Abstract: A lightweight automotive vehicle door assembly incorporates a modular concept having an outer door panel, an inner door panel, a reinforcement beam, and a hardware mounting module. The outer panel is preferably formed from aluminum, polypropylene or steel, while the inner door panel is preferably cast from magnesium with the hardware mounting module formed of thermoplastic. The magnesium inner panel is mounted to the outer panel by a hemming process while hardware is mounted to the inner panel through the use of two-piece thermoplastic inserts creating a dielectric barrier between the fasteners and the magnesium inner panel. The reinforcement beam is formed of a composite material consisting of a glass and carbon fiber reinforced outer skin with an interior core of polyurethane.