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Study of synergistic toughening in a bimodal epoxy nanocomposite

Keivani, M ; Sharif University of Technology | 2015

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  1. Type of Document: Article
  2. DOI: 10.1177/0731684415570373
  3. Publisher: SAGE Publications Ltd , 2015
  4. Abstract:
  5. Toughening of epoxy with different types of modifiers produces a bimodal blend that might show better fracture resistance in comparison with single-modified ones. In this research, bimodal epoxy formulations including mixtures of glass microsphere and silica nanoparticles are explored for possible synergistic toughening. The influence of composition on the glass transition temperature (Tg), tensile characteristics, and fracture toughness (KIC) is investigated. Interestingly, a synergism in fracture toughness is observed when mixtures of modifiers were incorporated. For the fixed overall modifier content, KIC is higher when the volume fraction of glass microsphere is lesser than the volume fraction of nanosilica. Fractographs reveal that glass microsphere increases the toughness of epoxy matrix by crack pinning/bridging mechanisms. On the other hand, nanosilica enhances the toughness by increase in plastic deformation via shear banding/particle debonding. Interestingly, the origin of synergistic toughness in bimodal epoxies is the interaction between the glass microsphere and crack-tip damage zone which provides comprehensive stable crack deflection within the nanosilica-toughened epoxy. This mechanism results in a mixed-mode crack growth that reduces the strain energy release rate in bimodal formulations
  6. Keywords:
  7. Bimodal epoxy nanocomposite ; Crack deflection/branching ; Synergistic toughening ; Crack tips ; Cracks ; Fracture ; Glass ; Glass transition ; Microspheres ; Mixtures ; Nanocomposites ; Strain energy ; Strain rate ; Volume fraction ; Crack deflections ; Epoxy formulations ; Epoxy nanocomposites ; Glass microspheres ; Mixed-mode crack growth ; Silica nanoparticles ; Tensile characteristics ; Toughened epoxies ; Fracture toughness
  8. Source: Journal of Reinforced Plastics and Composites ; Volume 34, Issue 4 , February , 2015 , Pages 281-292 ; 07316844 (ISSN)
  9. URL: http://jrp.sagepub.com/content/34/4/281