On January 13, 1942, Henry Ford received U.S. Patent No. 2,269,451 on an Automobile Body Construction:

The body comprised a steel tube frame supporting plastic panels. Henry Ford began work on the plast car in the 1930s, resulting in a 2,000-pound vehicle (an average of 1000 pounds lighter than a conventional car) with a tubular steel framework surrounded by 14 plastic panels that were made from soybean and hemp. The “Soybean Car,” was first displayed at a community festival in Dearborn, MI, in August 1941. Ford eschewed petroleum-based plastics, hoping to integrate agriculture and industry with plant-based plastics.

Ahead of its time, Ford’s problem was timing — with the world ramping up for World War II, production of the car was deferred and never started.