In this study, the mechanical performance of melamine-urea-formaldehyde (MUF) resin plywood composed of an orthotropic material, which is used as a structural material in liquefied natural gas (LNG) cargo containment systems (CCSs), is evaluated. With a decrease in temperature, the plywood changes from ductile to brittle under compressive loads; thus, it may fail to distribute the compressive loads caused by sloshing impact as well as lose its stiffness, which helps maintain the shape of the structure. However, only a few studies investigated the mechanical characteristics of MUF resin plywood under compressive loads caused by sloshing impact as well as the crack propagation and change in material features with decreasing temperatures. Therefore, the present study investigated the mechanical performance of MUF plywoods of different thicknesses under different temperatures and grain orientation parameters. The results indicate the mechanical properties of MUF plywood for compression with decreasing temperatures. Furthermore, based on thermomechanical analysis, this study shows that the critical temperature at which the plywood material tends to transition from ductile to brittle behavior is − 110 °C. This finding will help in the design of MUF plywood-based LNG CCSs considering its low-temperature brittleness.

Plywood is a laminated wood material where alternating layers are perpendicular to each other. It is used in a liquefied natural gas (LNG) carrier for an insulation system because it has excellent durability, a light weight, and high stiffness. An LNG cargo containment system (LNG CCS) is subjected to loads from gravity, sloshing impact, hydrostatic pressure, and thermal expansion. Shear forces are applied to an LNG CCS locally by these loads. For these reasons, the materials in an LNG CCS must have good mechanical performance. This study evaluated the shear behavior of plywood. This evaluation was conducted from room temperature (25 °C) to cryogenic temperature (-163 °C), which is the actual operating environment of an LNG storage tank. Based on the plywood used in an LNG storage tank, a shear test was conducted on specimens with thicknesses of 9 mm and 12 mm. Analyses were performed on how the temperature and thickness of the plywood affected the shear strength. Regardless of the thickness, the strength increased as the temperature decreased. The 9 mm thick plywood had greater strength than the 12 mm thick specimen, and this tendency became clearer as the temperature decreased.

As novel and innovative design concepts are developed for Arctic commodity transport, relevant ice-structure interaction scenarios and corresponding ice load models will be pivotal for direct design practices and the development of new codes and standards. For example, the parallel midbody region of membrane-type liquid natural gas carriers (LNGC) is comprised of the hull structure and delicate mastic materials, integral to the cargo containment systems (CCS). For Arctic LNGCs, this type of hull geometry can be susceptible to flat-on flat ice impacts. The current ice-structure interaction models which form the basis of classification requirements do not explicitly consider this scenario. However, these impacts can potentially induce a shock response beyond the hull structure and through the CCS which can compromise the integrity of the CCS and may result in loss of cargo or other extreme consequences. Preliminary numerical simulations of ice floe impacts on ice-class LNGC hull structures have shown this type of shock response as a result of flat-on-flat collisions. This paper aims to investigate the nature of flat-on-flat ice collisions and subsequent structural response through controlled physical experiments and further analyzed thought explicit dynamic finite element analysis.

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Arctic and sub-arctic regions of Russia are home to some of the large gas reservoirs, attracting numerous energy development projects. A ship-borne transportation system connecting these potential gas fields to gas terminals in Gulf of Mexico will likely be established. In this case, the integrity and safety of LNG cargo containment systems under impact of the iceberg-ship collision should be carefully considered at conceptual and detailed design phase. The collision impact by an undetected iceberg should be considered to be an accidental load. Thereby, plastic deformations of the hull structure may be accepted provided the LNG will not leak out. Till now, view points of the safety evaluation have been limited to structural hull deformations by the collision. They have not examined effects of vibratory acceleration induced by the impact on the structure of LNG containment systems, even though it seems rather rational in case of substructure such as LNG containment systems in independent type or membrane type LNG carriers. In this paper, the iceberg-ship collision scenario is established based on International Ice Patrol’s reports. The comparative safety assessment of cargo containment systems for independent type (spherical and SPB) and membrane type (Mark-III and NO96) LNG carriers is performed through a computational simulation and the related experimental research works.