Impact Load-induced Interlaminar Short-fiber Reinforced Composite Laminates Toughening Research

In recent years, continuous fiber-reinforced composite laminates have been used in many important structures. The properties of high ratio strength and modulus to weight make it become one of the most evaluative potential materials. But the strength of laminates in direction along thickness is much lower than that along fibres. This disadvantage has seriously limit its development. Delamination is a main failure mode and a serious hidden danger of the composites. How to improve its toughness and anti-delamination capability have been a research focus among scholars all over the world. So, the research of improving its toughness and anti-delamination capability will be more signification and valuable. Hence, the methods for characterizing and improving its toughness have been discussed in a great amount of literatures in recent years. Owing to the complex natures of these problems, though some works have been done to improve interlaminar toughness, further study has been still needed till now. A simple and low-cost interlaminar toughening method using sparsely distributed chopped fibers originally developed by Sohn and Hu may potentially provide a satisfactory answer to the above question. In this paper several major problems about the toughness by bridging fiber with impact load have been studied thoroughly in theoretical and numerical analysis. Some valuable conclusions have been gained.In this paper, base on compound material mechanics and fracture mechanics theory, a nonlinear finite element program is developed to study interlaminar short-fiber toughness by the mode of secondary development of ANSYS software. The practice proves, this method is feasible.The augments Lagrange method is used to compute contact question, in the crack place add contact element, used for to simulate the material can not penetrate with each other. The Newmark method is used to solve dynamics equation, in each step revise the computed result.The impact process between the impact object and composites laminates is studied. Results indicate, impact process is interrupted. In each process, the impact time is very short, the impact force is very big.Discrete crack model is used to simulate crack and using the method of nodes coupling to simulate crack spread. First calculates the energy release during numerical analysis. When it achieves a definite value release, the nodes coupling constrain and add short-fiber bridging force.Fracture mechanics method is used to analyze energy release rate in different layer form.