13th International Conference on Fracture June 16–21, 2013, Beijing, China One of the advantages of the FE simulation is that the whole deformation and damage process can be observed clearly in the simulation. From the FE results, three obvious stages of mechanical properties of the interface were found: the linear elastic stage, the damage initiation stage and the crack propagation stage, as is shown in Figs. 4-6. The unit of the labels of the stress distribution nephogram is GPa. Figure 4. Stress distribution at linear elastic stage In the linear elastic stage, the epoxy matrix and the CNT were bonded by the interface. The high cohesive strength ensures the effective transfer of the stress between CNT and the matrix. CNT takes more load than the matrix, the properties of CNT composites have been improved by the strong interface. The stress in the matrix where near by the CNT end is larger than the other positions in the matrix, and the stress in the CNT where near by the interface is larger than the other positions in CNT. In addition, the stress concentration appears at the corner of the CNT end. Figure 5. Stress distribution at damage initiation stage As the displacement increasing, the damage initiation stage comes up, the damage initiated at the corner of the interface due to stress concentration. The damage of the interface leads to the stiffness reduction and stress redistribution in the composite, although the composite still has the capacity to bear the load. Then the microcracks at the corner grows, the crack extends to the end side of the interface. Figure 6. Stress distribution at crack propagation stage At the crack propagation stage, the shear sliding comes up after the normal debond in the corner of
RkJQdWJsaXNoZXIy MjM0NDE=