A method of forming a composite article includes constructing a preform having a strand layer including an interior portion and a peripheral portion surrounding the interior portion. The strand layer includes a plurality of strand segments traversing the interior portion and defining a first strand segment population density and a second strand segment population density. The preform is inserted into the mold cavity so that the interior portion of the preform is received in a molding region of the mold cavity. The molding region has a first thickness corresponding to the first strand segment population density and a second thickness corresponding to the second strand segment population density. Following the inserting, the mold is closed and the interior portion of the preform is compressed within the molding region. In the closed mold, the peripheral portion of the strand layer may be maintained in a loose state within the relief region.