Bearing strength

[STpipe]

Hey everyone,

I have a question concerning the bearing strength in FRP. The ASTM D953 standard defines the bearing strength taken as the force at 4% hole deformation divided by the bearing area (hole diameter x thickness).

What is the reason for choosing 4% hole deformation as the strength limit instead of the ultimate load?

 

[SWComposites]

Maybe to avoid excessive deformation.

 

[STpipe]

Which is fair. But in that case, is it more of a serviceability requirement as opposed to an ultimate strength requirement?

For example I've seen some design guidelines which state disregard this provision completely and to simply take the ultimate failure load as the bearing strength.

 

[ESPcomposites]

ASTM D5961 considers both the bearing offset strength and the ultimate strength. From ASTM D5961, "Discussion—Two types of bearing strengths are commonly identified, and noted by an additional superscript: offset strength and ultimate strength."

Also, from "Practical Analysis of Aircraft Composites":
"The bearing strength design value may also be limited by program requirements, fatigue requirements, or other limitations. For some structures,such as those that require fuel seals, excessive hole elongation may be unacceptable."

Brian

http://www.espcomposites.com

 

[STpipe]

ESPComposites,

Thank you very much for the additional references. I wasn’t aware of the existence of D5961. I think that one gives me a much better indication for which way to go forward.

Thanks!