FATIGUE BEHAVIOR OF CROSS-PLY CFRP LAMINATES MADE OF T300 OR T400 FIBERS

The determination of the transverse cracking which occurs during the fatigue of cross-ply materials with two different fibres (T300 or T400) has been undertaken. The study includes an experimental part and a theoretical part containing both an analytical and a numerical approach for modelling the observed stiffness reduction. In particular, this paper gives improved solutions to the well known modified shear lag analysis, due to Garrett and Bailey, concerning the stress distributions in the cross-ply composite after transverse cracking. These methods have been used in a fatigue context to model transverse-ply crack development. The difference between the theoretical model and the experimental results-especially for the T300-based composite-enables an evaluation to be made of the stiffness reduction due to fibre failure in the 0° plies. It is thought that this last mechanism is activated by the extension in two directions of the stress concentration zones existing in the region of the transverse-ply crack tip: along the fibres by delamination and across the 0° layer by rupture of fibres. © 1990.