Fiber Beads: Development of a numerical method for the synthesis of fiber-reinforced bead patterns

该研究项目的目标是通过单向纤维增强塑料(UD-FRP)在钢珠顶部翼缘区域的局部集成来有针对性地和可调节地增加钢珠金属构件的刚度。为此，将开发一种方法，该方法根据主弯应力轨迹并考虑生产限制，确定适合于特定载荷情况的最佳位置和配筋程度(横截面面积、位置)。因此，从经济的角度来看，可以用单个成形工具生产适合于载荷情况的不同部件变体。钢铁和铝被考虑在研究项目中。钢材的轻量化设计潜力来自于这样一个事实，即在减小壁厚时，可以通过整合加筋纤维来补偿刚度的损失。在铝的情况下，电势是由于材料的低比密度造成的。根据显示出最大潜力的材料进行验证。为了为UD-FRP层创建尽可能大的粘合面，将在钢珠(用于钢和铝板)的顶部法兰区域引入额外的粘接珠。为此，首先将这种粘接珠的可能横截面形状识别为剩余可成形性能力的函数。研究的重点是复杂成形零件的原理和经济可制造性。将开发两种不同的加固等级，可根据所需的加强程度(UD-FRP层数)来使用。为了改善UD-FRP层与金属板件之间的粘结性能，研究了合适的微观结构。此外，还对两种材料的非加筋和加筋钢珠进行了试验研究，同时开发了一种计算机辅助的方法，用于计算加固的最佳位置及其加固度。为此，本文对UD-FRP粘结珠进行了详细的模型模拟，以期对这种加固方式的性能进行数值研究。对于后续的有效优化，从所获得的详细模型的知识导出替换模型。这种替代模型是以这样一种方式开发的，即借助壳单元的适应的材料特性，可以以简化的方式表示包括无尽纤维增强的粘结珠的特性。在此基础上，建立了一种参数优化方法，根据载荷情况确定连续纤维增强材料的局部最优使用情况，从而可以通过使用不同的增强材料，从单一的金属板基构件中产生不同应用的优化构件变体。

The objective of this research project is the targeted and adjustable increase of the stiffness of beaded sheet metal components by a local integration of unidirectional, fiber-reinforced plastic (UD-FRP) into the top flange area of beads. For this purpose, a method is to be developed which determines the optimal position and the degree of reinforcement (cross-sectional area, position) adapted to the specific load case based on main bending stress trajectories and under consideration of production restrictions. Thus, from an economic point of view, different component variants adapted to the load case can be produced with a single forming tool. Steel and aluminum are considered within the research project. The lightweight design potential of steel results from the fact that the loss of stiffness can be compensated by integrating stiffening fibers when reducing the wall thickness. In case of aluminum, the potential is due to the low specific density of the material. Validation is carried out based on the material showing the greatest potential.In order to create the largest possible adhesion surface for the layers of UD-FRP, an additional adhesion bead is to be introduced into the top flange area of a bead (for steel and aluminum sheets). For this purpose, possible cross-sectional shapes for such an adhesion bead are first identified as a function of the residual formability capacity. The focus of the investigations is on both the principle and the economic manufacturability of the complex formed part. Two different reinforcement grades are to be developed that can be used depending on the degree of desired stiffening (number of UD-FRP layers). For the improvement of the adhesion properties between the UD-FRP layers and the sheet metal component suitable microstructures are investigated. Furthermore, an experimental investigation of the non-reinforced and reinforced bead variants for both materials is carried out.Concurrently, a computer-aided method for numerical calculation of the optimal position of the reinforcement and its degree of reinforcement will be developed. For this purpose, the simulation of the adhesion bead with inserted UD-FRP is carried out as a detailed model in order to numerically investigate the properties of this type of reinforcement. For a subsequent efficient optimization, a substitution model is derived from the gained knowledge of the detailed model. This substitution model is developed in such a way that the properties of the adhesion bead, including endless fiber reinforcement, can be represented in a simplified manner with the aid of adapted material properties of shell elements. Based on this, a parameter optimization is created, which determines the locally optimal use of continuous fiber reinforcements depending on the load case.As a result, it is possible to produce optimized component variants for different applications from a single sheet metal base component by using different reinforcement variants.