Development of the Simplified Evaluation Method for Strength of FW-FRP Pressure Vessels using Ring Burst Tests

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Filament wound (FW)-FRP composites have played an increasing role in engineering components, i.e. fuel gas containers for the compressed natural gas vehicle rocket motor cases and flywheels. It is important subject for the designer concerning composite materials to obtain the accurate material properties of FW-FRP composites. However, the internal pressure tests of actual vessels need a lot of cost and time.From these reasons, the simplified evaluation technique for the strength of FW FRP pressure vessels, Ring Burst Test, was developed in the present study. In the ring burst tests, the tapered rod was inserted into the 12 divided segments, among which the ring type FW FRP specimen was set. It was demonstrated in the previous study that the uniform **op stress was then obtained in the ring specimen. However, since friction forces were subjected between components of testing apparatus, it was difficult to investigate the fracture behavior of FRP specimen under cyclic loading.Therefore, the modification of test apparatus was carried out. The needle bearings were used to decrease the friction force. Finally the fatigue properties of FW FRP specimens were successfully understood in the present study.On the other hand, one of the objects of this study was the expanding of the test ability to the evaluation of residual strength of FW FRP pressure vessels with impact damages. Unfortunately, it was not accomplished sufficiently because of the large degree of plastic deformation of aluminum liner by impact loading. However, another new simplified tests for the residual strength of FW FRP pressure vessels was introduced by using the FW specimens with aluminum pipes as liners. It can be concluded that this is an additional accomplishment of the present study.