A goal-oriented, inverse decision-based design method to find satisficing solutions for multiple football helmet components that all work together to achieve a set of conflicting goals is presented. The efficacy of the method is illustrated with the design of the top region of an American football helmet. The prototype helmet was first constructed and tested with a twin-wire drop tower to study the different components effect on the system response. The inverse design method is used to design the foam liner to dissipate the maximum impact energy, and then the composite shell is designed to reduce the weight. The Concept Exploration Framework and the compromise Decision Support Problem are used to find satisficing solutions to the system-level performance goals under uncertainty. The proposed goal-oriented, inverse decision-based design method is generic and will be used to design additional components, the complete helmet, and ultimately helmets for other sports.

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Materials have traditionally been selected for the design of a product; however, advances in the understanding of material processing along with simulation and computation techniques are now making it possible to systematically design materials by tailoring the properties of the material to achieve the desired product performance. Material design offers the potential to increase design freedom and enable improved product performance; however, this increase in design freedom brings with it significant complexity in predictive models used for design, as well as many new design variables to consider. Material selection, on the other hand, is a well-established method for identifying the best materials for a product and does not require the complex models needed for material design. But material selection inherently limits the design of products by only considering existing materials. To balance increasing design costs with potentially improved product performance, designers must have a method for assessing the value of material design in the context of product design. In this thesis, the Design Space Expansion Strategy (DSES) and the Value of Design Space Expansion (VDSE) metric are proposed for supporting a designer s decision between material selection and material design in the context of product design. The strategy consists of formulating and solving two compromise Decision Support Problems (cDSP). The first cDSP is formulated and solved using a selected baseline material. The second cDSP is formulated and solved in an expanded material design space defined by material property variables in addition to other system variables. The two design solutions are then compared using the VDSE metric to quantify the value of expanding the material design space. This strategy is demonstrated in this thesis with an example of blast resistant panel design and is validated by application of the validation square, a framework for the validating design methods.