Thesis

Single crash use helmets: does material density affect Peak G

Thesis (M.S., Mechanical Engineering)--California State University, Sacramento, 2016.

This thesis is a study of how stiff or soft outer shells interact with soft or hard energy
 absorbent liners in order to protect human lives in the event of a crash. Finite Element
 Analysis (FEA) is utilized to see how the layers of a helmet interact and how they
 manage energy in an impact scenario. Density of each layer of the helmet is changed to
 reflect different cases of extremes that may occur in designing the helmet. Customers and
 testing facilities have long thought differently how hard each material should be to
 achieve the same result. Manufacturers also currently have to manufacture a prototype
 and test it at a lab. 
 FEA models greatly reduce cost of testing and allow the designer to quickly try new ideas
 for constant product improvement. At first thought, a 2000 kg/m3 dense polycarbonate shell with a 60 kg/ m3 dense EPS liner would seem to be the ideal fit, a stiff shell that would easily transfer energy into a soft absorbent liner. Other combinations of densities were simulated and the combination that stood out ended up being a 500 kg/m3 dense EPS liner coupled with a 1200 kg/m3 dense polycarbonate shell.

This thesis is a study of how stiff or soft outer shells interact with soft or hard energy absorbent liners in order to protect human lives in the event of a crash. Finite Element Analysis (FEA) is utilized to see how the layers of a helmet interact and how they manage energy in an impact scenario. Density of each layer of the helmet is changed to reflect different cases of extremes that may occur in designing the helmet. Customers and testing facilities have long thought differently how hard each material should be to achieve the same result. Manufacturers also currently have to manufacture a prototype and test it at a lab. FEA models greatly reduce cost of testing and allow the designer to quickly try new ideas for constant product improvement. At first thought, a 2000 kg/m3 dense polycarbonate shell with a 60 kg/ m3 dense EPS liner would seem to be the ideal fit, a stiff shell that would easily transfer energy into a soft absorbent liner. Other combinations of densities were simulated and the combination that stood out ended up being a 500 kg/m3 dense EPS liner coupled with a 1200 kg/m3 dense polycarbonate shell.

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