In this study, interfacial shear strength of resin particles added carbon fiber/maleic acid anhydride grafted polypropylene under water temperature was investigated. Water temperature range was from room temperature to 80 oC. The maximum immersion time was 24 hours. Micro debonding tests of non and resin particles added composites were conducted. Fracture surface of resin particles added composite were observed by Scanning Electron Microscope (SEM). As a result, interfacial shear strengths of non particles added composite monotonously decreased with an increase of water temperature. Interfacial shear strength of resin particles added composite was higher than that of non resin particles added composite under all water temperatures except for 50 oC. From SEM observation, large resin particles on surface of carbon fiber after water immersion at 50 oC were found. And, many matrices and large resin particles on surface of carbon fiber after water immersion at 80 oC were found. Therefore, interfacial shear strength of composite was improved because resin particle addition prevented water penetration into the interface between fiber and matrix under water immersion less than 50 oC. And, interfacial shear strength of composite was probably improved by anchor effect of resin particle under water immersion at 80 oC.

We have previously reported on the improvement of the interfacial shear strength of carbon fiberreinforced polypropylene (CFRPP) using carbon fiber with added resin particles (uneven carbon fiber). This study was conducted to assess the interfacial shear strength of CFRPP with uneven carbon fiber under a hot-wet environment for long-term safety of vehicles. The matrix was maleic anhydride grafted polypropylene. The matrix concentration was 10%. Reinforcement was done with uneven carbon fiber. Water absorption tests of CFRPP were conducted using uneven carbon fiber. The range of water temperature was from room temperature (RT) to 80°C. The maximum immersion time was 112 days. After water absorption testing, a micro-debonding test of CFRPP using uneven carbon fiber was conducted at RT. Fracture surfaces of carbon fibers were observed using scanning electron microscopy (SEM). Results show that when the maximum immersion time was 112 days, interfacial shear strength of water-immersed CFRPPs using uneven carbon fiber at RT, 50°C and 80°C decreased by 54%, 94% and 96% respectively, compared with that of non-immersed CFRPP using uneven carbon fiber. However, interfacial shear strengths of water-immersed CFRPPs using even and uneven carbon fiber under 50°C and 80°C showed almost no change at 112 days. SEM observations revealed large resin particles on the fracture surface of carbon fiber at temperatures higher than 50°C. Large resin particles and matrix on fracture surface of carbon fiber were found at 80°C. The viscoelasticity and interfacial adhesion property of water absorbing polymer matrix probably decreased when CFRPP using uneven carbon fiber was immersed at temperatures higher than 50°C. Therefore, the interfacial shear strength of CFRPP using uneven carbon fiber was strongly affected because of water absorption by polymer matrix and water penetration into interface between fiber and polymer matrix under a hot-wet environment.