Research On Forming Mechanism And Optimization Of Plant Fiber Winding Composite

Composite composed of resin matrix,glass,aramid and carbon and other traditional reinforced fibers,have been widely used in aerospace,leisure,automobile,architecture and sports fields.However,they are not degradable and are not easy to be recycled,resulting in environmental pollution and waste of resources.Applying plant fiber instead of traditional reinforced fiber in composite molding can effectively alleviate environmental damage and resource crisis on the basis of ensuring product performance requirements.However,compared with the traditional composite fiber,the plant fiber has unique cavity structure,the twist structure of fiber bundles and the special winding structure caused by the twist structure,which affect the forming quality and mechanical properties of the plant fiber-reinforced composite.In order to realize the structure and process design,performance analysis and prediction,forming quality control of the new material-plant fiber reinforced composite,it is necessary to study the mechanical and physical properties of-plant fiber bundle considering structures,forming process of composite and mechanical properties of composite after forming.This paper has carried out the following research:the prediction of modulus and thermophysical properties of plant fiber bundle considering structures,the prediction of the modulus and thermophysical properties of the plant fiber winding composite during the curing process,the analysis of multi physical field and residual stress and strain in the curing process of the plant fiber winding composite,and the analysis and optimization of the molding process of the plant fiber winding composite.The main work and research results are as follows:In the application of plant fiber in winding composite,it is necessary to twist the short plant fiber to realize the continuity.Based on micromechanics,slip and strength theory of twisted fiber bundle,homogenization theory and mathematical model of heat conduction,a fiber bundle model considering structural characteristics of plant fiber bundle was established by using COMSOL platform.Through the simulation analysis,it was found that the existence of cavity structure reduces the modulus and heat conduction performance of plant fiber.Twisting structure makes the mechanical strength and modulus of plant fiber bundle exist extreme value in a certain twist range,which also has a significant impact on the thermal conductivity in different directions.In order to improve the simulation accuracy of curing process and obtain the dynamic change law of physical parameters,based on the influence of cavity and twist structure on the mechanical and thermophysical properties of continuous plant fiber bundle,the thermal conductivity and modulus equivalent model of plant fiber winding composite were established by using the theory of micromechanics and equivalent homogenization.The linear increasing law of thermal conductivity and the parabola increasing law of the equivalent modulus of the composite with the change of the curing of the resin matrix were obtained,and then the regression equations of the equivalent parameters of the composite with different twist and fiber volume content were obtained,which provided the dynamic input for the simulation of the curing process of the plant fiber winding composite.In order to reveal the change law of temperature field,curing degree field and stress-strain field in the process of plant fiber composite molding process,an accurate prediction model of composite curing process considering plant fiber bundle structure was established based on the research of modulus and thermophysical properties of plant fiber composite.The results show that the prediction accuracy can be effectively improved by using the thermal and mechanical properties of the composites considering the plant fiber structure as the dynamic input of the curing process simulation,and the curing temperature process and the thickness structure of the composite material have a relatively significant impact on the physical field and stress-strain during the molding process.The twist of fiber bundle,moisture content of fiber and volume fraction of fiber have relatively small influence on the multi field variation of composite molding process.The structure,material and process specificity of plant fiber winding composite and their influence on the mechanical properties of the composites were analyzed,based on the forming and testing experiments of plant fiber winding composite and the performance test of composite.Then,a multi-objective optimization model based on satisfaction function and response surface of molding process of plant fiber winding composite was established to obtain the optimal molding process parameters within the parameter design range.The reliability analysis of the optimization results and the sensitivity analysis of the optimization design were carried out.The results show that:the response surface method and satisfaction function method can effectively carry out the multi-objective process optimization design.The curing temperature has a significant impact on the mechanical properties of the plant fiber composites,and the pore content of the composites formed by different process parameters is the main reason for affecting the mechanical strength of the composites.The optimized process results can effectively improve the molding quality and mechanical properties of the plant fiber winding composites within the design range.Based on the research of structural modeling,simulation,test and process optimization,it is found that the structural characteristics of plant fibers and fiber bundles have an important impact on the fiber bundle,the forming process of composite and the mechanical properties of composite after forming.Therefore,in the study of the structure,material,technology and mechanics of the green recyclable new material-plant fiber reinforced composite,the influence of the structure of plant fiber and fiber bundle on the material,process and mechanical strength cannot be ignored.We should make full use of the structure of plant fiber bundle and the functional characteristics of plant fiber composites to develop functional composites,and reduce the impact of structure on the structural properties of the composites.