Vanishing notch sensitivity approach to fatigue life prediction of notched cross-ply CFRP laminates at room temperature

Abstract

The effect of notch on the constant amplitude fatigue behavior of cross-ply carbon fiber-reinforced polymer (CFRP) laminates with different stacking configurations is examined. An analytical procedure that allows the prediction of the S–N relationships for notched cross-ply CFRP laminates for any notch size is also developed. Fatigue tests are first performed at room temperature on unnotched and center circular notched specimens of three kinds of non-woven cross-ply laminates, A:[90/0]3S, B:[903/03]S, and C:[03/903]S, respectively. The results from these tests show that the notched fatigue strengths of the cross-ply laminates, regardless of stacking configuration, become lower than the unnotched fatigue strengths in the range of short life according to a reduction in static strength due to notch, but the effect of notch on fatigue strength turns insignificant in the range of long life. A new engineering method for predicting the notched fatigue strengths of composites is then developed assuming that notch sensitivity vanishes during fatigue loading. The proposed fatigue model for notched composite laminates is formulated using a fatigue life prediction model for unnotched specimens and a residual strength prediction model for notched specimens. It is demonstrated that the S–N relationships for notched specimens of the three kinds of cross-ply CFRP laminates can successfully be predicted using the proposed vanishing notch sensitivity model for fatigue, regardless of notch size and stacking configuration.