TY - JOUR
T1 - Measurement of the fracture toughness of a fiber-reinforced composite using the Brazilian disk geometry
AU - Liu, C.
AU - Huang, Y.
AU - Lovato, M. L.
AU - Stout, M. G.
N1 - Funding Information:
This research was supported financially by the Department of Energy, Defense Programs, Technology Transfer Initiative Program. Y. Huang also acknowledges the financial support from the National Science Foundation (Grant INT-94-23964 and Grant CMS-95-22147).
PY - 1997
Y1 - 1997
N2 - 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.
AB - 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.
KW - Brazilian disk specimen
KW - Composites fracture
KW - Crack initiation
KW - Fracture toughness measurement
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U2 - 10.1023/A:1007419406590
DO - 10.1023/A:1007419406590
M3 - Article
AN - SCOPUS:0003084972
SN - 0376-9429
VL - 87
SP - 241
EP - 263
JO - International Journal of Fracture
JF - International Journal of Fracture
IS - 3
ER -