An analysis of the fatigue behavior of Al-Al3Ni composites

Commercial purity Al-Al₃Ni eutectic composites have been prepared by directional solidification at growth rates ranging from 9.63 x 10^-3 to 1.0 mm/s. The composites were tested under rotating bending fatigue conditions and the results were analyzed using a model taking into consideration the difference in Poisson’s ratio of the phases, interfiber spacing and premature fracture of fibers. The calculated fatigue lives were shown to be in good agreement with the experimental results at all stress levels. Both the experimental results and calculations show that the composite fatigue life is not sensitive to large changes in the growth rate. The fatigue limit was also found to be insensitive to the mode of fatigue loading and notches. At high stress levels, however, smooth specimens tested under reversed bending exhibited longer lives than notched specimens tested under cyclic tension-tension conditions.