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.

Source of Variation

SS

df

MS

F

P Value

Fcrit

Between groups

1.95

2

0.97

24.58

0.001288

5.14

Within groups

0.24

6

0.040

Подпись: TABLE 3—Experimental results of tension pull-out test specimens. Epoxy Type A Epoxy Type B Epoxy Type C Specimen Load, kN Stress, MPa Load, kN Stress, MPa Load, kN Stress, MPa 1 9.2 4.5 10.7 5.3 3.1 1.5 2 6.7 3.3 8.5 4.2 1.6 0.8 3 7.6 3.7 7.7 3.8 1.1 0.5 4 a a 3.4 1.7 1.7 0.8 5 2.7 1.3 3.4 1.7 4.8 2.4 6 4.4 2.2 1.4 0.7 1.3 0.7 7 12.3 6.1 13.4 6.6 1.0 0.5 8 2.9 1.4 2.9 1.4 4.0 2.0 9 2.5 1.2 3.7 1.8 2.6 1.3 10 3.1 1.5 6.7 3.3 2.8 1.4 11 2.2 1.1 7.8 3.8 0.4 0.2 12 2.7 1.3 11.7 5.8 0.4 0.2 13 2.6 1.3 3.8 1.9 0.4 0.2 14 5.6 2.8 7.6 3.7 2.2 1.1 15 a a 13.5 6.6 7.8 3.8 aAccidental movement during steel disc bonding process prevented these specimens from being tested.

_ 4P

Подпись: (2)pd2

where:

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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Tension Pull-out Tests

FIG. 9—Photographs at failure for tension pull-out specimens.