Cumulative damage of hollow glass microsphere weight fraction in polyurethane foam in response to cryogenic temperatures and repeated impact loading

Abstract

The sloshing impact load of liquefied natural gas (LNG) carriers is an important issue that can cause failure of the insulation system of LNG cargo containment systems, leading to cryogenic leakage from the hull of the ship and generation of boil-off gas. Thus, insulation systems should be designed by considering the repeated impact loading based on the design life as well as the cryogenic temperature. Polyurethane foam (PUF), epoxy resin, and plywood are acceptable materials that can be used to fabricate a typical insulation system to protect the load from the environment. In this study, we investigated the effect of adding hollow glass microspheres (HGMs) to the epoxy resin on the reinforcement of the insulation material. Specimens were fabricated using PUF, plywood, and an HGM/epoxy composite matrix with varying weight fractions of embedded HGM (0, 10, and 20 wt.%). The sloshing impact loads were estimated by the statistical method of the Weibull model, and the top 2% level of the Weibull distribution was selected. The calculated sloshing impact load was 3 J as calculated from the experimental results, and then repeated impact loadings under ambient (290 K) and cryogenic temperature (110 K) were realized in a drop tower facility. To obtain details of the dynamic behavior, microstructural analyses were performed using scanning electron microscopy (to detect the agglomeration of HGM embedded in the epoxy resin). Experimental results show that 10 wt.% HGM showed the best performance in absorption and dynamic behavior. The 10 wt.% HGM specimen also exhibited superior thermal conductivity.