Effect of Interfacial Chemical and Physical Bonding on The Interfacial Shear Strength of Glass Fiber/Polyamide Resin and Mechanical Properties of The Composites

The main factors that contribute to the adhesive strength at the fiber/matrix interface of fiber reinforced thermoplastics (FRTP) are considered to be the chemical and physical bonding between the fibers and matrix resins. The chemical and physical bonds have not been evaluated separately, and the effect of each bond to the mechanical properties of FRTP has not been clarified. In this study, by using glass fibers with a sizing agent and glass fibers in which the sizing agent was removed and chemical bonding was deliberately not applied, we measured the fiber/matrix interfacial shear strength with several polyamide resins of different densities and terminal group concentrations by the microdroplet test. Thereby, the effects of physical and chemical bonding on the fiber/matrix interfacial shear strength were clarified. The mechanical properties of FRTP were also evaluated to clarify the effects of the chemical and physical bonding. The contribution of physical bonding was larger than that of chemical bonding in the fiber/matrix interfacial shear strength. The contribution of physical bonding was positively correlated with the density of resins, meanwhile the contribution of chemical bonding resulting from the application of the sizing agent was positively correlated with the terminal group concentration of resins. The interlaminar shear strength and bending strength of FRTP were positively correlated with the fiber/matrix interfacial shear strength regardless of the application of sizing agent to the glass cloth used to FRTP. These interlaminar shear strength and bending strength of FRTP using glass cloth with sizing agent were higher than that without sizing agent. This result indicates that the contribution of chemical bonding to the interlaminar shear strength and bending strength is different from the fiber/matrix interfacial shear strength and larger than that of physical bonding. © 2023 Society of Materials Science Japan. All rights reserved.