The present technology relates generally to protective helmets with non-linearly deforming members. Helmets configured in accordance with embodiments of the present technology can comprise, for example, an inner layer, an outer layer, a space between the inner layer and the outer layer, and an interface layer disposed in the space. The interface layer comprises a plurality of filaments, each having a height, a longitudinal axis along the height, a first end proximal to the inner layer, and a second end proximal to the outer layer. The filaments are sized and shaped to span the space between the inner layer and the outer layer. The filaments are configured to deform non-linearly in response to an external incident force on the helmet.