Effects of the Number of Fatigue Cycles on the Hoop Tensile Strength of Glass Fiber/Epoxy Composite Pipes

Abstract

Glass fiber-reinforced plastics (GFRPs) composite materials are widely used in many areas due to their superior properties such as high strength, corrosion resistance against many chemicals, duplicate production, the possibility of production in very large dimensions, and lighter weight than metals and alloys. As the use of GFRP pipes increases, many test methods are performed to determine their mechanical properties. Hoop tensile strength of GFRP pipes was determined by hoop tensile strength test according to ASTM D 2290 standard, and fatigue tests of GFRP pipes were carried out by applying internal hydraulic pressure according to ASTM D 2992 standard. In this study, six-layered E-glass epoxy composite pipes which were manufactured by the filament wound method for winding angle ± 55° were subjected to fatigue tests at the different number of cycles, and hoop tensile strength of fatigued pipes was determined. The samples were subjected to a fatigue test at a stress ratio of 0.05 and a frequency of 0.42 Hz according to ASTM D 2992 standard. Fatigue tests were performed on samples with a stress value of 35% static burst pressure. As a result of experiments, the effects of the number of fatigue cycles on the hoop tensile strength of the GFRP pipes were investigated, and the damage occurred in the GFRP pipes was evaluated. The increase in the number of cycles from the fatigue tests applied to the samples resulted in a reduction in the tensile strength of the samples.