IMPROVING CRYOGENIC MAXIMUM STRAIN OF POLYMERS VIA ROOM TEMPERATURE PLASTIC DEFORMATION

Francis Dunne

doi:10.7273/000006587

Hydrogen is the only combustible fuel that can be cleanly utilized without implementing secondary systems to trap and store harmful byproducts such as CO2, CO, or NOx. Private industry, governments, and research institutions are collaborating to implement hydrogen into the energy sector. One challenge of utilizing hydrogen is its low volumetric energy density. To overcome low energy density, it is common practice for hydrogen to be compressed to 700 Bar or liquified. Liquified hydrogen is the highest energy density form of hydrogen, however, liquifying hydrogen requires cooling gaseous hydrogen to 20K (-423 °F) at atmospheric pressure. Cryogenic environments cause exponential changes in materials’ thermal, electrical, and mechanical properties, which make engineering systems compatible with liquid hydrogen (LH2) expensive and reduces reliability. Liquid hydrogen storage is a critical challenge that must be addressed to enable current and future LH2 vehicles. The research in this dissertation focuses on polymeric origami bladders, which can reduce several of the primary storage challenges of LH2. Chapter 2 is a literature review covering two important overarching themes for this work. First, a review of state-of-the-art LH2 storage technologies is provided, including historical attempts at LH2 bladders. Next, a review of low-temperature properties and physics of polymeric materials is provided, which is relevant to the thermoplastic bladders developed by NASA in the 1960s and the polycarbonate origami bladders presented in this dissertation. Key milestones of the experimental work conducted during the development of the origami bladders are presented in Chapter 3. First, the initial demonstration of small-scale hand-folded origami bellows is described. A vacuum-forming manufacturing procedure is provided, which enables the production of single-body origami bladders with only one open face remaining at the bottom of the structure. Next, expulsion experiments were conducted using a borosilicate test cell capable of collapsing the origami structure by applying pressure gradients to the bladder while monitoring expulsion flow rates. The expulsion rates out of the bladder using liquid nitrogen are reported as a function of time, as well as the relationship between the applied pressure and the flow rate out of the bladder. Finally, a hypothesis for the effects of crazing on PC at cryogenic temperatures is presented, followed by tension tests of plastically deformed PC specimens.

IMPROVING CRYOGENIC MAXIMUM STRAIN OF POLYMERS VIA ROOM TEMPERATURE PLASTIC DEFORMATION

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