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

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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.