Badania kompozytowych butli wysokociśnieniowych w podwyższonych temperaturach

Przedstawiono metodykę badań ciśnieniowych butli na podstawie dostępnych standardów oraz opis testów zmęczeniowych z wynikami badań w podwyższonych temperaturach i wilgotności. Omówiono wybrane standardy ze szczególnym uwzględnieniem wymogów dotyczących materiałów kompozytowych stosowanych do budowy butli. Scharakteryzowano również laboratorium badań butli znajdujące się na PWr. W pracy badano partię wysokociśnieniowych butli hybrydowych (włókno szklane i węglowe) przeznaczonych do magazynowania paliwa CNG w pojazdach. Były to butle typu 4 o objętości wodnej 40 litrów. Podwyższona temperatura (do 100°C) i wilgotność (95%) w czasie badań zmęczeniowych kilkakrotnie obniżają wytrzymałość zmęczeniową zbiorników. Należy także podkreślić nagły charakter zniszczenia zbiorników typu 4 w czasie badań zmęczeniowych, niespotykany przy badaniach zbiorników metalowych lub z linerem metalowym. Także miejsce zniszczenia w czasie badań zmęczeniowych i niszczących może być inne, np. dennica i część walcowa.

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This work presents methodology of hydrostatic pressure tests and pressure cycling tests based on available regulations. The selected tests procedures and obtained results at increased temperatures are described. Besides selected regulations especially concerning composite materials applied for vessels manufacturing are discussed. Moreover laboratory of high pressure vessels at Wroclaw University of Technology is presented. Hydraulic test setup as well as applied in laboratory test procedures are characterised. In the work a batch of high pressure composite hybrid vessels (glass fibre + carbon fibre) designed for CNG storage in automotive application was tested. These vessels were so called type 4 with 40 litters water-capacity. At the first step hydrostatic pressure burst test of three tanks were realised. The fuel tanks were filled with a working fluid (degassed water) and the pressure was gradually increased with pressurisation rate of 5 bar/s until 470 bars. Next after 5 seconds hold the test was continued until burst occurred. The defect was localised at the vessel dome. The second step was cycling tests. Two vessels were cycled in a pressure range between 20 and 260 bars. The working medium was hydraulic oil which temperature was maintained between 40-46°C. A cycling rate was about 7 cycles per minute. Tested vessels stand for 14.500 cycles (first vessel) and 16.200 cycles (second one). Similarly like in burst test the defect was localised at the vessels domes. The third step of tests includes hold at a temperature of 100°C and pressure of 260 bars for 200 hours. After this test the same tank was put into the cycling test at ambient temperature. The vessel stands for 3.300 cycles and burst at the dome area. The fourth step were cycling test of two vessels at extreme temperature. During the test vessels were spayed with a hot water (60°C). Tested vessels stand for 2.800 and 3.200 cycles, but both of them burst at the domes. An increased temperature (up to 100°C) and humidity (95%) during the cycling test few times decrease fatigue strength of vessel. It is worth to underline the damage in form of burst during type 4. cylinders cycling test, which is unusual for vessels with metallic liner. Also the defect location during the cycling and burst test can be different.