Effects of Cooling Speed of Specimen at Preparation, Temperature during Test and Sizing agent on Glass Fiber / Polyamide Resin Interfacial Shear Strength

It is important to evaluate the fiber/matrix interfacial shear strength (IFSS) of Fiber reinforced thermoplastics (FRTP) as their mechanical properties are greatly affected by the IFSS. Moreover, IFSS is considered to be affected by chemical bonding and physical bonding occurring by the force with which the resin tightens the fiber. Although single fiber pull out tests have been well studied for evaluating the IFSS, it has not been clarified whether chemical bonding or physical bonding is the dominant factor in IFSS. In this study, single fiber pull out tests were conducted using glass fibers with sizing agent, and glass fibers without sizing agent which are considered to be less capable of chemical bonding. The effects of cooling speed on the specimen at preparation, and the temperature during single fiber pull out tests were revealed. There was no significant difference between the IFSS obtained by the single fiber pull out test under 25℃ using glass fibers with sizing agent and without sizing agent. This means that the effect of chemical bonding does not appear on the IFSS under high tightening force of resin in the radical direction of the glass fiber. Although the IFSS evaluated with specimens prepared through high cooling speed or under high temperature was degraded regardless of the presence or absence of sizing agent on the glass fibers, the decrease of IFSS could be reduced by using glass fibers with sizing agent. This result means that the chemical bonding can be evaluated by single fiber pull out tests under the condition of relatively low tightening force in the radial direction of the resin, such evaluation under high temperature and with specimens prepared through high cooling speed.