Prediction of Thrust Force and Torque in Drilling of Glass Fiber Reinforced Plastic Using Mechanistic Force Model Approach

Abstract

High strength to weight ratio along with non-corrosive characteristics make glass fiber reinforced plastics (GFRPs) most promising material in aerospace, navel, automobile and construction sector. However its non-homogeneous and anisotropic nature leads to unfavorable hole quality when subjected to drilling. Among all the drilling induced defects delamination has received considerable attention. Delamination of the material at drill entry occurs above critical torque where as it occurs above critical thrust force at drill exit which adversely affect product quality and results into rejection. Paper presents, a mechanistic approach to develop cutting force models to predict thrust force and torque in GFRP drilling. The mechanistic approach exploits different set of fundamentals of the process including speed, feed rate and tool geometry. Tool point angle, diameter and primary cutting edge effects are mainly considered in this model to predict thrust forces and torque for cutting speed and feed rate combinations. Drilling experiments were conducted on unidirectional glass fiber with stacking sequence of (0/90) sheet with carbide drill to study the influence of various combinations of speed and feed on thrust force and torque. Proposed model is validated for the drill point angle, drill diameter and primary cutting edge of drill bit for GFRP drilling over a wide range of machining conditions.