Diagnostic technology is still based on C-scan ultrasonics. It will give pretty conclusive results for voids, cracks etc. We did CF tests with water immersed C-scan which would be more than inconvenient for a major structure...I think air-based types are now available. I've been out of that line of business for some years now.
Optimum loading of any composite structure can be tuned by fibre orientation(s), shape etc. so its not necessarily isotropic.