Characterization of interlaminar shear properties of nanostructured unidirectional composites

ABSTRACT

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.

KEYWORDS:

• Composites
• carbon fiber
• carbon nanotubes
• tensile strength
• interlaminar shear strength

Acknowledgments

The authors wish to acknowledge support from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), in the Instituto Nacional de Pesquisas Espaciais (INPE), the Aeronautical Technology Institute (ITA) and the Aeronautics and Space Institute (IAE), in São José dos Campos, São Paulo, Brazil. The authors would like to thank EMBRAER for acknowledge support on this work and Toho Tenax for supplying materials.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Instituto Nacional de Pesquisas Espaciais (INPE); Aeronautical Technology Institute (ITA); Aeronautics and Space Institute (IAE).