Fine blanking of carbon fibre reinforced plastics (fine blanking CFRP)
Final Report Abstract
Carbon fiber reinforced plastics (CFRP), commonly referred to as CFK, are of high relevance for lightweight construction due to their high specific strength. However, the high manufacturing costs associated with CFRP, combined with the increasing demand for such composite materials across various industrial sectors, including automotive, necessitate the development of mass production methods to reduce production costs at scale. One potential manufacturing process for trimming automotive components or creating cutouts within them is fine blanking. Nevertheless, fine blanking of CFRP remains inadequately researched. To address this gap, experimental investigations were conducted to analyze the cause-and-effect relationships during the fine blanking of CFRP. Data analysis revealed that the blanking force generally decreased drastically after approximately 25% of the blanking path, which was attributed to extensive failure of the material bond. Key parameters contributing to an increase in blanking force included greater laminate thickness, higher blank holder forces, a larger relative fiber volume fraction, and fiber orientation. The quality of the blanked surfaces was characterized on a macroscopic level using light microscopy and profile measurements, while microscopic evaluation was performed through scanning electron microscopy (SEM) and computed tomography (CT) imaging. It was found that higher blank holder and counter force and smaller die clearance improved surface quality. Additionally, aligning the blanking line parallel to the fiber direction, thereby minimizing the number of fibers being severed, enhanced blanked surface quality. Although profile measurements did not reveal a significant impact of relative fiber volume fraction on surface quality, CT scans indicated a reduction in material chipping at the highest fiber volume fraction used (70%). Furthermore, a numerical model was developed that enabled representation of anisotropic mechanical properties during fine blanking. One challenge was the damage modeling, in which a directional dependency of the mechanical properties was mapped in the constitutive model. However, this significantly overestimates the required blanking force. One possibility for optimization is a separate modeling of fiber and matrix using suitable material and damage models, but this is significantly more complex to implement.
Publications
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Numerical modeling for shearing of unidirectional carbon fiber reinforced plastic laminates by means of near-net-shape blanking. Procedia Structural Integrity, 61, 206-213.
Stoel, T.; Uhlmann, L.; Schweinshaupt, F.; Müller, M.; Herrig, T. & Bergs, T.
