Use of the frequency dependence of the impedance to monitor viscosity during cure

Abstract The ability to conveniently and continuously measure the processing properties of polymer resins is important both to the resin supplier and to the fabricator. Frequency dependent electromagnetic sensors (FDEMS) provide an in‐situ technique for continuous measurement of the resin's rheological changes both in a laboratory press and in manufacturing tools in an autoclave. In this paper the frequency dependence of ϵ*( w ) is used to quantitatively monitor the viscosity for a tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) amine epoxy, to quantitatively monitor the viscosity during processing In a styrene‐polyester resin, and to monitor the cure process in an autoclave during cure of a high temperature polyimide‐graphite prepreg. In addition, the technique is used to measure the viscosity at various ply positions in a thick TGDDM graphite epoxy laminate during processing in an autoclave.