The aeroelastic instability of a high-aspect-ratio wing including anisotropic composite wing–spar in an incompressible flow is investigated. Combining a nonlinear Euler–Bernoulli beam theory and a composite laminate theory, the third-order expansion of nonlinear structural equations of motion and associated boundary conditions are obtained for vertical, forward/afterward, and torsional motion of the high-aspect-ratio composite wing undergoing large deformations and small strains, neglecting warping, shear deformation, and small Poisson effects. The unsteady aerodynamic strip theory based on Wagner’s function is used for determining the aerodynamic loading of the wing. Combining these two sets of equations gives a set of nonlinear integro-differential aeroelastic equations of motion. The governing partial differential equations are discretized using Galerkin’s method, and the obtained equations are solved with a numerical method with no need to add any aerodynamic state-space degrees of freedom. Some test cases are analyzed and the results are evaluated based on the results given in other references. Also, a study is conducted to show the effects of fiber orientation variations on nonlinear aeroelastic instability speed and nonlinear aeroelastic instability frequency of the composite wing. The study shows that fiber orientation strongly affects the aeroelastic characteristics of a non-isotropic wing where the aeroelastic instability speed dominantly decreases for the fiber orientation between − 90° and − 45° or 0° and + 45°. It is also shown that in the fiber orientation between − 45° and + 45°, the bending–bending stiffness and in the other fiber orientation, the bending–torsion coupling stiffness have a significant role in decreasing or increasing the nonlinear instability speed of the wing.

研究了包括各向异性复合翼梁在内的大展弦比机翼在不可压缩流动中的气动弹性不稳定性。结合非线性 Euler-Bernoulli 梁理论和复合材料层压板理论，获得了高展弦比复合材料机翼的垂直、向前/向后和扭转运动的非线性结构运动方程的三阶展开和相关边界条件经历大变形和小应变，忽略翘曲、剪切变形和小泊松效应。基于瓦格纳函数的非定常气动带理论用于确定机翼气动载荷。结合这两组方程给出了一组非线性积分微分气动弹性运动方程。控制偏微分方程使用伽辽金方法离散，得到的方程用数值方法求解，无需添加任何气动状态空间自由度。分析了一些测试用例，并根据其他参考文献中给出的结果对结果进行了评估。此外，还进行了一项研究，以显示纤维取向变化对复合材料机翼的非线性气动弹性失稳速度和非线性气动弹性失稳频率的影响。研究表明，纤维取向强烈影响非各向同性机翼的气动弹性特性，其中气动弹性不稳定速度主要在 - 90° 和 - 45° 或 0° 和 + 45° 之间的纤维取向降低。还表明，在 - 45° 和 + 45° 之间的纤维取向中，