Cryogenic rolling shear characteristics of birch plywood for LNG cargo containment systems

Abstract

Birch plywood is widely used as a reinforcement material in the insulation panels of liquefied natural gas (LNG) cargo containment systems (CCS) to protect polyurethane foam (PUF) insulation from mechanical damage. The plywood must endure inplane shear stresses generated by sloshing impacts, thermal contraction, and loads transferred through mastic ropes and anchoring plates. In this study, a cryogenic rolling shear test apparatus was designed to evaluate the in-plane shear properties of birch plywood under cryogenic conditions, focusing on the effect of panel thickness. Test results indicated that 12 mm thick plywood exhibited lower in-plane shear strength than 9 mm thick plywood. Furthermore, cryogenic conditions increased the in-plane shear strength of the 9 mm panels but reduced that of the 12 mm panels. The 9 mm plywood also showed pronounced anisotropic behavior depending on the grain orientation of the outer veneer layers, whereas this anisotropy diminished in the 12 mm panels.