Modification of the edge crack torsion specimen for mode III delamination testing. Part II – experimental study

Experimental studies of carbon/epoxy edge crack torsion specimen have been conducted using a specially designed twist test fixture. Of particular concern was verification of the recommendations expressed in the analytical part of this study (Part 1), where it was suggested that overhang (sections of specimen laying outside of the loading and support pins) in the x- and y-directions should be minimized, and fracture testing at longer delamination lengths should be avoided. The experimental test results verified that the specimens with the smallest overhang produced the most consistent delamination toughness data, G_IIIc. Specimens with large overhangs exhibited high apparent G_IIIc values at long delamination lengths. This was most likely due to nonuniform loading and associated nonuniform delamination extension.