unibody

Unibody, also known as unitized construction, is a design in which the vehicle's body and frame form a single integrated structure rather than a separate frame plus body. It is the dominant architecture for modern passenger cars and many light trucks.

In unibody vehicles, the shell itself carries most of the structural loads. Exterior panels and subframes are part of the load paths; manufacturers use high-strength steel or aluminum, advanced joining methods (spot welding, adhesive bonding, rivets), and computer-aided design to optimize stiffness and crash energy management.

In contrast with body-on-frame designs, unibody systems typically weigh less and deliver improved rigidity, handling, fuel efficiency, and interior space. However, repairs after severe crashes can be more complex and costly, and heavy-duty applications still employ body-on-frame for durability and ease of replacement.

The unibody concept originated early in the 20th century and became the standard for most passenger cars during the latter half of the century, with widespread use in crossovers and modern SUVs. Some light trucks still use body-on-frame.

In the context of consumer electronics, "unibody" describes a single-piece enclosure machined from a solid block of material, often aluminum, that provides stiffness and a seamless appearance. This approach can complicate repairs and upgrades but enables thin, rigid devices with minimal seams.

Related concepts include monocoque construction and partially unibody designs used in aerospace and automotive engineering.