Christina,

There are some significant features of FRP stress analysis.

Let's get down to the throretical part a little bit.

FRP pipes are orthotropic and need nine material constants for analysis. However for a stick element, they can roll down to four.

The failure theories that are applicable for isotropic materials are not valid for orthotropic materials.Tsai-Hill ( a modification of the Von Mises criteria for isotropic materials)and Tsai-Wu ( stress tensor polynomial) theories address the failure mechanism for these materials.

If you are inetersted . kindly provide youe-email address and I can send you some documents on FRP analysis.

Thanks and Regards

Anindya