This may be repairable, or it may be a sign that the frame has failed and is absolutely not safe to ride.

In general terms, if you wanted to fashion a replacement for missing carbon fiber, you'd want to use another fiber and epoxy. Chromed metal doesn't take to glue. You can use carbon fiber, glass fiber or even thin cotton cloth after degreasing all surfaces and fibers. The strength of the added piece will come from its fiber density.