A composite material comprises plies 2, 4, 6, 8, which may be prepregs. Film elements 10 are provided between at least two adjacent ones of the plies 2, 4, 6, 8. The film elements are made from a release material which inhibits adhesion between regions of the resin on opposite sides of the respective film elements, and are randomly distributed. The film elements 10 provide delamination sites within the component. The component may be a test piece for assessing the delamination behavior of the material. Alternatively, the delamination behavior caused by the film elements 10 may have a useful purpose, for example to control regions of a component in which delamination occurs following events such as a bird strike on a fan blade of a gas turbine engine.