They reduce fuel consumption and last a long time. Even so, the use of fiber composites in ship structures is limited, largely due to their combustible nature. However, a new pre-study from Lighthouse and the Swedish Transport Agency has given new fuel to the clearing of the obstacles that stand in the way of the composites.
In the early 2000s, the Swedish Armed Forces launched their first Visby corvettes. Since then, it has thus been possible to manufacture large composite ships with good strength and seaworthiness with low maintenance requirements. Despite this, development came to a standstill, above all because fire safety could not be guaranteed.
“Lightweight materials are used today on smaller ships that go close to the coast, but with larger ships, for example cruise ships, there are problems because they are subject to other safety regulations”, says Anna Sandinge at Rise, one of the authors of the pre-study Kompositer för en hållbar sjöfart.
Anyone who wants to build a Stena ferry has problems 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.
“You can use composite material, and it is also done to some extent today, but then you have to insulate in a special way that protects the material against fire
Steel is the predominant shipbuilding material on which all safety regulations are based, and rightly so, the requirements are also very tough, says Anna Sandinge.
“The requirements are difficult to fulfill with composites, especially a test which means that you should not get over-ignition in a small room, for example a cabin.”
And how to approach that problem?
- We have a solution that is very promising, a sandwich construction with a combustible core that is surrounded by a durable laminate that does not spread the fire. A fire-resistant paint is also painted over it. Of course, this costs a lot to develop and then someone has to take the first step and use it.
But there is no doubt that composites belong to the future of shipping. Just like in the aviation and car industries, it is a prerequisite to be able to go from a fuel with a high energy density to one with a lower one. Lightweight is, for example, an enabler for an electric fleet. And according to the report, "Electricity and fossil-free energy carriers also mean direct innovation opportunities linked to material selection. Structural batteries, airframe technology, thermally and electrically conductive lightweight materials are areas we see emerging in the wake of the progress of electric operation.”
- The project has led to a lot, both new questions and solutions. For example, we have concluded that the test methods for fire need to be developed and that a simplified guide to the risk analyses, which are very complex, needs to be produced. Another important result is that the project actually tied together so many actors. We have arranged work shops where representatives of shipyards, material manufacturers, research institutes, authorities and academia discussed together, which led to a broadened and deepened collaboration and new project applications linked to fire protection, sustainability and production technology, says Anna Sandinge.
The report Kompositer för en Hållbar sjöfart was written by Peter Sjögren (RISE), Anna Sandinge (RISE) and Zhiyuan Li (Chalmers)