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HANSA 01-2017

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Schiffstechnik | Ship

Schiffstechnik | Ship Technology Lightweight ships – not an easy task Composite materials have proven to be a feasible solution for maritime applications – yet not for the construction of vessels. But properties of lightweight components could make a difference in the fierce market. By Felix Selzer Composite materials are used extensively in the aviation and automotive industries, as well as in the oil & gas and wind energy markets. The technology’s adoption rapidly developed during the last 30 years. But the commercial shipping market is still giving the cold shoulder to the technology. Composites typically are a mix of glass or carbon fibres with an epoxy, vinylester or polyester matrix to distribute the load between them. A reason for the shipbuilding industry’s reluctance to adopt the technology can be found in regulation on ship safety, such as the International Maritime Organisation’s (IMO) rules for Safety for Lives at Sea Artwork: Felix Selzer (SOLAS). A main challenge is to reach the required fire retardancy, Julien Sellier, Managing Director of STRUCTeam says. His company supports clients in the development of composite structures across market sectors. »If you tell a captain, that some parts of his ship are made out of plastic, it freaks him out« He explains: »When it comes to hulls and primary structures, the IMO says the material must not be combustible. Composites being formed on an organic basis with the resins are combustible. So you need special approvals, a lot of negotiation with the regulatory and certification bodies, to get it accepted on a case-by-case basis.« SOLAS Regulation II-2/11 requires ship structures to be constructed of steel or other equivalent material, that must not be combustible. According to Sellier there are solutions such as additives, but they come at a cost, and: »You can use composites in some parts that need certification. Everything is negotiable, it depends on how much pain you are willing to go through.« Besides regulation, there seems to be another problem. »There is a lot of misconception and people have a tendency to trust what they have seen and done and to be suspicious about innovations and novelties – especially in the shipping business«, Sellier says. In his opinion, mindset is quite critical for the adoption of composite materials in ship construction. But in certain areas there are still opportunities to use composite materials. To reduce the overall weight of a vessel and save fuel costs, components such as railings, stairs, light columns, davits, deck structures, walkways and balconies could use the technology. In ferries and cruise vessels lighter cabins, bulkheads and superstructure could significantly increase fuel efficiency. Sellier thinks, that this might even make ballast systems obsolete, as the lighter superstructure improves stability. The additional space could be use for storage or extra cabins. Also on cargo vessels there is potential for composites used in topside structures and accommodation blocks. »According to regulation we can only use it in secondary structures. However, if you push it a little bit further, rudders, accommodation modules, hatches or doors could 58 HANSA International Maritime Journal – 154. Jahrgang – 2017 – Nr. 1

Schiffstechnik | Ship Technology straight forwardly be done in composites«, Sellier says. He especially sees great additional benefits in lightweight cargo hatches. A twelve by 15 m hatch would lead to collateral savings in the actuation mechanisms of the hatches because of their lower weight. Composites show further benefits compared to steel or aluminium, when it comes to the strength and stiffness to weight ratio. Values for specific strength, stiffness and fatigue strength are mostly significantly higher than for metal at the same thickness. Compared to steel between 40 and 75% weight savings, compared to aluminium 10 to 35% savings are possible, depending on whether it is glass or carbon. By using a »sandwich« technique with a different material as a core – PVC, PET or Balsa wood –, these benefits can be fully exploited, Sellier explains: »If you take the cargo hatch as an example, with a steel plating of 10 mm, you can either match the stiffness and strength with a single skin of composite, only fibre and matrix with another thickness, or you can achieve good weight savings by using a core that spaces the two skins.« The cored solution is chosen, if the panel is pressure loaded. If the panel is loaded in-plane, a single skin would be the best option. Compared to steel or aluminium material cost for composites is still much higher, especially for carbon fibre reinforced polymer. »But if a part is reproduced a number of times, you can achieve a very cost effective solution«, Sellier is convinced. Another important issue the industry is working on, is recycling. While there are relatively effcient solutions to recycle scrap during the manufacturing process, when it comes to the finished product, the level of maturity is very high, yet. The wind industry is driving the search for recycling processess for the highly durable material mixes. Their properties and longevity are also an advantage, as further savings come from the non-corrosiveness of the material. Maintenance would be very low with no need for anti-corrosion coating. Steel is a well known material for shipyards and engineers. Patching and welding in case of damages can be done in every dock or during the voyage. But what about cracks in a carbon fibre structure? According to the expert, the reparability of the lightweight material is also comparable to that of steel: »Today, all the wind turbine blades are made in composites. Every year you have about 50,000 blades made, the average one weighing between ten and 15 tons. The majority of those are being repaired and maintained on an ongoing basis in the field.« Doing such repairs would require trained personnel. Instead welding, knowledge of bonding and glueing would be necessary. »It is more a dedication rather than a feasibility issue« »You can do repairs that match and exceed the initial strength. It requires a bit of knowledge, but it is fairly straightforward«, Sellier says. An opportunity for the shipping industry is that the wind energy sector has already established a supply chain and trained people all over the world. Besides regulation and mindset, money plays an important role, of course. While the cruise industry witnesses a boom, cargo shipping still suffers from overcapacity and a slow global economy. At low earnings, there is little willingness to invest in expensive new technology. The low oil and bunker prices are a small comfort for operators. For the development of new technologies or new fuels such as liquefied natural gas, it is believed to be another hurdle. A rising oil price could be an incentive for the end users to think about new materials, that reduce operational costs, Sellier thinks. But making the carbon fibres is quite energy intensive, so if the oil price goes up, that could also affect the raw material prices. »Also bisphenol A, which is the base for epoxy resins, is derived from oil. But even if the oil price would double, the raw materials would not double in cost«, he says. Notwithstanding all the diffculties and concerns that make it hard for the »new« technology to get a foothold in the commercial marine sector, Sellier is convinced of the benefits and opportunities: »It is evident now, that composites work. They started to be used widely in the 80s and 90s. So there are now a few decades of use and good feedback and experience from a number of applications.« M Instandhaltung aller Schiffshaupt - und Hilfsdiesel-Motoren bis 7.000 kW Motoren- und Ersatzteile im Tausch Service für Abgasturbolader und Einspritzpumpen Mechanische Bearbeitung und Fertigung August Storm GmbH & Co. KG · August-Storm-Straße 6 · 48480 Spelle Fon +49 5977 73-0 · Fax +49 5977 73-138 · HANSA International Maritime Journal – 154. Jahrgang – 2017 – Nr. 1 59

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