Single Fibre Pull-Out Rate Tests
These tests were done in order to determine whether there is a rate effect with regards to the pull-out load and also the pull-out displacement at the maximum load. The results for the 0.5 mm/s is shown as an example in Fig. 5a.
Fig. 5 a the pull-out responses of the 0.5 mm/s tests, and b, the displacement at the maximum load resisted over the range of pull-out rates tested
The results show there is no change of maximum load resisted of the fibre during pull-out over the pull-out rate range from 0.25 цш/s to 2.5 mm/s. The pull-out displacement at maximum load was however affected by the loading rate and the pull-out at maximum load increased with 22 % from the highest to the lowest pull-out rate as can be seen in Fig. 5b. This gives rise to the hypotheses that stiffness of the interfacial transition zone (ITZ) between the fibre hooked-end and the matrix is affected by the loading rate, but the ITZ does not influence the strength capacity of the hooked-end. One can thus postulate that the ITZ “collapsing” at lower pull-out rates could be one of the causes of the fibre pull-out creep observed in the results shown in this paper.