with regard to absorbing impact energy... the vast majority of energy is absorbed during plastic-deformation.
very true and it relates directly to the area under the stress/strain curve taking into account strain rates, and their effect on the area that can be placed under strain in a very short time before the G-loads kill the passenger.
A car has much less velocity so it has time to bring in large crumple zones before the G-loads are exceeded.
With a composite (non-homogenous- metallic) you are dealing in energy absorption by friction between the fibers as they separate from the glue holding them together. Ideally if you had no glue the whole thing would act like a blanket, Unfortunately it wouldn't stay together long enough to fly.