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Ultrasonic characterization of changes in viscoelastic properties of epoxy during cureA technique for using the longitudinal velocity (LV) of an ultrasonic wave to monitor the extent of cross linking (CL) during the cure of thermosetting resins is described. The method was developed by monitoring the rate of change in LV during the cure of a bisphenol-A epoxy resin with an amine adduct. The experiment included variations in the temperature and stoichiometry in order to express the rate of change in terms of the reaction kinetics. The pulse-echo method was used with a single transducer operating at 20 MHz. Numerical models were defined to account for the acoustic response of a single layer, the attenuation and the reflection coefficient. A linear relationship was observed between the inverse of the temperature and the log of the rate of change in the velocity, supporting the theory that the velocity could be used to monitor the extent of the cross-linking reaction. An activation energy of 11.9 kcal/mole was calculated for the mixture being investigated.
Document ID
19860056890
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Winfree, W. P.
(NASA Langley Research Center Hampton, VA, United States)
Parker, F. R.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1985
Subject Category
Nonmetallic Materials
Accession Number
86A41628
Distribution Limits
Public
Copyright
Other

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