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

Elisa Borowski,Mahmoud Taha,Usama Kandil,Eslam Soliman

doi:10.3390/polym7061020

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.

Highlights

Like most high-performance composites, carbon fiber reinforced polymers (CFRP) feature favorable material properties of a high strength-to-weight ratio and notable stiffness, making them ideal candidates for use in a broad range of industries, including aerospace, marine, armor, automotive, electronic, and infrastructural applications [1,2]
The experimental results show that the incorporation of multi-walled carbon nanotubes (MWCNTs) increased the interlaminar fracture toughness GIC compared with neat CFRP
Limited increases of 20% and 17% in GIC were observed for specimens incorporating 1.0 wt% and 1.5 wt% MWCNTs contents respectively, compared with neat CFRP

Summary

Introduction

Like most high-performance composites, carbon fiber reinforced polymers (CFRP) feature favorable material properties of a high strength-to-weight ratio and notable stiffness, making them ideal candidates for use in a broad range of industries, including aerospace, marine, armor, automotive, electronic, and infrastructural applications [1,2]. While CFRP composites have many optimal qualities, they present several drawbacks, including poor in-plane compression, tension-compression fatigue, and restricted resistance to interlaminar fiber-matrix cracking and delamination due to the limited fracture toughness of the polymer matrices [5]. Interlaminar delamination is a major challenge in the design of composite structures. Within the matrix-dominated interlaminar region, brittle failure has been reported to manifest in the form of matrix transverse cracking and/or fiber-matrix interface debonding, both of which can severely affect the structural integrity of the composite laminate [3]. Many studies have successfully quantified the relatively low fracture toughness of laminated composites. For the past several decades, the improvement of interlaminar fracture toughness in composites with brittle matrices has been a critical area of research and investigation

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Conclusion