3D Needle Felt Virtual Reconstruction And Mechanical Properties Researc

Needling technology is a simple,low-cost and designable 3D(three-dimensional)fiber preform forming technology.At present,needled composites prepared by needled technology are widely used in aerospace,automobile manufacturing and other fields.Needled nonwoven preforms are prepared from nonwovens by needle-punched process.In the needling process,the in-plane fibers of nonwovens are grabbed to the out-ofplane by needle hooks.The fiber structure of needled nonwoven preforms is extremely complicated.When the needled nonwoven preforms is deformed by external force,the fiber structure inside the preform will change greatly.It is very difficult to study the deformation mechanism of needled nonwoven preforms.Accurately characterizing the internal geometry of needled nonwoven preforms and establishing refined fiber structure model are important prerequisites for analyzing mechanical properties of needled nonwoven preforms and needled nonwoven preforms reinforced composites.However,due to the unique 3D needling forming process,the fiber structure of the needled nonwoven preforms is extremely complex.It is very difficult to establish a refined model of 3D needled nonwoven preforms.The purpose of this paper is to propose a numerical modeling method for 3D fiber structure preforms,to study the effect of needling process on preforms fiber structure,and realize the high-fidelity 3D virtual reconstruction of needled nonwoven preforms.In this paper,a “quasi-fiber”scale mechanical analysis model of needled nonwoven preforms is constructed by using hybrid element technique.In this paper,the researching development of needled preforms and composites at home and abroad is reviewed and analyzed in detail,including the development history,experimental analysis and micro-structure modeling methods.The micro-structures of needled nonwoven preform are researched by Micro-CT technique.The geometric parameters(fiber length,orientation and fiber bundle aggregation width)of preforms are statistically analyzed.The tensile and compression behaviors of needled nonwoven preform are studied experimentally,and the macroscopic deformation characteristics and microstructure deformation mechanism of the fabric are analyzed.A refined numerical modeling method for 3D needled virtual nonwoven preform is proposed.Based on the statistical parameters,the 3D virtual reconstruction of the needled nonwoven preform is realized,and the model has a good consistency with the MicroCT image.In this paper,the hybrid virtual fiber is constructed by coupling the degree of freedom(DOF)of rod element and beam element with the hybrid element technology.The hybrid virtual fiber can accurately describe the higher tensile stiffness and lower bending stiffness of real fibers.The "quasi-fiber" scale mechanical analysis model of needled nonwoven preforms is constructed by hybrid virtual fibers.The mechanical responses of needled preforms under compression or tension loads are studied.Compared with the traditional micro analysis model,the model proposed in this paper has higher computational accuracy and can accurately reproduce the fiber structure changes inside the preform.In this paper,the high-fidelity 3D virtual reconstruction of needled preforms is constructed by using virtual fibers.The modeling method proposed will be helpful to understand the internal fiber structure of the needled preforms.The needling forming process,internal fiber structure and the mechanical properties of needled preforms are linked to form a complete analysis route of mechanical properties of 3D needled preforms,which provides theoretical guidance for the process design and engineering application of needled preforms.The research results of this paper will further provide a good foundation for the analysis of resin flow permeability of needled composites during the molding process and the study of mechanical properties of needled composites.