Tension Test Method and Thermal Degrandation of Fatigue Strength for Unidirectional CFRP Ring
Tomohiro NARUSE, Toshio HATTORI, Haruo MIURA and Kazuki TAKAHASHI
Abstract:Fiber reinforced plastic (FRP) rings, reinforced along the hoop direction of the ring are used in high speed rotors and pressure vessels because of their high strength and rigidity and their low density. To confirm the reliability of these products, we must evaluate how they degrade in humidity, sunlight, and under thermal load. Thus, we studied the thermal degrading properties of unidirectional carbon FRP (CFRP) rings. Firstly, we developed an evaluating method of hoop directional strength based on the ring tensile test. During the ring tensile test, hoop stress at the inner surface becomes much larger than mean stress. This distribution is based on its bending force, and the hoop stress distribution is influenced by its thickness and the frictional force between the FRP ring and the cylindrical jig. We measured the tensile strength of CFRP rings by doing the ring tensile test, and also calculated hoop stress distribution using the Finite Element Method along with considering frictional problems. Then, we measured the thermal reduction of fatigue strength of unidirectional CFRP rings by doing the ring tensile test. To evaluate the fatigue strength degrading property, we applied Arrheniusfs equation to confirm the relation between the temperature and the time. Using these evaluating methods we can predict thermal reduction of fatigue strength under the temperature and exposure time. Key Words:FRP, Finite element method, Strength analysis, Fatigue strength, Thermal degradation