So, why aren’t warships armored with composites, like most modern tanks? Would composites even work in this context, or are they better used in land vehicles where weight seems to matter more? What if the composite was layered over the steel hull?
Finally, would titanium be a good armor for ships? I read an article on the internet somewhere that talked about upgrading a USS Iowa with a titanium hull, along with some sort of synthetic material.
They apparently do this according to this article.
Mostly it’s called “all or nothing armor” you can read up here.
Well, it has to float. And the enemy can (and the Russians have built) just send a bigger missile. Also, you can’t armor the underside. So instead the strategy seems to be to only lightly armor the warship and rely on long range, defensive missiles and guns, jamming, and so on. Also, smaller cruise sizes and smaller warships - so you lose less each time the enemy sinks one.
The effectiveness of any armor depends on how thick it is. Modern ships have armor made out of air. Which is a very good material for armor, when you use it in hundred-mile thickness.
Primary defense strategy for USN though is overlapping defensive weapons of the fleet tied together with the latest Aegis system. Smaller crews are the goal and being achieved but not really smaller ships overall. The destroyers keep getting larger and the carriers are largely the same size as they were 50 years ago. Battleships are gone of course and cruisers are disappearing but only as the larger destroyers are as big as most cruisers ever were.
There is some armor strategy to protect vital areas of the “tin can fleet” though. Rough idea is 2 thinnish layers of armor with Kevlar or equivalent to protect against hull fragmentation that caused many casualties and damage on earlier destroyers.
What missiles would be effective against well-armoured ships? Could someone attack a carrier group with just ship engines attached to giant hunks of mostly watertight scrap steel blocks acting as decoys that the carrier group would waste all of their missiles on trying to destroy, then followed up by an actual offensive force, now that the carrier group has mostly run out of ammunition?
Well put ! 
Back at the turn of (last) century (god I feel old). Torpedo netting was used for harbored ships.
[quote = wiki]
nets of galvanized iron hung around each battleship from projecting 40 ft spars
[/quote]
I guess you could call that one of the first types of composite armor.
My guess would be cost. That’s a lot of surface area to cover in composite armor. My guess as to the advantage of composite armor would be some form of weight reduction which is not really a factor for ships since they can weight as much as they need too*. Just keep adding conventional armor as required.
For land/air based vehicles this will be a real factor as, sure, you can make a huge tank with the surface area on the treads to support the weight but it’d be so big it probably couldn’t go anywhere aside from a wide open field. For aircraft, this is obvious.
Missiles are built to defeat what they expect to meet.
Warships these days are basically un-armored so missiles need not be all that big.
The Soviets built the P-700 Granit (aka ‘Shipwreck’) missile to defeat carriers (not that carriers are particularly armored but that they are really big so need a bigger missile to kill one).
The USS Stark and HMS Sheffield were done in by a single missile. That same missile would have done little damage to a WWII battleship. But then a WWII battleship is an incredibly expensive thing to build and run.
Armor is expensive. Better to build five un-armored destroyers than one well armored battleship.
Nah, you just use five of them, instead of the four you’d use for a battleship.
Then why build a missile as big as I cited?
I submit that four Exocet missiles are about as useful as one against a battleship. Consider the punishment the Bismarck took before sinking. Four missiles ain’t gonna do it.
It (the Granit) is that big to be that fast and that long-ranged. The warhead is the same size as an ordinary gravity bomb we’d use against a similar sized ship. IOW, it’s not really all that big a boom.
Unless they install the optional 500KT nuclear warhead. Then the boom is rather larger.
Battleships only exist in museums and in story books. If navies had battleships today then we’d have missiles that turn battleships into beercans. Since battleships are imaginary weapons we haven’t bothered building those missiles.
Look at the amount of punishment Bismarck took to become basically helpless. Was it two torpedos from biplanes?
Battleships could withstand a shytload of punishment and not sink. The could absorb substantially less of a pounding and still not be dead in the water. If your Battleship is not sinking, its scant comfort if it is dead in the water with no power and ablaze from bow to stern.
4 Exocets won’t sink an Iowa. They will certainly damage her radar and communications, possibly knockout power, and also start fires all around. The ship will be out of any battle its in and also will need to be protected just in case the enemy returns to finish the job.
Compare with Carriers. Sure they are easier to sink. But the gao between “going to sink” and “can longer fight” is much smaller. As the Enterprise and several British carriers proved, a carrier can be patched up and returned to action that evening, instead off after 6 months in dry dock.
How well does a composite armored tank fare when soaked in salt water for years on end?
The boat has to float and has to do so in salt water, for long periods without falling apart.
Plus, look at the square surface feet of exposed material on an aircraft carrier.
Imagine how much extra material and bulk to wrap that in composite armor.
Could you even put that on the flight deck?
Most composite armor in use it made from ceramics.
I know something the size of a carrier must be able to “bend with the breeze” so to speak, or it would break, would large pieces of ceramics be willing to bend too?
And composite armor is expensive, ships are a whole lot of surface to cover.
And will it actually help with something i would send to sink a carrier?
Armor is great but if you drop a small bomb or a fat arty round on a composite armored tank, you get a pile of rubble that used to be a tank for your troubles, i assume we are going to hit ships with something magnitudes more effective than 120mm rounds?
I also think the idea now days is, if you have your ship in a slugging match, you are already doing it wrong.
I think you mean as museums. 
4 Exocets still have to get past the fleet defenses though. If prepared, that would be very hard. Even in the 80s when I was in the overall fleet defense for a BB or carrier group were pretty impressive. Our worries weren’t really missiles, ships or jets but torpedoes mainly from subs and Nuclear, Biological or Chemical attacks.
The USS Stark did not have her defenses on don’t forget. Sad but true, the Stark was only hit due to a gross failure in communications. If the Phalanx was up and running, no hit. 2 missiles got past and the Stark still returned to port under her own power.
I guess I maybe should have put smileys in that last post?
As a side note, one fairly obvious weapon - though not currently deployed - would be a cruise missile that drops a torpedo. It would drop the torpedo just before getting into Aegis defense range, and since the U.S. navy has no actual hard kill anti torpedo weapons, if it doesn’t get fooled by decoys, there went a ship. Apparently, if you blow up a torpedo right under the keel, it’s a one hit kill. Might take more than one hit to take out a supercarrier, but it seems like the obvious weapon for the enemy to try to use against the U.S. navy, which has anti missile missiles, gatling guns, and lasers up the wazoo.
Don’t worry, your joke got a red peg.
Mother Russia has you covered with the SS-N-15 and SS-N-16; They launch from a torpedo tube, use rockets to fly through the air and drop a torpedo. So it’s a torpedo that turns into a missile that drops a torpedo.
Couldn’t the USN use light torpedoes as anti-torpedo torpedoes?
The USN also had ASROC & SUBROC which were *almost *the same idea: RUR-5 ASROC - Wikipedia UUM-44 SUBROC - Wikipedia
IANA expert, but ISTM the problem with active torpedo defense is detecting and tracking something that small embedded in the surface noise far enough out to have time to notice, react, track, decide, launch, and intercept.
Then you still have the same “hit a bullet with a bullet” problem in the end game just like anti-missile missiles have. Two automated vehicles of similar maneuverability closing more or less head-on is a tough problem to solve with high reliability.
Certainly one could use an existing torpedo hull, propulsion, launcher, warhead, etc., as the starting point. But that’s the easy well-solved part.