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：本文研究了几何非线性和结构柔性对高空长航时飞行器构型中大展弦比机翼飞行动力学的影响。建立了一个耦合气动弹性飞行动力学框架，该框架结合了几何精确梁理论用于结构建模、非定常二维片条理论用于气动分析，以及基于四元数的刚体方程用于飞行动力学建模。三个子系统通过在每一时间步一致载荷与运动传递实现整体耦合。通过将机翼刚度跨越多个数量级变化（从近乎刚性到非常柔性的构型），开展了系统参数化研究。研究表明，增加柔性会从根本上改变配平条件、颤振边界和动态阵风响应。特别地，大幅静态变形会产生有效上反角，改变升力方向并需要更高的配平攻角。在高柔性水平下，沉浮模态出现失稳，这与文献中的发现一致。颤振速度退化量被量化为刚度参数的函数，表明当正确考虑预应力平衡时，非常柔性构型的颤振速度显著降低。该框架通过已发表的飞行器基准数据进行验证，在固有频率、颤振速度和非线性静态变形方面显示出良好一致性。研究结果为线性分析的适用界限以及完全耦合非线性工具的必要性提供了定量指导。