Paint layer thickness measurement on composite

[dutchguy]

Dear all,

I have a general question about paint layer thickness measurements on Glass/PPS (Poly Phenylene Sulphide) thermoplastic composite aircraft structures.

Does anyone know an accurate measurement method to define the paintlayer thickness on a PPS structure ?

Besides this question, I have second thoughts about the ability of a lightning strike layer on a composite structure underneath a thick painting layer to do what it is suppose to do: conducting lightning strike in a proper way.

Any remarks are welcome.

Andre

 

[CoryPad]

Do you need a non-destructive method? If not, then a cross sectioned sampled should be mounted and polished, then observed with a microscope. You can use a printed image, the magnification, and a rule to measure the thickness.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dutchguy]

I am looking for a NDO method Cory

thanx for your early reply

Andre

 

[Compositepro]

Paint does not interfere with the lighting protection. Lightning will blow through the paint and then the protection works as it is supposed to.

 

[CoryPad]

How thick is the paint? There are ultrasonic systems that are supposed to be able to differentiate coatings (I think the coatings need to have a relatively high thickness, like greater than 100 [µ]m) on a substrate. Try GE Inspection Technologies and Olympus NDT.

http://www.geinspectiontechnologies.com/index.html

http://www.olympusndt.com

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[CompositeGeek]

There is a device that scribes a line in the part. Then you look at the scratch with a jewlers loop and verify prime and top coat.

This is the only direct measure that I am aware of. I have tried inumerable NDT techniques and found them less than repeatable for the ranges required.

Another approach is to use a metal test coupon attached strategically to the part and use the coupon with an Isoscope to validate thickness. I was able to sell this to Customer QA based on a comparison with the scratch technique.

Good Luck. This can be a hard task to get through.



Composites and Airplanes - what was I thinking?

There are gremlins in the autoclave!

 

[CoryPad]

This is a device that works as described by CompositeGeek:

http://www.byk-gardner.com/englisch/products2.php?lv3=3&pgroup=3&pgroup2=10&pgroup2id=20&product=188

We use it in the auto industry to measure paint on plastics.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dutchguy]

We use a comparison test too, based on test strips.

However, in the field it is not usefull.

Cory, I hope that this equipement will be helpfull.

Regards,

Andre