Helium permeability of polymer materials as liners for composite overwrapped pressure vessels

Abstract

Polymers have been identified as replacement materials for metallic liners in composite overwrapped pressure vessels (COPVs) for future space launchers. PEEK, Nylon, and PVDF plastics formed from base powder grades have been permeability tested to determine their susceptibility to the diffusion of helium through flatwise panel cross sections. Permeability, diffusion, and solubility coefficients have been obtained for each material with PVDF and PA11 grades showing the lowest permeability coefficients and hence the best barrier properties to permeation. Crystallinity percentages and internal air void contents in the polymer samples have also been used to assess the differences in permeability between materials with an analysis of void dispersion effects given through X-ray CT scanning techniques. The measured permeability coefficients have been used to assess the ability of all materials tested to act as a functional polymer liner in a standard COPV with final leak rates predicted based on liner thicknesses and weights. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43675.

Permeability of carbon fibre PEEK composites for cryogenic storage tanks of future space launchers

“…All CF-PEEK samples are coded in accordance with their supplier (C for Cytec, S for Suprem and T for Tencate), fibre type (4 for AS4 and 7 for IM7) and manufacturing method (AC for autoclave, P for press and ATP for automated tape placement). For example, in sample C4AC, "C" indicates that the material is supplied by Cytec,"4" indicates the fibre type is AS4, and "AC" indicates the samples were manufactured using the autoclave.…”

“…The weight reduction achievable due to the high specific strength of carbon fibre reinforced polymers (CFRP) has led to their use in cryogenic storage applications in the space industry. Composite overwrapped pressure vessels, which consist of low permeability liners wrapped in CFRP, are currently used to store cryogens such as liquid hydrogen (LH 2 ) and liquid oxygen (LO 2 ) [2][3][4]. The low permeability liner, typically aluminium or titanium, limits the leakage of the cryogen, and the CFRP provides strength and stiffness to the structure.…”

“…Furthermore, they have superior toughness and recyclability. This has lead to research into the application of thermoplastics to cryogenic storage [3][4]. Laser assisted ATP is an out of autoclave manufacturing technique, which involves automated, in-situ placement, and consolidation of CF thermoplastics with laser heating.…”

Gas barrier properties of oxyfluorinated graphene filled polytetrafluoroethylene nanocomposites

“…Hence, the gas permeation properties of PTFE and its copolymers is not as comprehensively studied compared to its well-known thermal and mechanical properties [7]. Gas permeation studies utilising helium as a tracer gas has been effective to measure the gas barrier properties of polymer and composite membranes [8][9][10][11]. Furthermore, there exists a good correlation between helium permeation and the permeation of some other gases like hydrogen, oxygen, and carbon dioxide through polymer membranes [12].…”

Rotational moulding of PEEK polymer liners with carbon fibre/PEEK over tape-placement for space cryogenic fuel tanks

“…Titanium and aluminium have been the preferred liner materials for space applications [11][12][13], with Kevlar and carbon fibre epoxies being employed in the overwrapping of the liner [14]. While COPVs have proved exceptional at storing fuels, their main drawbacks are the associated cost of the metallic liner material and the subsequent liner manufacturing costs [15], with recent research focused on creating new and innovative COPV designs [16][17][18][19][20][21][22][23]. To this end, polymers have been identified as a viable replacement material for metallic liners in future COPV designs due to their light weight characteristics, low permeability properties, and reduced material costs.…”