Research And Analysis Of Automobile Components Based On Polylactic Acid Composites

As a bio-based material,polylactic acid(PLA)composites are polymerized from polylactic acid,which is mainly extracted from starch-rich crops by biological fermentation technology.Then polylactic acid is reinforced to generate the composite material.In addition to having the similar performance with the traditional modified plastic,Polylactic acid composites also have the rich material source and renewable,in material processing less harmful substances and small impact,healthy and safety in the usage for human and environmental,waste recovery and other advanced characteristics.PLA composites are green materials and can replace some of the traditional modified plastics used in automobile components,to make the vehicle more eco-friendly.In this thesis,polylactic acid composites are tested to obtain the mechanical performance parameters.Then the feasibility of polylactic acid composites in automotive application is analyzed.A typical automotive part is chosen as the object of application of polylactic acid composites.The structural strength analysis,vibration test,structural optimization,strength and modal verification,creep deformation analysis are performed.Finally,the environmental test and verification of the polylactic acid composite battery tray are carried out to expand the application of the material.The main research work is as follows:(1)Analysis of mechanical properties of polylactic acid composites: a)The static tensile tests of PLA30 and PLA40 composites are worked out to obtain the tensile strength,tensile modulus and Poisson's ratio of the two materials.It shows that the strength of PLA30 composites is lower than that of PLA40 composites,but the toughness is better.b)The bending test of PLA30 composites is carried out to obtain the flexural strength and flexural modulus of PLA30 composites.c)The tensile and tensile fatigue tests of PLA30 composites is worked out to obtain the fatigue limit strength of PLA30 composites.d)The tensile creep test of PLA30 composites is carried out and the creep characteristics of PLA30 composites are analyzed.e)Compared with the commonly used vehicle modified plastic,The performance of PLA30 composites is close to the modified PP,and PLA30 composites can replace the modified PP used in automotive interior parts,exterior parts and some structural parts.(2)Analysis and optimization of battery tray structure of polylactic acid composite: a battery tray is selected as the object of application of PLA30 composites.And the battery assembly structure is modeled.Its strength analysis is performed in the acceleration / braking conditions,left and right turning conditions and turning braking under the joint conditions.The results show that the maximum stress of PLA30 composite battery tray under the left turn brake joint conditions is larger than the fatigue limit strength of the material and it is prone to fatigue failure.So the vibration test and verification of the battery assembly structure is setup.It can be seen that crack failure occurs on the PLA30 composite battery tray sample.So it is assumed that the structure has fatigue failure.The structure of the original battery tray is optimized,and the strength and modal analysis of the optimized battery tray are worked out to verify the effectiveness of the optimization of the battery tray structure.(3)Creep deformation analysis of polylactic acid composite battery tray: The creep strain-time curve of PLA30 composites is fitted to obtain the creep model parameters of the material.The creep model of PLA30 composite is established.The creep deformation analysis of PLA30 composite battery tray with optimized structure is performed.The displacement range of the critical position area of the tray is calculated to be 0.12 ~ 0.28 mm.The longitudinal displacement of each point is smaller,lateral displacement and vertical displacement deformation are larger,indicating that the creep inherent mechanical behavior determines the creep equivalent strain has gradually increased trend and creep relaxation makes the equivalent stress in the creep process showed a decreasing trend.(4)Environmental reliability test and verification of polylactic acid composite battery tray: For the application of PLA30 composite in the battery tray of the functional components,the low temperature test,the high temperature test,the temperature change test,the aging resistance test,the resistance to industrial solvent test and the flame retardancy test are carried out.The test results showed that the PLA30 composite can meet the performance requirements of the automobile battery tray.And that the PLA30 composite battery tray environmental tests are universal,thus the material can be extended to other automomotive components.It is concluded that these PLA30 composite automobile components also meet the automotive environmental reliability requirements.