The Finite Element Analysis Of Interlaminar Short-fiber Toughening Effect Under Low-velocity Impact

Fiber reinforced composite has 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 property of the laminate between layers of composite materials constraint the application of this kind of material, poor impact resistance is the most fatal shortcoming. The delamination of the composite panels was the main form of damage. So how to improve the toughness and resistance capacity of the laminate between layers had become the focus of scholars from different countries. Therefore, studying the impact of laminated composite plate finite element analysis has important theoretical significance and application value.The delamination behavior of the composite laminates with imbedded delamination under impact has been analyzed by3D nonlinear finite element method base on composite materials mechanics and fracture mechanics theory. The virtual crack closure technique has been used to calculate the energy release rate of the delamination front, and the mixed mode crack growth principle has been used to judge delamination growing. Contact element has been placed between delamination faces and the contact area of ball impacting composite. Nonlinear spring elements set between delamination faces have been used to simulate the short-fiber and the short-fiber force has been modified by adjusting the tensile stiffness and shear stiffness. The delamination front energy release rate of the laminated composite plate with different overlay occasions under different impact energy have been studied calculated. The influence of interlaminar short-fiber on energy release rate and stresses field has been studied, and the interlaminar toughness has been discussed.The results show that:in the impact process, type Ⅱ is the main energy release rate. The delamination crack propagation area is affected by overlay occasions. The delamination growth may occurs at0°and180°region in [0]12laminate and at the90°region in [0/90]3S laminate. The short-fiber can reduce energy release rate in crack tip, increase the threshold of energy release rate, effectively improving the interlaminar toughness.