Load-specific variant generation of bead cross sections in sheet metal components by unidirectional carbon fibre reinforcement

Beads are widely used to stiffen sheet metal components subjected to bending loads. Often, these bead-stiffened parts are used in product variants that differ significantly in the amount of acting loads. Lamination of unidirectional carbon fibre reinforced plastic (UD-CFRP) on the top flange area of individual beads represents a method for further increasing weight- specific stiffness: By varying the number of plies, a specifically configured component is obtained for each of the load cases. As a result, no changes to the forming tools are necessary and a minimum amount of the UD-CFRP material is required. In this work, a complete manufacturing process for a fibre reinforced bead was developed: First, a bead cross section geometry with an adapted top flange area to accommodate the UD-CFRP plies was designed and stamped into pre-stretched sheet samples of DX56 steel. Subsequently, the suitability of several surface pre-treatment processes to achieve sufficient bond strength of the composite bead was experimentally investigated and the UD-CFRP plies were applied by lamination. Final bending tests quantified the achievable stiffening effect of the investigated bead variants, showing a significant increase of the maximum supportable load compared to the standard non- reinforced cross-section