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effects of nitric acid and silane surface treatments on carbon fibers and carbon/vinyl ester composites before and after seawater exposure

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Date Issued:
2008
Summary:
This research focuses on carbon fiber treatment by nitric acid and 3- (trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface treatments are often prescribed for improved wetting and bonding to carbon, but good results are not always achieved. Furthermore, there is the unanswered question of environmental durability. This research aimed to form a better understanding of oxidizing carbon fiber treatments, determine if silanes can be bonded to oxidized surfaces, and how these treatments affect composite strength and durability before and after seawater exposure. Nitric acid treatments on carbon fibers were found to improve their tensile strength to a constant level by smoothing surface defects and chemically modifying their surfaces by increasing carbonyl and carboxylic acid concentrations. Increasing these surface group concentrations raises fiber polar energy and causes them to cohere. This impedes wetting, resulting in poor quality, high void content composites, even though there appeared to be improved adhesion between the fibers and matrix. Silane was found to bond to the oxidized carbon fiber surfaces, as evidenced by changes in both fiber and composite properties. The fibers exhibited low polarity and cohesion, while the composites displayed excellent resin wetting, low void content, and low seawater weight gain and swelling. On the contrary, the oxidized fibers that were not treated with silane exhibited high polarity and fiber cohesion.
Title: The effects of nitric acid and silane surface treatments on carbon fibers and carbon/vinyl ester composites before and after seawater exposure.
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Name(s): Langston, Tye A.
College of Engineering and Computer Science
Department of Ocean and Mechanical Engineering
Type of Resource: text
Genre: Electronic Thesis Or Dissertation
Issuance: monographic
Date Issued: 2008
Publisher: Florida Atlantic University
Physical Form: electronic
Extent: xvii, 265 p. : ill. (some col.).
Language(s): English
Summary: This research focuses on carbon fiber treatment by nitric acid and 3- (trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface treatments are often prescribed for improved wetting and bonding to carbon, but good results are not always achieved. Furthermore, there is the unanswered question of environmental durability. This research aimed to form a better understanding of oxidizing carbon fiber treatments, determine if silanes can be bonded to oxidized surfaces, and how these treatments affect composite strength and durability before and after seawater exposure. Nitric acid treatments on carbon fibers were found to improve their tensile strength to a constant level by smoothing surface defects and chemically modifying their surfaces by increasing carbonyl and carboxylic acid concentrations. Increasing these surface group concentrations raises fiber polar energy and causes them to cohere. This impedes wetting, resulting in poor quality, high void content composites, even though there appeared to be improved adhesion between the fibers and matrix. Silane was found to bond to the oxidized carbon fiber surfaces, as evidenced by changes in both fiber and composite properties. The fibers exhibited low polarity and cohesion, while the composites displayed excellent resin wetting, low void content, and low seawater weight gain and swelling. On the contrary, the oxidized fibers that were not treated with silane exhibited high polarity and fiber cohesion.
Summary: Their composites displayed poor wetting, high void content, high seawater weight gain, and low swelling. Both fiber treatment types resulted in great improvements in dry transverse tensile strength over the untreated fibers, but the oxidized fiber composites lost strength as the acid treatment time was extended, due to poor wetting. The acid/silane treated composites lost some transverse tensile strength after seawater exposure, but the nitric acid oxidized fiber composites appeared to be more seawater durable.
Identifier: 317287558 (oclc), 172669 (digitool), FADT172669 (IID), fau:2845 (fedora)
Note(s): by Tye A. Langston.
Thesis (Ph.D.)--Florida Atlantic University, 2008.
Includes bibliography.
Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.
Subject(s): Silane compounds -- Testing
Surface chemistry
Composite materials -- Biodegradation
Carbon compounds -- Testing
Held by: FBoU FAUER
Persistent Link to This Record: http://purl.flvc.org/FAU/172669
Use and Reproduction: http://rightsstatements.org/vocab/InC/1.0/
Host Institution: FAU