The Study On Mechanical Properties And Constitutive Model Of Carbon Fiber-Aluminum Alloy Composite Laminate

Lightweight is an important research in the field of automobile and transportation equipment.Aluminum alloy and carbon fiber composites can meet the urgent need for lightweight due to their high strength,light weight and high designability.As a superhybrid material with both advantages of composite material and metal,fiber metal laminates(FMLs)have been gradually applied in automotive and transportation equipment lightweight field.However,the mechanical properties and stress response of FMLs under complex working conditions are complex and need to be clarified.Therefore,carbon fiber aluminum alloy composite laminates(CARALL)were taken as the research object in this thesis.The deformation behavior of laminates under unidirectional,bidirectional and triaxial stress states was studied.The mechanical properties of uniaxial tension and its variation were analyzed.The constitutive model of bending deformation behavior was established and the accuracy of the model was verified.The forming limit of laminates was studied.These studies provide theoretical support for the application of CARALL.Carbon fiber aluminum alloy composite laminates were prepared.5 series aluminum alloy and epoxy resin reinforced carbon fiber were selected as the component materials of the laminates.The reasonable curing temperature of prepreg was determined by differential thermal analysis.The preparation process of FMLs with anodic oxidation as the pretreatment process of aluminum alloy was established.In order to obtain the unidirectional stress state strength variation rule of carbon fiber aluminum alloy laminates,the tensile tests of aluminum alloy,carbon fiber and laminates with different layering methods were carried out.The variation mechanism of tensile strength under different layering methods was analyzed.The tensile strength of the laminates was between aluminum alloy and carbon fiber.The content of carbon fiber and the weak bonding surface of carbon/aluminum increased with the increase of the number of layers.The maximum tensile strength of the laminates reached 316.5MPa when the laminates were laid at 3/2 layers.In order to obtain the deformation behavior of carbon fiber aluminum alloy laminates under bidirectional stress state,a constitutive model of CARALL bending deformation was established based on the metal plastic bending theory and the modified classical laminates theory.The variation mechanism of bending strength of CARALL was analyzed,and the accuracy of the theory was verified by experiments.Under different layering methods,laminates with 3/2 layering had better bending properties.The strength prediction error of the constitutive model was 8.4%.The influence of the composition of laminates and the bending radius on the bending strength was further analyzed.The increasing of the thickness of the carbon layer or the decreasing of the thickness of the aluminum layer would increase the bending strength of the laminates.The bending stress of laminates was inversely proportional to the bending radius.In order to study the forming response of laminates under triaxial stress states,the cup-forming experiments of laminates were carried out.The forming strain variation of the laminates with different layering was analyzed.The results showed that the loadthickness ratio and rupture displacement of 3/2 laminates were the largest.The fiber fracture of 4/3 laminate was accompanied by obvious delamination failure,which lead to its low formability.The strain and thinning rate of 3/2 laminates were the largest and its formability was the best.The strain and thickness reduction rate of 3/2 laminate were the largest among the cracking strains of different laminates and its formability was the best.This research provides theoretical support for the practical application of CARALL in transportation equipment and the research on the response behavior of working conditions.It is of great significance for the development of lightweight.