A bicycle helmet is intended to protect a bicycle rider from head injury in the case of an accident. This is important, because head injuries are very common, and can often last a lifetime. When a human head meets strong force, the brain remains stationary while the skull is jolted around. This pulls at blood vessels and nerve, causing damage. All bicycle helmets must be tested to ensure that they do not block the rider’s vision through the Peripheral Vision Test, that they do not come off if the rider falls through the Positional Stability Test, that the straps are not long enough for the helmet to fall off through the Retention Strength Test, and that the helmet significantly lessens the force to the rider’s head in the case of an accident through the Impact Attenuation Test. Different types of helmets for different activities must pass different tests, unique to each activity. Helmets typically contain an interior lining, often made of crushable foam. The liner of a helmet performs two functions: to redistribute the force over a larger area, and to set an upper limit to the level of the distributed force. The maximum level of tolerable deceleration to the human head (a) is 300 g, and the mass of a head (m) is approximately 3 kg, so the maximum allowable force equation is F=m k=9kN. As the liner crushes between the skull and the surface, it distributes the force over the area (A). To prevent the force from rising above 9 kN, the liner must crush with force at sc(0.25) = F/A = 0.9 MPa. It is important for helmets to have a hard outer layer, which are typically made of Carbon Fiber. It is not optimal for helmets to be particularly thick, because thicker helmets cause more strain on the neck and brain in the case of a crash. They often include internal padding, which serve the purpose of comfort, but do not provide any real protection. Helmets should have a g- force that is below 200 g’s for a 2 meter drop. They should stay put on your head during an accident, and should be able to handle multiple impacts.
We have decided to create an innovative mountain bike helmet, designed for the most complex terrains, using Koroyd and Carbon Fiber. The helmet we have created theoretically fits all of the Helmet Safety Standards. It would not block the rider’s vision (Peripheral Vision Test), it would not fall off of the rider’s head in the case of an accident (Positional Stability Test), it passes the Retention Strength Test because it is designed with an alternative to loose straps, and it passes the Impact Attenuation Test because it significantly lessens the impact to the rider’s head in the case of an accident. A helmet is considered safe if it passes an acceleration drop test of 2 meters at 14 miles per hour. Theoretically, if we subjected our helmet to these tests, it would pass. We decided to use a new state of the art core material called “Koroyd” which can be 3D printed to cover 90% of the user’s head. Koroyd is a material that serves as the crumple zone of the helmet. This creates a cushion for impact crashes.The Koroyd material yields a low coefficient of friction, which minimizes the impact of force on the skull. We will cover the Koroyd with a layer of carbon fiber material. Carbon fiber forms a strong barrier on the helmet for crashes producing kinetic friction that involve scraping and sliding. Because every skull is different, we are including a padded mesh material for the chin area of the design. This allows for many different face structures to fit inside the helmet, while still staying snug around the head. Our helmet was designed based off of the endless variations of head shape and size, making it flexible yet sturdy.