Continuous crack monitoring of metallic structures using carbon nanotube-based epoxy thin films

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TypeArticle
Proceedings title2nd Joint US-Canada Conference on Composites - American Society for Composites, 26th Annual Technical Conference: Canadian Association for Composite Structures and Materials
Conference2nd Joint US-Canada Conference on Composites - American Society for Composites, 26th Annual Technical Conference: Canadian Association for Composite Structures and Materials, 26 September 2011 through 28 September 2011, Montreal, QC
SubjectContinuous monitoring; Crack evolution; Crack length; Crack monitoring; Crack sensors; Crack surfaces; Electrical and mechanical properties; Electrical discharges; Epoxy nanocomposites; Fatigue cycles; Growth monitoring; Host structure; Linear correlation; Measured currents; Metallic hosts; Metallic structures; Nanocomposite thin films; Resistance change; Stable modes; Visual inspection; Aluminum; Carbon nanotubes; Electric discharges; Epoxy resins; Fatigue testing; Mechanical properties; Nanocomposite films; Nanocomposites; Sensors; Structure (composition); Cracks
AbstractThis work focuses on the application of epoxy nanocomposite thin film sensors for continuous monitoring of crack evolution in metallic structures. The approach taken was to monitor the current or resistance change in these nanocomposite films as cracks developed and propagated in the metallic host structure. Based on optical, electrical and mechanical properties of epoxy resins modified with different contents of singlewalled carbon nanotubes (SWCNT), two different nanocomposites (with 0.3 wt% and 1.0 wt% of SWCNT) were chosen for the development of a crack sensor. The performance of the nanocomposite sensors was evaluated under tension-tension fatigue tests on aluminum coupons with centrally located through thickness electrical discharge machined (EDM) notches. Crack growth in the aluminum was found to transfer to the nanocomposite films in a stable mode. Once the crack was established, a linear correlation was found between the measured current and crack length with a slope of -10 -11 A/mm and -10 -8 A/mm for nanocomposites, with 0.3 wt% and 1.0 wt% of SWCNT, respectively. Contact between the asperities formed on the crack surfaces in the nanocomposite film while the crack was closed was found to be an important limiting factor causing a large variation in measured currents during each fatigue cycle. In summary, the nanocomposite thin film sensor developed in this work offers continuous crack growth monitoring. The sensor is also suitable for visual inspection of the host structure due to the transparency of the developed nanocomposite film.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); Aerospace (AERO-AERO); NRC Steacie Institute for Molecular Sciences (SIMS-ISSM)
Peer reviewedYes
NPARC number21271343
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Record identifier22832c6f-36cc-41cc-a91a-36c773dc8d35
Record created2014-03-24
Record modified2016-05-09
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