Fatigue crack propagation behavior of fiber metal laminate - influences of initial notch length and pre-stretching
Miyata Takashi; Tagawa Tetsuya; Takahashi Fumio; Hira Hirohito
Abstract:Fatigue crack propagation was investigated in fiber metal laminates which have been developed as the aerospace materials. Two kinds of fiber metal laminates were prepared for the fatigue crack propagation test. One was the laminates in which an unidirectional aramid fiber/epoxy prepreg was sandwiched between aluminum alloy sheets, and another was the laminates of a glass fiber/epoxy prepreg and aluminum alloy sheets. The fatigue crack growth in aluminum alloy sheets is strongly influenced by the bridging behavior of unbroken fibers. The effects of difference in reinforcing fiber, initial notch length and pre-stretching were investigated. In comparison with conventional aluminum alloy sheet, the crack propagation rate was extremely small and the decrease in propagation rate was observed in spite of the K increasing test, depending on the initial notch length and the stress ratio. The glass fiber/aluminum alloy laminates showed the noticeable effect of pre-stretching on crack growth rate. The mechanism for the improvement in fatigue crack propagation was also investigated on the basis of the compliance variation with crack propagation and the stress distribution analysis of infrared spectra. Key Words:composite, fiber metal laminate, fatigue crack propagation, crack shielding