Adhesive Receiving Inspection Test Requirements

[audacious2121]

Hello,

We use number of OEM adhesives for Aicraft Interior Applications, they come with receiving insection testing requirements such as lap shear & flamability. These are batch tested by the supplier, so wondering why there are requirements to test again after you receive them? Is there a risk of the properties change during transportation? These adhesives do have freezing storage requirements. Trying to figure out why we need to do these testing?

Thanks!

 

[SWComposites]

If, a) you trust the supplier’s test data, b) the material is properly shipped and stored (with temperature recorders during shipping), there really is no value in repeating the tests. If not properly shipped and stored, yes the material properties may change. HOWEVER, if receiving tests are a spec requirement, then you have no option but to run the tests, unless you get a written approval from the spec owner to omit the tests.

 

[audacious2121]

I agree with what you are saying, however I want to understand logic behind these receiving insection test requirements

 

[SWComposites]

OEM conservatism and/or not trusting the suppliers and/or not trusting the shipping.

 

[audacious2121]

So basically chemical properties might alter during shipping and also supplier may have issues. Thanks you!

 

[WKTaylor]

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

 

[audacious2121]

WKTaylor Great info, we had very similar experience in how we prepare lap shear coupons and any incosistencies results in high variation in results. However, I don't understand why would FLAM/ fire properties test need to be done as well. I assume lap shear alone satisfy needs of potential screw-ups during shipment, am I right?

 

[SWComposites]

someone requires a fire/flam test for material receiving? really? maybe this is for some sort of critical interiors application. but seems crazy. but if it is in the spec then you are stuck doing the tests.

 

[SWComposites]

and I agree with Wil, adhesive testing (mechanical, fire/flam, etc) is an "art" and requires significant attention to detail, otherwise highly variable results are likely.

 

[audacious2121]

Yes, it is for aircraft interior products

 

[3DDave]

There are environmental indicators that can be attached to and placed within the packaging to detect if any storage limits have been exceeded. The primitive one is dry ice - if the packaging is insulated and if the dry ice is still there then one can be sure the dry ice kept the temperature low.

Nowadays, there are so many electronic sensors one could record the temperature and humidity at many places in the packaging.

Here's one:

https://microdaq.com/lascar-cold-chain-ambient-pharma-temperature-humidity-data-logger.php

(not a firm recommendation, just proof of concept. contact the supplier to see if it meets your needs)

They are about $40 each, but last 1 year and appear to be reusable. If you are doing on-site testing that has got to cost more than $40 from loss of product, time to prepare, and time to run the test, then report the results.

 

[WKTaylor]

A21...

Are these adhesives used for...
metal-to-metal?
plastic/composites/rubber-to-metal?
fabric-to-metal or plastic/composites/rubber?
fabric-to-cushion material?
fabric-to-fabric?
Fabric to thermal/sound/fire insulation?
thermal/sound/fire insulation-to-thermal/sound/fire insulation
etc?

I'm sorta surprised that DOT/FAA/AR-00/12 Aircraft Materials Fire Test Handbook [rev 2021] doesn't seem to provide You enough 'insight' RE: baseline data/information/processes to get the process started.

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