BS in Materials Engineering
Materials Engineering Department
Common Fibers, a company founded by Cal Poly alumni, produces carbon fiber wallets. The invention of their built-in fiber-matrix composite hinge reduces the need for extra complexity and added mass that is inherent with using standard metal hinges to join standard composite panels. Replacing the polyurethane tape on the wallet hinge allows for improved protection while maintaining flexibility and other performance properties is critical to the success of such a design. The most important material property in this project is the bond strength between carbon fiber and a variety of flexible resin candidates. The silicone and urethane based elastomer resins include CF19-2615, Encapso K, Flex-It 10, and Econ 80, which were chosen as a partially representative sample of the wide range of flexible resin systems. A fiber bundle pull out test was designed and implemented to directly and quantitatively measure and compare fiber-matrix bond strength. Additionally, two separate methods for applying the resin to a hinged panel were investigated: resin transfer molding (RTM) and vacuum bagging. A modified RTM was designed and fabricated in-house, and a standard vacuum bagging setup was assembled. In order to determine the best overall application method, several criteria were selected based on the wetting of the fibers and the overall aesthetic feel and appearance. Based on these criteria, the best and most efficient method is vacuum bagging. Econ 80 displayed a significantly higher mean bond strength compared to all other resins.