Influence of weave structure on delamination when milling CFRP

• In order to investigate delamination, slots have been milled into plain weave CFRP.
• The trimmed edge position relative to the weave yarn exerts a significant influence on delamination.
• The fiber protrusion is influenced by the distance between the trimmed edge and the intersecting yarn.
• Surface damage is prevented with positive undulation angles or promoted with negative undulation angles.
• The influence of tool geometry on delamination is far less significant.

The increasing use of carbon-fiber-reinforced plastic (CFRP) is, in addition to weight reduction, driven by decorative elements especially in the automotive industry. Different kinds of woven CFRP laminates are applied for visual effects, which, however, demand a high level of surface quality of the workpiece including the trimmed edges. This study is the first to investigate the correlations between weave induced fiber undulation and delamination when machining CFRP with a woven fabric. In order to analyze the influence of the undulation, several slots were milled into CFRP with a plain weave structure using polycrystalline diamond cutters. The relative position of the trimmed edge to the weave undulation was varied by inclining the milling path slightly relative to the fiber orientation. Surface damage and fiber protrusion from the trimmed edge were determined separately. To identify the fiber undulation angle and thickness of the top matrix layer, tomographic measurements of the laminate were used. Additionally, a theoretical model for maximum fiber protrusion was established. It became apparent that the combination of fiber undulation angle and thickness of the top matrix layer are responsible for different occurrences of delamination. The influence of tool geometry on delamination is less significant.