The Multi-scale Simulation Of Hygrothermal Resistance Of CFRP Plates

Fiber reinforced composite(FRP)for rehabilitation has become a popular technology due to the advantages of its light weight,high strength,high temperature resistance and designability.The complex diversity of the civil engineering structure's service environment makes the durability of FRP materials an important research factor.The relationship between the microscale and macroscale properties from the moisture molecules is not clear during FRP material degradation.The multi-scale method is used to analyze the performance degradation mechanism of FRP materials at the microscale,which is an important method to establish the evaluation method under the hygrothermal environment.In this paper,the ABAQUS finite element model at multi-scales,theoretical analysis and calculation methods and experimental data verification are used to study the performance evolution and mechanism of FRP materials in hygrothermal environment.The main research contents in this paper are given as follows:The model of moisture absorption of carbon fiber reinforced composites(CFRP)on the microscale scale was established.The diffusion of moisture molecules on the microscale of CFRP materials and their mechanical properties were studied.The epoxy plays a decisive role in the water uptake process.The relationship between the distribution of the fibers and the internal stress distribution in the material is clarified.It is determined that the transverse stretching and shear failure are the main forms of failure controlled by the matrix,which are greatly affected by the hygrothermal environment.The characteristics of the fiber-resin interface and the influence of the interface on the material properties were studied.The relationship between the interface thickness and the diffusion coefficient was determined.The higher the proportion of the interface,the difference between the interface and the matrix performance is the more obvious.The relationship between the water uptake concentration rate of the interface and the matrix is determined in the near-fiber water uptake stage.The influence of the interface strength on the ultimate strength of the material is clarified.The macroscale failure mode of CFRP sheet was established.And the relationship between macroscale performance change and microscale was studied.It was found that the wet heat environment had greater damage to the transverse performance of the material than the longitudinal performance,and the period was short.The direction of internal stress is determined.It is clear that the first stage of the moisture absorption process of the material mainly causes the change of modulus,the aging and structural damage of the matrix and interface in the second stage,causing the degradation of the long-term performance of the material properties.