Damage development in CFRP laminates under monotonic and cyclic stressing

Abstract

Simple [0°/90°/0°], [±45°] and quasi-isotropic carbon fibre reinforced epoxy laminates were tested in uniaxial tension. The first sign of damage was fibre/resin debonds in the transverse plies. The transverse (90°) ply cracking strain was found to increase with decreasing transverse ply thickness. A similar effect was found in the [±45°] laminates—thinner plies being able to support higher loads. The failure mode in quasi-isotropic laminates was found to depend on the ply stacking sequence. Again, the transverse ply cracking strain was greater for thinner transverse plies. In fatigue, the transverse ply cracking strain of [0°/90°/0°] specimens was found to be lower than that of similar specimens tested in uniaxial tension. A resin-rich area between the transverse and longitudinal plies delayed the propagation of transverse ply cracks under fatigue loading, thus delaying the appearance of delamination along the 0°/90° interface.