Considering the stress concentration and the similarity of stress distribut
ion near the notch root, we have obtained a fatigue failure criterion for n
otched FRP plates in terms of a combination of the maximum elastic stress,
the notch-root radius and the number of loading cycles to fatigue-damage in
itiation. To evaluate the fatigue damage near the notch root during fatigue
test; we measured successively the luminance distributions by means of the
luminance measurement technique with a CCD camera. The aims of the present
research are to provide experimental evidence of the validity of the fatig
ue failure criterion as mentioned above and to show that the decrease of lu
minance is associated with irreversible damage and microfracture, The inves
tigation is accomplished by obtaining experimental data of fatigue tests on
the notched plates of a glass fiber-reinforced polycarbonate. To reveal th
e initiation and growth of microfracture along with the luminance decline,
we observed the transverse section of the fatigue-damage zone near the notc
h root. The experiment shows that numerous microcracks initiated the end co
rner of a glass fiber and it is likely that several microcracks joined toge
ther and grew into a main crack.