This paper investigates the effects of geometric nonlinearity and structural flexibility on the flight dynamics of high-aspect-ratio wings representative of high-altitude long endurance aircraft configurations. A coupled aeroelastic flight dynamic framework is developed, combining a geometrically exact beam formulation for the structure, unsteady two-dimensional strip theory for the aerodynamics, and quaternion-based rigid-body equations for the flight dynamics. The three subsystems are monolithically coupled through consistent load and motion transfer at each time step. A systematic parametric study is conducted by varying the wing stiffness across several orders of magnitude, spanning from nearly rigid to very flexible configurations. The study reveals that increasing flexibility fundamentally alters trim conditions, flutter boundaries, and dynamic gust response. In particular, large static deformations create an effective dihedral that modifies the lift direction and necessitates higher trim angles of attack. The phugoid mode is shown to destabilise at high flexibility levels, consistent with findings in the literature. Flutter speed degradation is quantified as a function of the stiffness parameter, showing significant reductions for very flexible configurations when the pre-stressed equilibrium is correctly accounted for. The framework is validated against published aircraft benchmarks, demonstrating good agreement in natural frequencies, flutter speeds, and nonlinear static deflections. Results provide quantitative guidance on when linear analysis is acceptable and when fully coupled nonlinear tools become essential.

翻译：本文研究了高海拔长航时飞行器典型的大展弦比机翼中，几何非线性与结构柔性对飞行动力学的影响。我们建立了一个气动弹性飞行动力学耦合分析框架，其中结构采用几何精确梁模型，气动力采用非定常二维条带理论，飞行动力学基于四元数表示的刚体方程。三个子系统通过每个时间步的载荷与运动一致传递实现整体耦合。通过将机翼刚度在多个数量级范围内变化（从近似刚性到高度柔性构型），开展了系统的参数化研究。研究表明，柔性的增加从根本上改变了配平条件、颤振边界和动态阵风响应。特别地，大静态变形产生了有效上反角，改变了升力方向并需要更高的配平迎角。在高度柔性水平下，沉浮模态呈现失稳特征，这与文献中的发现一致。颤振速度的下降被量化为刚度参数的函数，结果表明，当正确考虑预应力平衡时，高度柔性构型的颤振速度显著降低。该框架通过与公开的飞行器基准结果进行验证，在固有频率、颤振速度和非线性静变形方面展现了良好的一致性。研究结果为何时采用线性分析可接受及何时必须使用完全耦合的非线性工具提供了定量指导。