Application of a Sandwich Construction on a Superstructure of a High Speed Ferry

Licentiate thesis, 2007

Usage of light weight materials has gained momentum in the marine market in the last few decades. This rise has lead to some ships using parts fabricated out of materials like glass and carbon fibre. A major advantage of the usage of light weight materials in shipping is that it either increases the cargo carrying capacity of the vessel or reduces the fuel consumption or both. Different kinds of problems and issues need to be addressed when using new and innovative materials. These problems range from issues of both technical and non-technical nature. Technical problems are generally related to structural strength, fire safety and joining materials of different kinds. Non-technical issues would include maintenance and most importantly getting a good idea about the economics and pay back time of using light weight materials. This thesis discusses the possibility of using light weight materials like glass and carbon fibre as a super structure on board the 88 m long Stena Carisma catamaran. Sandwich construction is the recommended method of employing light weight construction. Different concepts have been generated using the spacing of pillars and the materials used. Analytical structural analysis for each concept is performed. The concept that has the lightest weight is further evaluated using the finite element (FE) method. Thus both analytical calculations and FE analyses have been used to confirm the feasibility of having a sandwich superstructure for the vessel. Both static and dynamic analysis are conducted for the study of the superstructure. Classification society regulations are used as the base to do the structural calculations. Considering the various criteria of the society, a structural optimisation is also performed. Based on the results obtained from the analysis performed, it is shown that a conventional aluminium superstructure for such a vessel can be replaced by innovative light weight materials. This replacement would be accompanied by a reduction in the weight of the vessel as well as by reduced maintenance requirement. Thus there is a two fold benefit from application of light weight materials. This work includes the structural analysis of the superstructure made of composite materials and also about the interaction of the two materials namely aluminium and the composites. FE analysis has been done to understand the structural behaviour of the structure. This analysis is carried out in ANSYS.