Study Of Flow-induced Short Fiber Orientation Behavior And Coupled Model Of Filling

The processing of injection molding of Short fiber reinforced plastics is complicated for the fluxion, flow induced fiber orientation in filling stage causes the molded part to show advanced mechanical properties and affects the final shape of the product. The configuration of the melt has coupled micro-scale, semi-macro scale and macro scale during mold filling, these three scales are coupled in physics. Predicting the flow induced fiber orientation in processing with multi-scale method, thus, the relationship among processing, structure, and property of injection molded short fiber composites can be understood, much more important, two scale simulation of the orientation of short fiber will be possible for our work, and then, it is possible to provide basic data for the exploitation of advanced plastic parts, the work is sensible both in theory and engineering.For the short fiber reinforced thermal plastics, we mainly investigate the effect of shear stress, elongate stress, the effect between fibers and effect of fiber and mold surface .the reciprocity between fibers has significant effect to the microstructure and macrostructure for fiber suspension.Firstly, we investigate the dilute suspension (c<(d/L)~2 ), Jeffery's kinetic equation has been used to describe fiber's rotation, the rotation discipline of immersed fiber in shear stress flow and the mixture flow of shear and elongate stress have been studied ,the study here focuses on the aspect ratio and initialization .In addition, basing on fiber orientation distribution function, we used fiber orientation tensor to describe fiber orientation status, fiber orientation tensor evolvement function has been put forward based on the Fokker-Planck function and Folgar-Tucker function, in order to get a closure function , we adopt hybrid closure approximation to reduce the higher fourth-order orientation tensor to the lower second -order tensor, further more ,we got a two-dimensional orientation tensor evolvement function for simply shear stress flow.At last, in a thin triangle cavity, basing on the analysis of filling process, we make the fill into mainly flow and front flow, in the mainly flow, there are only length and width velocity, neglect the thickness velocity, but in the front flow, the thickness velocity can't be neglect. We present control function both for front and mainly flow which coupled both macro-scale and semi-macro scale, from the function we can receive the data of velocity field, pressure field and temperature field, these data make foundation for two-scale simulation of fiber orientation.