Tension Pull-out Tests
A summary of the ultimate applied tension load for all of the specimens tested is shown in Table 3. The maximum tensile strength of each specimen was determined using
TABLE 2—ANOVA F-test results for double shear test specimens.
r = the shear stress at each bond interface (MPa),
P = the recorded ultimate applied load (N) and,
d = the diameter of the bonded area (mm), equal to 50 mm for this experiment.
Failure of the specimens that used epoxy types A and B under pull-out tension forces occurred as a combination of both separation in the epoxy layer as well as fracturing of the bonded aggregates. In the case of the specimens that used epoxy type C for bonding of the aggregates, the bulk of the failure occurred in the epoxy layer with very little to no fracturing of the aggregates. Representative photographs showing the failure of the three different types of tension pullout specimens are shown in Fig. 9. The distribution and variance of the tension strength provided by the specimens are shown in Fig. 10, which shows that epoxy type B provided the highest resistance to tension pull-out forces. The F-test ANOVA results for the tension pull-out tests are shown in Table 4. Similar to the conclusion made in “Double-Lap Shear Tests" for the double shear test specimens, the value for F was noticeably greater than the value for Fcrit, leading to the conclusion that the average tension strength provided by the three different epoxy adhesive types were statistically different from one other.
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FIG. 9—Photographs at failure for tension pull-out specimens.