Abstract
Plane bending fatigue tests were carried out on notched specimens of a glassfiber / epoxy laminate for a wide range of notch-root radii and stress amplitudes. Our attention was focussed on the damaged zone near the notch root of specimens. The process of fatigue damage was studied by measuring the luminance at a limited spot near the notch root. Closer observation by means of a scanning electron microscope revealed that the initiation of microcracks at the notch root was accompanied with the decrease of luminance near the notch root. The experiment shows that the number of cycles to failure is determined by both the maximum elastic stress at the notch root and the notch-root radius. On the basis of the concept of severity near the notch root, the experimental results can be clarified. Applying the fatigue failure criterion derived here, we can make an accurate estimate of the life of notched specimens of FRP.
