A three-level discretization framework for dynamic behaviors of graphene-coated rotational blades with preset-angle sandwich structure under complex loads

To address the urgent demand for high-performance and durable rotational blades in turbomachinery, e.g., aero-engine turbine blades operating under harsh environments and complex pulse loads, this study proposes a novel rotational sandwich plate model with a pre-set angle for investigating the dynamic responses of rotational composite turbine blades with graphene coating layers under pulse loads to capture both structural stagger angle effects and layered reinforcement mechanisms. A unique three-level discretization method of Chebyshev-Ritz-Galerkin is established to overcome the solving difficulty of partial differential governing equations (PDGEs), efficiently transforming them into numerically solvable ordinary differential governing equations (ODGEs), a key innovation that addresses the convergence challenge of traditional finite element methods (FEM) under high-speed rotation and large deformation and that ensures high computational efficiency and accuracy. Based on the first-order shear deformation theory and Hamilton principle, the model comprehensively integrates rotational centrifugal effects, material anisotropy of graphene-reinforced composites, and geometric nonlinearity. Three typical pulse loads, that is, step load, sinusoidal load, air blast load are considered to mimic real-world extreme working conditions, e.g., bird strikes, gusts, ice impacts. The modified Halpin-Tsai micromechanical model is adopted to accurately characterize the effective material properties of graphene-reinforced composites coating layers, while a systematic parametric study is conducted to reveal the effects of blade aspect ratio, graphene platelet (GPL) geometry length-to-thickness ratio, GPL weight fraction, rotational speed, damping, and excitation parameters on dynamic responses with a special focus on the synergistic effect of GPL weight fraction and rotational speed. Meanwhile, the integration of multi-physical field loads and graphene reinforcement to fill the gap in dynamic modeling of graphene-reinforced composites-based rotational blades under pulse loads. This work provides a robust theoretical framework and quantitative design guidelines for optimizing rotational composite turbine blades with graphene coating layers with superior vibration suppression, impact resistance, and fatigue performance, advancing the engineering application of advanced composite materials in high-speed turbomachinery.