Abstract: A protective helmet comprises an inner layer and an outer layer separated from the inner layer by a space. An interface layer is positioned in the space between the inner layer and the outer layer and includes an impact absorbing material that non-linearly deforms in response to an incident force on the protective helmet. For example, the impact absorbing material includes multiple filaments each having an end proximate to the inner layer and another end proximate to the outer layer interface, with the filaments configured to non-linearly deform in response to an incident force on the helmet.