Numerical And Experimental Study On Damage Behavior Of Woven Carbon Fiber Laminated Composites Under Low Velocity Loading

Nowadays,woven carbon fiber laminated composites are widely used to aviation,automobile industry,energy industry,medicine and other fields,especially for the automobile industry.Compared with the traditional metals,the advantages of the woven carbon fiber laminated composites are as follows:(1)low density,high specific strength and modulus;(2)high integration,reducing the number of parts,which is suitable for autobody modeling;(3)good crashworthiness;(4)high damping;(5)excellent fatigue resistance.Compared with the unidirectional carbon fiber composites,it not only improves the in-plane properties of the composites,but also improves the impact resistance of the composites.However,woven carbon fiber laminated composites have more complex damage characteristics.Under different low velocity loadings,the woven carbon fiber laminated composites can produce many kinds of invisible damage.The difference and irreversibility of the damage will lead to a serious reduction in the mechanical properties of the woven carbon fiber laminated composites in the process of use.Hence,it is an important research direction to study the correlation of structure,properties and damage of woven carbon fiber laminated composites.In this paper,with the guidance of the damage behaviour and damage simulation,the innovative finite element simulation analysis was conducted,on the basis of experimental data,the mechanical properties,damage mechanisms and failure modes of woven carbon fiber laminated composites under a variety of low velocity loadings were studied at the macro level.It provides theoretical basis and technical support for the damage behaviour and damage simulation of woven carbon fiber laminated composites.Firstly,this paper studied the basic theories of anisotropy elasticity and continuum damage mechanics related to damage mechanics model of woven carbon fiber laminated composites.The basic damage theory of woven carbon fiber laminated composites and its simulation basis were also introduced,it mainly includes: the damage and fracture basis,crack propagation,interlaminar damage model and failure criterion etc.of woven carbon fiber laminated composites.Secondly,a constitutive damage model based on the continuum damage mechanics of fiber laminated composites was established,and it improved the Matzenmiller Lubliner Taylor(MLT)damage model.The constitutive damage model which used macroscopic mechanical methods to simulate microscopic damage evolution was suitable for a variety of stacking angles and layup sequences,and could accurately simulate the damage behavior of laminated fiber composites.Furthermore,this paper studied the damage behaviour and damage simulation of woven carbon fiber laminated composites under tensile loading.By comparing the experimental and simulation results,the accuracy of the constitutive damage model was verified.Thirdly,this paper studied the damage behaviour and damage simulation of carbon fiber laminated composites under low velocity bending loading.The Scanning Electron Microscope(SEM)was used to observe the damage evolution of the woven carbon fiber laminated composite under the three-point bending loading.The damage behaviours such as matrix cracking,delamination and fiber breakage were described in detail.According to the main damage behaviours of woven carbon fiber laminated composite including delamination and fiber breakage,a finite element model had been established.In this model,Tiebreak algorithm had been used to simulate delamination,and equivalent stress model had been used to to simulate fiber breakage.The nonlinear finite element simulation was applied to analyze the bending damage evolution of woven carbon fiber laminated composite,and the reliability and accuracy of the simulation results are verified by experiments.Fourthly,this paper studied the impact respond,damage progatation and damage area of woven carbon fiber laminated composites under low velocity impact through experimental method.The damage progatation and damage area of the woven carbon fiber laminated composites were observed by digital imaging and non-destructive testing(ultrasonic C-scan)respectively,the effects of different impact velocity and stacking angle on the low velocity impact response and damage behavior of woven carbon fiber laminated composites were further studied.Furthermore,through the user defined material model and MAT_ADD_EROSION failure model,a nonlinear dynamics of finite element model of woven carbon fiber laminated composite had been established,the model could accurately predict the damage progatation and damage area of woven carbon fiber laminated composites under the low velocity impact,the simulation results in accordance with the experimental results.Fifthly,in this paper,finite element method was used to study the damge behaviour of automotive woven carbon fiber laminated composites B pillar.The damage and fracture of the automotive woven woven carbon fiber laminated composites B pillar under flexural and impact loadings with a variety of stress states were analyzed.Two kinds of design methods including changing the strength and the stacking angles were adopted to change the damage behaviour of the automotive woven carbon fiber laminated composites B pillar,and could improve the engineering performance of the automotive woven carbon fiber laminated composites B pillar.Furthermore,the damage evolution of automotive woven carbon fiber laminated composites B pillar was studied under the side crashworthiness,which provided engineering theory basis for the application of woven carbon fiber laminated composites in automobile application.