Wind energy is gaining support in the U.S., both on ground and in the ocean. And the design specs for wind turbines are getting pretty sophisticated as they require exact performance requirements, including super lightweight material and a potential to operate for decades without maintenance. Meanwhile, the turbines are becoming longer, measuring as much as 75 meters, close to the wingspan of an Airbus jet. Most of the turbines in North America and Europe are made of balsa wood: It's durable, dense and yet lightweight... but it's expensive. So there is a new solution coming from materials scientists at Harvard.
Balsa's cellular structure has high strength per volume of space, as its cell walls carry the weight, but it has a lot of empty space which makes it extraordinarily lightweight. This new material is engineered with the same design (see photo above), so it can mimic the best qualities of balsa. But it is made from epoxy-based thermosetting resins and it's fabricated with 3D printers, which provide unprecedented precision.
Check out how they did it in the video here:
Typically 3D printing uses thermoplastics and resins, but these are not usually used in any sort of engineering solutions. This new material—based in epoxies—opens up another channel for 3D printing that has structural applications.Below are images of the various structures of the composite.
Jennifer Lewis and Brett Compton...developed inks of epoxy resins, spiked with viscosity-enhancing nanoclay platelets and a compound called dimethyl methylphosphonate, and then added two types of fillers: tiny silicon carbide "whiskers" and discrete carbon fibers. Key to the versatility of the resulting fiber-filled inks is the ability to control the orientation of the fillers.
You can see these carbide "whiskers" and discrete carbon fibers in the photos on the right, above.
The direction of the fillers makes all the difference when it comes to in strength. Just think about how easy it is to split a piece of firewood, versus chopping it against the grain. This new composite is 10 to 20 times stiffer than any 3D-printed polymers on the market.
Below is a photo of the process: On the left is an optical image of the 3D printing of a triangular honeycomb composite. On the right is an illustration of the alignment of the fillers.
Photo credit: Brett G. Compton
This ability to control the direction of the fillers is a big leap forward in man-made materials that mimic wood. Wind energy may be the perfect large-scale test industry for this material, but it could be used for any product where "super lightweight" and "amazingly strong" are required qualities.