Fatigue Failure Criterion for Notched Plates of a Glass Fiber-Reinforced Polycarbonate
Toshihiro Yamamoto and Hiizu Hyakutake
Abstract:Failure of notched FRP plates under static or fatigue loading is govern ed predominantly by the severity near the notch root. The severity is deter mined by both stress concentration and similarity of stress distribution nea r the notch root. In the present paper, a fatigue failure criterion based on the concept of severity near the notch root mentioned above is subjected to further experimental scrutiny. The investigation is accomplished by obtai ning experimental data on intermediate notch-root radii specimens of a glass fiber-reinforced polycarbonate in pulsating tension. The process of initiation and growth of fatigue damage near the notch root was measured by means of the luminance-measuring technique using a CCD camera. Closer observation of the microfracture in the fatigue-damage zone revealed the process of the luminance decline along with the increase of loading cycles. The experimental result shows that the number of cycles at the fatigue damage initiation, Nd was governed predominantly by both notch-root radius r and the maximum elastic stress smax at the notch root, while it was independent of notch depth. Furthermore, the smax has a one-to-one correspondence with the Nd when the size of fatigue-damage zone reached the half value of the notch-root radiusr. On the basis of the concept of severity near the notch root mentioned above, the experimental results can be explained Key Words:Fatigue, Notch, Stress concentration, Short fiber-polymer composites, Fatigue damage, Luminance