Amplitude effect on micro-hole drilling of 3D needled Cf/SiC by ultrasonic vibration

Abstract The poor quality of the micro-hole in the conventional drilling (CD) of 3D needled Cf/SiC composites seriously limits its application in modern industry. Ultrasonic assisted drilling (UAD) is a hybrid machining technology that combines CD with ultrasonic vibration. When processing holes in the Cf/SiC composites, the UAD has great advantages of improving hole wall quality and reducing cutting force, and it has been widely applied to Cf/SiC manufacturing. This study mainly focuses on the influence of amplitude in UAD on the manufacturing of micro holes in the Cf/SiC. By analyzing the micro-morphology of the hole wall and outlet edge under different amplitude in UAD, the influence of amplitude on the fiber removal mode and material damage mechanism is studied. Meanwhile, the thrust force in CD and UAD is also obtained. The results show that the defects of the hole are reduced with the alteration of the fiber removal mode in UAD. And with the increase of the amplitude, the hole quality is further improved. However, the excessive amplitude leads to the damage of the matrix. The thrust force curve shows a “multi-peak” shape with a regular interval due to the layered structure of Cf/SiC in CD and UAD. Compared with the CD, the thrust force of UAD is reduced by up to 70.1% as the amplitude increases from 3 μm to 9 μm. Furthermore, the hammering effect caused by ultrasonic vibration alleviates the material damage around the outlet edge in UAD. With the increase of amplitude, the matrix damage and the fracture of the fiber around the outlet are alleviated. The fracture feature of the fiber around the outlet is more regular than the CD. Consequently, UAD is a beneficial method for Cf/SiC composites micro-drilling with better hole quality and it plays an important role in the future of Cf/SiC processing.