Progress Failure Analysis And Strength Prediction Of Composite Bolt Joint

Composite material is increasingly popular in the use of marine structure design and manufacture.It is inevitable to connect two components in engineering.Bolt joint has advantages of transferring high loads and ease of assembly or disassembly,which is a popular choice in composite material joining.However,for the properties of anisotropy and brittleness of composites,the strength of joint is affected by many factors.Also,the bearing capacity of composite structure is mainly determined by the strength of bolt joints.Therefore,it is important to understand the damage mechanisms and predict strength of joints accurately,which can obtain better design and optimization of composite joints.Taking full advantage of composite structures has important engineering and application value.In this paper,the strength of composite bolt joints is studied and the main work is divided into three parts:Firstly,the bearing strength of composite single bolt is studied.The USDFLD user subroutine is written and progressive failure analysis method is adopted to simulate the experiment of composite bolt joints in this paper,verifying the validity of the finite element method.The bearing strengths of single lap joint and double lap joint are compared,which can be obtained that the bearing strength of double lap joint is higher than single lap joint about 80.2%.On this basis,the effects of geometrical parameters,laminate plate thickness,lap joint plate thickness and aperture on the bearing strength of double lap joint are analyzed.It is found that the geometrical parameters can affect the damage mode.Also,within certain limits,these structural parameters have significant impacts on the bearing strength of joints.Secondly,the bearing strength of composite multi-bolt joints is studied.The quasistatic method is adopted,which can avoid the non-convergence problem in composite multi-bolt joint calculation,and the VUSDFLD user subroutine is written.Then the bearing strengths of square arrangement and diamond arrangement are compared,and the effects of two arrangements array and row pitch on bearing strengths are discussed.It is found that diamond arrangement is 10.9% high than square arrangement in the bearing strength with the same geometric size,and the influence of row pitch on the multi-bolt joint bearing strength is obvious.Thirdly,based on similarity theory and empirical formula deduction method,and the data support of finite element experiments,the empirical formula of composite single bolt and double lap joint is established according to similarity criterion function,which is verified by correlation model,providing a reference for engineering application of composite material bolt joints.