Delamination Propagation and Load Ratio Effects in DCB MD Woven Composite Specimens

Double cantilever beam (DCB) specimens fabricated from 15 plies of a plain woven prepreg (G0814/913) arranged in a multidirectional (MD) layup were tested by means of constant amplitude fatigue cycles under displacement control. Four different displacement cyclic ratios were used, namely 0.1, 0.33, 0.5 and 0.75. The delamination propagation rate da/dN was calculated from the experimental data and plotted with respect to different functions of the mode I energy release rate GI. When one of those functions, denoted here as ΔKI was used, all of the data obtained for the different displacement ratios collapsed into one master curve.