Buckling and postbuckling of curvilinearly grid-stiffened variable-stiffness composite fuselage panels

网架加劲结构因其在强度、稳定性和损伤抗力等方面的优点和较高的结构性能，在航天结构中得到了广泛的应用。使用自动纤维放置和添加制造(也称为3D打印)等先进技术，可以制造由两个放置的可变刚度复合蒙皮和曲线加强筋组成的集成结构。在这个拟议的项目中，将研究曲线网格加筋复合材料结构的屈曲和后屈曲性能。将采用基于两个放置的导向纤维的变刚度(V-S)概念来开发能够改善飞机结构的屈曲和后屈曲性能的创新的定制复合材料设计。这项研究的主要目标是同时确定蒙皮的最优纤维路径和加筋板的最优轨迹，以获得最大屈曲能力，同时考虑制造约束。为了实现这一目标，首先，将利用基于能量的方法得到精确而快速的半解析解，以求取适用于飞机结构的曲线早期加筋V-S复合材料板壳的屈曲响应。然后，开发了包含不同设计剪裁场景的优化框架，以研究不同参数对壁板屈曲性能的影响。将每种情况下得到的设计屈曲性能与传统加筋直线设计基线的屈曲性能进行比较。此外，还将使用有限元方法研究在前面的方案中获得的设计的后屈曲行为，以评估最大屈曲抗力优化的壁板的剩余刚度。

Due to their benefits and high structural performance in terms of strength, stability and damage tol-erance, grid-stiffened structures are used on a large scale in aerospace structures. Manufacturing of an integrated structure consisting of a tow-placed variable-stiffness composite skin and curvilinear stiffeners is possible using advanced techniques such as automated fibre placement and additive manufacturing (known also as 3D printing). In this proposed project, the buckling and postbuckling performance of curvilinearly grid-stiffened composite structures will be addressed. The variable-stiffness (V-S) concept based on the tow-placed steered fibres will be adopted to develop innovative tailored composite designs that are able to improve the buckling and postbuckling performance of aircraft structures. The primary objective of this research is to concurrently determine the optimal fibre paths of the skin and the optimal trajectories of the stiffeners for maximum buckling capacity taking into account the manufacturing constraints. In order to achieve this objective, as a first step, accurate yet fast semi-analytical solutions using energy-based approaches will be developed for ob-taining the buckling response of curvilinearly stiffened V-S composite plates and shells applicable to aircraft structures. Then, an optimization framework that includes different design tailoring scenari-os will be developed to investigate the effects of different parameters on the buckling performance of panels. The buckling performance of the designs obtained in each scenario will be compared with that for the traditionally stiffened straight design baselines. Additionally, the postbuckling behav-iour of the designs obtained in the previous scenarios will be addressed using the finite element method to assess the residual stiffness of the panels optimized for maximum buckling resistance.