ABSTRACT
There are three factors that need to be especially considered when conducting tests on large laminated aluminum-faced panels in regard to their sensitivity to delamination under solar heating conditions: (1) test panels of maximum overall size to evaluate highest service stress levels, (2) test panels with color facing that will absorb highest thermal energy (Alcoa used flat black painted aluminum facings), and (3) use the same physical attachment system for mounting panel to frame that will be employed in field erection. It should be remembered that the use of smaller panel sizes, lighter paint colors, or a method of attachment that permits greater panel bowing with solar heating could underestimate what conditions the adhesive must pass under the worst set of service conditions. The difficulties associated with passing such rigorous tests was the basis for only being able to find a few contact adhesives of 200 tested that could be used in production. The same adhesives were also tested for their long-term weathering resistance by exposing portions to continuous soaking in 1000Jo RH at l25°F (52°C) for a minimum of 6 mo. Production panels were also exposed in an experimental building to natural industrial weathering conditions for indefinitely long periods of time. Periodically panels were removed and evaluated in simulated thermal stress and tensile testing of the bondline. Other duplicate panels were exposed to a wet/freeze/thaw cycling exposure as the common wall between two chambers whose temperature and humidity could be exactly controlled. Finally, quality control test procedures were developed which predicted for each lot of production panels whether the same quality of bonding had been achieved that was equivalent to those in laboratory panels which had passed all the contrived longer-time exposure testing. The details of how these quality control tests were conducted has been described earlier in Chapter 9.
