Composite laminates with elliptical pin-loaded holes

This experimental and analytical study addresses the effect of the elliptical shape of pins and holes on the failure mode and stress distribution around pin-loaded holes in composite laminates. Specimens exhibiting either net-section or bearing failure mode were considered. Measured and computed strain values at specific points were compared in order to establish the fidelity of the analysis method. By using acoustic emission probes on a few of the specimens, the load level could be related to the frequency of microscopic damage occurrences. Acoustic emission measurements show that, with a sharp increase in the number of microscopic damage occurrences, a loss of stiffness occurs close to the ultimate failure load. The analytical predictions and experimental measurements indicate that the load-carrying capacity of a pin-loaded hole can be altered by changing the shape of the pin.