Drilling Characteristics of Multiple Fiber Reinforced Polymer Composites

Abstract

Drilling is one of the most used machining processes for creating holes in composite materials. However, unlike conventional materials, drilling fiber-reinforced polymer (FRP) composites poses greater challenges due to their heterogeneous and anisotropic nature. In this study, flax-epoxy composites with and without steel wire mesh reinforcement are fabricated and tested using a Taguchi L9 orthogonal array. The effects of spindle speed, feed rate and drill diameter on thrust force, torque and delamination are analyzed using the Taguchi method. ANOVA results indicated that drill diameter has the greatest influence on thrust force and torque, while feed rate significantly impacts the delamination. Regression models are developed for predictive analysis, achieving accuracy levels above 92%, demonstrating high reliability. Additionally, chip formation mechanisms are examined and the morphology of drilled holes is analyzed to identify chip types and understand the underlying causes of delamination, including fiber pull-out, matrix cracking and thermal damage in the drilling zone.