Prestressed, hybrid stringer sheet structures

本研究的目的是对平面和管状结构进行刚度优化制造。在该项目中，通过在液压成形过程中对纵梁板施加额外的应力，进一步增加了纵梁板的刚度。因此，纵梁板与纤维增强材料相结合。由于两种材料的弹性模量不同，导致了所需的预应力状态，目前还没有考虑两种材料的单独成形性和接头成形性的加工策略。此外，组合成形工艺的成形性极限、失效模式和有效可实现的预应力格拉德是未知的。这些空白将由拟议的项目填补。它的目标是混合纵梁板的技术基础，这是在成型过程中预应力。这种预加载可以预见到以后的加载情况。由于其在结构轻量化优化方面的潜力，预应力纵梁板注定要在运输和汽车行业、航空工业和建筑结构中应用。该提案的指导假设是，金属纤维接头的特定设计能够产生所需的应力状态，并解决塑料和热材料性能方面的不兼容性。该提案的目标包括机械和粘合接头以及纵梁和预应力元件之间的连接的建设性设计方法。此外，考虑到联合形成和不同材料的组合成形的工艺策略将被开发。因此，化合物的可成形性的限制进行了研究数值和实验。此外，将设计能够实现温度控制成形的工具。目标的进一步部分是开发用于确定特征温度、压力和保持力的控制曲线的方法，从而导致与所需应力状态相结合的良好混合结构。另一个目标是确定和预处理有前途的材料组合。本提案的重要目标还包括开发和验证数值计算方法，以便在成形和使用阶段对接头部件和接头本身进行真实建模。最后，形成的结构和开发的方法将进行评估方面的总体目标，增加性能略有增加的重量。

This research proposal aims for stiffness-optimized manufacturing of plane and tubular structures. Within this project the stiffness of stringer sheets is further increased by applying an additional stressing of the stringer sheet during hydroforming. Therefore, stringer sheets are combined with fiber reinforced materials. Due to their different Young's moduli, the desired state of prestress is induced.So far, there are no processing strategies available, which consider the individual formability and the joint formation of both kinds of material. Furthermore, the formability limits of the combined forming process, the failure modes and the effective achievable grad of prestressing are unknown. These gaps will be filled by the proposed project.It aims for the technological basics for hybrid stringer sheets, which are prestressed during forming. This kind of preload anticipates later load scenarios. Due to their potential for structural lightweight optimization, prestressed stringer sheets are predestined for later applications in the transport- and automobile sector, in aviation industries and in architectural structures. The proposal is guided by the hypothesis, that the specific design of the metal-fiber joint enables the generation of the desired state of stress and solves incompatibilities with regard to the plastic and thermal material behavior.The proposal's objectives include constructive design approaches for mechanical and adhesive joints and the link between the stringers and the prestressing-elements. Furthermore, processing strategies considering the joint formation and the combined forming of the different materials will be developed. Therefore, the limits of the compounds' formability are investigated numerically and experimentally. Furthermore, tools enabling a temperature controlled forming will be designed. Further parts of the objective is the development of methods for the determination of control curves for characteristic temperatures, pressures and holding forces leading to a sound hybrid structure combined with the desired state of stress.A further objective is the determination and pretreatment of promising material combinations. The development and validation of the numerical calculation methods for a realistic modelling of the joint parts and the joint itself during the phases of forming and utilization are also important objectives of this proposal. Finally, the formed structures and the developed methods will be evaluated with regard to the overall aim, increased performance at slightly increased weight.