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:[90 3 /0 3 ] S , and C:[0 3 /90 3 ] 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.

Notch effect on strength and fatigue life of woven composite laminates

“…According to ASTM standards D7615-11 and E739-10 [40,41] , the constant-amplitude fatigue tests were conducted under tension-tension (T-T) and compression-compression (C-C) cyclic loading at the stress ratios of 0.05 and 10. For each specimen type, at least four groups of fatigue tests were conducted under different stress levels to achieve four target fatigue lives, namely 10 , 5 10 , 5 5 10  and 6 10 cycles. Each group contained at least three specimens to ensure the reliability of the test data.…”

“…To understand the fatigue damage mechanisms of 3238A/EW250F and 3238A/CF3052 laminates, the run-out specimens tested up to the nominal fatigue life of 6 [8] .…”

“…A great deal of research has been conducted to investigate the effect of notches on the mechanical performance of fibre reinforced composite laminates under static and fatigue loads. It has been reported that the strength and fatigue behavior of both the UD-based laminates and woven composite laminates are significantly affected by the notch location (single-edge notch [1] , double-edge notches [2] and central hole [3][4][5][6][7][8][9][10][11][12] ), notch shape (circular hole, elliptical hole and rectangular slot [3,4] ), and notch size [4][5][6][7] . Fatigue damage mechanisms of notched composites are different to those of un-notched composites.…”

Fatigue Behavior of Open-Holed CFRP Laminates with Initially Cut Fibers

“…Yashiro and Okabe [10] studied fatigue damage identification in open-holed CFRP laminates by using embedded fiber Bragg grating (FBG) sensors. Kawai and Shiratsuchi [11] investigated the effect of notch on fatigue behavior of CFRP laminates with different stacking configurations. More recently, Fujita et al [12] investigated mechanical properties such as com- were measured for the above three laminates.…”

An investigation into the damage development and residual strengths of open-hole specimens in fatigue

“…Kawai and Shiratsuchi [3] studied the effects of centrally located circular holes on the constant amplitude fatigue behaviour of cross-ply CFRP laminates of various stacking sequences. They showed how the notched fatigue strength of cross ply laminates becomes lower than for un-notched specimens in the range of short fatigue life.…”