Fiber Orientation Control of Short-Fiber Reinforced Thermoplastics by Extrusion and Prediction of Young's Modulus

This paper examines the fiber orientation and Young's modulus of extruded short-fiber reinforced thermoplastics such as polypropylene. Axial orientation distributions are presented to illustrate the influence of extrusion ratio on the orientation state of the fibrous phase. Fibers are remarkably aligned parallel to the extrusion direction with increasing the extrusion ratio. The orientation state of extruded FRTP is almost uniform through the section. The fiber orientation can be easily controlled by means of ram extrusion. Experimental results also show that Young's modulus of FRTP in extrusion direction follows a linear relation to extrusion ratio because the degree of the molecular orientation and the fiber orientation to be higher with increasing the extrusion. By comparing the prediction of Young's modulus with experimental results, the validity of the model proposed by Cox and Fukuda et al. elucidated. The mean fiber length linearly decreases with increasing extrusion ratio because of the fiber breaking caused by plastic deformation of the matrix. The effect of the fiber breaking on Young's modulus is almost negligible.