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Polymers 2015, 7(6), 1020-1045; doi:10.3390/polym7061020

Interlaminar Fracture Toughness of CFRP Laminates Incorporating Multi-Walled Carbon Nanotubes

1
Department of Civil Engineering, University of New Mexico, MSC01 1070, Albuquerque, NM 87131, USA
2
Department of Civil Engineering, Assiut University, Assiut 71516, Egypt
3
Polymer Nanocomposites Center, Egyptian Petroleum Research Institute, 1 Ahmed El-Zomor Street, Nasr City, Cairo 11727, Egypt
*
Author to whom correspondence should be addressed.
Academic Editors: Alper Ilki and Masoud Motavalli
Received: 28 March 2015 / Accepted: 29 May 2015 / Published: 5 June 2015

Abstract

Carbon fiber reinforced polymer (CFRP) laminates exhibit limited fracture toughness due to characteristic interlaminar fiber-matrix cracking and delamination. In this article, we demonstrate that the fracture toughness of CFRP laminates can be improved by the addition of multi-walled carbon nanotubes (MWCNTs). Experimental investigations and numerical modeling were performed to determine the effects of using MWCNTs in CFRP laminates. The CFRP specimens were produced using an epoxy nanocomposite matrix reinforced with carboxyl functionalized multi-walled carbon nanotubes (COOH–MWCNTs). Four MWCNTs contents of 0.0%, 0.5%, 1.0%, and 1.5% per weight of the epoxy resin/hardener mixture were examined. Double cantilever beam (DCB) tests were performed to determine the mode I interlaminar fracture toughness of the unidirectional CFRP composites. This composite material property was quantified using the critical energy release rate, GIC. The experimental results show a 25%, 20%, and 17% increase in the maximum interlaminar fracture toughness of the CFRP composites with the addition of 0.5, 1.0, and 1.5 wt% MWCNTs, respectively. Microstructural investigations using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) verify that chemical reactions took place between the COOH–MWCNTs and the epoxy resin, supporting the improvements experimentally observed in the interlaminar fracture toughness of the CFRP specimens containing MWCNTs. Finite element (FE) simulations show good agreement with the experimental results and confirm the significant effect of MWCNTs on the interlaminar fracture toughness of CFRP. View Full-Text
Keywords: carbon nanotubes; fracture toughness; FTIR; XPS; finite element modeling carbon nanotubes; fracture toughness; FTIR; XPS; finite element modeling
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Borowski, E.; Soliman, E.; Kandil, U.F.; Taha, M.R. Interlaminar Fracture Toughness of CFRP Laminates Incorporating Multi-Walled Carbon Nanotubes. Polymers 2015, 7, 1020-1045.

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