Determination of Optimum Process Parameters for Cutting Hole in a Randomly-oriented Glass Fiber Reinforced Epoxy Composite by Milling Process: Maximization of Surface Quality and Cut-hole Strength

The epoxy based randomly-oriented glass fiber reinforced polymer (GFRP) composites are used to construct structures intended to support multi-directional loading. Due to random orientation of the fibers, cutting of high quality hole is a difficult task in such composites. In the present study, a composite with 60% glass and 40% epoxy (by volume fraction) was fabricated by hand lay-up. To begin with, the performance of two machining processes, namely twist-drilling and end-milling, was compared to cut hole in the composite. It was found that the milling performed better than the drilling process. Later, a design of experiments following the response surface methodology was conducted to determine the effect of milling parameters (i.e., feed rate and speed) on the surface quality and cut-hole strength of composite. The results showed that the parameter-response relationship was not straight rather the parametric effects were interactive and complex. Further, the relative value of speed and feed rate was observed to have controlling influence on the process performance. To predict the process performance for a given set of conditions, empirical models were proposed. Finally, the optimal parameters minimizing the surface roughness and maximizing the tensile strength, employing desirability function approach, was carried out so as to provide guidelines to the users.