Numerical Simulation And Experiment Of Fiber Orientation During Filling Phase Of Short-Glass Reinforced Polymer

The mechanical and physical properties of fiber reinforced composites are strongly dependant on the quality of their reinforcement, such as situation of fiber orientation, aspect of fiber and so on, but the research of the influence fiber orientation made on properties of fiber reinforced composites is especially wide. Injection molding still occupies an important position on productions of plastic parts all over the world, however a majority research about fiber orientation of molded parts concentrate on filling stage. In actual manufacturing processes, there is great difference on different position of parts, and that will bring imbalance residual stress due to anisotropy when fibers orient themselves along some direction, in finally some unexpected behavior will be produced, such as shrinkage, warp and so on. In most of research about suspending fluid of fiber, the situation of fiber orientation usually be described with two Euler angles in space, then after the function between the Euler angles and the time's change can be obtained, the situation of the fiber orientation can be got in kinds of flow field.In this paper, there are mainly two aspects of work, firstly the velocity field of the Center-gated disk model will be reduced, then on the base of Jeffery motion function, the situation of fiber orientation of the model can be obtained through the Co-rotational coordinate system and computer programme. On the other hand, the fiber orientation of two actual disk models can be got through experiment by Polarized optical microscopy(POM), then there will be comparison and discussion between numerical simulation and experiment result. Through combination of numerical simulation and experiment, the general situation of fiber orientation can be got in the Center-gated disk model, and then there are some conclusions below:(1) The fibers endure different shear action and stretcher action along the height of flow field in the Center-gated disk model, and there is no influence on velocity grads due to initial angle of fiber.(2) In the surface layer of the model, under pure shear action, the fibers will mainly orient parallel the flow direction and keep along this direction for a long time, but overturn within quite short time.(3) In the central layer of the model, only stretcher action acts on fibers, and the fiber orientation is mainly parallel the stretcher direction(i.e. perpendicular to the flow direction).(4) In the layers between the surface layer and the central layer, the fibers will be influenced by both shear action and stretcher action, so the fiber orientation will be combination of two conditions in the front. Some fibers are parallel the flow direction, and others are perpendicular to the flow direction. Along the height of the flow field, most of the fibers will be parallel the flow direction when the shear action is on the dominance, but on the opposite way, the majority fiber will parallel the stretcher direction.