Thanks
Thanks OT. I really appreciated all of the support both on and off line. Adhesive bonding is a truly amazing technology when the basic fundamentals are understood and correctly implemented. However there are problems with the certification basis and these deficiencies are combined with management that follows what worked last time (but didn't really work if they understood the basics). Iwas astounded to find that over 75% of aircraft designers base their designs on an average shar stress approach which was shown to be incorrect as far back as 1936. The only way that these designs work is that they have a high level of conservatism built in to the design allowable stress levels, and they undertake extensive testing. The stupid thing is that if they udnerstood the fundamentals of adhesive joint design developed in the late 1960's not only would their designs be just as conservative, they could save millions in certification costs.
It is actually possible to design a bond between aluminium up to about 0.15 inches thick such that the aluminium breaks, not the adhesive. If this rule was applied, then every one of the thousands of tests normally undertaken would result in only breaking the metal. So why do all of those tests? Design the joint, undertake a few tests to demonstrate that the bond is stronger than the metal and certification is a lot cheaper.
Regards
blakmax