A micromechanical model for prediction of mixed mode I/II delamination of laminated composites considering fiber bridging effects

In unidirectional laminated composites, fiber bridging as a toughening mechanism has a significant effect on the behavior of mixed mode I/II delamination. In the present paper, effects of fiber bridging and related micro mechanisms were investigated quantitatively. To this end, a novel micromechanical model called "mixed mode I/II micromechanical bridging model" was proposed based on the calculation of the delamination crack bridging zone energy absorption. Firstly, different failure micro-mechanisms, occurring during the fiber bridging process, were identified. Then, different loading conditions on the bridged fibers were applied. In the next step, the absorbed energy of each failure micro-mechanisms was calculated. Finally, the energy absorbed by the fiber bridging zone was obtained by summation of the absorbed energy of each failure micro-mechanisms. The traction-separation behaviors in both the normal and tangential directions of the crack plane are the outcome of the proposed model. Moreover, the mixed mode I/II delamination failure response of the laminated composite was extracted by plotting G(I) versus G(II) and compared with the available experimental data. The results show that the proposed model is able to predict the mixed mode I/II delamination behavior of laminated composites considering fiber bridging effects.