Permeability is one of the key issues in the design of molds and in the molding process for composite manufacture. As a disordered fibrous assembly, 2.5- dimension （2.5 D） woven reinforcement materials have complex ...Permeability is one of the key issues in the design of molds and in the molding process for composite manufacture. As a disordered fibrous assembly, 2.5- dimension （2.5 D） woven reinforcement materials have complex structure. It poses a challenge to the study of pore structure and the establishment of the theoretical permeability model. Toward addressing this problem, a powerful tool called fractal theory emerged. According to the analysis of 2.5 D woven reinforcement material stmcture using fractal theory, it is found that the structure has an obvious fractal character. Therefore, a permeability fractal model of 2.5D woven reinforcement material was established by cormbining the Hagen-Poiseulle equation with Darcy law according to the capillary vessel fractal model in this paper. The permeability was expressed as a function of the fractal dimension and microstructure parameter of the porous media in this model. The theoretical model is verified by experimental tests and the measurement data are in good agreement with the results obtained from the fractal medel .展开更多
A continuum damage mechanics (CDM) meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane aniso...A continuum damage mechanics (CDM) meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane anisotropic damage constitutive model of a 2D woven composite ply was derived based on CDM within a thermodynamic framework,an elastic constitutive model with damage for the fibre directions and an elastic-plastic constitutive model with damage for the shear direction.The progressive failure behavior of a 2D woven composite ply is determined by the damage internal variables in different directions with appropriate damage evolution equations.The interface between two adjacent 2D woven composite plies with different ply orientations was modeled by a traction-separation law based interface element.An isotropic damage constitutive law with CDM properties was used for the interface element,and a damage surface which combines stress and fracture mechanics failure criteria was employed to derive the damage initiation and evolution for the mixed-mode delamination of the interface elements.Numerical analysis and experiments were both carried out on a 2D woven glass fibre/epoxy laminate.The simulation results are in agreement with the experimental counterparts,verifying the progressive failure model of a woven composite laminate.The proposed model will enhance the understanding of dynamic deformation and progressive failure behavior of composite laminate structures in the low velocity impact process.展开更多
基金Science and Technology Support Program of Jiangsu Province of China(No.BE2008017)
文摘Permeability is one of the key issues in the design of molds and in the molding process for composite manufacture. As a disordered fibrous assembly, 2.5- dimension （2.5 D） woven reinforcement materials have complex structure. It poses a challenge to the study of pore structure and the establishment of the theoretical permeability model. Toward addressing this problem, a powerful tool called fractal theory emerged. According to the analysis of 2.5 D woven reinforcement material stmcture using fractal theory, it is found that the structure has an obvious fractal character. Therefore, a permeability fractal model of 2.5D woven reinforcement material was established by cormbining the Hagen-Poiseulle equation with Darcy law according to the capillary vessel fractal model in this paper. The permeability was expressed as a function of the fractal dimension and microstructure parameter of the porous media in this model. The theoretical model is verified by experimental tests and the measurement data are in good agreement with the results obtained from the fractal medel .
文摘A continuum damage mechanics (CDM) meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane anisotropic damage constitutive model of a 2D woven composite ply was derived based on CDM within a thermodynamic framework,an elastic constitutive model with damage for the fibre directions and an elastic-plastic constitutive model with damage for the shear direction.The progressive failure behavior of a 2D woven composite ply is determined by the damage internal variables in different directions with appropriate damage evolution equations.The interface between two adjacent 2D woven composite plies with different ply orientations was modeled by a traction-separation law based interface element.An isotropic damage constitutive law with CDM properties was used for the interface element,and a damage surface which combines stress and fracture mechanics failure criteria was employed to derive the damage initiation and evolution for the mixed-mode delamination of the interface elements.Numerical analysis and experiments were both carried out on a 2D woven glass fibre/epoxy laminate.The simulation results are in agreement with the experimental counterparts,verifying the progressive failure model of a woven composite laminate.The proposed model will enhance the understanding of dynamic deformation and progressive failure behavior of composite laminate structures in the low velocity impact process.
