In-situ temperature monitoring during rotary ultrasonic-assisted drilling of fiber-reinforced composites

Abstract

Drilling polyetherimide composite is difficult due to the anisotropic and inhomogeneous structure of fiber and matrix. Drilling of fiber-reinforced composites is a thermo-mechanical friction procedure required in various aerospace and automotive applications. The major reason for component rejection during manufacturing processes is due to thermal damage and temperature elevation defects such as delamination and fiber pullout caused during drilling. This work aims to propose a rotary ultrasonic-assisted drilling technique for composite materials to reduce thermal damage using diamond-impregnated tools. The influence of drilling parameters such as rotational speed, feed rate, abrasive grit size, and ultrasonic power was monitored on temperature elevations. The temperature was monitored using thermocouples located at different distances of 1.0, 2.0, and 3.0 mm from the main drilled hole. The response surface methodology was used for the design of experiments during the drilling of composite material and optimization of process parameters was carried out using analysis of variance. Rotational speed and abrasive grit size were observed to have the highest contribution of 42% and 37% for temperature elevations respectively. It was witnessed that temperature increases with an increase in rotational speed, feedrate, and abrasive grit size. Increasing the ultrasonic power during drilling temperature can be minimized. The temperature elevations at the tool-composite interface can be reduced by leveraging the application of rotary ultrasonic-assisted drilling.