You can refer to an attitude that someone has in order to protect themselves as their carapace. The arrogance became his protective carapace. a hard shell on the outside of some animals such as a crab or tortoise = shell (carapacho)
In crustaceans, the 'shield' covering the upper surface of part of the body of various species e g the broad shield forming the upper body cover of crabs
\KAIR-uh-pace\, noun: 1 The thick shell that covers the back of the turtle, the crab, and other animals 2 Something likened to a shell that serves to protect or isolate from external influence
A hard bony or chitinous outer covering, such as the fused dorsal plates of a turtle or the portion of the exoskeleton covering the head and thorax of a crustacean