Process Optimization in Hole Machining of Glass-Fiber Reinforced Polymer Composite

ABSTRACT: As Fiber Reinforced Polymer composites (FRPC) in the defense, space and aerospace industries have enjoyed a steady upward trend in usage in recent years, the importance of their machining processes have inevitably been brought to the foreground.Our knowledge of machining FPRC does not seem to be yet fully developed to be applied in its copious fields of applications. As a result, material properties and theoretical mechanics are of great significance in the relevant field of research. Cost effectiveness in production techniques is important to obtain manufacturing cycles which are completely automated and large-scale. There is a need for a certain degree of machining FPRCs to be performed to achieve close fits and tolerances and to get to near-net shape, even though they are normally molded. Unfortunately, as they are anisotropic and non-homogeneous, more often than not, FPRCs encounter serious problems while being machined such as fiber pull-out, delamination, burning and the like. This issue is the significant and dividing difference between machining composite materials and other commonly used metals and their alloys. Because of different mechanical behavior, hole-machining in glass fiber reinforced polymer composite (GFRPC) is substantially different from that in metallic materials. The drilling of this material may generate delamination of drilled holes on work piece. The purpose of this thesis is to investigate the influence of the cutting parameters, such as rotational speed of spindle and feed rate, on delamination and surface quality of holes in GFRPC and material strength after machining. The said effect of parameter variation was studied for two machining processes namely, milling and drilling. A comprehensive test plan was prepared using a robust design of experiments method, called D-optimal method (a statistical technique). It was found that end milling is better than drilling process to machine holes. Further, in order to control surface quality and delamination, the ratio of rotational speed to feed rate needs to be set around 1. Moreover, in the applications where strength of machined components is an important factor, the processing should be carried out with intermediate values of parameters (i.e., rotational speed= 4100rpm and feed rate= 3100mm/min). Finally, an empirical formula was developed. This formula is deemed to serve as guideline to choose optimal parameters and process in order to produce good quality holes in GFRPCs. Keywords: GFRPC, Drilling, Milling, Composite, ANOVA. …………………………………………………………………………………………………………………………