Research on milling hole of AFRP based on cryogenic cooling processing

The aramid fiber–reinforced composite (AFRP) has special the structure and physical properties. Although, the dry helical milling hole method could improve the machining precision and reduce the cutting force for AFRP. There were still some problems such as hole defects, limited hole depth, and low machining efficiency. In this paper, the tool cutting point trajectory model based on sample and tool coordinate system was established. The cutting force model of milling hole considering fiber orientation was constructed. A series of cryogenic cooling milling hole tests were carried out using liquid nitrogen internal jet cutting equipment. The results show that the cutting path and cutting force are mainly related to axial feed, tangential feed, and center distance between tool and hole axis. Similarly, type I and II defects are serious at low-speed dry milling hole, as well as obvious type III ablative defects at high speed. Compared with dry milling hole, the cutting force in cryogenic cooling is greater at the same cutting speed. And the influence of tool axial feed on axial force and tangential force is larger than that of tangential feed. Meanwhile, the property changes of resin base and composite in cryogenic are the main reasons for inhibiting type I and II milling hole defects. Furthermore, the cryogenic medium cooling is the reasons for inhibiting type III defects, as well as passivation and adhesion of tool side edge and flank. So the cryogenic cooling milling method can improve milling hole effect and restrict machining defects for AFRP.