A2121... In addition to SWC's comments...
When a batch of adhesive... 2-part paste, 1-part paste, film, pre-preg resin into fabric, primers, etc... is shipped from the OEM there are many way's to 'screw it up' in delivery to end-user. As long as Your receiving inspection testing is valid... and presumably represents all the material 'LOT as shipped/stored, etc under identical conditions, this inspection is valid and worthwhile... especially 'at the ends of the earth'... and for flight critical applications. Believe me... when I was on a tropical island in the pacific, shipment delays, warm exposure, etc took it's toll on epoxy-based adhesive reliability and usefulness.
Likewise, at the end of it's 'freezer/shelf-life' we used these same tests to validate extending the 'life' of this precious material [1] up-to [2] or more months.
The ONLY thing I can caution You about is that the skills and training for the qualification testing technician are all-important... which I learned the hard way.
In one instance [overseas] some very expensive high temp/toughness film adhesive was about to over-run its shelf life. When the lap shear coupon testing was accomplished, the adhesive oddly failed 'all-over map'... from 2100-PSI to 4100-PSI [4000-PSI was the spec for this adhesive]... with no apparent trends... definite FAIL and definitely 'odd' failure trends... failing partially within the adhesive and on the metal coupon surfaces.
A week later, the shop supervisor approached me and wanted to repeat the tests... with a different technician making/pulling the test coupons. OK. So, the test results were significantly improved... all were 3900-to-4050-PSI and consistently failed within the adhesive... no surface disbonds. Say WHAT? I had a long conversation with that technician and discovered he was a trained in adhesive bonding, had a eye/sense for details/workmanship and knew the test procedures 'cold'. He told me that he'd made fresh test coupons... since the adhesive-primer on the originals 'stock' test coupons was 'too-thick and old'... and told me a lot other 'good-stuff' RE this process. WOW he knew his stuff!! THAT is when he explained/complained that the original technician doing the work had a reputation in the shop for poor quality [sloppy] workmanship and for lack-of-attention to details. At this point, I 'OK'ed' that LOT of film adhesive for another 30-days usage... but no more. AND AT THAT TIME I qualified that second technician and disqualified the original technician for all future adhesive testing and critical adhesive bonding operations [repairs, etc].
Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov
