Multi-scale Research Of Mechanical Properties Of 2D Braided Composites With CNTS Random Distributed In Matrix

2D braided composites have become one of the important materials for the design of modern aircraft because of its good structural integrity,designability and impact resistance.However,some research show that the matrix performance is one of the important factors affecting the key mechanical properties of 2D textile composites.In order to improve the mechanical properties of 2D braided composites,study on modification and toughening of resin has become one of the important measures to improve the comprehensive mechanical properties of 2D braided composites.At present,carbon nanotubes are highly concerned by composites academia and industry because of their excellent mechanical properties,which can be used as an important reinforcement for modifying the properties of resin matrix.Therefore,it has great academic value and engineering significance to study the mechanical properties and toughening mechanism of 2D braided composites with randomly distributed carbon nanotube in matrix.In this paper,based on the idea of homogenization equivalent and multi-scale modeling,studided the elastic properties and influencing factors of randomly distributed carbon nanotube resin-based 2D textile composites.First,at the nanometer scale,based on solid fiber equivalent model of carbon nanotubes and a modification of random sequential adsorption alogrithm,the geometrical model of polymer composites reinforced by wavy and random carbon nanotubes was established.Then,based on continuous medium mechanics and characteristic cell,developed a parametric finite element model and the validity of the model is verified by the experimental data.Secondly,based on the 2D fabrication technology,established the solid cell model of2 D 11? biaxial braided composites.Based on the idea of homogenization;equivalent,embedded the equivalent properties of polymer composites reinforced by wavy and random carbon nanotubes,and combined with periodical boundary condition,a finite element analysis model of elastic properties of 2D braided composites was established.The effect of carbon nanotube modified resin on the elastic properties of 2D braided composites was analyzed in detail.Comparing with the experimental data,it proved that the the model is valid.It is found that when the diameter of carbon nanotubes is 30 nm and the volume fraction is 0.5%,the transverse elastic properties of2 D two-axis braided composites are improved about 10% ~16%,and the enhancementeffect of axial elastic modulus is highly correlated with braiding angle.Finally,the effects of braiding angle and fiber volume fraction on the elastic properties of 2D two-axis braided composites reinforced by carbon nanotubes were systematically discussed.