Lightweight Thermoplastic Composite Fuel Tanks for Space Applications

C.M. Ó Brádaigh, University of Edinburgh, Edinburgh, Scotland, UK
D.M. Grogan, National University of Ireland, Galway, Ireland
B.R. Murray, National University of Ireland, Galway, Ireland and University College Cork, Cork, Ireland
S.B. Leen, National University of Ireland, Galway, Ireland

Abstract:
Composite overwrapped pressure vessels (COPVs) have become a critical component in the storage of cryogenic fuels aboard rockets, satellites and spacecraft. Recent research has focused on reducing the cost of COPVs by replacing the inner metallic liner with a low cost alternative, or by removing the liner in its entirety. An integrally heated rotational moulding tool has been constructed and used to produce PEEK polymer liners which have been permeability tested using helium gas. PEEK samples have been overwrapped in a laserassisted tape placement (LATP) process with a CF-PEEK tape. Cryogenic cycling of liner-overwrap samples has shown crack resistance over multiple cycles. A combined experimental and numerical approach to the design of linerless CF/PEEK LATP composite cryogenic tanks is also presented. Defect characterisation using 3D X-ray CT scanning, optical microscopy and cryogenic cycling has been undertaken. A novel XFEM cohesive zone methodology is used to predict damage in an internally pressurised cryogenic tank, to define an optimised tank lay-up which is resistant to microcrack formation.