Sandwich Structures for Naval Ships: Design and Experience

In Sweden we have a long experience with different types of vehicles and ships in sandwich construction, especially Navy ships such as minesweepers, mine-counter-measure-vessels and corvettes. GRP (Glass fibre Reinforced Plastic) and FRP (Fibre Reinforced Plastics) have been the most common face materials, but metallic materials such as Al-alloys, coated carbon steel and stainless steel have also been used. Core materials have usually been cellular plastic foams of cross-linked PVC (Polyvinyl-chloride), but also extruded PS (Poly-styrene), PUR (Poly-urethane), PEI (Poly-ether-imide) and PMI (Poly-methacryl-imide). Different continuous and discontinuous manufacturing processes have been used. Vacuum assisted infusion has been introduced recently, because it is a closed process, gives high fibre content and a good quality of the laminates. Sandwich design has mainly been used in the transportation area, where lightweight design is needed to give higher performance and load bearing capacity. The use of sandwich construction will give high stiffness- and strength-to weight ratio. This is usually not enough from an economic point of view to justify the introduction of sandwich construction, but other integrated functions must be considered, i.e. insulation, energy consumption, damping, fewer components, lower manufacturing costs, low maintenance, signature effects (military) etc.