Interesting comment from DennisD regarding the "helicopter blade".
I remember when I bought my Applause, the salesman said it was made of the
same material as rocket ship nose cones. I dug out my "Applause Owner's Manual" from 1978 but no info on the material that forms the back.

However, here's a couple of quotes from the Kaman website:

"Through intense research and development, Kamans engineers made discoveries about the physics of vibration and acoustics- critical factors in the design and fabrication of helicopter rotor blades, missile nose cones, and other aerospace components exposed to high vibrational stress."

and

"Once our engineers had settled on the body design, they turned their attention to developing a substance that could be molded into this bowl-like shape. Using their knowledge of high-tech aerospace composites, they developed Lyrachord, a patented material comprising interwoven layers of glass filament and bonding resin. Our lab team also discovered how to tune Lyrachord at the molecular level so it would resonate musically."

****************

Quite a feat considering all ordinary acoustic guitar bodies (as far as I know) up to that time were made entirely of wood.

LLOYD S