Abstract
Damage development in the later stages of the fatigue life of a glass/epoxy non-crimp 3D orthogonal woven fabric composite has been examined using a combination of mechanical testing and damage observations. Changes in both the stiffness reduction rate and the energy dissipation per cycle suggest that there are three stages in the fatigue lifetime. Observations of damage using X-ray micro computed tomography (CT) and optical microscopy within specimens cycled to the beginning of the third stage show extensive matrix cracking extending between surface weft tows, with associated resin pocket cracking. It is suggested that the observation of extensive fibre fractures within sections of warp tows closest to z-crowns is a consequence of stress concentrations due to these cracks.