The present invention relates to methods of stabilizing and/or sealing core and stabilized and/or sealed core for manufacturing molded composite structures. In particular, the present invention relates to methods of stabilizing and/or sealing core and stabilized and/or sealed core for manufacturing aircraft. In one implementation, the core is stabilized or sealed by applying a layer of roll-coated adhesive on the core, applying a layer of stabilizing material on the roll-coated adhesive layer; and applying a layer of thermoplastic barrier film on the stabilizing material.