Study On The Influence Of Assembly Clearance On Mechanical Properties Of Composite Joints

Carbon fiber composites are considered to be the most ideal structural materials due to their high specific strength and stiffness,high temperature resistance,corrosion resistance and light weight.Carbon fiber composites are widely used in the contemporary automobile industry due to the above advantages.However,due to the difficulty in controlling the manufacturing precision of the composites,it is easy for the anisotropic composite parts to be cured and deformed after curing.In addition,parts assembled connectors at the interface should be naturally tend to generate assembly clearance,forced assembly most likely will cause damage between layers of composite material component and stress concentration on the side of hole,thus for component bearing performance has certain negative influence,and padded compensation is to eliminate composite component assembly clearance of the most common measures.At present,most of the existing literature starts from the load application mode,the interstitial material and other aspects to explore the impact of the law on the mechanical properties of composite assembly parts,but there is no more detailed study on the impact of the size of the assembly gap itself on the mechanical properties of the assembly parts.Therefore,in this paper,the influence of assembly gap on the mechanical properties of composite components is studied by combining experiment and simulation.The main contents of this paper are as follows:The experiment is mainly composed of three-point bending experiment and stretch experiment.The experiment flow and the size of the experiment parts are designed according to relevant standards.For the three-point bending experiment,with the assembly gap size,assembly nail distance and interstitial material as experimental variables,the corresponding experimental groups were established respectively;the single-shear tensile experiment was subdivided into single-nail single-shear and double-nail single-shear tensile experimentsFinite element model was established by Abaqus: according to several damage modes of carbon fiber composites,failure and stiffness degradation criteria were selected to construct UMAT subroutine.The three-dimensional finite element model of bending and stretching is established according to the actual experimental situation.Firstly,the network irrelevance is discussed,and the mesh size is selected reasonably on the premise of ensuring the computational efficiency and accuracy of the model.After the model calculation results are obtained,the model results are compared with the experimental results,and it can be found that the failure forms of the assembled parts in the model are basically the same as those in the experiment,and the strength prediction of the assembled parts by the finite element model is also within the allowable error range.The experimental results are in good agreement with the model results,and it is proved that the 3D finite element damage model can simulate the actual failure of the component well.In this paper,by exploring the hole edge damage expansion law and failure form in the assembly model,the failure law of the composite material assembly with assembly gap under different load forms is explored.The model data and the experimental data were used as the support,and the analysis is carried out from the aspects of the ultimate bearing load of the component,the sequence of the complete failure of the component,the stiffness of the initial stage,etc.,and the comprehensive analysis of the effects of different assembly strategies and assembly gaps on the mechanical properties of the composite material assembly.