It's titanium laminated with Kevlar.
4 seconds sound clip from the RoboCop (1987) movie soundboard.
You can hear this line at 00:27:53 in the Blu-ray version of the movie.
Quote context
[...]
- He's legally dead. We can do pretty much what we want to.
- Shut him down. Prep him for surgery.
- The entire outer skin will be like this.
- It's titanium laminated with Kevlar.
- Come here often? How you doing?
- Oh, God! He's got a hell of a grip.
- It's 400 foot-pounds. He could crush every bone in your hand.
[...]