Analytical Damage Zone Size Predictions for Notched Laminated Composites

The purpose of this study was to investigate the significance of damage zone size as a parameter for evaluating the fracture strength of center-cracked laminated composites. Using experimental data for a symmetrical, generally orthotropic graphite-epoxy laminate, the damage zone sizes predicted by the Average Stress Criterion and Point Stress Criterion, as well as the D-Criterion, were compared. Additionally, limited data for the Quadratic Surfaces and Sequential Fiber Failure Criteria were evaluated. Experimental measurements of crack-tip damage zone size were used to establish a physical reference point by which all of the theories were compared. The preliminary results of this study indicate that the characteristic lengths defined by the Quadratic Surfaces and Sequential Fiber Failure Criteria are not representative of the measured damage zone size and need further investigation.