Micro- and nano-structured materials for shock attenuation in sport helmets
Liliia PYLYPCHYK (Politecnico di Milano)
Recent surveys revealed that every year in Italy around 13,500 bikers are involved in street accidents, and around 30,000 accidents occur inside ski parks, of which more than 5% lead to head injuries with neurological effects. Even if helmets have to be compulsory worn by people under 18 in ski areas and are strongly recommended while riding a bike, accidents still cause hospitalizations and relevant loss of public money.
To enhance the performance of sport helmets, in this work we propose the use of microstructured, or even nanostructured polymeric materials able to damp acceleration peaks (already recognized by international standards to cause injuries) at least for frequencies considered dangerous for the human brain. The aforementioned goal is achieved thanks to the insertion of a thin layer of phononic crystal-like composite between the external hard skin of the helmet and the soft, impact-absorbing liner made of expanded foam. With the help of an extensive numerical campaign, the feasibility of the proposed approach is discussed; moreover, a way to optimize the material microstructure, accounting also for scale effects, in provided.
