| Polyethylene terephthalate(PET)has been widely used in the manufacture of geogrids for its high temperature and chemical resistance,high-tensile strength and excellent creep properties.At present,there are two kinds of processes using PET as raw material,that is,knitting and welding.However,these processes are complex and inefficient,and there products have problems,such as the externally damage occurring at the nodes.Among different geogrid forming processes,the extruded and punched-stretched process can solve these problems.However,it is still in the early stages of stretched PET geogrids and there is a demand for a systematic and deep understanding of this process.In this study,a kind of extruded and punched-stretched process which is used in the production of PET geogrid was explored.In this way,a new kind of high performance product can be made to give full play to the advantages of PET and the stretching process.This kind of PET geogrid can be used in the freezing and alkaline conditions.Which can also make contribution to theoretical research and engineering manufacture.First of all,the PET dumbbell and rectangle shaped specimens were selected as the research object,and the high temperature tensile tests under different tensile temperature,speed and distance and room temperature tensile tests were carried out.Through the analysis of the tensile process and mechanical properties of PET specimens under different processing conditions,the deformation characteristics of PET sheet during high temperature stretching were obtained.Through the influences of process parameters on the mechanical properties of PET,a combination of high temperature stretching process parameters suitable for PET geogrid was summarized.Secondly,according to the punching process,geogrid specimens with different widths of transverse and longitudinal ribs were made.By tensile test at high temperature and room temperature,the influences on the deformation of node and the strengthen of longitudinal ribs by widths of transverse and longitudinal ribs were studied.Based on the analysis of the mechanical properties at room temperature of PET specimens with different transverse and longitudinal ribs,a guidance for the selection of the transverse and longitudinal rib parameters of PET geogrid was put forward.By comparison,it is found that PET geogrid obtained by the stretching process has higher tensile strength than PP geogrid with the similar shape and size and the same thickness of the sheet.Finally,the finite element technique was employed to establish the numerical analysis model of the PET sheet material according to the data of stress and strain.Based on the tensile process simulation of PET specimens and geogrid specimens,distributions of stress,strain and thickness variation during the tensile process were revealed,and the influences on the deformation of geogrid by punching conditions were summarized.Based on the experiment and simulation results,the feasibility of punched-stretched process of PET geogrid was proved. |
