Flutter-oriented isogeometric optimization of rotating temperature-dependent functionally graded sandwich blades with variable thickness

Blade structures in rotating machinery, such as aircraft engines and gas turbines, are subjected to multifarious excitations including centrifugal load and aerodynamic load. Blade material optimization is an effective way to make blades resistant to complex excitations. In this work, an isogeometric flutter optimization model for sandwich functionally graded (SFG) material distribution of the rotating blades is developed. With Non-Uniform Rational B-Splines (NURBS) basis functions and material parameters at limited control points, the model can achieve continuous variation in blade materials, addressing parameter jumps between optimization elements in conventional optimization techniques. The vibrational solution model of blades considers the variable thickness shape characteristics and temperature-dependent materials. The direct stress integration method is used to calculate the rotating centrifugal force, and the first-order piston theory is employed to obtain the aerodynamic work. The critical flutter pressure is increased through research on optimizing the distribution of sandwich materials in the thickness direction, with material compositions at the control points as design variables. To demonstrate the effectiveness of the current model, the obtained optimization results are compared with those from traditional models. On this basis, the effects of thermal conditions, airflow parameters and rotation speed on the optimal material profiles of the rotating variable thickness blades are investigated. • A flutter optimization model of blade for the material distribution is established. • The NURBS basis functions unify modeling, analysis, and optimization processes. • The high-order continuity of NURBS basis functions handles parameter jumps between optimization elements. • The effects of varying working conditions on the optimization results of the blades are investigated.