Assessment of test methods for a cryogenic liquid containment system

Abstract

This paper presents a study demonstrating the selection and use of adhesive joint test methods for the design and validation of an adhesively bonded, foam-composite membrane, cryogenic insulation system for the marine transportation of liquefied natural gas (LNG). The study considered the performance of epoxy and polyurethane adhesives under ambient and sub-zero operating temperatures. Double-lap, sandwich panel and double cantilever beam (DCB) joint tests, essential in “calibrating” the interpretation of finite element analysis (FEA), were performed along with FEA in order to assess the stress states (in-plane, peel and shear stress) in the adhesive layer that, under defined loads and extensions, are comparable with the stress levels in the LNG container under service conditions.The study reinforces the view that the presence of barrier film substrates has a major effect on performance, and that the critical state of stress for the integrity of the flexible composite barrier film (FSB) to rigid composite barrier film (RSB) bond in the cryogenic containment system is the tensile peel stress at the ends of the joint. Sandwich panel tests conducted using the two adhesives indicate that failure tends to occur when the peel stress exceeds the tensile strength of the bulk adhesive with the polyurethane adhesive exhibiting more robust adhesion properties than the epoxy with consequences for future design of LNG containers.