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Thesis Format



Master of Engineering Science


Mechanical and Materials Engineering


Mao, Haojie


Impacts to the head can be observed from contact sports such as hockey, lacrosse, football, soccer, and rugby. Other activities due to accidents including falls from bikes, falls from motorcycles, and car crashes can also result in head impacts. When these impacts to the head do occur, they have the implication of causing brain trauma ranging from concussion to diffuse axonal injury (DAI) or subdural hematoma (SDH) and even death. It is because of these severe injuries that protection of the head is paramount. Helmets have been designed for these sports and offer great protection from injuries such as skull fracture. However, concussion still occurs in sports today in the highest rates to date. The design of these helmets can vary greatly for each activity. Current helmet designs focus on reducing the total amount of energy the head receives during an impact. In recent studies there has been little focus on reducing the rotational components of an impact which is known to cause diffuse brain injuries in the form of axonal damage or concussions. The results of this study demonstrate that the STAR scores, which include a head rotation component, can inform uses greater information beyond strictly evaluating linear kinematics, and also what STAR scores are associated with certain materials. The main focus of this study was to explore various designs of helmets that could potentially reduce rotational velocities of the brain and hence, brain strains. The results of this study demonstrated that structural modification of the interior foam of a helmet could help reduce rotational velocity. This study also investigated the influence of outer shell soft padding by changing the stiffness and friction. Surprisingly, the smallest friction coefficient between the outer shell padding and the impactor tip did not contribute reducing head rotation compared to the best case. These computational results provided important guidance for the next-step, physical helmet development.

Summary for Lay Audience

Head injury has been documented since biblical times and the (KJV) of the bible in 1 Samuel 17 documents the story of David and Goliath. Goliath was noted to be wearing a helmet, however, he suffered defeat at the hands of David. Today the concussion in contact sports and other types of mTBI is still a problem even with recent advancements in helmet technology. It is important to understand the current state of concussion research to introduce new designs thereby, reducing the instance of concussion. The goal of this paper is to define the current state of the art helmet technology and demonstrate how novel design approaches that specifically target and try to mitigate concussion pathology.

By demonstrating how new ideas can be developed better protection methods can be developed. This paper dissects the STAR study scores of various helmets by comparing the designs and materials used of both hockey and football. This study introduced a new design that is iteratively improved upon until a design is reached that performs better than the original helmet design. Lastly, a small study was conducted that investigated the kinematics of an outer shell foam layer helmet design.

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Available for download on Sunday, December 14, 2025