APPAREL  AND  FOOTWEAR DESIGN

GRADUATE THESis
3D PrintED FUNCTIONAL MATERIALS FOR SneakerS

Abstract:

Since the late 20th century, sneakers have become the epitome of status and fashion. Often seen as emblematic of innovative styles and technological advances, sneakers have become synonymous with that idea of innovation. One recent technological development has been the integration of 3D printing (3DP) within the sneaker industry. Not only has 3DP allowed sneaker companies to prototype sneaker components more efficiently, reduce logistical costs, and produce less waste during manufacturing, but 3DP could also provide consumers with sneakers tailored to their unique specifications. However, while 3DP has already been used to manufacture components for mass-produced sneakers, these specific polymer materials developed for footwear and their respective printing processes are often considered confidential or proprietary property of the sneaker companies who developed them. As a result, very little information about 3DP technologies within the sneaker industry is publicly available, specifically regarding the polymeric materials best suited for sneakers, how polymers might be optimally structured and printed, and how they perform compared to traditional sneaker materials.

This thesis tested several polymeric materials' printability and mechanical properties to determine which materials could be utilized to engineer an entirely 3D-printed sneaker prototype that could theoretically perform similarly to traditionally manufactured sneakers. This research used fused deposition modeling (FDM) and stereolithography (SLA) 3DP methods to compare the properties of thermoplastic and thermoset samples. The polymers tested FDM filaments, including polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and the Ninjaflex thermoplastic polyurethane (TPU) filaments, and SLA resins, including the ANYCUBIC basic UV curing resin and the Formlabs polyurethane (PU) Rigid 650 resin. Tensile, abrasion, impact, flexural, and compression tests were conducted to evaluate the mechanical properties of these 3DP polymers and study their suitability for the different parts of a 3DP sneaker, including the upper, midsole, and outsole. Test results showed that the Ninjaflex was the most suitable material for every component of the prototype sneaker and outperformed the other polymers concerning tensile elasticity, tensile strain, abrasion resistance, impact strength, and compressive elasticity. In addition, the Ninjaflex was also found to have similar compressive resiliency compared to the midsole foams used in Nike running shoes. A 3DP sneaker was designed utilizing test data to determine optimal print configurations for the sneaker's upper, midsole, and outsole, and was successfully printed using the Ninjaflex filament.