Well, like the British issue with the material the main wing spars of their V-bombers (especially the Valiants) were made of becoming more brittle sooner than planned, there is plenty of documentation of the material of C-130 wings.
The C-130A used basically the aluminium grades used by the B-29s, etc-which had stood up well. However, before production of the C-130E began is was learned that the stresses experienced by a tactical airlifter were different than those of a high-altitude strategic bomber (much like the change in stresses when the RAF went to low-level operations with the V-force), and cracks in wing spars and the center wing box were being found much earlier than expected.
This led to the C-130E wings being constructed with different alloys - ones designed to hold up better. The earlier models had "doublers' added in many points in their wing structures to enable them to serve longer (more below).
The C-130Hs had yet another material change, as the C-130Es also eventually began to be fitted with "doublers" - although fewer in number.
I learned all this doing research after the 2002 crash of a civilian-operated fire-tanker C-130A - the center wing box failed, and both wings broke off in flight - the crash was filmed, and can be found on youtube.
The cause was found to be corrosion-amplified fatigue cracks in the original structure, which had been hidden from inspection by the doublers - the only way to find these cracks would be to periodically drill out the rivets holding the doublers in place to expose the underlying material, then re-rivet the doublers back into place.
Last edited by GreenKnight121; 13th Nov 2014 at 01:49.