Research On The Bolt-load Distribution Of Multi-bolt Composite Joints

With the wide application of composite in aerospace engineering,the connection of composite materials is unavoidable.The composite material plates used for main force-bearing components mainly adopts mechanical connection.At present,research on the multi-bolt composite joints is mainly focused on two aspects of bolt-load distribution and structural strength analysis.However,the structural connection strength will be affected by the non-uniformity of bolt-load distribution of the composite connection structures.Therefore,how to improve the uniformity of bolt-load distribution of the connection structures is a research topic with practical application value.In the analysis of bolt-load distribution of multi-bolt composite joints,the application of the traditional elastic mechanics method is limited despite its clear principle and computational easiness and exactness in the problem of bolt-load distribution of multi-bolt composite joints.This paper presents an improved elastic mechanics analysis method to determine the load distribution multi-bolt composite joints,which included the effect of bolt-hole clearance,bolt preload and the friction effects between the laminates.Compared with the results of detailed three-dimensional finite element model,the method can accurately estimate the load distribution of multi-bolt joints.The effect of different bolt preload and bolt-hole clearance on the proportion of load distribution is analyzed based on the improved method.Compared with the results which adopt the traditional elastic mechanics method,the necessity of improve the traditional elastic mechanics method is demonstrated.Based on finite element method,the influence of laminate and bolt parameters on the bolt-load distribution ratio is discussed.A reasonable parameter selection scheme is given from the point of uniformity of bolt-load distribution.Finally,based on the improved elastic mechanics method and the progressive damage analysis model,the optimal configurations of single-lap and double-lap joints are proposed by changing the bolt-hole clearance,and the carrying capacity of the connection structure is improved significantly.