Frequency dependent electric field measurements using in situ micro sensors, FDEMS, is a particularly useful technique for monitoring the changing state of a polymer in a composite (or in an adhesive joint or as a coating) during fabrication and aging during use in the field. Measurements can be made in the laboratory to monitor the polymerization process and to monitor durability and aging in an environmental chamber or other degradative environment. Equally important, the FDEMS in situ micro sensor monitoring technique can be used to monitor cure in production ovens and autoclaves on the plant floor as well as outside, for example, coatings on the surface of a ship in dry dock. Durability and aging can be monitored while the object is in use. Examples are a marine coating on a ship, the protective coating on the liner of an acid containing tank, a rocket propellant, an adhesive in a bond joint, or the polymer in a composite structure.