EXPERIMENTAL AND NUMERICAL STUDY OF THE INTRA/INTER LAMINAR DAMAGE COUPLING OF LAMINATED COMPOSITES

Coupling between intralaminar and interlaminar damage largely influences the evolution of damage in laminated composites. A well-known example is the transverse crack induced local delamination. In the early stage of loading, the matrix is prone to diffuse matrix damage, followed by macroscopic transverse cracks. Stress concentration in the crack tip would then leads to local delamination in the interlaminar region. In this work, we implemented both experimental and numerical study to dig into the intra/inter laminar coupling mechanism. Our experiments indicated that preset intralaminar damage could be both detrimental and helpful to the interlaminar damage performance [1]. In one aspect, the transverse crack induced delamination will decrease the delamination resistance. In the other aspect, the preset intralaminar damage could cause crack branch inside the layers during delamination progress. The arrested delamination crack would pull out fiber bridging in mode I fracture. Both the wavy delamination crack and pulled out fiber bridging will, in the end, prohibit delamination propagation and dissipate more energy. Furthermore, we proposed a hybrid cohesive element to involve the coupling mechanism [2]. In this hybrid cohesive element, we not only use the classical displacement jump, but also the displacement field of the top and bottom surface of the cohesive element. The displacement field of the cohesive element's top and bottom surface is used to estimate the strain and damage level of the adjacent layers of this interested interface. The estimated in-plane strain could then be used to operate an appropriate strategy.