Process-independent force and surface model for oblique cutting of fiber reinforced polymers
Final Report Abstract
The increasing significance of energy and resource efficiency is leading to a rise in lightweight structures made of fiber-reinforced plastics (FRP). The high specific strength and stiffness are achieved by combining a matrix material with high-strength fibers, whose targeted orientation results in the desired direction-dependent properties. Due to the inaccuracies of the forming processes, machining post-processing is usually required. FRP are anisotropic and orthotropic materials, so the identical cutting parameters can lead to different machining forces and surface damages depending on the fiber orientation, complicating the simulation of component quality and the control of machining. The fiber cutting angle θ has a decisive influence on the machining result. However, other process angles such as the lead angle λ in milling also have an impact. Current approaches to machining force modeling do not consider this oblique cut and have limitations in the fiber cutting angle range or inaccuracies in modeling. A focus of the project is the process-independent modeling of machining forces and surface topography in the machining of FRP, using carbon fiber-reinforced plastics (CFRP) as an example. For this purpose, a process-independent model describing the spatial engagement conditions in the machining process, taking into account the orthotropy of the FRP material, has been developed. By transforming the workpiece coordinate system into the tool coordinate system, the process-independent spatial engagement angles θ0 and φ0 could be defined. Regardless of the machining method, the machining force components Fc, Fkt , and Fkn are identified based on the spatial engagement angles θ0 and φ0 . Through turning investigations, the key influences on machining forces and surface topography were determined. The machining forces are most influenced by the fiber cutting angle θ, the setting angle kr, the chip thickness ℎ, the cutting depth ap, and the inclination angle λs. The cutting speed vc had no influence on the machining forces in the investigated range. Surface topography was primarily influenced by the fiber cutting angle θ, the setting angle kr, and the chip thickness ℎ. The results were used for machining force modeling. The model was validated through sawing and peripheral milling investigations. For the modeling of surface topography, a wavelet transformation of the primary profile at different setting angles was used to model surface topography under any engagement conditions and manufacturing processes. The obtained results enable the prediction of the occurring machining forces and surface quality in the machining of CFRP, allowing for a targeted adjustment of the machining process to optimize component quality.
Publications
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CFK-Zerspanen für alle – Verfahrensunabhängiges Kraft- und Oberflächenmodell beim Zerspanen von CFK mit definierter Schneide. CU-Reports #02-2023, Composite United e.V.
Brouschkin A.; Dege J. & Hintze W.
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Model Based Prediction of Force and Roughness Extrema Inherent in Machining of Fibre Reinforced Plastics Using Data Merging. Lecture Notes in Production Engineering, 42-51. Springer International Publishing.
Hintze, Wolfgang; Brouschkin, Alexander; Köttner, Lars & Blühm, Melchior
