On the Radio-Frequency Inputs in Dipolar Heating of Adhesives

The form of the radio-frequency (RF) or dielectric input expression in the heat equation which arises in the modeling of the curing of epoxy adhesives in bonding of composites was considered. Two standard derivations of a commonly used expression for the RF heating source term were reviewed. In this context difficulties involving the associated inherent polarization assumption and asymptotic behavior of dielectric parameters as a function of the frequency of the RF signal were discussed. These difficulties cast doubt on the validity of the standard RF expression. Two standard polarization models (Debye and Lorentz) then were used to demonstrate how one can systematically derive general RF heating expressions which do not suffer the inconsistencies that arise in the standard RF expression.