220 Characteristic of Fatigue in Quasi-Isotropic Alumina-Fiber Reinforced Plastic : Internal Damage Progression and Fatigue Life

Abstract

This paper describes the results of an experimental investigation of cumulative damage development in quasi-isotropic [0/+45/-45-90]_s alumina FRP laminates subjected to tension-tension fatigue loading. The onset and growth of matrix cracks and delamination were monitored with an optical microscope. The matrix crack density and the normalized length of delamination were measured as a function of the normalized number of stress cycles by edge observation. It was found that a decrease of the stiffness was observed in an early stage due to the initiation of the matrix crack, and that a different pattern of the damage evolution was observed in each lamina under tension-tension fatigue. Results of the study include a detailed description of the chronology of the damage development prior to failure. Additionally, the mechanism of the fracture of quasi-isotropic alumina FRP laminates under tension-tension fatigue was evaluated from the result such that the static strain of [0]_8 Alumina FRP laminates and fatigue failure strain of quasi-isotropic alumina FRP laminates are equivalent.