Testing Methods- Shear Strength
Shear Strength:
To test the cohesion, or the internal strength of the adhesive, a shear test is performed. The test comes in two versions; The Static Shear and the Dynamic Shear test. In both cases, the tested tape is applied with a roller of specified weight to the test panel at an area of normally 25 x 25 mm.
Static Shear-
The static shear test shows the ability of the tape to withstand a fixed load over time. After the dwell time, the specimen is clamped in a static shear jig, a weight of 0.5, 1 or 2 kg is hung to the free end of the tape, and timing is started. The test is carried out until the tape either slips a certain distance in a specified time or the bond fails and the weight drops. Result is expressed as the load in kg/625 mm² and slippage in mm or the number of minutes to bond failure.
Static shear can also be tested at a high temperature (+70°C) and at continuously increasing temperatures from 23°C to 225°C until the bond fails. This test gives meaningful data (e.g. softening point) about the performance of the adhesive at the elevated temperatures. Higher temperatures cause the adhesive to act more like a liquid, and will decrease the adhesive cohesion. The test is useful for example, for determination of a suitable tape for higher temperature splicing applications.
Static Shear test performed with 1 kg weight
Dynamic Shear-
In the dynamic shear test, the panels of the tested substrate are clamped on
a tensile tester, and pulled apart at a constant speed. The result shows a peak load where the bond fails, and this measurement is expressed as the dynamic shear per the tested area, normally N/625 mm²
Dynamic Shear testing machine