Observations on damage development in fibre reinforced polymer laminates under cyclic loading

Abstract The response of cross-ply [0 2 /90 3 ] s and multi-directional [±45/90 3 ] s laminates subject to quasi-static and cyclic loading is investigated. Life curves for transverse crack initiation, delamination initiation, and final failure of the laminates are determined. A linear line in a maximum applied stress versus logarithm of life coordinate system appears to be a good fit to the experimental data. In addition, transverse crack growth in 90° laminae at various life cycles and its effect on stiffness reduction of the laminates has been quantified. Here too, a linear relationship between the normalized stiffness and crack density is a good representation of the data. It is observed that damage growth in these laminates occurs in four different modes: microdamage, matrix cracking, delamination, and fibre failure. These damage modes interact resulting in a complex failure pattern.