Measurement of the fracture toughness of a fiber-reinforced composite using the Brazilian disk geometry

C. Liu*, Y. Huang, M. L. Lovato, M. G. Stout

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


A technique, using the Brazilian disk specimen, for measuring the fracture toughness of unidirectional fiber-reinforced composites, over the entire range of crack-tip mode mixities, was developed. The fracture toughness of a graphite/epoxy fiber-reinforced composite was measured, under both mode-I and mode-II loading conditions. We found that for certain material orientations the mode-II fracture toughness is substantially higher than the mode-I toughness. The complete dependence of the fracture toughness on the crack-tip mixity was determined for particular material orientations and the phenomenological fracture toughness curves were constructed. Using the Brazilian disk specimen, together with a hydraulic testing machine, the fracture toughness of the composite under moderate loading rates was measured. We observed that the mode-I fracture toughness was not sensitive to the loading rate at the crack tip, K̇, while the mode-II 'dynamic' fracture toughness increased approximately 50 percent over the quasi-static fracture toughness. A qualitative explanation of the dependency of fracture toughness on crack-tip loading rate is discussed. Finally, a mechanical fracture criterion, at the microscopic level, which governs the crack initiation under mixed-mode loading conditions is presented; these theoretical predictions closely follow the trend of experimental measurements.

Original languageEnglish (US)
Pages (from-to)241-263
Number of pages23
JournalInternational Journal of Fracture
Issue number3
StatePublished - 1997


  • Brazilian disk specimen
  • Composites fracture
  • Crack initiation
  • Fracture toughness measurement

ASJC Scopus subject areas

  • Computational Mechanics
  • Modeling and Simulation
  • Mechanics of Materials


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