Papers by Author: Sang Wuk Park

Abstract: Nowadays, researches for replacing material systems for cryogenic propellant tanks by composites have been being performed for the purpose of light weight of a launch vehicle. In this paper, a type III propellant tank, which is composed of the composite developed for cryogenic use and an aluminum liner, was fabricated and tested considering actual operating environment, that is, cryogenic temperature and pressure. For this aim, liquid nitrogen (LN2) was injected into the fabricated tank and in turn, gaseous nitrogen (GN2) was used for pressurization. During this test procedure, strains and temperatures on the tank surface were measured. ESG (electric strain gage) and thermocouple were used for the measurement of strain and temperature, respectively. Delamination between hoop layer and helical one, was detected during the experiment. Finally, Tsai-Wu criterion for the tank and microscopy for the composite/aluminum ring specimen were carried out to investigate the reason why delamination had happened.

Abstract: Composite pressure tanks are rapidly expanding in their range of use. However, for high pressure flammable or toxic gases, there is less confidence about their reliability. In this study, fiber Bragg grating (FBG) sensors embedded into a composite pressure tank monitored strain and detected damage. The sensor heads and fiber optic lines were protected with an acrylate recoating, adhesive films, PVC tubes and Teflon
film to survive under the harsh environment of the filament winding process. During the quasi-static loading test, the internal strain was measured with embedded FBG sensor arrays. In order to detect damage occurred during the test, impacts were applied on three different positions in each side by an impact hammer. The difference between damaged and undamaged sides in impact response was analyzed. An interrogation system using a wavelength-swept fiber laser (WSFL) was used for measuring strain, and an erbium-doped fiber amplifier (EDFA) laser source with a tunable Fabry-Perot filter was used for measuring impact response.