I have some m2 of expired - if the rule of 1 year is right - prepreg . Is it possible that it is still ok to use it or by fact even if it looks normal it has lost part of its strength ?
The parts that i do look ok but havent done the same exact part with the same material before some months to see if there is a difference between the 2 normally identical parts. 15 months have past since i bought the roll and i think it was 2 months old by then…
Expiration dates are generally used by the manufacturer as a guarantee for usefulness if stored in the prescribed conditions and for parts that require material teaching and certification, I.e. Aerospace parts. If you can still get the resin to flow and cure it should be fine.
soudns like you’ve made some parts with it already?
If the resin flowed and allowed any air to get sucked out, and there were no big dry spots. You should be good. I’ve used some prepregs that were 3 or 4 or even 5 years old. At a training I went to recently the instructor told me that he’s even used 7 year old pre preg!?
I’m always psyched if I get hold of a cheap expired roll. From what I heard they don’t sell them because of liability… Not sure if I believe that but, it could be true coming from aerospace.
Expired prepreg will not gel as well (less air extraction) and will have reduced properties even if the void content is low. If it’s still tacky, you should still be able to make cosmetic parts. If you are planning on using it for structural use, you’ll need to account for the loss of strength.