Application of backface strain monitoring technique to delamination test

Abstract

(Times New Roman 12 pt, bold, single-line spacing, left-aligned text) DCB test is a popular method for measuring interfaces toughness but also for indentifying cohesive zone models. However, since the measured quantities are global, the test results generally show poor sensitivity to the local cohesive law shape. To improve the test protocol we use backface strain measuring technique to monitor the cohesive forces along the interface facing the crack. A test protocol and data reduction method is proposed based on simple beam on elastic foundation model. From the additional strain measurement, crack position is precisely determined, so as the extension of the cohesive zone. Experimental crack propagation results are presented in case of Mode I delamination test, but also in case of mode I fracture test on CFRP bonded joints.