Occurrence and propagation of delamination during the machining of carbon fibre reinforced plastics (CFRPs) – An experimental study

The machining of carbon fibre reinforced plastics (CFRPs) is often accompanied by delamination of the top layers of the machined edges. Such damage necessitates time-consuming and costly post-machining and in some cases leads to rejection of components. The work described in this paper systematically investigates the occurrence of delamination of the top layers during the machining of CFRP tape, with the focus being on the process of contour milling. The occurrence and propagation of delamination were studied by milling slots in unidirectional CFRP specimens having different fibre orientations and mainly analysing the slot tip. This allowed the key mechanisms to be clarified. The results show that delamination is highly dependent on the fibre orientation and the tool sharpness. The experiments allow derivation of a novel system for describing the occurrence and propagation of delamination during milling. Furthermore, the principles also apply for drilling. The results allow customisation of the machining procedure to reduce and in some cases totally avoid delamination, leading to a significant increase in the quality of components.

► Novel method for analysing top layer delamination in milling of CFRP tape.
► Discovery of critical cutting angle range where delamination occurs.
► Observed component edge delamination is explained by delamination propagation.
► Derivation of favourable cutting strategies for delamination avoidance in milling.