Non-Destructive Measurements of the Glass-Fibre Content in Reinforced Plastics by Means of Microwaves

So far, the usual means of measuring the glass content in glass-fibre reinforced plastics has involved destruction of the material. A new method developed at ELAB allows such measurements to be made non-destructively by means of microwaves. The method is based upon the difference in permittivity between the glass and the plastic material. The resonance frequency of a measuring coaxial probe is influenced by the permittivity of the composite material, and by use of probes with differences in field penetration into the material information of the fibre distribution can be acquired.