Lightweigting in maritime applicatiions

Lightweighting has been de rigeur in most forms of transportation for a long time now, but maritime has been one exception. Until now.

In comparison to planes, trains and automobiles, the maritime industry tends to be a little more resistant to change. The enormous investments required, the long lead times, and the many centuries of peril on the open seas, all add up to a sector that is risk averse and which relies on materials and methods that have got the job done in the past.

But the maritime industry is now also under more pressure than ever before to expedite change. Shipping is responsible for 90 per cent of global trade and a consequent 3 per cent of global CO2 emissions. The International Maritime Organisation (IMO) has targeted a 50 per cent reduction in emissions by 2050, but with petroleum-free shipping all but a distant dream, alternative solutions to reduce the environmental impact of the sector are essential.

At the forefront of one pathway is RAMSSES (Realisation and Demonstration of Advanced Material Solutions for Sustainable and Efficient Ships), an EU Horizon 2020-funded project featuring 36 industrial and academic partners from across Europe. Running since June 2017, it is now approaching the end of its four-year span, with many of the individual components coming to fruition.

RAMSSES is broken down into 13 different clusters, ranging from the development and application of new composite materials, to advanced manufacturing methods for tried and tested materials such as steel. The underlying theme is that all technologies being explored have a sustainability angle, with lightweighting the most prevalent feature, but other environmental benefits also coming into play.

“We have industry partners that are involved in the production and construction of more or less all kinds of ships,” said Matthias Krause, an engineer and researcher at Hamburg’s Centre of Maritime Technologies (CMT), one of the RAMSSES project coordinators.

“Really small work boats and leisure boats all the way up to the largest cruise ships that are built. When you start off thinking about reducing the weight of such different vessels, you need to think of different approaches.”

From the outset, one of the project’s biggest concerns has been certification and type-approval. The IMO’s safety framework is based on traditional, steel-based shipbuilding, reflecting an industry that has not fundamentally changed in the

70 odd years since the maritime body was formed. Introducing composites on any sort of scale presents challenges for this framework, not only with regard to structural integrity, but also around issues such as flammability.

“When it comes to new materials, it gets difficult, because there are no such rules in place and you have to demonstrate that you are able to achieve an equivalent level of safety compared to the conventional solutions,” Krause explained.

“That makes things difficult, because you have to negotiate with the classification societies and you have to undergo tests, first on the materials you want to use and then on the structures. It’s a long process and it’s costly, and in the beginning you don’t even know if you will achieve approval in the end.”

A dialogue with the IMO on the use of fibre-reinforced materials has been ongoing, with the organisation issuing guidelines around the time RAMSSES kicked off in 2017. As with many things in the shipping industry – particularly around standards and safety – progress is necessarily slow, and in this instance hampered even further by the COVID pandemic. But Krause is confident that things are moving in the right direction.

“We don’t have the power to make new rules, but we can make suggestions,” he said.

“We’ve proposed a concept for a ‘smart track’ to approval, to improve the capabilities for putting materials innovation in place in the maritime industry.”

Of the 13 innovation ‘clusters’ that RAMSSES covers, 10 involve composites in some shape or form. One of the flagship projects - and perhaps the most ambitious - was the creation of a 6m tall section of hull made from composite material, using a one-shot vertical infusion technique. Production required not only experimental manufacturing methods, but also completely novel materials in the form a new resin, developed specifically for the task.

“It’s the first time this vacuum infusion process has been used like this, which allows us to produce very large ship sections in one shot,” said Krause.

“[Dutch shipyard] Damen teamed up with a couple of partners, some of them from the aeronautic industry (Airborne UK), some from the chemicals industry, that is Evonik from Germany. They developed the resin which has the ability to cover this 6m height in the vacuum infusion process, because with conventional resins it is not possible to produce structures this high.”

With a 24 per cent weight saving and an estimated 25 per cent reduction in environmental footprint versus steel, the composite hull begins to make the IMO 2050 targets look a little more attainable, particularly if it could be coupled with advances in greener propulsion.

Mercifully, not all of the RAMSSES projects have relied on the creation of entirely new materials. Another headline-grabbing component developed under the programme was a propeller blade built from that old shipyard favourite, steel, but using a method more befitting a 21st century R&D project. The 2m demonstrator blade was made using wire arc additive manufacturing (WAAM), layer upon layer of melted steel gradually deposited to create a hollow structure that not only reduces weight, but which also brings additional environmental and performance benefits.

“That is being developed by colleagues from another group in France,” said Krause. “The hollow structure allows blades to be produced with a larger volume, which is beneficial when it comes to cavitation problems, and the propeller can operate at higher speeds without causing these cavitation issues. Cavitation means vibration and noise, so avoiding this has benefits for the environment, and if you think about naval vessels, for obvious reasons, it’s also beneficial.”

With the RAMSSES drawing to a close later this year, the logical question is when we might see some of these technologies adopted by the industry at large.

“In some areas it’s already taking place, especially if you look at electrification,” said Krause. “Batteries are so heavy, you have to compensate…each kilogram you can save there is really helping you.”