Design of the composite sandwich panel of the hot pad for the bonding of large area adhesive films

A light-weight hot pad system for curing large area adhesive films for the secondary barrier of cryogenic cargo containments of Liquefied Natural Gas (LNG) has been developed with a composite sandwich panel. In order to apply uniform pressure to the adhesive on unlevel insulation panels and to obtain an adequate adhesive thickness, a flexible stainless steel foil heater supported by a butyl rubber air pressure bag has been utilized for the lower part of the hot pad system, and a temperature controller provides reliable curing of the adhesive. To decrease the weight of the hot pad system and mitigate heat loss through the pad, the upper part of the hot pad system has been built with a composite sandwich panel composed of glass fiber epoxy composite face, polystyrene (PS) and polyvinyl chloride (PVC) foam cores with low thermal conductivity. Through finite element analysis and experimentation on hot pad systems, a light-weight hot pad system that is able to cure a 0.3 m by 3.5 m area has been developed with an autoclave cure quality.