Effect of Cutting Environments on Drilling Induced Damage in GFRP Nanocomposites

Abstract

Drilling is most commonly used secondary machining process for structural joining of Glass Fiber Reinforced Plastic (GFRP) composites. Performing drilling operations on GFRPs/Multi-Walled CarbonNanoTubes (MWCNTs) reinforced GFRPs is really a challenging task due to their non-homogeneity and anisotropic behavior, which directs to generation of material damages. The prime focus of current work is to identify the suitable process parameters for enhancing the performance of drilling of GFRP nanocomposites. In this study, the drilling experiments are conducted on 0.3wt.% MWCNT-GFRP nanocomposites with solid carbide, TiCN and TiAlN coated drills (6mm diameter) under dry and chilled air cutting environments. The dry drilling experiments are conducted without any assistance of cooling fluid in ambient condition. The chilled air at a temperature of 3°C was supplied from the vortex tube. Experimental data is used for ANOVA (balanced) analysis. The cutting parameters such as feed rate, cutting speed and tool type (coating) are considered as input and the measured thrust force, delamination factor and AE RMS signal are treated as output responses. From ANOVA results, it is observed that the influence of feed rate is more on thrust force as compared to cutting speed. The coefficients of determination (R2) shows good fit between thrust force and cutting parameters and the corresponding confidence levels are above 98% for all cutting environments. Similarly, R2 values of delamination factor and AE RMS signals are above 90% and 96% respectively. The minimum thrust force and torque values are noted as 12.61 N and 0.152 N-m respectively at lower feed rate (10 mm/min) and higher cutting speed (1500 RPM) using TiCN coated drill under chilled air cutting environment. The delamination factor is also low (1.025) under the same cutting conditions of minimum cutting forces. A good correlation exists between the thrust force vs. delamination factor (> 0.85) and the delamination factor vs. AE RMS signal (> 0.80) for the selected cutting environments. The recommended range of RMS voltage is 0.083 to 0.121 volts for producing the delamination free holes on GFRP nanocomposites.