On another point about composites, when I was at Airbus working on VTP structures we always used hot/wet testing (both heat and moisture degrade composite structural properties). I don't know about the fatigue work as I wasn't involved but I don't think it would have been done differently. Thats not the same as fluid getting into a sandwich structure, as with the rudder failures, which is a more serious problem.
Fatigue testing is usually done at room temperature ambient conditions with a LEF (Load Enhancement Factor) to account for hot/wet / cold conditions. LEF is usually around 15% for most composite structure.