Assessing the integrity of CFRPs through nanomechanical mapping: the effect of CF surface modification

Elias P Koumoulos,Panagiotis Kainourios,Costas A Charitidis,S Pantelakis,S Koubias

doi:10.1051/matecconf/201818801006

Elias P Koumoulos, Panagiotis Kainourios + Show 3 more

Open Access

https://doi.org/10.1051/matecconf/201818801006

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Abstract

The purpose of this study is to assess the effect of CF surface modification in enhancement of the wetting properties of carbon fibers in order to improve the adhesion force between the fiber and the polymer matrix; for this, the integrity of CFRPs through nanomechanical mapping was evaluated. The surface of commercial carbon fibers was functionalized through cyclic voltammetry in aqueous electrolyte solutions of H2SO4, in the presence of acrylic acid, methacrylic acid, acrylonitrile and N-vinylpyrrolidone monomers. The produced surface modified carbon fibers were embedded in epoxy resin. Elastic modulus nanoindentation mapping was performed in order for elastic modulus to be calculated, as a qualitative assessment of fibre – matrix interaction. For this, a grid protocol was set up for the integrity assessment of CFRPs through nanomechanical mapping.

Highlights

Over the last decade carbon fiber (CF) has been considered as one of the most promising reinforcement materials, while epoxy based resins or thermoplastic polymers are mainly utilised as matrices for the synthesis of composite materials, meeting a large variety of application requirements, i.e. from automobile to aerospace, medical and structural operations
According to the literature [3], due to lack of fiber-matrix strong chemical bonding, the application of stress to the carbon fiber composite results in poor mechanical properties, e.g. decreased interlaminar shear strength (ILSS) and toughness, as stress transfer from one carbon filament to another occur via the matrix material [3]; CF is pulled out of the matrix
Elastic modulus mapping for all samples at 200 nm of displacement revealed that for the case of PMAA-CFs, increased values (~3.5 GPa) are recorded; this is consistent with the data of figure 5, as it is evident that higher applied loads are required for reaching the displacement of 200 nm, when compared with all other samples

Summary

Introduction

Over the last decade carbon fiber (CF) has been considered as one of the most promising reinforcement materials, while epoxy based resins or thermoplastic polymers are mainly utilised as matrices for the synthesis of composite materials, meeting a large variety of application requirements, i.e. from automobile to aerospace, medical and structural operations. According to the literature [3], due to lack of fiber-matrix strong chemical bonding, the application of stress to the carbon fiber composite results in poor mechanical properties, e.g. decreased interlaminar shear strength (ILSS) and toughness, as stress transfer from one carbon filament to another occur via the matrix material [3]; CF is pulled out of the matrix (pull-out effect). This drawback is confronted with several approaches of surface treatment in order to introduce active groups on the fibers surface that will enhance the bonding with the matrix resin.

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