Theoretical Modeling And Xfem Simulation Of The Damage And Corrosion Interface Effect Of Composites

Composite materials with light weight,high strength,high toughness,corrosion resistance,high electrical conductivity and high thermal conductivity and many other excellent properties,is widely used in construction engineering,daily necessities,medical instruments,aerospace,military supplies and other fields.From carbon fiber composite housings for airplanes and spacecraft,to concrete used in construction,to bulletproof helmets made of fiberglass composite,to carbon fiber sports equipment in daily life.The research on the properties of composite materials has been a hot topic.Currently,many researchers have explored the microscopic and macroscopic properties of composite materials by theoretical,experimental and numerical methods.A large number of studies have shown that the interface area between matrix and inclusion in composites is the weakest link in the performance of composites,and is also an important factor restricting the macroscopic properties of composites.The interface area is very sensitive to the surrounding environment,especially in the harsh environment,it is very easy to damage,corrosion,detachment,micro-crack and other behaviors,which will seriously affect the normal use of the whole composite material or structure.In order to explore the interface effects of damage and corrosion of composites and the relationship between the interface properties and the macroscopic mechanical properties of composites,a series of studies were carried out on the theoretical modeling of the damage and corrosion interface and the numerical simulation based on the extended finite element method.The concrete research content includes three parts:(1)Based on the geometrical substitution idea,the damage variable is introduced to build the damage corrosion theory model of the interface,and the relationship between the displacement and the force at the interface is described.The innovation of this part of work is mainly reflected in the following aspects: a)the establishment of the model is through strict mathematical derivation,and the interface parameters have clear physical significance;b)The established damage interface model is universal and can be degenerated to the existing nonlinear interface model in literature according to the difference of damage evolution formula;c)By introducing the time-varying damage formula,the damage interface model is extended to describe the interface characteristics under corrosive environment.(2)Based on the meso-mechanical homogenization theory and the energy continuity condition,the analytical form of the macroscopic mechanical properties of composite materials is given,and the influence law of the interface damage and corrosion on the macroscopic mechanical properties of composite materials is described.a)The substitution method of imperfect interfaces based on energy equivalence is extended to the corrosion interface problem,so that the appropriate mathematical formula of equivalent modulus in the literature can be applied directly;b)Analytical mathematical form of interface effect of macroscopic properties of corroded concrete is given through strict mathematical derivation;c)The analytical expression of the physical field in the simplified mechanical model of concrete under interface corrosion is given,which can be used as the standard solution for the rationality analysis of numerical method.(3)In the numerical simulation of the damage and corrosion interface of composite materials,a program suitable for the nonlinear interface was written with the advantage of the extended finite element method in dealing with the discontinuous row problem,and the influence of the damage and corrosion process on the overall displacement and stress field of the composite materials was explored.These three parts further enrich the theoretical modeling and numerical simulation of the damage and fatigue interface of composite materials.It is found that the size of the inclusion particles has a serious effect on the macroscopic equivalent bulk modulus and stress intensity of the composites.With the increase of the degree of interfacial damage and corrosion,the macroscopic equivalent bulk modulus and stress intensity of the composites decrease significantly.The results show that the interface properties and the damage and corrosion effect are very important to the macroscopic mechanical properties of the composites.