Cutting forces and machining quality in edge trimming of MD-GFRP composites with diamond-coated burr tools

Glass fiber reinforced polymers (GFRP) manufacturing generally involves edge trimming operations to finish the periphery of the part after curing. This milling stage may lead to defects occurrence on the GFRP part, in particular delamination and uncut fibers on external plies. Such defects are affected by the cutting tool geometry, especially when it induces an axial force. To reduce defects occurrence, it is therefore relevant to use specific geometries like burr tools, which consist of many pyramidal teeth. This work aims to study the cutting forces and defects on external plies when edge trimming multidirectional (MD) GFRP composites with this type of tool. Two different stacking sequences are tested. A dedicated device and specific image processing are used to quantify uncut fibers. Our main conclusions are the following. The average cutting forces correspond to the weighted sum of the average forces induced by each fiber orientation, despite the complex geometry of the burr tool. The stacking sequence has no significant effect on cutting forces. Defects on external layers are mainly located on the lower face of the laminate, due to downward axial forces. They can be effectively avoided by adding a single ply parallel to the cutting direction on each side of the laminate, which induces a more favorable cutting mechanism.