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.
Frequency-dependent electromagnetic sensing (FDEMS) is a convenient and sensitive technique for monitoring in situ infiltrationand cure in the tool during the resin-transfer molding (RTM) process. The magnitude of the fluidity and viscosity as a function of the time and temperature, the time to infiltration at various ply depths, the effects of aging and elapsed time before infiltration of the RTM process, and monitoring of the cure cycle are four important areas where FDEMS is shown to significantly help in determining the RTM process procedure. l\ NONDESTRUCTIVE IN SITU FREQUENCY-DEPENDENT impedance sensing technique was reported previously (1-10) for measuring cure-processing properties of both thermoset and thermoplastic resins. The technique uses the frequency dependence of the resin's impedance to measure molecular ionic and dipolar diffusion rates. These molecular parameters can be used continuously throughout the process cycle to monitor the time and temperature dependence of events such as reaction onset, maximum flow, viscosity, gel, the buildup in modulus, evolution of volatiles, and reaction completion (1-10). The measurements can be made in a research environment to evaluate resin processing properties and in the manufacturing tool
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