Unidirectional Versus Woven Carbon Fiber
Appleman Bicycles prioritizes strength, durability and using the right material for the job. That’s why I use unidirectional carbon fibers to build all of the structural tubing that goes into a custom bike + woven/braided carbon in the joints.
Unidirectional (UD) fibers are carbon fibers that run in one direction, similar to the grain of wood.
Woven fabrics have carbon fibers that run in two directions.
Against the Grain
Carbon fibers are 70 times stronger with the “grain” than against it. When I design a carbon layup, I understand the forces applied to the frame and lay the carbon fiber to resist those forces. The angle of thefiber is critical. A layup must be designed with multiple angles and layers to resist different types of forces while riding.
Straight Up Stiffness
UD fibers are the perfect tool to build a bike with because they are twice as strong and twice as stiff as woven carbon fibers! The weave of the fabric crimps the fibers and they are constantly bent in an “S” shape to go over and under each other. When force is applied to a woven fabric, the fibers bend and try to straighten out which reduces strength and stiffness.
UD fibers lay flat and there is no flex when force is applied.
So why use any sort of weave? Drape. UD fibers are great when the are flat and straight, but when they need to be wrapped around the complex curves of the joint areas of a bike frame… woven is ideal. Woven fabrics can drape over curves while minimizing fiber waviness, crimping, bridging, and excessive cutting/darting that would normally be found in unidirectional fibers.