Research On Analytical Methods For Multi-bolt Composite Joints

The development of analytical methods for composite multi-bolt joints is a subject which has been greatly concerned in recent years.In the preliminary phase of structural design,neither finite element method(FEM)nor experimental method is efficient.Furthermore,it is not rigorous only using engineering design experiences.The spring-mass analytical model proposed by McCarthy et.al may address this issue well.This model can greatly improve the computational efficiency in the premise of ensuring the accuracy of the computational results,and it is able to consider a variety of factors including the bolt clearance,preload,friction,geometric size and mechanical properties of the laminate.Therefore,the computational results of analytical methods can be a good reference in the preliminary design phase of composite multi-bolt joints.In this thesis,a three-bolt joint which was also studied by McCarthy et.al is selected as a basic model.By studying the principle of analytical method,a uniform expression of stiffness matrix was established to extend the basic model to a regular array of n-column n-bolt composite joint.And the extended analytical method was coded in Python language.Then,the extended analytical method was applied on a three-column four-bolt composite joint.Global bolted joint model(GBJM)and 3D FEM were also performed to prove the accuracy of the analytical method.The effects of layup and clearances were accounted in the study,and they were qualitatively analyzed by comparing the results obtained by three different methods.Finally,a methodology for global sensitivity analysis of multi-bolt composite joints was developed.It can rank the importance of various sources of uncertainty that lead to the uncertainty of structural responses of composite joint.Two kinds of uncertainties were considered in this thesis,i.e.,the uncertainties in mechanical properties of composite lamina and assembly uncertainty.With two sampling strategies,the sensitivity indices of input random variables were estimated through simulation-based methods.Based on the computational results,the global sensitivity analysis of multi-bolt composite joint is performed quantitatively.