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Structural Weight Optimisation of a Carbon Fibre Ferry
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The Damen Ferry department is developing a concept of fast ferries (DFFe) built of composite materials. Based on the previous experience in composite shipbuilding of Damen modular waterbuses (DWBu) and Water Taxies the Ferry department tries to utilize the existing experience and use it in production of larger vessels that are capable to develop higher speeds and carry more passengers. The key objective is the weight saving - that results in a lighter and therefore more sustainable craft that consumes less fuel and is capable to carry more payload. The expectations are at least 30 per cent of weight saving comparing to the aluminium version of the craft.

A general structural plan of the vessel is the basis of this thesis. The structural design is as much as possible defined based on the regulations according to classification society Det Norske Veritas. Three global load cases are considered: longitudinal bending, transverse bending and torsional bending. Besides, five local load cases are considered: sea pressure on the hull, impact pressure on the bottom of the hull, wet deck slamming, deck loads and superstructure loads.

Lightweight is one of the important reasons to develop the vessel in composite materials. The material combination of carbon fibre (CF) and vinyl ester (VE) resin is chosen for this vessel. This combination of materials has superior mechanical properties but is considered relatively expensive comparing with glass fibre (GF). The preference is given to CF due to its high strength-to-weight and stiffness-to-weight ratios, which give possibility to obtain the same strength and higher stiffness with lower weight and better mechanical properties than GF. All structural members except the wheelhouse that is not included in this thesis will be sandwich construction because of the much increased strength and stiffness regarding weight. As core material cross-linked PVC will be used. The vessel will be produced with vacuum infusion, which enables relatively fast production and ensures good and consistent material properties. The material properties and safety factors for strength are determined according to Bureau Veritas. Robustness of the laminates is defined by describing minimum laminate thicknesses.

Based on the analytical considerations and design requirements a set of optimisation tools has been developed to optimise various composite structures in order to achieve a lightweight solution for the composite craft. The approach used for the development of the tools is fully analytical and can be called as Simple FEA Approach giving the possibility to mesh the analysed structural members in order to get a full picture of the responses due to the applied loads. The developed tools are relatively easy to handle, yet some knowledge in composite structures is needed in order to be able to give critical judgement upon the design of the craft. The tools can be used not only for the preliminary design of the craft and weight estimation needed for the proposal documents provided to the client but also for later design stages when the final scantlings of the craft are estimated.

The validation of the developed tools and global analysis of the vessel is performed using Siemens NX. A CAD model is created and linked to a Finite Element environment where different load cases can be evaluated. Adjustments of the material definition could be necessary depending on the results of the Finite Element Analysis.

Place, publisher, year, edition, pages
2014. , 96 p.
TRITA-AVE, ISSN 1651-7660 ; 2014:49
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-163696OAI: diva2:801943
Available from: 2015-04-10 Created: 2015-04-10 Last updated: 2016-02-04Bibliographically approved

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