Introduction Objectives Scope of Project Problem Statements

1 CHAPTER 1 INTRODUCTION

1.1 Introduction

Drilling is one of the major machining operations which are currently carried out on fiber-reinforced composite materials. There are typical problems encountered when drilling fiber-reinforced composites. These problems include the delamination of the composites, rapid tool wear, fiber pullout, presence of powdery chip, etc. The delaminating of the composites is generally the main concern. This is so because the occurrence of delamination wil1 reduce the strength against fatigue which result in a poor assembly tolerance, and affect the composite’s structure integrity Delamination usually occurs when the last plies of the material do not withstand to force exacted by the drill bit’s chisel edge. Several authors studied their phenomena and some avoid delaminating by means of controlling the thrust force at breakthrough. Most of the researcher studied the effect of various parameter cutting, peed , feed, depth of cut and machining time on drilling composite but none of the research investigate the effect of tool diameter. This research will dealt with the effect of cutting speed and cutter diameter on drilling composite. 2

1.2 Objectives

The objectives of this experiment are: 1. To study the effects of drilling parameters cutting speed and drill diameter in drilling carbon graphite composite. 2. To analyzed the surface integrity of the material after the machining operation.

1.3 Scope of Project

The scope of this project is to: a Perform the machining operation using drilling machine and high speed steel cutting tool with carbon graphite composite. b To obtain the surface roughness value of the workpiece with different parameter cutting speed and cutter diameter. c To characterize type of defects occurs.

1.4 Problem Statements

The use of fiber-reinforced composite materials in automobile and aerospace industries has grown considerably in recent years because of their unique properties such as high specific stiffness and strength, high damping, good corrosive resistance, and low thermal expansion. Drilling is usually the final operation during the assembly of the structures in these applications. Any defects that lead to the rejection of the parts represent an expensive loss. For example, in the aircraft industry, drilling-associated delaminating accounts for 60 of all part rejections during final assembly of an aircraft. The economic impact of this is significant considering the value associated with the part when it reaches the assembly stage. The quality of the drilled holes such as wavinessroughness of its 3 wall surface, axial straightness, and roundness of the hole cross-section can cause high stresses on the rivet, which will lead to its failure. Stress concentration, delamination, and microcracking associated with machined holes significantly reduce the composites performance. Several hole production processes, including conventional drilling, ultrasonic drilling, laser-beam drilling, water jet drilling, etc., have been proposed for a variety of economic and quality reasons. Conventional drilling is still the most widely used technique in industry today. A major concern that has received considerable attention in drilling holes in FRCM is the delamination, especially at the bottom surface of the workpiece drill exit. The thrust force developed during the drilling process affects the width of the delamination zone. This study is important in order to analyze the performance of HSS twist drill with different speed and drill diameter in drilling with carbon graphite composite. 4 CHAPTER 2 LITERATURE REVIEW

2.1 Introduction