Damage performance in drilling of carbon fiber-reinforced polyetheretherketone composites using drills with different geometries

The matrix of carbon fiber-reinforced polyetheretherketone (CF/PEEK) composites is easy to soften when heated. During the cutting process, the matrix exhibits strong plasticity under the action of force-thermal coupling. Compared with thermoset composite materials, a certain difference can be observed in processing damage. CF/PEEK composites are investigated by drilling experiments that adopt different geometries for drill bits (twist, brad, and dagger drill). The effects of drill bits geometry on drilling temperature, thrust force, and damage are analyzed. The cutting mechanism between different geometric drills and fibers is investigated. The results indicate that PEEK resin is softened by heat and matrix generates plastic deformation, burr-generated agglomeration, and crimp at both the entrance and exit. Under the action of the outer brad drill tip, no burrs are observed at the edge of the hole. Moreover, tearing damage is more serious at the exit. The dagger drill of the thrust force slowly returns to zero and generates lower delamination, and more burrs are produced. The hole wall damage is relatively less for brad drills. The continuous and crimped chips are produced during drilling.