Abstract
The mechanical properties of carbon fibers, especially their tensile properties, are affected by internal and surface defects. In order to asses in what extent the generation of surface defects can result in a loss of the mechanical properties, non-surface treated carbon fibers were oxidized with three different surface treatment processes: electro-chemical oxidation, oxidation in nitric acid, and oxidation in oxygen plasma. Different surface topographies and surface chemistries were obtained, as well as different types and densities of surface defects. The density of surface defects was measured with both a physical approach (Raman spectroscopy) and a chemical approach (Active Surface Area). The tensile properties were evaluated by determining the Weibull modulus and the scale parameter of each reference, after measuring the tensile strength for four different gauge lengths. A relationship between the tensile properties and the nature and density of surface defects was noticed, as large defects largely control the value of the tensile strength. When optimized, some oxidation surface treatment processes can generate surface functional groups as well as an increase of the mechanical properties of the fibers, because of the removal of the contamination layer of pyrolytic carbon generated during the carbonization of the polyacrylonitrile precursor. Oxidation in oxygen plasma revealed to be a promising technology for alternative surface treatment processes, as high levels of functionalization were achieved and a slight improvement of the mechanical properties was obtained too.
Original language | English |
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Pages (from-to) | 185-193 |
Number of pages | 9 |
Journal | Applied Surface Science |
Volume | 322 |
DOIs | |
State | Published - Dec 15 2014 |
Externally published | Yes |
Funding
ANRT (Association Nationale de la Recherche et de la Technologie) is gratefully acknowledged for the PhD grants assigned to F. Vautard. S. Ollivier, P. Wagner and J. Ducret from IS2M are sincerely thanked for their assistance with the AFM imaging, Raman analysis and tensile testing of the single fibers, respectively.
Funders | Funder number |
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Association Nationale de la Recherche et de la Technologie |
Keywords
- Active surface area (ASA)
- Atomic force microscopy (AFM)
- Carbon fibers
- Raman spectroscopy
- Surface defects
- Tensile strength