inserts 2

[engroma]

Hi all

I have to install some inserts in a sandwich panel (honeycomb+skins or foam+skins).
But I dont have any idea how to calculate the undercut for the adhesive or how to calculate the ultimite load that the insert can withstand.
is there any particular formula or procedure to follow to calculate the ultimate load for the inserts?
could you advise any papers or book about it?

thanks

Engroma

 

[SWComposites]

Insert strength is typically determined empirically from test data. Generally too many variables and unknown material properties to make an accurate prediction.

 

[RPstress]

You can do a few basic calcs on it. It's usual to assume that all the through-thickness shear goes into the core and that all the in-plane shear goes through the bond between the insert and the skin.

For the through-thickness load the core is generally weaker than the adhesive.

Depends on your exact geometry and how the insert is glued in.

These sorts of methods are usually safe, but will undercook the actual strength by a fair margin. As SW says, knocking up a test rig and ripping a few inserts out somehow is the only really sure way to get a true strength.

 

[Deckard]

You can refer to ESA "Insert Design Handbook", ESA-PSS-03-1202

 

[SandwitchPanel]

As SW said, the insert strengths are typically determined by panel coupon batch testing. The typical strength values include insert tension and insert shear strength values, similar to sanwitch panel bending and shear strengths.