Roles of different organic-inorganic hybrid interfaces in enhancing the mechanical properties of continuous basalt fiber/epoxy composites

In order to enhance the interfacial adhesion between continuous basalt fibers (CBFs) and epoxy (EP) matrix and the mechanical properties of resultant composites, the organic - inorganic hybrid compatibilization layer (OIHCL) composed of flexible 1,6-hexanediol diglycidyl ether (HDE) chains and rigid nano-silica (SiO2) is grafted on CBFs surface. With increasing the SiO2 content in the OIHCL, the structure and composition of the OIHCL change from a single layer composed of a well-dispersed SiO2 phase and continuous HDE phase to a double layer composed of an HDE/SiO2 inner-layer and aggregated SiO2 outer-layer. And, the effects of different OIHCLs on the mechanical performances of resultant composite are studied in details. The results show that the single-layer OIHCL exhibits stronger reinforcing effects in the interfacial shear strength (IFSS), tensile strength, and flexural strength of resultant composite. For example, the IFSS, tensile strength, and flexural strength of the CBFs-g-12.5%-(HDE/SiO2)/EP composite can reach 47.1 MPa, 466.1 MPa, and 660.5 MPa, respectively. Furthermore, the impact strength of the CBF/EP composites can be effectively enhanced by only grafting a flexible HDE layer on CBF surfaces. Finally, the aggregated SiO2 derived from the outer-layer of double-layer OIHCLs can deteriorate the interfacial adhesion, and all mechanical performances of resultant composites.