Characterization of interlaminar shear properties of nanostructured unidirectional composites

Composites are key materials in the aerospace and aeronautics industry. However, a disadvantage is their susceptibility to interlaminar fracture because of poor adhesion at fiber surface and matrix interface. Carbon nanotube (CNT) growth onto carbon fiber (CF) surface is a promising method to increase CF-matrix adhesion. This work studies interlaminar properties of unidirectional CF composites and thermoset matrix, with CNT deposition on CF surface. CNT growth goes along in chemical vapor deposition with a floating catalyst of ferrocene and flow of CO2 and C2H2 precursors. Tensile strength tests on single-filament and CF tow showed the preservation of tensile properties after preparation and growth. Results of the interlaminar shear strength study presented a 35% increase in shear strength and a 15% increase in fracture toughness at the initial delamination crack. An overall analysis reveals an improvement in the interlaminar interface on mechanical tests; however, fracture toughness analysis is limited by fragile pathways in intralaminar regions.