Research On The Properties Of Polylactic Acid Composites And Optimal Design For Ecological Vehicle

The burden on ecological environment has been increased dramatically because of the sharp rise in automotive output.In this case,it is more important to improve the ecological quality of automobile products and increase the recovery and utilization rate of automobile,which is seen as an effective means to reduce the emission of VOC using of the petroleumbased materials.Based on the principle of ecological automobile design,it is put forward that the application of recyclable material in automobile product design is an effective way to improve environment.Owing to the requirements of automobile product design for materials,in this paper,the properties of PLA are improved through reinforcement,and the component is designed by the optimization algorithm.Finally,considering the fatigue characteristics of automobile products,the composites are further improved.The researches have important significance and provide supporting example for improving the ecology of automobile products and increasing the application of recyclable materials.Firstly,the relationship between basalt fiber and mechanical properties is studied by experimental characterization and SEM analysis.Basalt fiber enhances the mechanical properties effectively.The tensile properties can be significantly enhanced,which reach the peak at 141 MPa and the modulus gets 5GPa.Nevertheless,when the fiber content exceeds 50%,the tensile mechanical properties decline with the increase of fiber.When the fiber content reaches 40%,the bending strength climbs to 159.5MPa,bending elastic modulus reach the maximum value at 18.2GPa.When the fiber content accounts for 30%,it leads to the largest impact strength.Under Voigt hypothesis and S.Y.FU-Lauke model,the modified coefficient is improved,and the prediction model of elastic modulus of PLA composite is established.The interface between fiber and matrix is fully combined under the condition that the value of mass fraction is in a certain range.The volume fraction and the modified coefficient show a linear relationship.Theoretical model is verified by test data and the result shows a high accuracy.The thermal properties and aging properties are studied.The thermal properties are analyzed by DSC and DMA tests.Aging test is carried out according to the technical conditions for the supply of interior and exterior decoration for a passenger car-heat resistance.The results show that basalt fiber plays an active role in improving the thermal properties According to DSC test results,the crystallinity of the material optimized with the increase of basalt fiber.When the fiber content is 60%,the crystallinity is 20% higher than that of the pure PLA and reaches 54.6%.DMA test results show that basalt fiber has positive influence on the storage modulus.The increase of crystallinity and storage modulus is the sign of better mechanical properties.The aging test shows that basalt fiber can delay the degradation of the PLA,and the composite with higher fiber content still has better elastic modulus.The stability of relationship between mass fraction and the tensile properties is very important for the design and the performance prediction in future work.Based on the elastic modulus database of composite materials,the multi-materials PLA automobile parts are designed.Combined with the OLHD and the existing material database,three sets of effective agent models are established respectively.The parameters satisfying the minimum mass under the constraints are found using three sets of models with MIGA algorithm.Optimization results are verified by FE analysis.By using this method,the mass of part reduces 21 g from 253.7g with single material.Differences between results are guaranteed in a reasonable range.It is proved that this multi-materials design method is effective to realize the lightweight design.Comparing these three optimization methods,MIGA-Kriging method is superior to the other two models in this case.At last,brittleness of PLA composite restricts its application in automobile products under complex load,which can be improved by adopting PBAT.The research shows that the fatigue limit of the composite materials is significantly enhanced when 20% PBAT + 80% PLA is used as the matrix and 0.5% MDI is added as the compatibilizer.Using Kriging-MIGA method,the automobile auxiliary instrument panel assembly is designed by 20% PBAT + 80% PLA as matrix and composites with different basalt fiber contents.The finite element model of vehicle and multi-materials parts,subsequently,is established.Based on the damage theory of Miner and fatigue load of the whole vehicle life cycle,the damage of PLA composite parts is analyzed under the load spectrum.The results show that the PLA composite component meets the requirements of vehicle durability.