Research On Microscopic Damage And Fracture Behavior Of The Continuous Fiber Reinforced Aluminum Alloy Composites Subjected To Quasi-static Tensile Loading

Advanced carbon fibers have such excellent properties as low density,high strength and modulus,stable performance with high and low temperature,low thermal expansion coefficient and so on;The continuous fiber-reinforced aluminum matrix composite(CF/Al composite)composed of the two combines the properties of two component materials,and exhibits high specific strength and high specific modulus,and is anti-fatigue and wear resistance,and a series of advantages and good dimensional stability,are superior to traditional structural materials such as titanium alloys and polymer composites,are advanced composite materials that meet the lightweight and high-precision technical requirements of future aerospace structures.At present,the researches on CF/Al composites mainly focuses on the preparation method,microstructure,and interface reaction control.However,the studies on the damage and fracture behavior of CF/Al composites under load bearing deformation are not enough,Grasping the damage evolution rule and the inherent failure mechanism not only provides theoretical guidance for further improving the preparation process and improves the material properties,but also is a fundamental problem to be solved in the composite material performance design and engineering application.In this paper,carbon fiber M40J(6K)was selected as the reinforcement,and ZL301 of the cast aluminum alloy was used as the matrix alloy.The unidirectional continuous fiber reinforced aluminum matrix composites were produced by vacuum pressure infiltration,and then the longitudinal tensile specimens and transverse tensile samples were processed in the way of wire cutting.Firstly the mechanical performance parameters such as elastic modulus,poisson ratio,tensile strength,strain,interface bonding strength were got in the fracture process of longitudinal and transverse quasi static tensile and the properties of the components in composites.Then researched the the key technologies to establish finite element RVE unit cell model and Setted up an appropriate RVE numerical simulation three dimensional model.Then simulated the deformation process in longitudinal and transverse quasi-static stretching to obtain the the fracture failure process of RVE model and related mechanical property parameters;Eventually by observing the experimental results and comparing the results of finite element numerical simulation,At last obtained damage failure characteristics of interface,matrix and fiber of CF/Al composites in the process of quasi-static tensile fracture,and then revealed the CF/Al quasi-static tensile fracturedeformation characteristics and mechanism from micro-level,the main conclusions are as follows:In the tensile fracture process of longitudinal tensile samples and transverse tensile specimen,when the model deforms to a certain extent,interface material always cracks first,As the loading continues,the crack extends to most of the interface material until it becomes invalid and cannot bear the load.Then the crack extends to the aluminum alloy matrix,and some of the matrix starts to damage,as the loading persistence,the aluminum alloy matrix damages to a certain limit and partial complete cracking loss of carrying capacity.In the end,when the deformation of the whole model is to a certain extent,the stress caused by the deformation of the carbon fiber met its tensile limit and partial fracture occurs,the overall bearing capacity reaches the limit,and finally completely break.In the process of preparing unidirectional CF/Al composites,the overall performance of composites can be significantly improved by reducing the damage degree of carbon fiber,especially the tensile strength of carbon fiber.Further simulation results show that the composite transverse tensile deformation behavior in the transverse tensile process of the fiber does not bear the load,just the interface and the aluminum alloy matrix mainly bear the load,so the mechanical properties of the fibers do not affect the transverse tensile strength and modulus of elasticity.With the increase of interfacial bonding strength,the capacity of composites to resist lateral deformation is stronger and the bearing capacity is higher and higher.As the interfacial bond strength increases,the ability to resist lateral deformation of composites is stronger and the bearing capacity is more and more high,Therefore,the greater the interfacial strength,the greater the transverse tensile strength of composites;The transverse tensile strength and elastic modulus of composites are basically unchanged during the change of interface stiffness;In a certain range,the larger the fiber volume fraction is,the transverse elastic modulus and tensile strength of composites are smaller and smaller.Further simulation results on the longitudinal tensile deformation behavior of composites show that the better the mechanical properties of fibers,the greater the tensile ultimate strength and elastic modulus of the composites;the higher the interface strength,the greater the ultimate tensile strength of the composites.However,the elastic modulus do not change;during the change of the interface stiffness,the ultimate tensile strength and elastic modulus of the composite remain basically the same;within a certain range,the greater the volume fraction of the fiber,the longer the tensile strength of the composite.,The bigger the elastic modulus.