How the aircraft will burn depends on the matrix used in the composite. I think with the 787 the matrix isn't flammable. When exposed to a flame it will just decompose (maybe it'll also release some nasty gases? not sure) As far as I'm aware the only commonly used matrix that will burn is polyester but flame retardent can be added to it to stop combustion). Polyester isn't really used in aircraft. As for recycling a thermoset composite like that used in the 787 can only be recyled by grinding it down and using it in lower grade products (with current technology anyway). Thermoplastic composites on the other hand can be heated until the matrix melts and so you could possible separate the fibres and matrix for reuse. Thermoplastics are used alot less then thermosetting because they're harder to manufacture but their use is increasing. I think the leading edge of the A380 is thermoplastic composite. As for what will happen when something drives into the side of the fuselage, well with engine nacelles which are made of composites you can patch the hole if it is small enough. With primary structures such as the fuselage things could get a lot more complicated possibly you might have to replace the entire damaged part. Composites are hazardous waste and if the fibres get onto your skin they itch like crazy