Comparative study on cutting performance of conventional and ultrasonic-assisted bi-directional helical milling of CFRP

Chen Tao,Lu Yujiang,Liu Guangjun,Wang Yongsheng,Liu Gang

doi:10.1007/s00170-021-07418-3

Abstract

Compared with the conventional drilling, the helical milling has obvious advantages in making holes of carbon fiber-reinforced plastic (CFRP). Nevertheless, the rapid wear of cutting edges readily causes some defects in the outlet holes, such as burrs and tearing. In order to improve the hole-making quality of CFRP, a comparative experimental study on conventional and ultrasonic-assisted bi-directional helical milling of CFRP was carried out. The wear mechanism of the forward and reverse cutting edges was analyzed in the two types of machining, and the change laws of cutting forces and hole wall quality were obtained by different machining means. The experimental results indicated that the flank face of forward and reverse cutting edges was dominated by the abrasive wear mechanism in the ultrasonic-assisted milling. With aggravation of the tool wear, no obvious coating peeled off the forward cutting edge, the reverse cutting edge remained relatively intact, and the wear form of neither cutting edge changed. Furthermore, in the ultrasonic-assisted reverse milling, the axial force and hole diameter deviation were restrained better than in the conventional milling, and especially when the tool wear occurred, the cutting force fluctuation varied slowly. In the ultrasonic-assisted milling, the shear fracture predominated over bending fracture. Meanwhile, the time variation of effective rake angles improved the chip breaking and removing performance of cutters, and thus, the machining quality of hole wall was enhanced obviously.

Highlights

The carbon fiber reinforced composites (CFRP) have excellent physical properties of high specific strength, fatigue resistance and corrosion resistance, being widely applied to some advanced manufacturing fields such as aviation, aerospace, etc.[1, 2]
The wear mechanism of the forward and reverse cutting edges was analyzed in the two types of machining, and the change laws of cutting forces and hole wall quality were obtained by different machining means
In the process of assembly, Carbon Fiber Reinforced Plastic (CFRP) are mostly used as structural parts and need fixing and connecting by screws and rivets, and plenty of highprecision holes for assembly and connection need to be machined on CFRP

Summary

Introduction

The carbon fiber reinforced composites (CFRP) have excellent physical properties of high specific strength, fatigue resistance and corrosion resistance, being widely applied to some advanced manufacturing fields such as aviation, aerospace, etc.[1, 2]. In the process of assembly, CFRP are mostly used as structural parts and need fixing and connecting by screws and rivets, and plenty of highprecision holes for assembly and connection need to be machined on CFRP. By contrast with the conventional drilling, the helical milling, as a new technique of machining holes, can greatly reduce the axial force and cutting temperature in the cutting process. The bi-directional helical milling has a better solution, but there are still some problems, for instance, the effective cutting distance of reverse cutting edges is short, and the wear occurs etc.[6]. The reasonable improvement in machining techniques to achieve high-quality holes and prolong the tool service life, is the key to promotion of the helical milling technology [7]

Results

Discussion

Conclusion