Multilaers 2-D Biaxial Braided Layer Composite Mesoscopic Geometrical Model And Tensile Modulus Resarch

In order to use 2×2 biaxial braided composite material reasonably and effectively,it's important to simulate and calculate the tensile properties of 2×2 biaxial braided composites.As a result,this paper aims to establish a set of calculation method which can describe monolayer and multilayer over-braiding composites tensile modulus through mesoscopic geometrical model.Then tensile fracture mechanism was researched.By researching the tensile properties of 2×2 biaxial braided composites structures and the tensile fracture mechanism,a set of researching thought of 2×2 biaxial braided composite materials and detailed,experienced numerical calculation formula of tensile modulus were sumed up.This topic theoretical research basis of the existing researches on composite materials has been taken for reference.Considering the fiber buckling is the root which caused of the loss modulus,this paper combined the actual braided composites yarn cross section shape,buckling and braiding structure,braiding process and the factors influencing the curing process.Then put forward the equivalent modulus of loss point of view,a 2D biaxis 2 x 2 braided structure unit cell model of fiber yarn bundle,buckling mesoscopic geometrical model and the corresponding equivalent mechanical model were established.According to the hypothesis model concrete numerical,calculation method is given.Experimental data showed that the buckling damage model is proposed in this paper.What's more,the effective modulus of equivalent mechanical model calculated numerical calculation accuracy is higher than the current literature and simple operation.For braided composites in-plane tensile modulus,based on the corresponding processing method of the analysis of predecessors,this thesis in braided composites combined the actual surface geometry characteristics and the actual production conditions of use.Equivalent braided composites for skew symmetric layer composite materials assumption was put forward.Applying the relevant theories and methods,a reasonable in plane shaft-partial axial transformation was achieved and eventually braided composites processing in-plane effective partial axis tensile modulus value was found.As regard to multilayers braiding composite materials,the multi-layers between the geometric structure was observed.According to actual structure,more spring in parallel model is set up.And according to the mechanics model,concrete tensile modulus is deduced.This numerical method is simple and easy to operate.Final experimental results show that: tensile modulus numerical calculation value change trend and experimental value is consistent.Also,specific numerical results agree well with each other,which indicate the hypothesis model and calculation method is effective.Braiding layer composite materials tensile failure mechanism was analyzed,which combined the actual concrete tensile specimen tensile data and fracture failure mode.When it comes to the unusual failure mode,after combining the specific sample analysis,analysis of periodic tensile fracture process of composite sample internal structure change was processed.Relatively objective tensile fracture mechanism is given,which can provide the follow-up theoretical basis research of 2D braided composites tensile fracture.This thesis mainly adopts theoretical analysis method of 2D braided composites,considering the production conditions and the use of 2D braided composites,tensile modulus was studied.Mesoscopic geometrical model and the equivalent mechanical model was set up,which were closer to the actual situation than the former one.the calculation method built a relationship between 2D braided composites macroscopic as well as mesoscopic tensile modulus and structure basic parameters,which is significant for production of 2D braided composites.