Drilling mechanism of temperature‐sensitive non‐directional UHMWPE fiber composites

Abstract Ultra‐high molecular weight polyethylene (UHMWPE) fiber composites have been widely used in aerospace, construction, and other fields; however, chip winding and poor drilling quality was greatly influenced by the drilling temperature because of the fiber and substrate's inherent temperature sensitivity. Drilling Experiments of nondirectional UHMWPE short fiber composites was conducted with four different drill bits to investigate the drilling mechanism affecting by drill bits types and drilling temperature. A unique chip‐winding mechanism and its relationship with drilling temperature and drilling force was proposed. The results showed that the spindle speed was the key factor affecting the drilling force, drilling temperature, chips morphology and chip‐winding. The polycrystalline diamond (PCD) drill bit was better than the other drill bits in terms of chip removal capacity, hole wall surface quality, and drilling temperature. When the spindle speed was set at 135 m/min, the drilling temperature and quality were the most stable. The melting temperature of the fibers in the drilling process was about 20°C (24%) higher than its real melting point. In addition, when the drilling temperature was lower than the melting point of UHMWPE fiber (90–140°C), the fracture modes of fibers was mainly tensile and extrusion fracture; while fibers melted on hole inner wall to increase the roughness of the hole wall at temperatures above the melting point (140 ~ 175°C). Highlights The winding mechanism of UHMWPE fiber composites was analyzed for the first time. The spindle speed and drilling temperature are both determinants of the hole quality. PCD drill bit achieved better hole quality when drilling UHMWPE fiber composites. The fiber fracture mechanism under the influence of drilling temperature was analyzed.