Shear test long-term

Resistance to common aircraft fluids such as water, salt water, hydraulic fluid and jet fuel is determined by additional shear testing after exposure to these fluids. Since adhesives are typically only exposed at bond edges, are protected by secondary primers and enamels and are not expected to be exposed to these fluids (save for water) for extended periods, exposure time prior to testing is relatively short. Lastly, the adhesive is tested for propensity to creep rupture under load in standard and aggressive environments. This testing indicates whether the polymer is crosslinked sufficiently to resist long-term creep under low load. 

The better long term stability of PVC/EPR can be readily explained with its higher fluidity and lower effective test temperature, as measured directly on the sheared polymer melt (Table XI). 

Additional factors which must be taken into account are environmental effects (thermal as well as chemical), effects of defects, statistical variability of the material, long-term behavior, and cyclic versus static loading effects. Assessment of these effects requires the end user to conduct a large series of tests using multiple specimens. A typical series will examine a unidirectional material in tension in the 0, 90, and cross-ply directions 0, 90, and cross-ply in compression and 1-2, 1-3, and 2-3 shear at different temperatures ranging from —54°C to the expected service temperature creep rupture at temperatures up to the expected service temperature and fatigue at room and elevated temperature. This series of tests, shown in Table 12.1, may require over 400 specimens. 

Shearing force increase at the initial instant was mainly due to in-gap iron oxide (Fe304) depositions on surfaces of the tested SFAs after preliminary hold up in water. However no further densification of iron oxide depositions was revealed. Thus the performed tests confirmed the possibility of SFA imloading after long-term hold up inside imwatered reactors. 

A different proach is used to reflect the shearing of end supports for an arch over a non-mass flow hopper outlet. In this case, the principal stress causing the arch to fail is generated by the weight of product supported over the opening. For this purpose a vertical shear-type test is conducted, see Fig. 1.5. For all such tests, the condition of the sample must reflect the loading conditions experienced by the material in the situation under consideration. Many bulk materials exhibit long-term variations of condition, and may be... 

Adhesion of textnre particles (long-term shear strength test) ... 

Fig. 3. 22. Test device for long-term shear test with all components...

Durability tests performance based long-term tests under accelerated test conditions pipe pressure tests (Gebler 1989) and long-term shear strength test (Seeger et al. 2000) discussed in Sects. 3.2.13 and 3.2.18 can serve as illustrations... 

For these three reasons it is not possible to eonsider the time-to-failure in the long-term tensile creep shear test as a eriterion for the quality of the weld seam and the welding method in geomembranes at all. 

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