Engines and the cowlings are designed to contain fan blades should they ‘let go’ – imagine a red hot fan blade going through the engine (at enormous speed) and into the fuselage. ouch.

The fan case is designed to contain a blade off situation but the cowls are not. The fan case is made of steel or titanium and, in some cases is wrapped in carbon fibre. The Cowls are made of composite honeycombe and light alloy and have little or no containment ability.
The fan blades are in the “cool” bit of the engine and should not be red hot. The turbines are hot and do cause an imense abount of damage when the “Let go”, just ask American Airlines at LAX!

Rgds Cking