Composite Materials and Sustainable Ships
Using ships to transport goods contributes significantly to global greenhouse gas emissions, with about 940 million tons of carbon dioxide being released every year.
In Europe, maritime shipping is responsible for about 13% of all transport emissions. Shipbuilding itself consumes energy and produces waste at the end of a ship’s life with only some parts of a vessel repurposed.
Building ships that are less heavy is one tactic that can help reduce emissions. Using composite materials such as fibre-reinforced plastic (FRP) instead of steel, for example, should reduce a ship’s weight and lower fuel consumption. That also means less emissions per transported kilo of payload.
Steel ships are also damaged by corrosion until repair is no longer possible. This is not a problem when non-metallic materials are used. So, composite materials can extend a ship’s lifetime and reduce resources needed for construction.
There is also potential to better reuse vessels made from composite materials as they can be better recycled at the end of their life. Whereas about 34% of steel ships are repurposed, it is thought that up to 75% of composite ships could be given a second life.
Composite Ship Parts
Researchers investigating the use of new materials and technologies to make specific components of large vessels, from cruise ship cabins to rudders, as part of the EU’s RAMSSES project.
They are looking, for example, at how metallic propellers could be made using a 3D printing technique that would allow for hollow and more lightweight blades. Such a propeller would also be quieter and emit less vibration.
The research team produced prototypes of several parts such as a ship hull made of FRP. They were able to show that their composite ship hull would have a lower environmental impact than if it were made of steel.
The hull weighed over 24% less, which they calculated would lower its environmental footprint during operation by 25% when considering factors such as greenhouse gas emissions and aerosol formation, which impact air quality.
Composite materials could also be used to repair damaged steel ships and extend their life. A patch made of composite materials, for example, could be applied to cracks or to reinforce areas welded together.
Another approach is to focus on making an entire vessel out of composite materials. Researchers have investigated the feasibility of constructing large ships more than 50 metres in length out of FRP as part of the Fibreship project.
The main goal was to set the foundations for the design and construction of these vessels by defining design guidelines and performance criteria. These had not previously existed.
Members of the team designed three different FRP vessels: a container ship, a fishery research vessel and a vessel that can transport cargo, vehicles and passengers, known as a RoPax.
Since their container ship design would result in a more lightweight vessel, they calculated that it would be able to carry almost 17% more cargo when fully-loaded compared to a steel counterpart. With their fishery research vessel design, they were able to obtain a total weight reduction of 36%.
Their RoPax design would also result in a significant reduction in weight and hence fuel consumption. Since this type of vessel travels at much higher speeds compared to the two other vessels, which require high power from the engines, cost savings would also be most significant. This would make it a better investment opportunity when compared to a steel vessel.
Although the team’s budget didn’t allow for a full FRP ship prototype to be built, they constructed a block of a fishery research vessel at IXBLUE facilities in La Ciotat, France. With dimensions of 11 by 11 by 8.6 metres, it contained a bottom deck with part of an engine room and an upper deck with passenger accommodation. This showed that it is feasible to build large structures from composite materials.
But there are still hurdles to overcome before composite ships become a reality. One issue is that it’s tricky for a ship component to meet all the different requirements. One panel that was created, for example, was fire resistant and had satisfactory mechanical properties but it didn’t meet noise and vibration standards, which could hinder the comfort of passengers onboard.
Further work is also needed to address recycling FRP ships at the end of their life. Few facilities in Europe are capable of recycling composite materials, where fibres, resins and other materials need to be first separated.
For larger ships made entirely of FRP, the main challenge is to show that they meet fire safety standards set by the International Maritime Organisation (IMO). FRP is a combustible material and it would currently be difficult to evacuate an FRP vessel in time to avoid casualties.
Its material properties also don’t hold up at high temperatures and a vessel could therefore collapse. Manufacturers of composite materials are working on developing FRP resins that are non-combustible and the way spaces onboard are designed could help improve fire safety too.
The conclusion is that fully composite vessels are not about to appear but are on the horizon. A possible scenario is that large composite vessels could start navigating in about 15 years. This will require tectological improvements, but regulations and standards for design and construction will also be needed.
This article was originally published in Horizon, the EU Research and Innovation magazine.