Balsa wood isn’t just for building models and crafts, it also has many industrial uses, including being an essential part of the construction of wind turbine blades for wind farms. That may seem to be a very low-tech material for such a high tech machine, but so far balsa wood is still the strongest lightweight material currently available.
However, researchers at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute have created a lightweight yet extremely stiff composite material that they say can mimic and possibly improve on balsa wood and any other polymer composites available. They’ve published a paper detailing their process for using resins and 3D printing to create the material in the Advanced Materials journal.
“Balsa wood has a cellular architecture that minimizes its weight since most of the space is empty and only the cell walls carry the load. It therefore has a high specific stiffness and strength,” explains Harvard SEAS Jennifer A. Lewis “We’ve borrowed this design concept and mimicked it in an engineered composite.
The process involves creating epoxy resins that contain two types of fillers, silicon carbide “whiskers” and carbon fibers. By using a 3D printer to create the structures with the resin, the scientists were able to control the orientation of the fillers. This specific orientation allows the cured resins to mimic the tensile strength of wood. Think about trying to split a piece of firewood, it is much easier to do if you chop it with the grain rather than against it, the properties of the finished resin material work the same way.
The new 3D printing material is reportedly 10 to 20 times stronger than any available commercial 3D printer polymers and twice as strong as any 3D printer polymer composites. This new lightweight material could also have applications in the automotive industry where maximizing fuel efficiency is dependent on reducing the weight of vehicles. The new material is still being studied, and researchers promise that as they develop better ways to manipulate the filler alignment they can optimize the component design and improve the efficiency and strength of the material.
I looked into this via my network in the Wind Power industry. The material is unlikely to be suitable for blade production. There are apparantly two reasons for this: 1) The open structure does not work with vacuum infusion. All the voids would get filled by epoxy, and this would create high parasitic costs and additional weight. 2) The carbon fiber content is likely to be too costly.
The cost issue is likely to be solved over time, but the open structure will most likely be a showstopper.
Thanks for your thoughts.
Yes, it is probably too early to say that this will replace balsa wood, but it’s certainly an interesting process worth keeping an eye on.
IMO I don’t think think the vacuum infusion would be a problem. Just like using a hollow tube for a spar you are not going to want to fill the tube with epoxy. If they can 3D print this material then they can skin the whole section at the same time keeping the inside mostly hollow. Same as using honeycomb core panels inside a layup. You don’t want to fill the holes with epoxy either but bond to the skin of the component to carry the load.
I could see huge advantages with creating more complex 3D forms where the shape of the blade changes to mount to the hub. That is where building that compound shape with a core material can get more tricky. Here is an example used on Synergy a composite aircraft with a 3D printed component. https://scontent-ord.xx.fbcdn.net/hphotos-xap1/t31.0-8/1511761_613603935389820_1576835544_o.jpg
I think that the size of the part and and the speed of the 3D printing is the biggest hurdle at the moment for wind power blades.