Zc. Li et al., HIGH-FREQUENCY ELECTRICAL MEASUREMENTS OF ADHESIVE-BONDED STRUCTURES - AN INVESTIGATION OF MODEL PARALLEL-PLATE WAVE-GUIDE STRUCTURE, NDT & E international, 30(3), 1997, pp. 151-161
Analysis using a network analyser of the electrical response between 3
00 kHz and 200 MHz for a range of model waveguide structures is discus
sed. The structures chosen illustrate the variations to be expected in
real adhesive bonds and include changes in bond line thickness, width
and electrical conductivity of the substrate. A simple theoretical mo
del was used to simulate the time domain data and very good agreement
between experiment and theory was observed. Deficiencies in the model
appeared when it was used to simulate frequency domain data, and the l
imitations of these calculations ave critically discussed. The accurac
y to which this method can be used to calculate the dielectric permitt
ivity was assessed from a study of a number of polymers with well-defi
ned dielectric characteristics. Parallel plate structures were fabrica
ted using low density polyethylene (LDPE), high density polyethylene (
HDPE), polypropylene (PP), polystyrene (PS), polycarbonate (PC) and po
lymethyl methacrylate (PM MA). Good agreement between literature and e
xperiment was observed in all cases, validating the dielectric permitt
ivity values obtained using this approach. This paper illustrates the
potential of nondestructive electrical measurements to provide structu
ral and quantitative permittivity information on adhesive joint struct
ures. (C) 1997 Elsevier Science Ltd.