If I understand your question rightly, you should investigate expected properties.
as an example, when you use inorganic additive in your compound, the modules should increased, if not, your work has some problems. these problems may return to your mixing or not proper choosing of fillers. for a polar matrix you have to use polar filler and unlike.
If you measure the modulus of the pure polymer and the composite, then you can theoretically estimate the effective modulus of the filler by using one of the theoretical formulas in reverse to normal usage. A simple case is that the modulus of a composite is the volume fraction combination of the modulus of polymer and filler.
Ec = X·Ep + (1-X)·Ef
where E = modulus, c = composite, p = polymer, f = filler, X = volume fraction of filler.
A refinement assuming a less perfect filler reinforcement is to add an efficiency factor for the filler, to account for interfacial interaction, orientation and other variables making the composite less perfect. However you can only estimate the efficient factor if you know the modulus of the filler. You can bundle these factors into the filler modulus and as you have stated, called it the effective filler modulus.
A more thorough mathematical model for a polymer–filler composites is that of Halpin–Tsai for the prediction of the modulus of composites based on geometry and orientation of filler along with modulus filler and matrix. You may be able to apply this model to obtain and effective filler modulus.
In addition to Robert's comment, you should consider that most of the models are based on the assumptions are perfect interface and fully dispersed fillers which may not be necessarily valid for your system.