A method for manufacturing an inner door panel for a vehicle side door that employs a die casting process. The method includes providing a die cast mold having opposing mold halves that combine to define a die cavity configured to provide the inner door panel. An impact beam is positioned in the mold cavity prior to combining the first mold half and the second mold half, and a molten metal is provided to the mold cavity so that molten metal flows into all areas of the mold cavity and around the impact beam after the first mold half and the second mold half are combined. A solidified molded inner door panel is then removed from the die cast mold that includes an encapsulated impact beam.