Fig. 7 Crack growth rates in
rubber toughened epoxy resin. a) in terms of ΔK and b) in terms of
Kmax. c) ΔK –R plots for selected crack growth rates
showing two mechanisms. d) ΔK-Kmax plots showing two
L-shaped curves. e) Crack growth trajectory maps for the two mechanisms.
The results are compared with the trajectory of Epoxy material tested by
Osorio.
7b. From the data, ΔK-R plots are made as shown in Fig. 7c. Only one
line can be drawn through the data at low crack growth rates. On the
other hand, at high Rs, the data diverges into two levels indicating two
possible mechanisms operating at high R values. Thus, both mechanisms
seem to have the same Kmax limiting value but different
ΔK limiting values. It is the first time we are observing this type of
behavior. Fig. 7e shows the crack growth trajectories for