Preparation And Performance Study Of Ramie/UP Composite Materials For Rail Transit

Glass fiber reinforced conposites(GFRP)have high energy consumption in the field of rail transit due to its high strength and high modulus.However,there are some defects such as high energy consumption,great harm to human body in the process of processing,difficulty in recovery and environmental pollution.In contrast,bast fiber reinforced composites not only have higher specific strength and modulus,but also have the advantages of low energy consumption,low cost,degradability and sustainable development.Therefore,it has important economic and social benefits to use bast fibers instead of glass fibers to make composites,but there are still many problems that need to be solved.In this thesis,ramie reinforced unsaturated polyester resin composites(Ramie/UP)were prepared by moulding process.The performance and performance improvement of the composites were studied and analyzed.Ramie/UP composites with different ply angles were prepared,and the effects of ply angles on their mechanical and water absorption properties were studied.The results showed that,when ramie plain cloth was laid in the zonal direction(90°),the mechanical properties of the composites were the best.Tensile strength,tensile modulus,flexural strength,flexural modulus and shear strength were 56.52MPa,5.62GPa,81.28MPa,5.31 GPa and 7.09MPa,respectively.The change of the ply angle has little effect on the water absorption of the composites.In order to improve the interfacial compatibility between ramie fiber and resin matrix and further improve the properties of conposites,alkali,coupling agent and their co mbination treatment were carried out.The effects of alkali and coupling agent concentration on the properties of the composites were mainly studied.The results showed that,the mechanical properties of the composites treated with 1%alkali first and then 3%coupling agent reach the optimum.At this time,the tensile properties change slightly,but the bending properties and shear properties change greatly.Compared with untreated,the bending strength,bending modulus and shear strength increase by 34.1%,95.5%and 23.6%,respectively.When the alkali concentration was 2%,the water absorption of the composites was the lowest,which was 4.83%lower than that of the untreated ones.When the coupling agent concentration was 3%,the water absorption of composites was 12.2%lower than that of the untreated ones.SEM showed that the cross-section of the unmodified Ramie/UP was uneven,and the fiber was pulled out.After alkali and coupling agent treatment,the fracture surface of the composites was neat,and most of the fibers were pulled off,showing brittle fracture.In addition,the bending properties of Ramie/UP composite sheet were simulated by HyperWorks,and the failure process of the sample was simulated.The results show that the simulation results are in good agreement with the test results,which proves the correctness of the test.At the same time,the bending performance is optimized.When nine layers are laid,the maximum stress is 162.6MPa,which meets the mechanical properties requirements of composite materials for rail transit.