Research On The Effect Of Gap Compensation Method On Tensile Properity Of Titanium Alloy And Composite Structure

Composite materials have been widely used in the aircraft structures for their high specific strength,stiffness and stealth.However,due to the special manufacturing process of composite materials,the accuracy of the structure is hard to guarantee which leads to the fact that the assembly gap is easy to see.Shim compensation is the simplest and most effective way to eliminate gaps.However,the current research of uneven gaps in the composite titanium alloy structure is relatively rare,resulting in the lack of relevant theoretical support and guidance for the use of solid-liquid hybrid compensation methods which is widely used in industrial production.Therefore,in this paper,the assembly gap of composite titanium alloy laminated structure is studied to establish a model suitable for engineering use,to explore the effect of different shim compensation schemes on the performance of joints with different thickness and to help engineer choice an effective scientific compensation.The primary research contents are as follows:In chapter one,the present situation of research on composite materials,composite joints and shim compensation are analyzed in detail.Combined with the existing problems in engineering,this thesis gives its research object and content,and simply introduces the overall framework of the thesis.In chapter two,the related theories of composite materials are studied,including the mechanics theory of laminate,the theory of composite material failure.And the thesis introduces the material failure criterion and stiffness degradation model involved in the analysis of joints.In chapter three,the finite element simulation model is established,the validity of the model is confirmed by comparing with the experimental results in the paper,then the model is applied to the simulation of the shim compensation model.In chapter four,through the analysis of the assembly clearance in the project,the rules of the clearance change and the shape of the section line are determined,and the geometric model of the non-uniform clearance is proposed.Summing up the shim compensation methods in research and actual production,four common shim compensation schemes are given.In the case of three clearances of 0.6mm,1mm and 1.5mm,comparative analysis was carried out on different shim compensation schemes to determine the effect of various shim compensation schemes on the ultimate load carrying capacity,distribution of stress and strain,and composite's damage of the joints.The analysis provides a theoretical reference for the gap filling operation in the airplane assembly.In chapter five,the research contents of the shim compensation technology for composite titanium alloy laminated structures are summarized,the simulation results are discussed,and the contents that need further study are prospected.