Torsional Stress in FRP Piping

Hello fellow stressers!!

Is torsion not a failure mode in FRP piping?

Typically, the FRP stress failure envelope is based on hoop & axial load conditions, I believe.

How about torsion, how it's included in the stress evaluation?

Or it's unlikely that FRP will experience excessive torsion?

Thanks & Warm Regards,

We're on the same page on this case.

Cheers!!!

Is it possible to use SE= Saxial= SQRT [(\Sa\+Sb)^2 + (4St^2)] to include torsion?

You have a pipe element, created from unspecified material.

You have a bonding agent, created from unspecified material.

You have numerous fiber elements that can be wrapped, spun, braided, and/or weaved against the pipe, created from unspecified material, oriented in unspecified directions.

I would expect there will be no one-size-fits-all answer.

I would expect the forces and moments will combine in different ways to count against different allowable stresses, from one product to another. These properties may or may not be anisotropic.

If the FRP manufacturer doesn't know how a given pipe spool will react to torsion alone, bending alone, tension alone, compression alone, against pressure and temperature, then they do not know how it'll react to those loads in combination.

If the manufacturer does not know, the stress analyst does not know.

Thanks Michael for that very clear explanation. FRP is indeed not a straight forward material unlike steel.

Cheers!!