Domestic Gas Cylinders Manufactured by Using a Composite Hybrid Steel Glass Reinforced Thermoplastic Matrix Solution

Abstract

The use of polymer composites allows effectively minimizing the weight, improving aesthetics, promoting handling, and also increasing the vessels mechanical, impact, and corrosion behavior [1]. Since filament winding technique appeared in late 1950s as very suitable production process to manufacture rotationally advanced structures [2–7], such as rocket engine cases, an extensive work has been carried out on the development of new processing possibilities. The improvements occurred until the 1980s as consequence of the computer evolution, give finally birth to the modern polar and multi-axle CNC-controlled filament winding machines that are easily integrated in CAD/CAM environments and allow process almost all exotic shapes with very high accurate fiber placement, speed, and quality control [8]. In this work, continuous glass/polypropylene (GF/PP) commingled fiber tapes were employed to produce wrapped pressure gas vessels for domestic applications by using filament winding. The vessel structural-wall was built using a hybrid solution consisting in a very thin steel liner over wrapped by the filament wounded GF/PP commingled fiber tape layers. FEM analysis was used to evaluate if the composite gas pressure vessel based on the hybrid solution (steel liner plus glass fiber reinforced thermoplastic) is capable to withstand the following pressure requirements: the metallic liner, alone, a minimum burst pressure of 4MPa and whole hybrid composite vessel minima internal test and burst pressures of 3MPa and 6.75 MPa, respectively. Finally, gas pressure vessel prototypes manufactured in industrial conditions were submitted to burst pressure and electrostatic tests to prove that they accomplish all European standard strength requirements. The electrostatic tests were made to evaluate the risk of dangerous electrostatic discharges occurring in the worst service conditions described in the Annex C of the EN 13463-1 standard [9]. Two types of electrostatic discharge risks were evaluated: i) possibility of the brush discharge occur from the external non-conductive surface of the composite cylinders due to the accumulation of electrical charges generated in service by rubbing or contact of the cylinder with a high voltage power supply, and ii) possibility of the brush discharge occur through the gas cylinder metallic conductive filling valve due to the accumulation of electrical charges on the internal steel liner as result from the normal service cylinder shaking.