2019 : Fatigue behaviour of un-notched and open-hole quasi-isotropic pseudo-ductile thin-ply carbon/glass hybrid laminates
This paper investigates fatigue behaviour of a QI composite made from thin carbon plies and standard thickness glass plies. As illustrated in Fig. 2, this orientation-dispersed QI thin-ply carbon/glass hybrid laminate showed a successful pseudo-ductile un-notched behaviour with improved notch-insensitivity and suppression of free-edge delamination. In this study an experimental program has been carried out to investigate the damage development throughout the life of un-notched and open-hole thin-ply carbon/glass hybrid configurations consisting of thin ply T300 carbon/epoxy and S-glass/epoxy prepregs, before having any pseudo-ductile damage and at two different stress levels. The fatigued samples are illustrated in Figs. 3 and 4. The knee point is determined at the intersection of the lines fitted through the initial linear and the plateau parts of the individual stress-strain curves. It was observed that, for the un-notched samples, there is no stiffness reduction, after 100,000 cycles, for a stress level of 80% of the knee-point stress at which significant damage starts. By increasing the stress level to 90% of the knee point stress, there is a gradual stiffness reduction due to the appearance of matrix cracking and delamination.