Manufacturing a Boeing 787 aircraft wing out of carbon fiber is no easy task. It requires working with laminates that must be bonded together to create a single, strong piece. This creates several challenges that add to the time and expense of fabricating with carbon fiber.
Those same challenges are primarily responsible for keeping the automotive industry from embracing composite materials. Dealing with laminates is labor-intensive and time-consuming. Putting as much carbon fiber into a car as Boeing puts into an airplane would make the car too expensive for the mass-market.
Rock West Composites, a composite materials and prototyping provider based in Salt Lake City, explains that the industry is working hard to overcome the challenges. Once overcome, composite prices should come down.
The Labor Challenge
Laminate parts are made from multiple layers of fabric impregnated with an epoxy resin. Using the Boeing 787 as an example, a single wing starts with a tool (mold) fabricated in the shape of the desired wing. Multiple layers of impregnated carbon fiber fabric are laid into the tool until the desired thickness is achieved. Then the layup is sealed and cured.
Laying down all those layers of carbon fiber is labor-intensive. As such, it is also time-consuming and expensive. That is why Boeing and several other big-name companies are working on ways to automate their layups. There are other ways of utilizing carbon fiber apart from manual layups – including spinning, braiding, and 3D printing – but none are suitable for making large parts like airplane wings.
The Energy Challenge
Curing something as large as an airplane wing requires tremendous energy and pressure. Both are provided by a piece of equipment known as the autoclave. Think of the autoclave as a large pressure cooker. It applies both heat and pressure to force laminates to bond.
As effective as the autoclave is, it is terribly inefficient from a manufacturing standpoint. Autoclave curing takes time, time that could ultimately slow down the manufacturing process if things don’t go perfectly as planned. It also requires a tremendous amount of energy. As such, autoclave curing is expensive. Eliminate it and you change everything.
The Failure Challenge
Beyond manual labor and the prohibitive cost of autoclave curing is the possibility of failure. As tough as carbon fiber and fiberglass composites are, they are not immune to failure. The challenge is in controlling such failure when it does occur. Obviously, manufacturers want to avoid failure as much as possible.
When the aluminum or steel begin to fail, they exhibit signs that are easy to see. For example, you can see corrosion. You can see cracks and dents. Both steel and aluminum can absorb quite a bit of damage before failure occurs. Moreover, failure generally takes quite some time with steel and aluminum.
The same is not true for composites. Materials like carbon fiber and fiberglass fail suddenly and catastrophically. Worse yet is the fact that it is hard to detect signs of potential failure without specialized equipment. Even at that, you might not be able to detect failure in time to prevent it.
The big problem here is the laminate construction. Laminates tend to fail from the inside out. Before catastrophic failure occurs in an airplane wing, cracks begin to form inside where they cannot be seen. The challenge is to identify those cracks as soon as possible so that repairs can be affected.
Composite laminates have a lot of great applications. Yet they are not perfect. There are lots of challenges that come with using laminates in composite fabricating. They are challenges the industry is working to overcome.