Mechanical Properties Analysis And Application Of Fiber Reinforced Composites Based On Asymptotic Homogenization Method

At present,composite materials are being continuously applied to various fields,among which fiber-reinforced composite materials have received the most attention in engineering practice.A large number of research results show that this kind of material has excellent mechanical properties such as specific modulus,specific strength and damping.Compared with the traditional metal structures,the material itself becomes a new design variable in the design process of the composite structures.In order to consider the influence of new variables on the mechanical properties of the structure,scholars have proposed various approximate methods to calculate the equivalent effective properties of composite materials,including asymptotic homogenization methods.The asymptotic homogenization method is supported by rigorous mathematical theory to achieve process substitution,and the fiber-reinforced composite material is in line with the limitations of the asymptotic homogenization method.Therefore,the asymptotic homogenization method can accurately predict the equivalent performance of fiber reinforced composites.Here,using ABAQUS finite element software as the execution platform,two methods of transforming asymptotic homogenization theory are implemented.A method for predicting the equivalent mechanical properties of chopped carbon fiber reinforced concrete is proposed,and the asymptotic homogenization method is applied to the body layment structure for lightweight design.This article mainly includes the following:First,from the two different perspectives of general mechanics problems and the principle of virtual work,the gradual homogenization theory is deduced and summarized,and the finite element software and programming are used to implement the Cheng Gengdong method and the simplified shape function method.In order to select a more suitable method,the same example is calculated by two methods,and the results of the two and traditional numerical calculations are compared.After comprehensively considering the calculation accuracy and calculation efficiency,Cheng Gengdong's method with higher accuracy and easier implementation was selected as the subsequent research method.Secondly,taking the short-cut carbon fiber concrete structure as an example,a method for simulating the equivalent performance of a 3D out-of-order fiber structure by using a 2D orientation model is proposed.The effects of various factors in the process of simplifying the three-dimensional disordered model to two-dimensional oriented model on the prediction accuracy are discussed.The final results show that only the volume fraction has a significant effect on the prediction accuracy,while the fiber slenderness ratio,cross-sectional shape,fiber arrangement,and fiber spacing have little or no effect.This also shows that the proposed method can be used to calculate the stirring uniformity Chopped carbon fiber concrete and similar structures.Finally,taking the vehicle body floor under bending conditions as an example,a new method for designing the structure of long fiber-reinforced composite material laminates by using the method of progressive homogenization and the optimization method of lamination is introduced.Firstly,the equivalent mechanical properties of the single-layer CFRP is calculated by AH.And the results are used as the basis for the analysis of laminated structures.Then,the ply optimization of the laminated structures is divided into 3 parts: free-size optimization identifies the optimal ply shapes and locations of patches per ply orientation,size optimization identifies the optimal thicknesses of each ply bundle and ply stacking sequence optimization obtains an optimal stacking sequence.Taking the floor of BIW as an example,the optimization result finally reduces the mass to 40% of the original when the body strength is guaranteed.