“…However, upon stress hold we observe a relaxation towards tensile strains. Upon unloading, the behavior is linear (closed microcracks do not slide back immediately, and stiffen the material [20,21]), but upon application of a second cycle, the axial modulus slightly decreases, indicating that some permanent damage has been introduced (please note that the unloading branch of cycle 2 could not be recorded). Further cycling decreases the axial modulus, but it basically remains within a factor of 0.9 lower than the stiffness of the baseline sample.…”