Examples of the present disclosure present a composite material. In an example, the composite material may comprise: a carbon fiber composite and a surface treatment layer. The carbon fiber composite may comprise a core layer having a first side and a second side opposite to the first side, and a first set of two carbon fiber layers disposed over at least a portion of the core layer respectively on the first side and the second side. Each of the first set of the two carbon fiber layers may comprise carbon fibers aligned in a first direction in a plane. The surface treatment layer may be disposed on the carbon fiber composite.