It has been demonstrated in a previous study that carbon nanotube (CNT)/epoxy/basalt composites produce better flexural properties than epoxy/basalt composites. In this study, mode I fracture tests were conducted using CNT/epoxy/basalt composites with and without seawater absorption in order to investigate the effect of the seawater absorption on the mode I fracture toughness (GIC) of the CNT/epoxy/basalt composites. The results demonstrated that the compliance of the seawater-absorbed specimen was larger than that of the dry specimen at the same crack length, while the opposite result was obtained for the fracture load. The GIC value of the seawater-absorbed CNT/epoxy/basalt composites was approximately 20% lower than that of the dry CNT/epoxy/basalt composites.

The use of carbon nanotubes (CNTs) as a reinforcing material in a polymer matrix has in-creased in various industries. In this study, the flexuralbehavior of CNT-modifiedepoxy/basalt (CNT/epoxy/basalt) composites is investigated. The effects of CNT modificationwith silane on the flexuralproperties of CNT/epoxy/basalt composites were also examined. Flexural tests were performed using epoxy/basalt, oxidized CNT/epoxy/basalt, and silanized CNT/epoxy/basalt multi-scale composites. After the flexuraltests, the fracture surfaces of the specimens were examined via scanning electron microscopy (SEM) to investigate the fracture mechanisms of the CNT/epoxy/basalt multi-scale composites with respect to the CNT modificatio process. The flexuralproperties of the epoxy/basalt composites were im-proved by the addition of CNTs. The flexuralmodulus and strength of the silane-treated CNT/epoxy/basalt multi-scale composites increased by approximately 54% and 34%, re-spectively, compared to those of epoxy/basalt composites. A SEM examination of the frac-ture surfaces revealed that the improvement in the flexuralproperties of the silane-treated CNT/epoxy/basalt multi-scale composites could be attributed to the improved dispersion of the CNTs in the epoxy.