Study On Creep Properties Of Straw Plastic Composites

After the reform and opening up,all walks of life in China have made remarkable achievements.The research and development of composite materials,especially all kinds of new green composite materials,is particularly attractive.Straw fiber plastic composite(SPC)is a typical green environmental protection material,which mainly consists of crop straw and waste plastics.This new material is resistant to high and low temperature,and has good degradation ability.It is an environment-friendly and resource-saving environmental protection material.It has been certified as an environmental protection green material by many countries in the world.With the popularization and application of this material in various engineering fields,the research on the static and dynamic creep characteristics of this material has attracted great attention of scholars at home and abroad,and has become a research hotspot of materials and mechanics workers.The main research contents and conclusions are as follows:(1)On the basis of the classical Burgers model,the master curve and its expression of creep compliance are analyzed based on the reference temperature and stress by using the time temperature stress equivalence principle.The creep compliance of the material at lower temperature and stress is deduced by using the WLF equation of the time temperature stress equivalence principle.According to the short-term creep behavior of materials at higher temperature or higher stress,the long-term creep behavior of materials at lower temperature or lower stress level is predicted.(2)Based on the classical Burgers model,a differential viscoelastic plastic constitutive model of straw plastic composites is established.Based on the creep experimental data under different temperatures and different stresses,the parameters of the improved Burgers model are solved by using the least square method.The results of classical Burgers model,improved Burgers model and experiment are compared,which shows that the improved Burgers model is more close to the actual experimental results.(3)Based on Nishihara model,creep damage theory and humidity stress field theory,the effects of temperature and humidity are introduced into the classical Nishihara model,and the viscoelastic plastic constitutive equation of straw plastic composites under the combined action of temperature,humidity and stress was obtained.Based on the experimental results of compression creep of straw plastic composites,the influence parameters of temperature and humidity on the creep behavior of straw plastic composites were determined.The model can well reflect the influence of temperature and humidity on the rheological properties of straw plastic composites,and can be used to analyze the creep process of straw plastic composites under the combined action of temperature,humidity and stress.(4)Based on the classical Schapery model and the improved viscoplastic model,the nonlinear Schapery constitutive model of straw plastic composites is established.The model is used to predict the creep of straw plastic composites under different stresses,and the predicted results of nonlinear Schapery constitutive model are compared with the experimental results,which shows that the predicted results of the model are in good agreement with the experimental results.