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

本研究项目的目标是通过将单向纤维增强塑料（UD-FRP）局部整合到珠的顶部凸缘区域中，有针对性地和可调节地增加珠金属板部件的刚度。为此，需要开发一种方法，该方法根据主弯曲应力轨迹并考虑生产限制，确定最佳位置和加固程度（横截面积、位置），以适应特定的载荷情况。因此，从经济的角度来看，可以用单个成形工具生产适合于负载情况的不同部件变型。钢和铝被认为是研究项目的一部分。钢的轻量化设计潜力来自于这样一个事实，即刚度的损失可以通过在减少壁厚时集成加强纤维来补偿。在铝的情况下，这种可能性是由于材料的低比重。根据表现出最大潜力的材料进行验证。为了为UD-FRP层创造最大可能的粘合表面，将在卷边的顶部凸缘区域引入额外的粘合卷边（用于钢板和铝板）。为此目的，这种粘合珠的可能的横截面形状首先被确定为剩余可成形能力的函数。调查的重点是复杂成形零件的原理和经济可制造性。根据所需的加固程度（UD-FRP层数），将开发两种不同的钢筋等级。为了改善UD-FRP层和金属板部件之间的粘合性能，研究了合适的微观结构。此外，本文还对两种材料的无筋和筋筋的变形进行了试验研究，并提出了筋的最佳位置及其筋度的计算机辅助数值计算方法。为此，模拟的粘合珠与插入UD-FRP进行了详细的模型，以数值研究这种类型的钢筋的性能。对于随后的有效优化，从获得的详细模型的知识导出替代模型。该替代模型以这样的方式被开发，即粘合珠的特性，包括环形纤维增强，可以借助于壳单元的适配的材料特性以简化的方式被表示。在此基础上，创建参数优化，根据载荷情况确定连续纤维增强的局部最佳使用。因此，可以通过使用不同的增强变体，从单个钣金基础部件生产针对不同应用的优化部件变体。

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.