Dave wrote:

A major portion of 'stealth design' is to deflect the radar signal in
directions away from the transmitter [i.e. deflect the echo]. Hence, the
many flat panels on the F-117.

A secondary feature of the design is absorbent material.

A third feature is the hex filter designs in the windows/turbine
aperture etc [allow rf in but keep it from getting out].

But, your basic absorbing material is found in numerous graphite epoxies
whose composition is classified.

You may find useful information on basics by checking out 'space cloth'.
Space cloth is used for radar dummy loads and is available in Zo that
provide VSWRs from 5:1 to 1:1. At 1:1 there is no reflection.

I read somewhere that the absorbant material had an impedance of 377 ohm per
square. J Kraus showed that space cloth of this impedance reflects 30
percent of the incident wave.
Is space cloth still manufactured? A google search turned up zero hits.

Tnx es 73, Frank