The ULSAC frameless door structure is composed of two vertical hydroformed tubular parts that provide structural attachment points for the hinges (left) and latch (right). The frameless ULSAC door features a stamped, tailor-welded-blank inner front. The ULSAC design eliminates the need for a full door inner panel, which in current designs fulfills a structural responsibility. Stamping formed the outer door panel of the ULSAC door The dent test simulates the material's ability to resist everyday dings, while the oil canning test measures resistance to depression, such as by fingers or palms or brushes in a car wash. The complete ULSAC door features a trim-panel-integrated energy-absorbing foam block, electronic door latch and outer handle, power window and lock, and a heated, electronic rearview mirror.

Based on a design from the Concept Phase of the ULSAC program, the frameless ULSAC door is made from just nine major parts, and employs tailor-welded blanks, hydroformed tubes, and stamped parts. The door's structure eliminates the need for a structural full inner panel. It is comprised of hydroformed HSS-tube latch and hinge parts and two straight ultra-HSS tubes. These separate components allow for selection of a precise diameter, and a material grade and thickness combination for each part based entirely on functional requirements. The hydro-formed tube used for the latch component is 1.0-mm (0.04-in), 280-MPa (41-ksi) HSS and the tube for the hinge component is 1.2-mm (0.05-in), 280-MPa (41-ksi) HSS.

The two horizontal tubes provide stiffness and work together as side impact intrusion beams, simultaneously meeting both structural and crash-energy management responsibilities. In side collisions, they provide strength and absorption capabilities to manage impact energy forces effectively. In a front collision, the two parts provide load-carrying capabilities between the A- and B-pillars.

The frameless door also features a stamped tailor-welded-blank inner front, which incorporates the mirror flag inner. The upper portion of the blank is 1.0-mm (0.04-in), 140-MPa (20-ksi) mild steel, and the lower portion is 1.2 mm (0.05 in) of the same material. The material in the upper portion adds stiffness to the mirror flag for support of the rearview mirror and outer panel attachment. The thicker lower portion of the tailored blank is necessary to achieve acceptable structural performance in the hinge area. The inner front and outer mirror stampings form the glass drop channel and capture the outer belt reinforcement. This creates a strong structural node, which transfers loads to and from the hinge tube. It also consolidates as many functions as possible for attachment of the mirror and window components, with fewer parts.

The ULSAC door outer panel uses bake-hardenable (BH) 260-MPa (38-ksi) HSS in 0.7-mm (0.03-in) thickness. BH steels increase in strength when undergoing a "baking" treatment, such as that used to cure automotive paints. Engineers selected that material over two other grades of steel that represented a good range of grades for comparison purposes and that are at the leading edge of steel material use in closure panels. After the completion of dent resistance and oil canning testing of stamped parts made from the three materials, the BH 260-MPa (38-ksi) HSS proved to have the best qualities for this door design. The complete door features a trim panel-integrated energy-absorbing foam block (rather than a separate foam inner as is current practice), electronic door latch and outer handle, power window and lock, and a heated, electronic rearview mirror.