OceanGate claims in it's blurbs that the Titan had some kind of integrated hull health sensor system. I'd be interested in an acedemic way on what that was and how it worked.
I tried to go to their website and get the exact verbage they used, but their site is down.
I saw an article discussing (and dismissing) this. They were apparently strain gauge sensors embedded throughout the composite. The conclusion of the article was that, by the time a sensor like that reported an out-of-spec reading, it would already be too late to do anything about it.
IMHO, it's another example of OceanGate's (which probably means Lockton's) hubris. Apparently he was sort of a whiz kid. The problem with that is that he may have decided that he knew better than the cumulative expertise of people who knew more than he did to begin with. That's what led to firing the operations director who didn't think the Titan was safe. Unfortunately, Lockton didn't put just himself at risk. He put up a web site that seems to have greatly embellished on the purported safety of the vessel, thereby putting his customers at risk.
Engineering always includes a factor of safety, and the factor of safety generally gets larger as the risks become greater. Dogmush has posted that a 5-inch thick tube hull "should" be strong enough for a depth of 13,000 feet -- and it was, for a few dives. But I wonder what the safety factor was in that design? How much of a safety factor would you want in the vessel taking you down to where the external pressure is thousands of atmospheres? Lockton, according to articles, liked to "innovate," which probably means pushing the envelope. My bet is that he didn't design in much of a safety factor.