Embedded Delamination Growth In Interlaminar Short-fiber Reinforced Composite Panels Under Compressive Load

Fiber reinforced composite had features of high specific strength, stiffness and the material properties which can be designed, making it applied to many important structures, and it also became one of the most promising structure materials. However, low propertiy of the laminate between layers of composite materials constraint the application of this kind of material. The delamination of the composite panels was the main form of damage. So how to improve the thoughness and resistance capacity of the laminate between layers had become the focus of scholars from different countries. Therefore, the finite element analysis of crack propagation about the delamination of the composites panels had important theoretical significance and application value.In this paper, the delamination area was placed in the shallow position of the laminates in the three-dimensional finite element model. In considering the geometric nonlinearity and contact nonlinearity, this paper used the nonlinear finite element method, the mixed mode crack growth princeple and the virtual crack closure technique to analyse the delamination crack propagation process of the composite panel. The contact element was introduced in the interface of the delamination aera. The corresponding nodes were coupled in the contact element, using node separation law for analysing the crack propergation of the delamination process. First, we calculated the energy release rate of the delamination front. When the node met the node separation law, the coupleing of the nodes was disabled. Then the paper introduced a nonlinear spring element to simulate the short-fiber which was placed in the composite plate. By adjusting the tensile stiffness and shear stiffness, the short-fiber force was modifed, which avoided the complicated process of iterative calculation.The results showed:the delamination happened in the direction which was vertical to the direction of the compressive load, impacted by the direction of the fiber. The short fiber placed in the interface of the laminates can significantly postpone the delamination, improving the interlaminar toughness effectively.