Fig. 6. FCG behavior of
commercial PMMA plastics a) as a function of ΔK with three R-ratios and
one Kmean and one Kmax constant tests.
b) The data in terms of Kmax. c) ΔK-R plots at selected
crack growth rates close to the threshold value. d) The
ΔK-Kmax plot showing L-shaped curves. e) The FCG
trajectory showing its deviation from the pure-fatigue line.
behavior of the material under fatigue. Fig. 6e provides the crack
growth trajectory map for this material. Naturally, the data deviate
from the pure fatigue line toward the Kmax-axis.
Fig.7 shows crack growth rate data of Epoxy resin but toughened by
rubber, studied by Hamda et al.[23]. Fig. 7a shows crack growth
rates in terms of ΔK. Two values for some Rs imply that two tests were
done at those R-values. The crack growth data is represented in terms of
Kmax in Fig.