Motorcycles can travel the same speeds as automobiles but there is nothing between the motorcyclist and the environment except proper clothing and safety equipment. This means that the potential is high for serious injury or fatality in head impact accidents. Helmets are intended to protect the head from sudden impact against hard surfaces and sharp objects. Some types of helmets do a better job than others.
The great majority of sports helmets are made of fiberglass. While offering some protection, in most cases fiberglass is not strong enough to withstand the kind of shattering impact that can result from a motorcyclist's head hitting pavement. However, a helmet made from carbon fiber is a different story.
Carbon fiber is very fine strands of carbon that can be twisted together and then woven. Even though each strand of carbon layed fiber is thinner than a human hair, it is extremely strong. It is five times as strong as steel but only about one-third as heavy. It also has excellent tensile strength. This means that carbon fiber can 'give' or stretch quite a bit before it comes apart. All of these features indicate that fiber helmets are better able to absorb more of the force of an impact than most other helmet materials. It is also far less likely that sharp objects can penetrate a carbon fiber helmet shell.
Carbon fiber helmets are usually made by placing layers of fiber in a helmet shell mold and then coating the fibers with an acrylic resin or some other type of plastic. In some cases, this process is done under high pressure to make an even stronger laminate. The resulting products are helmets that are lightweight, extremely strong barriers between heads and hard surfaces.
States with helmet laws on the books require motorcyclists to wear helmets that meet safety standards established by the U.S. Department of Transportation (DOT). These standards include things like minimum visibility, impact force absorption, and amount of face/head covered. Before the advent of carbon fiber helmets, helmets that met all the approved DOT criteria could be quite bulky and heavy. The use of carbon fiber has allowed more latitude among helmet designers to create some smaller, more streamlined styles that are comfortable for the rider but still provide the safety the DOT requires.