shear out testing of glued insert into aluminum composite panel

[valib]

I have to test a glued insert into aluminum composite panel in shear and find the A and B basis allowables for the construction type. I prepared the samples and the fixtures and I need to know whether during the testing I need to use spacers between the inserts and the fixtures or not.
1.Without spacers, the insert rotation is locked by the fixture (which comes into contact with the panel skin as well, an additional friction force will be developed there on top of the insert capability) and the maximum shear out load comes out from the skin bearing capability.
2.With spacers, along with the tensile force, the fixture will create a moment which will try to rotate the insert, which finally will be pushed under the skin. The moment is strongly dependent on the spacer thickness.
When the spacer diameter is larger than the insert diameter I get the conditions of testing case 1, when the spacer diameter is equal or smaller than the insert diameter, I get the conditions of testing case 2.
The results are different, second test condition gives much smaller forces. Additionally, there is always a bracket on top of the insert in contact with the skin too, which will prevent the insert rotation.
Has anybody experienced such testing conditions?
I would like to know which is the best/right way of testing in shear this type of installation and whether there is any regulation I could use to document the way of testing. ESA PSS-03-1202 does not describe the way of testing this installation.

 

[SWComposites]

Your test condition should match as close as possible the actual loading condition in the vehicle. There is no general "best" way, and there probably is no regulation that covers such a specific case.

With that, if the attached bracket is in contact with the panel and prevents insert rotation, then testing without spacers is probably appropriate.

 

[valib]

Thank you SWComposites for your hints. I work for same industry as you, for an aircraft interior company. I have to do a change in my profile.
This is my understanding as well, I have to test exactly same installation conditions. There are other opinions about a more conservative way of testing this type of insert installation and spacer usage which confuses me. I do not agree allowing the insert to be loaded in bending. Anyway, I have to make a decission, I have to perform the test soon.

 

[SWComposites]

Since you are testing to get allowables, have you talked to a DER about your test plan? Have you submitted it to the FAA/EASA/CAA/? for approval?

 

[rjerome]

Please provide a little bit more information to your inquiry? What kind of glued in insert are you using? Have you used Spiralock potted inserts which are used in composite materials, install easily and is secured using a potting compound and have the self locking female thread form. The thread form is unique and resists vibration much better than conventional and prevailing torque. Please let me know if I can be of any assistance.

RJF

 

[YoungTurk]

If you're testing for pure shear, then you would not want to include the spacers. Ideally, test to determine the pure shear allowables and supplement the testing with a series of tests to determine the approximate effect of different spacer thicknesses. Alternatively, establish the shear/tension combined loading interaction curve by testing at some angles between the two and allow the designers and analysts calculate the tension induced by a given configuration and apply the interaction manually.

rjerome - it seems like you're here trying to sell stuff. read the site rules and knock it off.