For a long time there’s been a buzz about using lightweight composites in shipbuilding. But in recent years, development has stalled, mainly because fire safety could not be guaranteed. New research will speed it up again.
There are great benefits to lightweight composites. They reduce fuel consumption, save the environment and last longer. Nevertheless, the use of fiber composites in ship structures has been limited, primarily due to one thing - it's low fire resistance.
“Steel doesn’t burn. And steel is the predominant shipbuilding material on which all rules are based”, says Peter Sjögren, a researcher at RISE and project leader of the pre-study Composites for sustainable shipping, which is done within the Swedish Transport Administration's industry program Sustainable Shipping, which Lighthouse runs.
What he is talking about applies to larger ships. Smaller vessels that runs close to the coast are covered by other rules and Styrsöbolaget's composite ferries Valö and Rivö operate, for example, the Gothenburg archipelago. However, those who want to build a Stena Ferry will have problems with the regulations, especially with the IMO's international maritime safety treaty SOLAS. However, the IMO's new function-based rules allow alternative composite solutions provided that safety is not compromised.
"The ambition of the pre-study is to produce a number of type constructions that are relevant to the industry with proposals that these should be pre-approved for composites. Shipowners should know this already when they order a ship. That is not the case today. Ship orders are often sent directly to an aluminum shipyard because it’s not certain that composite constructions will be approved."
Another challenge when it comes to composites is the production technology that the material requires.
“It is generally easier to build in steel or aluminum because they are possible to weld. Therefore, we also look at how the aviation industry and others do when they manufacture composite constructions in larger series”
A third problem area concerns the sound-absorbing ability of composites, a fourth takes a look at lightweight and electrification, and a fifth theme concerns circulation and recycling problems.
"Let's say that we can build very large ships in composite. What happens to them in the future when they are to be scrapped?
Building large ships in composite is not an impossibility and Peter Sjögren and his colleagues aim is to raise an awareness of how it works in practice.
“Composites are demonstrably cheaper to operate than steel. It's a bit like electric cars. A composite vessel is more expensive to buy, but has significantly lower repair costs, which makes it cheaper overall. The thing is to get shipowners comfortable with this.”
The Pre-study Composites for sustainable shipping is ongoing throughout the year and is being carried out by researchers at RISE and Chalmers in collaboration with Saab Kockums, Swede Ship Marine, the Swedish Coast Guard and the Swedish Defense Materials Agency.