The main objective of the present study is to investigate the performance degradation of the plywood
used in a liquefied natural gas (LNG) cargo containment system (CCS). A plywood sheet features an
odd number of thinly layered wooden plies bonded perpendicularly to the previous layer to give it a very
strong and durable structure. Owing to this strong point, plywood is applied to a variety of interior and
exterior applications. Above all, it is widely adopted as insulation panels in an LNG CCS owing to a high
stiffness with low density and its superior mechanical capabilities. As an insulation material of an LNG
CCS, plywood is constantly exposed to repeated wave-induced thermal variations caused by the loading
(163 C) and unloading (20 C) of LNG during general operating periods of 25 years on average.
Therefore, the effects of cryogenic-level thermal loads on the material characteristics of plywood must
be analyzed with respect to the design and safety aspects of LNG CCSs. In the present study, the influences
of the estimated thermal load, testing temperature, and grain orientation on plywood adopted in an LNG
CCS are investigated. In terms of safety and design, the repeated thermal loads in a LNG CCS must be considered
because the modulus of elasticity (MOE), tensile strength (TS), and modulus of rupture (MOR) are
degraded by thermal treatments, such as cyclic thermal-shock and cryogenic immersion.