film adhesive bond strength

[groveri]

I'm designing/analyzing a carbon/epoxy filament wound aluminum lined pressure vessel with a film adhesive bond between the line and composite. I have a region of high adhesive shear, remote from the edges so the bond is in transverse compression (no peel stress) due to the internal pressure. Film adhesive engineering property data is usually limited to ASTM type tests or none at all. DOT-FAA-AR-02-97 has some good data for some adhesives. The literature doesn't seem to address bonds with transverse compression. From experience I have seen successful bonds with shear stresses much higher than the lap shear strengths. If failure is a function of the max principal tensile stress instead of shear stress alone, then transverse compression will reduce the max principal stress and enhance the bond strength. Does anyone have any more insight to bond failure?

 

[TugboatEng]

I have seen composite pressure vessels with a rubber intermediate layer. I wonder if this was done to control shear stress. This particular vessel had an Aramid liner and shell.

 

[Compositepro]

The way I understand it, transverse compression just describes a way that a material is loaded, or stressed. It is not a material property. The issue with liners is that they do not fail while there is pressure in the vessel. If the liner or adhesive exceeds it tensile yield strength due to pressure, it will plastically deform. Then, when pressure is released, it goes into compression. This can result in buckling of the liner and separation from the wall.