Prediction of delamination growth in laminated composites using acoustic emission and Cohesive Zone Modeling techniques

Mode I delamination is the most common failure mode in laminated composite materials. Determination of the crack growth has a vital role in the damage tolerance analyses of the structures which suffer from this type of damage. The main objective of this paper is to determine position of the crack tip during propagation of mode I delamination in the glass/epoxy composite specimens. To this aim, experimental investigation by mechanical and acoustic emission (AE) data and Cohesive Zone Modeling (CZM) technique are carried out. The crack tip position is identified using three methods. First, position of the crack tip is identified using visual observation of the crack tip during the test. The second method utilizes cumulative energy of the AE signals to predict the crack growth. Finite element analysis based on a CZM theory is used as the third method to investigate delamination growth. Because of poor performance of CZM technique, modified CZM based on the R-curve results of the interlaminar fracture toughness is proposed to predict the delamination propagation. The results indicate that AE method and modified CZM technique have a good performance to detect initiation stage and also to determine the crack length in the laminated composite structures.