Influence of Resin on Splitting Fracture Toughness in Unidirectional CFRP.

Influence of matrix resin on tensile strength properties and splitting fracture toughness in unidirectional carbon fiber-reinforced plastic (CFRP) laminates has been investigated. Tensile tests and splitting fracture toughness tests were carried out on two kinds of CFRPs (carbon/thermoplastic systems ; 3KCF/Nylon 6 and 3KCF/modified Nylon). The modified Nylon was developed to improve the adhesion on the basis of Nylon 6. The performance of the present CFRPs was discussed in comparison with that of carbon/epoxy system (AS4/3501-6). It is noted that the present CFRPs exhibit the high strength and high ductility in 90°and 45°directions to the fibers. This result predicts that the present CFRPs have the potential for high resistance to the splitting in unidirectional laminate and to the transverse cracking in multidirectional laminate. On all the unidirectional CFRPs, the splitting fracture toughness under pure mode II is higher than that under pure mode I and the splitting is controlled by the tensile stress intensity in the wide range from pure mode I to mixed-mode loading. The fracture toughness for splitting in CFRP is drastically increased by changing matrix resin from epoxy to Nylon 6, and furthermore is improved by modified Nylon.