Where can I find the academic research papers related to Cardano? I tried Google Scholar with no success.
IOHK has a list of papers and currently I see 103 of them: https://iohk.io/en/research/library/
In addition to https://iohk.io/en/research/library/ (as Joshua Chia mentions), you can then utilize Google Scholar to search for a paper's title and/or author names to also get a list of citing articles. I'm surprised you didn't have success with the site. Of course, you can also just search for cardano blockchain to get papers that are not necessarily written by IOG staff.
If Scite.ai would implement a better search and index more databases, I'd recommend them over Google Scholar due to the fact that there's also a sentiment analysis (supporting/contrasting in addition to Goggle's only type: mentioning cites) on citations.
Getting an idea on how other academics approach the paper you are interested in can aid in pre-digesting the Cardano-related papers.
You gotta go to crypto and or other tertiary domain specific archives. https://eprint.iacr.org/complete/ is one that I use myself quite frequently. Just look up IOG scientists if you're looking for Cardano specific papers.