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A facile in situ polymerization was developed for grafting renewable cardanol onto the carbon fiber (CF) surfaces to strengthen the fiber&ndash, matrix interface. CFs were chemically modified with hydroxyl groups by using an aryl diazonium reaction, and then copolymerized in situ with hexachlorocyclotriphosphazene (HCCP) and cardanol to build cardanol-modified fibers (CF-cardanol). The cardanol molecules were successfully introduced, as confirmed using Raman spectra and X-ray photoelectron spectroscopy (XPS), the cardanol molecules were found to increase the surface roughness, energy, interfacial wettability, and activity with the matrix resin. As a result, the interlaminar shear strength (ILSS) of CF-cardanol composites increased from 48.2 to 68.13 MPa. In addition, the anti-hydrothermal ageing properties of the modified composites were significantly increased. The reinforcing mechanisms of the fiber&ndash, matrix interface were also studied.

An effective approach to the fabrication of progressive epoxy nanocomposites by the incorporation of hydroxyl-terminated dendrimers functionalized graphene oxide (GO-TCT-Tris) is reported. The relationship between surface grafting, chemical construction, morphology, dispersion, and interfacial interaction as well as the corresponding mechanical properties of the composites were studied in detail. It was shown that hydroxyl-terminated triazine derivatives have been resoundingly bonded onto the GO surface through covalent bonding, which effectively improved the dispersion and compatibility of GO sheets in epoxy resin. The tensile and flexural tests manifested that the GO-TCT-Tris/epoxy composites exhibited greater tensile/flexural strength and modulus than either the pure epoxy or the GO/epoxy composites. For GO-TCT-Tris (0.10 wt%)/epoxy composite, the tensile strength and elastic modulus increased from 63 &plusmn, 4 to 89 &plusmn, 6 MPa (41.27%) and from 2.8 &plusmn, 0.1 to 3.6 &plusmn, 0.2 GPa (28.57%), and the flexural strength and modulus increased from 106 &plusmn, 5 to 158 &plusmn, 6 MPa (49.06%) and from 3.0 &plusmn, 0.1 to 3.5 &plusmn, 0.2 GPa (16.67%), respectively, compared to the pure epoxy matrix. Moreover, the fractographic analysis also illustrated the ameliorative interfacial interaction between GO-TCT-Tris and epoxy matrix.

We proposed an easy and effective method to prepare multiwall carbon nanotubes (CNTs) modified sizing agent suited for carbon fibers (CFs) reinforced methylphenylsilicone resin (MPSR) composites. In order to improve the dispersion of CNTs in sizing agent and interfacial adhesion between CNTs and MPSR, CNTs were covalently functionalized with 3-aminopropyltriethoxysilane (APS) and the silanized carbon nanotube (CNT-APS) was introduced into the interface by sizing process as well. The CFs with and without sizing treatment reinforced MPSR composites were prepared by a compression molding method. Scanning electron microscopy (SEM) showed a uniform distribution of CNTs on the fiber surface and the enhancement of the surface roughness. Compared with untreated CFs composites, the interlaminar shear strength (ILSS) and impact toughness of CFs after sizing treatment containing 0.1 wt.% CNTs composites increased slightly owing to the serious agglomeration of excessive CNTs. However, the sized fibers modified with 0.5 wt.% CNT-APS composites revealed a significant increase 46.52% in ILSS and 31.12% in impact properties. Moreover, the reinforcing and toughening mechanisms were also discussed. In addition, the tensile strength (TS) of sized CFs showed a slightly increase in comparison with that of untreated CFs. Keywords: Carbon fiber, Sizing agent, Carbon nanotube, Composite material, Interfacial property, Impact performance