Sf-tpu Composite Injection Filling Fiber Orientation Numerical Simulation And Its Structure - The Study Of The Performance,

Intensive researches have been carried out in this thesis on the relationship between processing, structure and properties of short fiber/thermoplastic polyurethane (SF-TPU)composite.The structure of the SF-TPU composite such as: fiber length, orientation and distribution, which determines the mechanical properties the material, is dependent on the molding process.In this thesis, a numerical model using finite-difference technique has been established to simulate the flow, heat transfer and fiber orientation of the SF-TPU composite in a thin rectangular cavity or a molding tensile specimen cavity. The model takes into consideration of the "fountain flow" in the front region of the filling material, in which a moving coordinate on the flow front is adopted to simplify the calculation.In order to verify our numerical method, the simulation results were compared with the experimental data obtained by Wales and Lui, and with our experiments on the molding SF-TPU specimen.In this thesis, the structural parameters of the SF-TPU composite: (1) short fiber length and distribution, and(2) short fiber orientation and distribution were tested and described by fiber length distribution index and orientation factor, respectively. Results show this method is feasible. The experimental observation showed that, like uneven distribution, zigzag and crunch, etc., the arrangement of the short fiber of the SF-TPU composite is very complicated.In this these, equations for predicting the longitudinal modulus and strength or heat expansion have been put forward for the SF-TPU composite. A larger amount of fibers with wide length range was used to investigate the relationship between mechanical properties and structural parameters of the SF-TPU composite and the coincidence of theoretical prediction and experimental results was studied as well.In our model, the Halpin-Tsai equation has been improved by using average length to place of the length distribution, using orientation factor to replace the fiber...