Short answers, pulled from the story.
Vehicle armour uses a wide range of materials including rolled homogeneous steel, cast steel, aluminium, titanium, depleted uranium, ceramic, polycarbonate glass laminates, and composite combinations of steel and ceramics. Newer materials under research include buckypaper and aluminium foam armour plates.
The USAF A-10 Thunderbolt II, the Soviet and Russian Sukhoi Su-25 ground-attack aircraft, and the Soviet and Russian Mil Mi-24 attack helicopter all protect their pilots with a bathtub-shaped titanium enclosure designed to absorb direct hits.
Explosive reactive armour, initially developed by German researcher Manfred Held while working in Israel, sandwiches layers of high explosive between steel plates. When a shaped-charge warhead strikes, the explosive detonates and drives the steel plates into the incoming metal jet, disrupting the flow of liquid metal, typically copper at around 500 degrees Celsius, before it can penetrate the main armour.
Plastic armour was a vehicle protection material developed by the British Admiralty in 1940 for merchant ships. Its original composition was 50 percent clean granite, 43 percent limestone mineral, and 7 percent bitumen, applied in a two-inch layer backed by half an inch of steel. The hard granite particles deflected armour-piercing bullets, causing them to lodge between the plastic layer and the steel backing plate.
Spaced armour protects against shaped charges by triggering premature detonation at the first plate. This causes the metal jet to lose its coherence before reaching the main armour, spreading the impact over a broader area. The principle has been in use since World War I, when the Schneider CA1 and Saint-Chamond tanks employed it.
The Whipple shield applies the principle of spaced armour to spacecraft protection against micrometeoroids and space debris. When a high-speed particle strikes the first wall, it melts or breaks apart, scattering fragments over a wider area before they strike subsequent walls with greatly reduced concentrated energy.