Working with Carbon Fiber
A quick summary of Carbon fiber manufacturing techniques
What is Carbon Fiber?
Carbon fiber reinforced polymer, also known simply as Carbon fiber, is a reinforced plastic composite made with (you guessed it) carbon fibers. These carbon strings are extremely tiny, usually less than 10 micrometers in diameter. Carbon fiber is mainly used in cases where a high strength-to-weight ratio is needed. Although expensive, carbon fiber has high stiffness, low weight, high tensile strength, low thermal expansion, and high chemical and temperature resistivity. It is for these reasons that carbon fiber is used increasingly more in many different industries (including aerospace) along with other composite materials.
UAS@UCLA uses carbon fiber to create our airframes for its high strength-to-weight ratio. Due to its high cost and our low budgets, it is extremely important to make sure that we use the material sparingly to prevent additional costs.
Working with Carbon Fiber
Before you begin, make sure that you've read over the Basic Lab Safety Rules.
All other lab safety rules apply.
Wear a face mask and safety glasses- There are lots of rumors out there that carbon fiber dust is toxic. While this is not true, it is still a mild irritant to the lungs, eyes, and skin. Wear a face mask to avoid breathing in the dust and safety goggles to protect your eyes. If you find that it is bothering your skin, wear long sleeves and pants and use gloves while handling carbon fiber.
Watch for cuts and splinters- Carbon fiber can be extremely sharp on the edges. Use caution when working with sheets and/or tubes and sand down cuts and edges so that others do not get hurt. Carbon fiber also has a tendency to splinter like wood, so be careful when holding it.
Clean up your workspace after you are finished- This should be a given, but carbon fiber is extremely messy and tends to leave a black powder everywhere. Make sure to clean up your workspace to keep the lab clean and prevent black soot-like powder from covering everyone's personal belongings.
Use blades with small teeth on slower speeds for cutting- Use a blade for cutting carbon fiber similar to one you would use for metal. This blade should should have at least 18 teeth per inch (TPI) and look similar to the bottom blade in Figure 1. Make sure that blade is set to a slower speed. It is also helpful to get carbide or diamond coated blades and wheels for cutting carbon fiber due to its abrasive nature and ability to wear down tools.
Figure 1: Different types of bandsaw blades. The top blades would most commonly be used at higher speeds for woods and the bottom blades for metals and composites at lower speeds.
Use Dremels when cutting tubes- It is best to cut carbon fiber tubes with a dremel tool, then sand down the end on a power sander. Make sure to use a diamond coated blade with smaller teeth and cut at slower speeds. It is also best to cut a few millimeters larger than the final size in order to sand the tube down to the correct size.
Using adhesives- There are several types of adhesives and techniques to apply them. These are summerized below:
- Make sure to wipe down and clean the contact surfaces before applying adhesives.
- One type is adhesive backing, which comes in sheets and acts a lot like double-sided tape. Simply take the one backing off and place the tape on the one piece and remove the other backing and place the other piece on top. Apply pressure for a few seconds. If this is not working as intended, try using a heat gun on the adhesive before attaching the two pieces.
- Another type is water-based epoxy. Follow the instructions on the bottle for mixing, application, and curing times.
- Contact cement can be used as well, though I recommend adhesive sheets or epoxy.
Sanding Carbon Fiber- You'll find that sanding carbon fiber is not too difficult and often you can get away with a relatively high-grit abrasive paper starting at 180 grit, later moving to 300-400 if needed. Try to sand along the line of the cut for the best finish.
Use tape for cutting lines- Due to carbon fiber's dark and glossy appearance, it is often hard to use traditional writing methods to mark for cutting. It is recommended to use opaque masking or painters tape when cutting pieces.
Here are some resources that may be helpful when working with carbon fiber:
Written by T. Kantner
Last Edit: 09/10/2018 by T. Kantner