[Verdun1916]

Originally Posted by Igo kyu

I'm not convinced that this is true. Tanks have heavy armour, and sit on sprung shock absorbing suspensions. Turning people into jelly is not something a shock wave will do if it doesn't get through the armour, and shrapnel probably won't go through armour unless it's pretty big shrapnel.

That's true. The bit about the crew getting turned to jelly is bullshit aslong as all hatches are closed and the shock wave can't enter the crew compartement.
But if a bomb, say 500 kg and above, or heavy artillery shells detonates next to tank it's very likely that the blast will rock the vehicle pretty violently or even turn it on it's side. If the bomb or artillery shell is heavy enough the blast might even throw a tank a far bit or turn it completely over.

Have you ever been inside a tank? Well I have. Historical tanks is what I work with for a living.
The inside of a tank is a damn cramped environment with lot's of hard surfaces aswell as pointy corners and lot's of euipment. If a tank gets flipped on it's side, not to mention turned over by a bomb or artillery shell blast it will cause injury to the crew because they will be thrown about inside the vehicle and hit themselfs on or against the many hard surfaces, corners and objects inside. It's enough to cause pretty severe crushing injuries or have bones break. Not to mention how exposed your neck and spine is to concussive injuries. The term whiplash would be a big understatement in this context. Even if you wear a modern day tankers helmet that protects your head far better than anything used by WWII tankers your knees, elbows, hands, feet and face are exposed to injury if something like this happens. Just accidentally dropping a hatch on your head, fingers or feet can be enough to ensure a trip to the hospital. Even the mental and physical shock for the crew when your tanks is suddenly rocked around like a maraca, not to mention if it's thrown over on it's side by a bomb or shell blast can be enough to put the tank out of action for a good while.
Imagine beeing inside this Tiger I for example when during the bombing raid that caused this: https://goo.gl/images/c6JS9F
Or inside this Sherman when it endet up on it's side: https://goo.gl/images/YpT2CQ
Or inside this Jagdpanther: http://photo.i.ua/user/991126/228596/6158930/

So to cut a long story short, as a tanker you don't need to be exposed to the direct pressure wave nor the shrapnel from an exploding bomb or shell to be able to get hurt.

Several WWII tanks (not to mention WWI tanks) also had issues with the armour plates spalling when hit by heavy shrapnell or projectiles that didn't penetrate. This could cause a swarms or small, sharp fragments from the tanks own armour plate to fly and ricochet around inside injuring or killing crew members aswell as damaging internal equipment.
Tanks with riveted armour were especially prone to this kind of damage since a shell fragment or a projectile hitting without penetrating could cause the rivets to pop and rivet heads on the inside to fly around causing injury and damage. The M3 Grant/Lee was known for having this happen.

But then again you don't have to injure or kill the crew inside a tank to put it out of action. A bomb or shell blast could throw a track = tank out of action.

Shrapnell or shell fragments from an exploding bomb or artillery shell could jam the turret, the gun, the running gear, damage the optics such as periscopes and sights or the engine. The Panzerjäger Tiger (P) belonging to the collections at the United States Army Ordnance Training and Heritage Center in Maryland, USA, was knocked out by a piece of shell fragment from the projectile from a 57 mm M1 AT gun jamming it's running gear and forcing the crew to abandon it. Otto Carius describes in his memoirs "Tiger im Schlamm" how his Tiger I was put out of action because a single piece of shell fragment managed to cut a hose or pipe to the engine cooling system. That could just as easily happen to the fuel lines. Especially if shrapnell or projectiles hit the engine compartement from above since there are plenty of weak points easily penetrated on most WWII era tanks.

So as far as I see it the reason why it might be so hard to put tanks out of action in the game might be because the in-game tanks doesn't have complex enough damage-models. This is after all a combat flight sim and not a tank simulator so it's very possible that the majority of the ways a tank can be put out of action was never considere when it was made.