SURFACE ROUGHNESS ANALYSIS IN DRILLING OF GFRP COMPOSITES BY TUNGSTEN CARBIDE TOOL

Abstract

Nonlaminated composites having superior mechanical properties than laminated composites is widely used in ballistic applications. Since literature on the machinability of nonlaminated composites is scarce, an investigation was carried out to study the hole quality in drilling thick nonlaminated Glass Fiber Reinforced Plastic (GFRP) composite rods using coated tungsten carbide twist drill. The GFRP composite rods were made by pultrusion method with high fiber weight fraction. The surface roughness of the drilled holes was measured using surface roughness tester. Taguchi’s orthogonal array and analysis of variance (ANOVA) were employed to study the influence of process parameters such as feed and spindle speed on surface roughness. The optimum level of process parameters towards minimum surface roughness of the drilled hole walls was obtained to achieve defect controlled drilling of pultruded GFRP composite rods. Correlation for surface roughness with process parameters was established using a statistical software MINITAB 16. The influence of feed and speed on surface roughness was insignificant. The optimal process parameter levels within the range examined was identified as 0.15 mm/rev feed and 750 rpm speed for drilling pultruded GFRP composite rods using 10 mm diameter twist drill. The influence of process parameters on hole quality in nonlaminated composite rods differs with drill geometry and also differs from the influence of process parameters on hole quality in laminated composites.