Abstract: A helmet, has a shell that includes a first portion and a second portion. The first portion has first, second and third layers. The second layer is positioned between the first layer and the third layer. The second layer is less dense than the first layer and the third layer. The second portion has a plurality of enemy dissipaters. Each of the energy dissipaters has a rod that extends in a spiraling manner from a fixed end to a free end. The rod tapers continuously along its length from the fixed end to the free end so that the fixed end exhibits a larger internal cross sectional area than the free end. The free end is capable of vibrating when the helmet is impacted by an object in order to dissipate impact energy.

Abstract: Described are helmets that include a shell that has a first layer, a second layer, and a third layer. The second layer is positioned between the first layer and the third layer. The second layer is less dense than the first layer and the third layer.

Abstract: A protective liner for personal protective equipment comprises a foam component and a polymer component. The foam component is embedded in parallel with the polymer component such that the foam component and the polymer component absorb energy in parallel during impact.

Abstract: A helmet comprises a shell, a gasket, and a facemask. A recessed region is formed on an exterior surface of the shell of the helmet. The gasket is disposed on the recessed region of the shell. The facemask is disposed on the gasket.