CRYOGENIC TYPE-V PRESSURE VESSEL DESIGN, MANUFACTURING AND TESTING

Type-V (Linerless) composite pressure vessels, which are frequently used in space applications, have an important place in launch vehicles in terms of weight. For linerless composite vessels, the composite shell should provide strength to the vessel; additionally, it should behave as a liquid and gas permeation barrier under pressure and environmental loads. One of the recent demands for pressure vessels in the space industry, is materials that are adaptable to cryogenic environment. This paper presents details of a low-cost hybrid structured linerless cryogenic composite pressure vessel development study. The study includes the fabrication methodology of the vessel, examining the concept design with hydro and cryogenic tests, and also using the multiscale finite element method. A composite case is composed of glass and carbon layers. The glass layer acts as a non-permeable barrier, and the carbon layer provides strength to the structure. The fabrication methodology for Type-V vessels is based on a liquefiable paraffin mandrel and the wet filament winding method. The paraffin-based mandrel is used with a cold-curing epoxy system, and the liquefaction process is completed in an autoclave with post-curing. The hydro leakage tests proved the structural integrity and non-permeable capability of the linerless pressure vessel for liquids; however, the tank cannot bear thermal loads under cryogenic conditions. The cryogenic thermal load damage is also observed with hydrotesting of the cryogenically tested vessel. Also, a micromechanical strategy with representative volume elements (RVE) has been utilized to understand stress distributions and damage initiation on composite structure as well as the relationship between constituent properties and large-scale (effective) properties of composite materials. All these phases are preliminary parts of the cryogenic Type-V development methodology in mechanical aspects.