LAUSR

A way to make short fiber get radial orientation in rubber matrix during extrusion has been studied. Firstly, a type of dam-expanding die has been designed according to theory analysis. Secondly, the physical model and mathematical model of short fiber radial orientation have been built, which indicates that half expansion angle and expansion ratio are important factors that affect radial orientation of short fiber. Therefore, the type of dam-expanding dies with different half expansion angles and expansion ratios has been manufactured to carry out radial orientation of short fiber. Finally, experiments have been done with the manufactured dies. The experiments’ results indicate that the mathematical model could be used to forecast radial orientation of short fiber, and the type of dam-expanding die with half expansion angle 75° and expansion ratio 5 can carry out the radial orientation of short fiber in rubber matrix with short fiber-rubber composite materials. Furthermore, with these conditions, short fibers could get orientation angle about 84°. Some physical–mechanical properties of composite materials can reach a new level, such as tensile strength 28.95 MPa, tear strength 87.82 kN/m and Akron wear 0.172 cm3/1.6 km. Moreover, physical–mechanical properties of composite materials got from S-test are much better than those got from V-test, which indicates that if short fibers are well radial orientated, the composites will be in obvious anisotropy.