Parametric study on drilling of GFRP composite pipe produced by filament winding process in different backup condition

Generally, there is a need for machining to complete the process of manufacturing and assembling composite pipes. One of the principal processes of composite machining is drilling. In this process, the mechanical strength of the composite pipes is reduced by the delamination. In this paper, the effect of drilling parameters such as spindle speed, feed rate, diameter and drill geometry on the thrust force and the delamination factor for the composite pipes produced by the filament winding process are investigated in a without backup state. Then, sample parameters which have the minimum and maximum delamination area are selected and these pipes are drilled in ice supported condition based on the selected parameters, by analyzing the results and determining the size of the delamination area. Then the drilled specimens are loaded under pressure test and their residual compressive strength is obtained. The results show that, thrust force variations and delamination factor decreasing is because of choosing twist drill and reducing feed rate, increasing spindle speed and drill diameter. Also by using ice as a backup, the delamination factor in the twist and brad point drills decreases significantly and the residual compressive strength of the drilled pipes increases meaningfully.