The effects of exposure to moisture on the mechanical properties of a
series of adhesively-bonded structures are reported. Changes observed
in the maximum load, shear modulus, strain at maximum load, fracture e
nergy, fracture toughness and stress are discussed and correlated with
variation of the dielectric parameters. An initial increase in fractu
re toughness observed in the joints correlates well with the uptake of
moisture having led to a lowering of the glass-rubber transition temp
erature. Differences in the ultimate strength and energy to failure fo
r different surface pretreatments are observed. Loss in mechanical pro
perties observed over the period of the study are paralleled by change
s in the dielectric properties of the joints.