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.