Study Of Induction Orientation And Crystal Morphology Of Glass Fiber Reinforced Polyolefine Pipe Extruded In Hoop Shear And Axial Tension Combined Stress Field

the modernization of developoed countries, the development speed of plastic pipe is faster than that of economy, and traditional pipe materials are gradually replaced by polymeric materials. However, the hoop intensity of common plastic pipe is low, and their thickness has to be made thick ,when they are used as bearing pipe in order to fulfill the mechanical property requirement, which both wastes raw material and makes forming difficult.Reinforce pipe technic has been widely studied, and most investigations used unidirectional stress field. The Reinforce technic is restricted on using the gyrate of core rod to increase hoop shear stress field, which is easy to cause extrusion instability and forming difficulty, and the production efficiency is far less than that of industry production. Based on the previous study, we have designed the combined stress field extrusion mold, which is capable to produce axial extend, hoop shear ,and two-direction reinforced PE pipes were produced. The outstanding advantage of this device is that it could adjust the size of assemble parts to produce two-direction reinforced pipes with different caliber, and changes the traditional mandril circumrotation to sleeve one. Since glass fibers are easy to arrange orderly along the force direction under external force field, and induce molecular chains to orientate, the investigation of hoop ,axial performance of glass fiber reinforced pipe using combined stress mold is extremely meanful. In this contribution, the reinforce mechanics, induction orientation, crystal structure, melting behavior and morphology of glass fiber reinforced pipes in combined stress field were investigated. It was found that after the treatment of combined stress field, the hoop intersity and axial intensity were both improved, and the former increased more. Modern analyzing techniques revealed that under combined stress field, glass fibers were orientated along the hoop and axial, and dispersed more equally. Induced by the glass fiber, the moleular chain orientation and crystallinity of bulk material were largely increase; Molecular chain orientation was also solidified by the glass fiber, and became less affected by temperature.In common glass fiber reinforced polyolefine pipe, when the volume faraction is less than the critical value, the glass fiber can not act as reinforcement, on the contray, it would reduce the whole intensity of the compound material. However, when extruded in combined stress field, the extend intensity of the compound system increases when the volume fraction of glass fibers is less than the critical value. When the glass fiber volume fraction is higher than the critical value, the required glass fiber volume fraction of compound fibers extruded in the combined stress field is less than theory value. It indicates than when extruded in thecombined stress field, the induction orientation of the bulk material chains caused by the glass fiber improves the intensity of the compound system.