This is taking us off topic but thought a bit clarification could be in order (objective better educating myself).
In my opinion better composite material would reduce the Radar signature of J-10 but would not reduce its RCS.
As RCS =Radar Cross-section, it deals with the shape and dimensions of a surface and the angles regardless of what the surface is made up of.
Radar signature is a totally different thing. Based on dimensions, angles between adjoining surfaces + the material of the surface determine the resulting radar signature of an object.
For example, if you have a spherical object, no matter what that sphere is made up of, the dimensions as in radius and diameter of that sphere would remain the same, as these are mere measurements. You take a measuring tape/scale and measure it, the results would be the same regardless of the sphere being made of wood or glass.
Now if you put same shaped spherical objects (same measurements) under a beam of light, one made of wood and the other of glass, the glass sphere would reflect more light than one made of wood.
Similar principle works when, radar beams strike an object and are reflected back. If the object is made up of more radar reflective material the higher signature you get back.
Now if an object with bad dimensions (angles between adjoining surfaces prone to more radar beams reflecting back to radar) and bigger size is made up of a more reflective material, then the Radar Signature would be even bigger than one made of less reflective surface.
Eurofighter benefits from advances over the past twenty years in the fields of metallurgy, polymer science and composites. Over 80% of the airframe is comprised of modern materials. This brings advantages not only in terms of the strength to weight ratio but also has implications for stealth.
What this translates into is
Based on dimensions, angles between adjoining surfaces + the material of the surface determine the resulting radar signature of an object.
The Idea here is to reduce Radar signature, be it with reduction in RCS or less radar reflective materials or combination of both.
Don’t know if the following statements have been paraphrased by the posters above, or put as they appear in the original script.
“The fact that stealth aircrafts are made from composites has already taken a deep hold in aviation folklore. After all , Such, At least is the popular theory. What may prove surprising is that the use of composites is not one of the most significant RCS reduction measures.”
“The role played by composites in reducing RCS is a more subtle one”