EFFECTS OF SEAWATER ABSORPTION ON FATIGUE-CRACK DEVELOPMENT IN CARBON/EPOXY EDT SPECIMENS

Fatigue and static edge delamination tests were performed on [45/0/-45/90](s) CFRP laminates. Both dry and seawater presoaked specimens were tested to examine any effect moisture absorption has on fatigue crack development, which was monitored by optical microscopy, scanning electron microscopy and ultrasonic C-scan. Seawater absorption changed the dominant edge-cracking mode from the -45/90 interlaminar delamination in unaged specimens to intralaminar cracking in 90 degrees plies in aged (seawater saturated) specimens. The edge-crack growth rates in both unaged and aged specimens, however, are similar. The effect of moisture absorption on strain energy release rate has been examined, and the change in dominant edge-cracking mode and edge-crack growth have been discussed in terms of strain energy release rate.