Helmets are designed to deform during a crash. How much is dependent upon the crash and the intended helmet design. It is impossible for a helmet designer to know the speed, the angle, the surface, and all other factors involved in any individual crash, so designers are left to try to cover as many situations as possible to ensure that you have the best protection over the widest range of impact scenarios. Essentially, helmet design is a ‘greater good’ effort for your brain based on the designer and the manufacturing technology available.
The major safety components of your helmet are the outer shell and the inner foam liner. The outer shell has several purposes. It protects the inner foam liner (the part of your helmet that dissipates the majority of energy upon impact) from penetrating and abrasive forces. It spreads the load of an impact over a greater area utilizing more of the energy absorbing foam, and it dissipates energy on its own depending on the rigidity.
So how hard should your helmet shell be? Tough and strong like an armored vehicle? Not so much. A helmet shell needs to have some ‘give’. That means that upon impact it must deform in the most efficient way possible. If there is no deformation the energy transfers past the inner liner to your head and consequently to your brain. When the shell is too hard the only deformation of the inner liner is that of the rider’s head being forced into the liner – the opposite of what should happen. The impact needs to deform from where the energy is applied, at the point if impact, the outside of the shell – the furthest point away from your brain.
When the outer shell deforms correctly, the impact energy is transferred to the inner liner. This starts the process of dissipating energy more quickly and efficiently. What does that mean to the rider wearing the helmet? It means forces resulting from an impact are slowed before they are applied to your brain.
Think about cars and crumple zones. The old school way of thinking was that we wanted a BIG car, one that is built like a brick shit house and able to withstand huge forces. These days, car manufacturers know that the vehicle needs to ‘give’ – to crumple, so the car takes the impact forces instead of everybody inside the car. Take a look at vehicle crash ratings. We know that energy does not just ‘go away’, it has to be acted upon by an alternate force. When a car’s crumple zone absorbs impact energy from a crash, the chance of survival is increased.
How do we know this works in helmets? We built the same model Kali helmet using traditional construction methods (foam and shell made separately then glued together) and then again with Composite Fusion, Kali's proprietary in-molding process. The helmets built with Composite Fusion reduced linear impacts by as much as 20-25% - same helmet model, same geometry, and same impact locations. Then we tried Composite Fusion with a thicker shell and found that the impact did not break the shell down quick enough to offer anywhere near as significant a reduction of linear deceleration.
We cannot change the amount of energy resulting from a crash, but we can manage that energy more efficiently. Thinner helmet shells allow for far better impact energy management. Composite Fusion allows us to refine how outer shells are made, particularly when it comes to making them thinner. The shell and foam are fused together which adds rigidity and support from the inner liner without having to add thickness, weight, and rigidity to the exterior shell. That starts the energy dissipation faster and handles it more efficiently.
Composite Fusion helmets provide better overall impact energy management, increased dynamic range and are smaller, lighter and stronger. Lighter and stronger means a helmet with less mass attached to your head. In a crash, less mass attached to your head reduces the linear and rotational impact forces acting on your brain. A better-engineered helmet shell means a more efficient and overall better performing helmet.