| Higher speed and lighter weight are the developing trends of the railway car.In this paper,the front cab of Changsha Line 2 metro is investigated in order to realize the light-weight design of the structure,meanwhile,the crashworthiness performance and the flame retardancy of the structure should not be sacrified.In detail,studies on mechanical properties and interfacial modification of particles filled resin composites,distribution of particles in the fiber reinforced polymer composites(FRP),tensile and compressive properties and interfacial modification of FRP filled with particles,optimal design on the crashworthiness property of FRP sandwich structure were conducted.The main work is listed as following:Studies on mechanical properties of aluminum hydroxide particles filled unsaturated polyester resin(ATH/UP)composites were conducted.Mechanical stirrer was used to disperse ATH particles,and then the ATH/UP composite samples were fabricated by casting method.Effects of particle content and particle size on the tensile,flexural and impact properties of the samples were studied.The results indicated that the mechanical properties are quite sensitive to the particle content and particle size.With increasing the particle content,the tensile strength decreased all through,but the flexural strength increased to a maximum value and then decreased.By contrast,the tensile modulus,flexural modulus and impact strength increased all the while.With increasing the particle size,the tensile strength increased at first,but decreased subsequently.The tensile modulus,flexural strength and modulus and impact strength decreased all through.In order to modify the interfacial property of ATH/UP composite,the silane coupling agent KH-570 and coupling agent of organic titanate PN-401 were chosen to treat the particle surfaces through the wet modification method.Effects of reaction temperature and dosage of coupling agent on the mechanical properties of ATH/UP composites were investigated.The results indicated that the mechanical properties of modified composite were better than those of unmodified.And the mechanical properties of the modified composites treated with KH-570 were better than those of the modified composites treated with PN-401.Besides,the mechanical properties were deeply dependent on the reaction temperature and dosage of coupling agent.With increasing the reaction temperature and the dosage,the mechanical properties increased to a maximum value and then reduced.For KH-570,the best reaction temperature was 50 ? and the best dosage was 2.0 wt%.For PN-401,the best reaction temperature was 70 ? and the best dosage was 1.0 wt%.Mechanical disperse and high-speed shear disperse methods were employed to fabricate the glass fiber reinforced unsaturated polyester resin composite filled with aluminum hydroxide particles(ATH-GF/UP).Distribution of particles in the ATH-GF/UP composites was analyzed,and effects of disperse process on the tensile and compressive properties of ATH-GF/UP composites were investigated.The results indicated that while using mechanical disperse method,the distribution of particles showed decreasing along the resin flowing direction and the thickness direction.However,while using the high-speed shear disperse method,the distribution of particles showed little vibrations along the thickness direction.In addition,the mechanical properties increased with increasing the disperse speed.Quasi-static and dynamic tensile tests were conducted for the modified and unmodified ATH-GF/UP composites using a universal testing machine and an impact tensile test technique,separately.The strain rate dependent behavior of ATH-GF/UP composite in tension was investigated at different strain rates.The results indicated that the tensile properties were quite sensitive to the strain rate.The tensile strength increased with increasing the strain rate.Besides,it showed good linear relationship between the tensile strength and ln ?(5).Effects of particle content and particle size on the tensile properties of unmodified ATH-GF/UP composites were studied.The results indicated that the tensile strength firstly increased with increasing the particle content and then decreased at the high strain rate.While the particle content was 40 wt%,the dynamic tensile strength was the highest.However,the particle size showed a little influence on the dynamic tensile properties of the unmodified composites.Effects of interfacial modification on the tensile properties of ATH-GF/UP composites were studied.The results indicated that,for KH-570,the dynamic tensile strength showed first increasing and then decreasing with increasing the reaction temperature and the dosage of coupling agent.The best reaction temperature was 50 ?,and the best dosage was 1.5 wt%.For PN-401,the dynamic tensile strength showed first increasing and then decreasing with increasing the reaction temperature,but it increased all through with increasing the dosage of coupling agent.The best reaction temperature was 80 ?,and the best dosage was 2.0 wt%.Quasi-static and dynamic compressive tests were conducted for the modified and unmodified ATH-GF/UP composites with a universal testing machine and a split Hopkinson bar technique,separately.The strain rate dependent behavior of ATH-GF/UP composite in compression was investigated at different strain rates.The results indicated that the compressive properties were quite sensitive to the strain rate.Both of the compressive strength and modulus increased with increasing the strain rate.Besides,it showed good linear relationship between the compressive properties and ln ?(5).Effects of particle content and particle size on the compressive properties of unmodified ATH-GF/UP composites were studied.The results indicated that the compressive properties increased with increasing the particle content.The in-plane compressive properties decreased with decreasing the particle size at high strain rate loading,but the out-of-plane compressive properties increased.Effects of interfacial modification on the compressive properties of ATH-GF/UP composites were studied.The results indicated that,for KH-570,the compressive properties showed first increasing and then decreasing with increasing the reaction temperature,and the in-plane compressive properties and quasi-static out-of-plane compressive properties also showed first increasing and then decreasing with increasing the dosage of coupling agent.But the dynamic out-of-plane compressive properties decreased all along.For the in-plane compressive properties,the best reaction temperature was 50 ?,and the best dosage was 2.0 wt%.For the out-of-plane compressive properties,the best reaction temperature was 30 ?,and the best dosage was 2.0 wt%.For PN-401,both of the in-plane and out-of-plane compressive properties showed first increasing and then decreasing with increasing the reaction temperature and the dosage of coupling agent.When the reaction temperature was 80 ?,the dosage of coupling agent was 2.0 wt%,both of the in-plane and out-of-plane compressive properties were the best.A simplified finite element model was established based on the ANSYS/LS-DYNA and LS-DYNA software and the crashworthiness property of ATH-GF/UP composite sandwich structure was simulated.The results showed that the composite sandwich structure target panel was not penetrated completely by the projectile.The penetrated depth and the rebounded velocity of projectile were 25.60 mm and 28 m/s,separately.The errors of penetrated depth and rebounded velocity between the numerical and test results were 2.4% and 3.7%,respectively.Therefore,the model was used to study the effects of facesheets material properties and thickness on the crashworthiness property of the sandwich structure.The results showed that the in-plane compressive modulus strain rate constant,the tensile strength strain rate constant of the outer facesheet and the tensile strength and its strain rate constant of inner facesheet were the most distinct influence parameters.While the total thickness of outer and inner facesheet didn't change,the crashworthiness property was improved by increasing the outer facesheet thickness for the unsymmetrical sandwich structure and it was better than the symmetrical sandwich structure with equivalent facesheet thickness.An unsymmetrical sandwich structure metro cab was designed and the facesheet thickness was optimized to reduce the weight ultimately.The optimal design structure was that the outer facesheet thickness was 2.52 mm,the inner facesheet thickness was 0.21 mm and the foam core thickness was 25 mm.The weight of this structure was 7.63 kg.Compared with the original symmetrical structure,the weight was reduced by 22.3 %. |
PDF Full Text Request