The effects of back-up on drilling machinability of filament wound GFRP composite pipes: Mechanical characterization and drilling tests

Abstract

Composite structures used in many engineering fields are produced using different production methods according to the design characteristic. The filament winding (FW) method, one of the most important of these production techniques, is preferred in the manufacturing of high-pressure vessels, pressure pipelines, and construction components. Composite pipes produced by the FW method are assembled using various processing methods depending on their usage. Drilling is one of the most used method among these processing techniques. The drilling-induced damages negatively affect the mechanical properties of the composite pipes during service. Therefore, it is important to determine the optimum cutting parameters and a suitable back-up material so that minimal damage occurs during the drilling process. In this study, firstly, mechanical properties of the glass fiber reinforced polymer (GFRP) produced by the FW method at ± 55° configuration were determined and damage characteristic based on ring tensile test was analyzed. Then, the effects of back-up use on the drilling machinability of FW GFRP pipes were investigated. Results showed that back-up use in drilling composite pipes plays a key role in reducing delamination, borehole damages, and surface roughness although it leads to occur higher thrust forces. Also, it helps prevent the propagation of interlaminar cracks around the hole. • Back-up use slightly increase the thrust force in drilling of FW GFRP pipes. • In drilling without using back-up, more severe delamination damages occur in the area close to the hole edges owing to intralaminar and interlaminar cracks. • Damage modes were intralaminar cracks, fiber breakages, uncut fibers, and debonding. • Back-up use improves surface quality in drilling FW GFRP pipes.