FORMATION AND GROWTH OF 90-DEGREES PLY FATIGUE CRACKS IN CARBON EPOXY LAMINATES

This study focuses on fatigue mechanisms of matrix cracking in carbon/epoxy cross-ply laminates. Tension-tension fatigue tests were conducted on two equivalent lay-ups, whose only difference consists in the stacking sequence and in the resulting 90° ply thickness. Transverse ply crack onset, accumulation and growth were measured. The 90° ply thickness was shown to have a considerable influence on the crack distribution in the transverse ply and on the fatigue crack growth rates. A fracture mechanics analysis for the strain energy release rate associated with 90° ply matrix crack formation and growth has been developed and compared with experimental results. © 1990.