4. Techniques for testing the homogeneity of composite materials

In their manufacture, composite materials can be heterogeneous, i.e. feature deposits of aggregates of conductive or magnetic particles that localize in certain areas of the resin (different density and chemical reactions between the particle and the host resin).

• This difficulty has led manufacturers to try and develop more reliable production processes, and experimenters to define and develop measurement techniques for checking sample homogeneity.

  In the microwave domain, measurement systems can be envisaged, which have the advantage of better assessing the behavior of materials in their operating band. On the other hand, a compromise has to be made: if we want to penetrate deep into the composite material to gain access to the different layers, we have to go down in frequency, but the achievable spatial resolution,...