Table 1 Summary of fracture toughness measurements.
Sample number1234
Thickness (nm)14.6 ± 0.121.1 ± 0.234.0 ± 0.3131.5 ± 0.2
Number of layers~21~30~49~188
Crack size (nm)416.7 ± 1818 ± 21244 ± 61279.6 ± 7
Crack size/sample width12%16%10%11%
Linear analysis (Griffith theory)
Critical stress intensity factor KIC (MPa√m)4.4 ± 1.25.9 ± 2.44.9 ± 1.74.0 ± 0.5
Critical stress energy release rate GIC (J/m2)*80–92140–167110–11576–262
Nonlinear analysis (J integral)
JIC (J/m2)34–3981

*Critical strain energy release rate for each sample was reported as a range because it is Young’s modulus dependent; the lower bound value was obtained by using the modulus of monolayer GO in the study of Suk et al. (26), whereas the upper bound value was determined using the modulus of GO nanosheets [calculated by fitting the modulus versus thickness trend in the study of Cao et al. (14)]