Frozen water in GFRP wing

Hello,

we have a sailplane that had some water inside one of the wings.
The sailplane is made in GFRP.
The sailplane was disassembled and stored but a nearby water pipe has
broken and sprayed some water inside the wing about 5-6cm (2-3in.)
deep along the leading edge.
The problem is that it happened during the winter and most probably
the water has FROZEN!!!

Visual inspection of the outside has given NO signs of damage!

We were planing to send the glider to the nearest authorized workshop
BUT someone with knowledge in GFRP says that inspecting GFRP for
damage from frozen water is quite complex and that only a few BIG
companies have such facilities/technology/know-how to do it!

Does anyone know anything about this subject or has more experience in
dealing with GFRP?

We are especially interested in the technology of such inspection,
which instruments are used, what are the most important tests and so
on!
You do not have to go into details, just enough info so we can ask the
workshops if they have that technology and/or know-how!

Blue Skies
Vladimir