Damage Quantification for the Machining of CFRP: An Introduction about Characteristic Values Considering Shape and Orientation of Drilling-induced Delamination

This study deals with new opportunities to quantify the phenomena of delamination during the drilling of carbon fiber reinforced polymers (CFRP). The focus lies on determining additional characteristic values to describe the shape of the damage dimensions. Therefore, an algorithm was developed enabling an automatic analysis of delamination by generating an involute of the damage contour. This makes it possible to create two different types of characteristics. The statistical distribution of the delamination around the drilling hole is derived from parameters in analogy to the surface metrology. Apart from that different form factors will be introduced, which are calculated on the bases of the delaminated area or the moments of inertia respectively. The suitability of these characteristics is evaluated by a series of drilling tests in different materials with varying feed rates and tool conditions. M21/T800S, which is a quasi-isotropic UD-laminate, and the woven fabric ECG-Carbon 12K were the main materials compared to each other. The tools used for drilling are twist drills (d = 6.0 mm) with a point angle σ of 85° and a spiral angle λ of 35° at different states of tool wear. The feed rate was varied from 0.02 mm/rev to 0.1 mm/rev at a cutting speed of 100 m/min.