I am not sure why the composite approach never worked as I am not an engineer. I would guess it was never durable enough. The idea of having a rust-free care was appealing to anyone from the MidWest. Many of the cars from the late 60’s and 70’s were really rust buckets. I remember reading that many used too much recycled steel.
In the film ‘Tucker’, I never did understand how Lloyd Bridges could be so mean and unfair to his son Jeff. Didn’t add up.
Automotive materials have to deal with heavy use in a tough environment. New and promising but unproven materials rarely do well. The plastic body panel technology originally intended for the DeLorean — two sheets of plastic with a foam core between them — was simply not up to the task, then or now.