By. Liu et Lb. Lessard, FATIGUE AND DAMAGE-TOLERANCE ANALYSIS OF COMPOSITE LAMINATES - STIFFNESS LOSS, DAMAGE-MODELING, AND LIFE PREDICTION, Composites science and technology, 51(1), 1994, pp. 43-51
The prediction of fatigue life and evaluation of progressive damage fo
r general composite laminates are studied analytically. From theories
of damage tolerance, residual-modulus degradation, and residual-streng
th degradation, a simple and approximate approach is proposed for the
prediction of progressive stiffness loss, matrix-crack density, and de
lamination area in terms of tension-tension fatigue load and number of
cycles for general laminates containing 0-degrees plies. The proposed
approach provides four choices for predicting tension-tension allowab
le fatigue life and for assessing fail-safety for structures made of c
omposite laminates, namely, a residual-modulus criterion, a matrix-cra
cking criterion, a delamination-size criterion, and a residual-strengt
h criterion. The ap-proximate analytical relationship between S-N curv
es for general laminates containing 0-degrees plies and for a unidirec
tional 0-degrees-ply laminate is proposed. Three glass/epoxy laminates
of [0/90]s, [+/-45/0/90]s, and [0/+/-45]s lay-ups, and one [0/90/+/-4
5]s T300/5208 graphite/epoxy laminate under tension-tension fatigue ar
e used to illustrate and verify the proposed approach. The analytical
results are in good agreement with experimental data.