Tow steering for the structural dynamics of launch vehicles

通常，结构元件占运载火箭干质量的60%，因此学术界和工业界都在努力开发高质量效率的结构。这种结构将允许下一代运载火箭将更大的有效载荷送入轨道。因此，NASA已经将轻量化材料和结构确定为下一代空间飞行器的重中之重，以实现未来的低地球轨道以外的载人探索任务。拖曳复合材料，其中的增强纤维遵循曲线参考路径，代表的结构可以由设计师调整，以满足理想的标准。拖曳复合材料在圆柱运载火箭结构轴向压缩载荷情况下已被证明具有良好的性能。在上升过程中，运载火箭结构所承受的载荷不仅仅是静态的，还有来自分段、发动机噪声和气动抖振等来源的显著动态载荷。因此，研究拖曳复合材料对薄壁圆筒动力响应的好处是有意义的。然而，很少有研究存在的潜在利益，这一概念的动态加载制度。因此，该项目旨在解决这种稀缺性。在文献中，制造牵引复合材料的典型方法是通过自动纤维放置（AFP），这很容易产生工艺缺陷。相反，该项目将研究使用连续牵引剪切（CTS）过程的牵引转向。CTS通过剪切而不是弯曲材料束来减轻AFP的工艺缺陷。材料束的面内剪切会产生方向-厚度耦合，这种耦合可以作为CTS圆柱体的整体加筋特征。该项目旨在通过数值和实验两方面的研究来开发牵引复合材料，以优化运载火箭结构的动态响应。此外，两种载荷情况之间的联系，轴向压缩和振动，应发展，以产生纤维路径，有利于结构在联合载荷下。项目目标应通过分阶段的工作计划来实现，以实现以下目标：通过数值模型的发展，探索拖曳复合材料的潜在设计空间。应该开发数字工具来量化和探索这些新的性能优势。2. 进行严格的优化研究，以确定拖曳式设计，除了揭示显著质量效率的潜力外，还能展示单负载和多负载情况下的性能优势。3. 利用CTS工艺制造优化的结构，并评估该结构的质量。4. 设计并进行实验测试，以验证预测的动态性能优势。应用和好处在本博士课程中发现的主要好处是为运载火箭结构提供的好处。通过改进薄壁运载火箭结构的动力性能，将揭示避免不稳定的机会。这种不稳定性可能会导致敏感有效载荷的损坏或整个飞行器的损失，因此在设计新结构时，避免这些不稳定性的机会将被证明是无价的。研究的新颖性本项目的新颖性在于确定薄壁CTS气缸的潜在动态性能优势。此外，多载荷箱优化将提出运载火箭结构的两种主要载荷箱之间的联系，并开发满足两种制度要求的方法。

Typically, structural elements account for 60% of a launch vehicle's dry mass, and hence significant effort is being undertaken by both academia and industry to develop highly mass-efficient structures. Such structures will allow for larger payloads to be delivered to orbit by next-generation launch vehicles. Consequently, NASA has identified lightweight materials and structures amongst the highest priorities for next-generation space vehicles to enable future manned exploratory missions beyond Low Earth Orbit. Tow-steered composites, those in which the reinforcement fibres follow curvilinear reference paths, represent structures which can be tuned by the designer to satisfy desirable criteria. Tow-steered composites have shown proven benefits to the axial compression load case of cylindrical launch vehicle structures.During ascent, the loads experienced by launch vehicle structures are not solely static, significant dynamic loading arises from sources such as staging, engine noise and aerodynamic buffeting. Hence, the investigation of the benefits of tow-steered composites to the dynamic response of thin-walled cylinders is pertinent. However, very little research exists into the potential benefits of this concept to the dynamic loading regime. Hence, this project aims to address this scarcity. The typical means of manufacturing tow-steered composites within the literature is by Automated Fibre Placement (AFP), which is prone to process-induced defects. Instead, this project will investigate tow steering using the Continuous Tow Shearing (CTS) process. CTS mitigates the process-induced defects of AFP by shearing instead of bending material tows. The in-plane shearing of material tows gives rise to an orientation-thickness coupling which can be exploited as integrated stiffening features on a CTS cylinder. Aims & Objectives This project aims to both numerically and experimentally develop tow-steered composites to optimise the dynamic response of launch vehicle structures. Furthermore, a link between the two loading cases, both axial compression and vibration, shall be developed as to produce fibre paths which are beneficial for structures under combined loading. The project aims shall be fulfilled by following a staged work plan to meet the following objectives: 1. Explore the potential design space of tow-steered composites through development of numerical models. Numerical tools shall be developed to quantify and explore these novel performance benefits. 2. Conduct rigorous optimisation studies to identify tow-steered designs which exhibit both single and multiple load case performance benefits in addition to revealing the potential for significant mass efficiencies. 3. Manufacture the optimised structure utilising the CTS process and evaluate the quality of this structure. 4. Design and conduct experimental tests to validate the predicted dynamic performance benefits. Applications & Benefits The primary benefits to be found in this PhD are those afforded to launch vehicle structures. By improving the dynamic performance of thin-walled launch vehicle structures the opportunity to avoid instabilities will be revealed. Such instabilities may cause damage to sensitive payloads or the loss of the entire vehicle, and hence the opportunity to avoid these will prove to be invaluable when designing new structures. Research Novelty The novelty in this project is in the determination of potential dynamic performance benefits of thin-walled CTS cylinders. Additionally, the multi-loading case optimisation will propose a link between the two primary loading cases of launch vehicle structures and develop methodologies to satisfy requirements in both regimes.