Cutouts are widely used to accommodate windows, openings for access purposes, or fasteners in the primary structural parts of airplanes. The presence of cutouts in composite panels results in stress or strain concentrations, leading to potentially reduced load-carrying capacity. Steering tows around cutouts using emerging techniques in three-dimensional (3-D) printing and advanced fiber placement can potentially alleviate such problems. Continuous tow steering around cutouts also eliminates fiber cutting, thereby precluding ply-level 3-D stress concentration, which could otherwise lead to delamination-induced damage. This work examines stress and strain concentrations, using continuous tow steering, around a representative wingbox access hole. Buckling response under compression loading together with stress and strain concentrations under both tensile and compression loads are examined. A steered configuration shows a 26% improvement in buckling performance in comparison with the equivalent straight-fiber configuration. Under tensile loading, the maximum stress and strain concentration factors around the cutout are 29 and 32% larger, respectively, for straight-fiber orientations than those with steered tows around the cutout. For the compression loading condition, the direct strain of the panel with straight-fiber orientations was found to be three times that of steered-fiber trajectories in the vicinity of the cutout.

切口广泛用于容纳窗户、用于进入目的的开口或飞机主要结构部件中的紧固件。复合板中切口的存在会导致应力或应变集中，从而可能降低承载能力。使用三维 (3-D) 打印和高级纤维放置中的新兴技术在切口周围引导牵引可以潜在地缓解此类问题。围绕切口的连续牵引转向还消除了纤维切割，从而避免了层级 3-D 应力集中，否则可能会导致分层引起的损坏。这项工作使用连续牵引转向，在代表性翼盒检修孔周围检查应力和应变集中。检查压缩载荷下的屈曲响应以及拉伸和压缩载荷下的应力和应变集中。与等效的直纤维配置相比，转向配置的屈曲性能提高了 26%。在拉伸载荷下，对于直纤维取向，切口周围的最大应力和应变集中系数分别比切口周围的转向丝束大 29% 和 32%。对于压缩载荷条件，发现具有直纤维取向的面板的直接应变是切口附近的转向纤维轨迹的三倍。与等效的直纤维配置相比，转向配置的屈曲性能提高了 26%。在拉伸载荷下，对于直纤维取向，切口周围的最大应力和应变集中系数分别比切口周围的转向丝束大 29% 和 32%。对于压缩载荷条件，发现具有直纤维取向的面板的直接应变是切口附近的转向纤维轨迹的三倍。与等效的直纤维配置相比，转向配置的屈曲性能提高了 26%。在拉伸载荷下，对于直纤维取向，切口周围的最大应力和应变集中系数分别比切口周围的转向丝束大 29% 和 32%。对于压缩载荷条件，发现具有直纤维取向的面板的直接应变是切口附近的转向纤维轨迹的三倍。