| 摘要 |
A sample of polymeric composite material is cured using conventional curing methods. The optimum time during the cure cycle for applying pressure to the sample is determined by standard resin advancement measuring techniques. A dielectrometer monitoring device (15) is then attached to another material of the same type which is cured under the same conditions to develop an analog signal denoting variations in dissipation of the material. The dissipation curve characteristically has a first and second maximum value, with the latter occurring in the general vicinity of the optimum time for applying pressure for a particular frequency. Thus by changing the frequency, the dissipation is shifted along the time axis so that the second maximum coincides with the optimum time for applying pressure. The generation of a readily recognizable and repeatable feature on the analog wave form, a minimum or maximum, is a prerequisite to triggering process control functions. Thereafter, a voltage at that particular frequency is applied to other similar materials during their cure cycles to obtain a dissipation curve which has a second maximum value coinciding with the optimum pressure application point. The dielectric monitoring unit (15) is connected to a microprocessor ( 20) which determines the time at which such maximum value is reached, in response to which a command signal is sent to a pressure control system (24) connected to the microprocessor (20) for applying pressure to the material, all in an automatic, closed-loop system.
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