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Why Are Composites Used?
Unlike metals, which have uniform properties in all directions (engineers call this isotropic),
carbon fibers can be placed in specific orientations to optimize the structure for particular loads.
The choice of where to place the carbon fibers gives engineers a powerful tool to create strong,
light Ebikes. Engineers may also orient fibers to suit other goals such as comfort and vibration
damping.
Carbon fiber composites are very corrosion resistant, much more so than most metals.
Think about carbon fiber or fiberglass boats.
Carbon fiber materials have a very high strength-to-weight ratio.
What Are the Limits Of Composites?
Well designed “composite” or carbon fiber Ebikes and components have long fatigue lives,
usually better than their metal equivalents.
While fatigue life is an advantage of carbon fiber, you must still regularly inspect your carbon
fiber frame, fork, or components.
Carbon fiber composites are not ductile. Once a carbon structure is overloaded, it will not bend;
it will break. At and near the break, there will be rough, sharp edges and maybe delamination of
carbon fiber or carbon fiber fabric layers. There will be no bending, buckling, or stretching.
If You Hit Something or Have A Crash,
What Can You Expect From Your Carbon Fiber Ebike?
Let’s say you hit a curb, ditch, rock, car, other cyclist, or other object. At any speed above a fast
walk, your body will continue to move forward, the momentum carrying you over the front of
the Ebike. You cannot and will not stay on the Ebike and what happens to the frame, fork and
other components is irrelevant to what happens to your body.
What should you expect from your carbon frame? It depends on many complex factors.
But we can tell you that if the impact is hard enough, the fork or frame may be completely
broken. Note the significant difference in behavior between carbon and metal in this Appendix.
Even if the carbon frame was twice as strong as a metal frame, once the carbon frame is
overloaded it will not bend, it will break completely.
WARNING: Be aware that high temperature in a confined environment can affect the
integrity of composite materials, resulting in component failure which could cause you to
lose control and fall.