Fabrication and Mechanical Characterization of Unidirectional FRTP with In-situ Polymerized Thermoplastic Urethane Resin as a Matrix

Thermoplastic resins have extremely high melting viscosity, making it difficult to impregnate long fibers with those resins at a high fiber content. Therefore, our laboratory has developed a new in-situ polymerizing thermoplastic polyurethane resin that is a low molecular weight, low viscosity liquid during molding, and quickly polymerizes into a linear polymer after fiber impregnation. In this study, UD prepregs with two types of in-situ polymerizing thermoplastic polyurethane resins with glass transition temperatures of 118℃ and 165℃ were fabricated using a specially made continuous pultrusion equipment, and UD-FRTP specimens were fabricated by subsequent press molding. Furthermore, the mechanical properties were evaluated by three-point bending tests and double cantilever beam (DCB) tests. As a result, it was shown that the UD-FRTP had the same level of bending strength and flexural modulus as general UD-FRP with epoxy resin as the matrix, but had higher interlaminar fracture toughness. It was confirmed that UD-FRTP with a low glass transition temperature has extremely high toughness because it exhibited a higher interlaminar fracture toughness value than UD-FRTP with a high glass transition temperature.