This study presents the use of variable stiffness concept via curvilinear fiber placement to achieve improved structural characteristics in composite thin-walled beams (TWBs). The TWB used in the study is constructed in circumferentially asymmetric stiffness (CAS) configuration. The variation of fiber angles along the span and the width of the TWB is included by defining two fiber path functions. A parametric study is performed to investigate the effects of different fiber paths on the structural performance metrics including frequency spacing, unit twist, and critical buckling load. For this purpose, a semi-analytical solution method is developed to conduct free vibration, deformation, and buckling analyses of the TWB with curvilinear fibers. The semi-analytical method is validated with several finite element (FE) analyses performed using ABAQUS. Elastic stress analyses of TWBs with selected fiber paths subjected to simplified distributed loading are also conducted using the FE method, and a ply failure criterion is applied to evaluate the strength of these TWBs. Overall results show that curvilinear fiber placement varied along the span leads to greater structural performance for a composite TWB than the straight fiber configuration.

这项研究提出了通过曲线纤维放置来使用可变刚度概念，以改善复合薄壁梁（TWB）中的结构特性。研究中使用的TWB以周向非对称刚度（CAS）构造构造。通过定义两个光纤路径函数，可以包括沿TWB跨度和宽度的光纤角度变化。进行了参数研究，以研究不同光纤路径对结构性能指标的影响，包括频率间隔，单元扭曲和临界屈曲载荷。为此，开发了一种半解析解方法，可以对曲线纤维进行TWB的自由振动，变形和屈曲分析。半分析方法已通过使用ABAQUS进行的几个有限元（FE）分析得到验证。还使用有限元方法对具有选定纤维路径并经过简化的分布式载荷的TWB进行了弹性应力分析，并应用了层破坏准则来评估这些TWB的强度。总体结果表明，曲线纤维的位置沿跨度变化会导致复合TWB的结构性能优于直纤维结构。