Experimental investigation on effect of tool geometry on thermal and crystallization characteristics in drilling of carbon fiber reinforced PEEK composite.

This paper comprehensively investigated the effect of the tool geometries on heat transfer and special crystallization characteristics in the drilling of carbon fiber‐reinforced polyetheretherketone (CF/PEEK) composite for the first time. Three tools with different geometries (twist, brad, and dagger drill) are carried out on CF/PEEK drilling experiments, and temperature, as well as crystallinity and surface roughness, are introduced to make a comparative evaluation on the effect of the tool geometries. The results show that the drilling temperature is determined by the contact length of the profile between the drill and the material. Correspondingly, better surface quality with lower surface roughness and smoother surface is obtained by using a twist drill due to the heat‐induced PEEK smearing effect. Further, in situ XRD and differential scanning calorimeter (DSC) were used to characterize the crystallization characteristics where crystal phase transformation at different temperatures was measured. The occurring temperature of the strongest crystallization characteristics for CF/PEEK is basically not affected by tool geometries, all at 300°C, and the limiting crystallization temperature is 344.5 ± 0.7°C. The crystallinity is found to be affected by drilling temperature and cooling rate and gradually decreases along the heat transfer direction. This work provides a new sight into the improvement of CF/PEEK drilling. Highlights: The effect of tool geometries on thermal and crystallization for CF/PEEK is provided.In situ XRD and DSC are used to characterize crystallization characteristics.The drilling temperature and cooling rate are both determinants of crystallinity.The limiting crystallization temperature of the CF/PEEK composite is 344.5 ± 0.7°C.Heat‐induced PEEK smearing effect improves the surface quality of CF/PEEK drilling. [ABSTRACT FROM AUTHOR]