University of Illinois Urbana-Champaign

Fatigue crack propagation in microcapsule toughened epoxy

Brown, Eric N.; White, Scott R.; Sottos, Nancy R.

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https://hdl.handle.net/2142/244

Description

Title
Fatigue crack propagation in microcapsule toughened epoxy
Author(s)
  • Brown, Eric N.
  • White, Scott R.
  • Sottos, Nancy R.
Issue Date
2004-04
Abstract
The addition of liquid-filled urea-formaldehyde (UF) microcapsules to an epoxy matrix leads to significant reduction in fatigue crack growth rate and corresponding increase in fatigue life. Mode-I fatigue crack propagation is measured using a tapered doublecantilever beam (TDCB) specimen for a range of microcapsule concentrations and sizes: 0, 5, 10, and 20% by weight and 50, 180, and 460 micron diameter. Cyclic crack growth in both the neat epoxy and epoxy filled with microcapsules obeys the Paris power law. Above a transition value of the applied stress intensity factor, which corresponds to loading conditions where the size of the plastic zone approaches the size of the embedded microcapsules, the Paris law exponent decreases with increasing content of microcapsules, ranging from 9.7 for neat epoxy to approximately 4.5 for concentrations above 10 wt% microcapsules. Improved resistance to fatigue crack propagation, indicated by both the decreased crack growth rates and increased cyclic stress intensity for the onset of unstable fatigue-crack growth, is attributed to toughening mechanisms induced by the embedded microcapsules as well as crack shielding due to the release of fluid as the capsules are ruptured. In addition to increasing the inherent fatigue life of epoxy, embedded microcapsules filled with an appropriate healing agent provide a potential mechanism for self-healing of fatigue damage.
Publisher
Department of Theoretical and Applied Mechanics (UIUC)
Series/Report Name or Number
TAM Reports 1048
ISSN
0073-5264
Type of Resource
text
Language
en
Permalink
http://hdl.handle.net/2142/244

Owning Collections

Technical Reports - Theoretical and Applied Mechanics (TAM) PRIMARY
TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.