Research On Virtual Weaving And Deformation Behavior Of Three-dimensional Woven Preforms

Three-dimensional(3D)woven preform reinforced composites have many advantages,such as light weight,high strength,good designability and easy overall forming.They are especially suitable for large-scale complex aerospace components,such as aircraft radomes,engine blades and casings.The preparation process of complex shape components mainly includes two key links of weaving and molding.During the weaving process,the preform structure will undergo significant microdeformation under the action of yarn tension,including yarn buckling,dislocation and cross-section compression.During the composite forming process,the preform will undergo complex macro-deformation under the action of mold extrusion,such as bending,shearing and positive and negative curvature conversion.The actual fiber structure of the preform is different from the initial design,and the complex macrodeformation is easy to cause the wrinkle defects of the structure.Therefore,considering the deformation of the fiber structure,a high-precision numerical model is constructed to investigate the deformation behavior of the 3D woven preform under various deformation modes,which has important theoretical significance and engineering practical value for predicting the wrinkle defects of the preform,guiding the overall structural design of the preform and promoting the application of textile composites.This paper summarizes and analyzes the research status of 3D woven preforms at home and abroad in terms of structural types,geometric modeling,deformation tests and numerical simulation.The basic route to study the deformation behavior of 3D woven preforms is proposed.According to the textile process,a high fidelity numerical model of the preform is constructed.The high-precision and high-efficiency macrodeformation simulation technology of the preform is developed to reveal the deformation mechanism of the micro-structure inside the preform under various macrodeformation modes.A set of digital evaluation method for deformation performance of3 D woven preform is formed.The main contents of the paper include:(1)The test matrix is designed and the preform samples are prepared with the woven structure and weft yarn density as variables.The micro-geometry inside the preform is accurately characterized by Micro-CT technology.The quantitative evaluation method of geometric structure deformation is proposed,and the influence mechanism of woven structure and weft density on preform fiber structure is revealed.It is found that the fiber structure is the most stable when the weft yarn density is 2.5picks/cm within the parameter range studied in this paper.The tensile,compression,bending and inter-ply shear tests of the preform under this weft yarn density are carried out.The typical mechanical curve characteristics of four tests are analyzed,and a method for evaluating the deformation performance of the preform is further proposed.The deformation capacity of three types of woven structure preforms is compared and analyzed,which lays an experimental foundation for subsequent numerical simulation and analysis.(2)According to the textile process,a virtual fiber model is constructed to accurately simulate the high tensile and low bending mechanical properties of real fibers.A virtual weaving technology is proposed to realize the ’quasi-fiber’ scale digital weaving of 3D woven preforms.The deformation behavior of each yarn system in the preform during the virtual weaving process is analyzed,and the relationship between the weaving process and the fiber structure is established.A high-fidelity numerical model of 3D woven preform is generated,and the accuracy of the model is verified by Micro-CT technology.(3)Based on the periodic unit cell model of the preform established by virtual weaving technology,the tensile,compression,bending and inter-ply shear deformation virtual tests of the preform are carried out.The shape control fixtures are designed and prepared corresponding to four deformation modes.The geometric feature information of the yarn inside the preform after deformation is extracted by Micro-CT technology,which verified the accuracy of the virtual deformation tests.Combined with experimental and simulation methods,the deformation mechanism of the microstructure inside the preform under four macro-deformation modes is revealed.(4)Aiming at the deformation problem of L-shaped preform sample,a highprecision and high-efficiency hybrid element modeling and simulation technology is developed to realize the numerical simulation of the macro-deformation of the preform and the variation of the internal yarn structure during the L-shaped forming process.The L-forming test of the preform and the Micro-CT scanning of the deformed sample are carried out.The mechanical curves,local geometric parameters and internal yarn geometric characteristics of the samples are obtained,and the reliability of the hybrid element model is verified.The influence of L-shaped angle and chamfer radius on the micro-structure of the preform is further studied by numerical simulation.The research methods in this paper are also applicable to the deformation analysis and evaluation of other types of textile structure preforms,providing strong guidance for textile process and structural design,and promoting the wide application of textile composite materials in engineering.