin of within 5%. Furthermore, this work investigates the impact of parametric optimization of stacking sequence on the CFRP spar. While maximizing shear modulus increases flutter speed, it comes at the expense of decreased divergence speed highlighting the importance of design trade-offs for improved aeroelastic performance. In conclusion, results of the aeroelastic tailoring showed that mass of the wing is reduced by 17.7% compared to baseline whereas divergence and flutter speed is increased by 10 and 22.8%, respectively.

Keywords

• Aeroelastic response
• aeroelastic tailoring
• bi-level framework
• composites spar
• Pazy wing