You may be mainly because this happened inside EU territory. But I am not sure of how it'd work. If these were two different flight numbers (india-frankfurt, and frankfurt-usa), then you may have better chance - as you are then flying on a flight originating in EU (for you at least - even if that flight came from somewhere else in India).

I doubt you'll get your answer in this forum. suggest to re-pharse your question (remove all AI bits) and just ask on travelbuzz or on the german forum something like. 'If i get delayed by 40 hours in transit at frankfurt due to aircraft going mechanical - am i entitled to compensation as per EU rules ?'

German forum is here

hope you get something back.

cheers!