In 2151, a ship of this type responded to a distress signal sent from a cargo vessel by the crew of Enterprise NX-01. There, the Axanar combat vessel discovered Enterprise had been captured by an unidentified starship. After discovering that the hostile vessel was responsible for killing the cargo ship's crew, the combat vessel freed Enterprise and proceeded to destroy the hostile vessel with very little resistance. (ENT: "Fight or Flight")
Assuming the combat vessel's hull was of similar construction to the cargo vessel's, it was comprised of tritanium and disilicon polymers.
In the script for "Fight or Flight", the Axanar combat ship is described thus; "It's similar in design to the cargo vessel, but larger, a warship." A description slightly later in the script reads, "We can tell by the interior architecture that the ship is similar, as well."