Stiffness tuning mechanism and nonlinear dynamics in bidirectionally graphene-reinforced TC4 blade-hub system under aerodynamic loads

Titanium-6 aluminum-4 vanadium (TC4), a titanium alloy, exhibits the excellent mechanical properties. The primary resonance and nonlinear vibrations are investigated for a functionally graded graphene platelet-reinforced TC4 (GPR-TC4) blade-hub system. This paper proposes a novel high-fidelity model to investigate the nonlinear resonant behaviors of a graphene reinforced blade-hub system under combined transverse two parameter aerodynamic loads and axial tip clearance excitations. The system couples the hub and blade utilizing the artificial spring technique to enforce interface continuity. The nonlinear governing equations are derived by employing the first order shear deformation theory for the hub and the classical plate theory for the pretwisted blade, incorporating the von Karman geometric nonlinearity. The model validity is confirmed through a comparison involving theoretical predictions, finite element analysis, and experimental tests. By evaluating the four distribution patterns for both the hub and the blade, natural frequency analysis reveals a coarse-to-fine stiffness tuning mechanism, demonstrating that the XX pattern maximizes the fundamental frequency. Furthermore, the combined nonlinear analysis reveals that the system exhibits an energy confinement phenomenon where the blade dissipates the majority of the vibrational energy, shielding the flexible hub. Numerical simulations, including amplitude frequency response curves, waveforms, Poincare maps, 2D and 3D bifurcation diagrams, maximum Lyapunov exponents, and phase portraits, collectively identify a unique transition route to chaos via spatiotemporal intermittency. The results provide a theoretical guidance for the topological design and stability control of advanced aero engine structures.