| The reliability of self-lubricating twill fabric liner,as an important lubricating part of aviation joint bearings,is directly related to the operational safety of aircraft.The performance and reliability of the bearings are mainly influenced by the performance of the fabric liner itself,where the performance of the fabric liner component materials and the woven form play a decisive role in the overall mechanical performance.It has been proven that it is not economical or even practical to obtain the mechanical properties of composites through tests,and that tests do not accurately obtain the dependencies between component materials,which need to be analyzed at a fine level to study the mechanical properties of component materials.Therefore,this paper investigates the out-of-plane compression damage mechanism of self-lubricating twill fabric liner with the finite element method by using the structure model of fabric liner,mechanical properties of component materials and their interaction,and the following work is carried out.Based on microscopic observation of the fiber bundle cross-section and path of the fabric structure,the meso-structure RVE model of self-lubricating twill fabric liner is established according to the fabric modeling theory with the professional textile modeling tools.The strength and stiffness properties of several different volume fractions of fiber bundles and resin matrix in the fabric liner are calculated based on the homogenization theory and monomer properties derived from the composite mechanical properties model based on the material properties of each component of the fabric liner.In this paper,the damage form,technical method and mathematical model of the composite structure of the fabric liner are studied,and based on the intrinsic model of each component material,the damage of the material under compression is simulated by introducing the stiffness reduction coefficient,and finally chosen the maximum positive stress damage criterion and the Mohr criterion to establish the damage intrinsic model of each component material.The above damage mathematical model is coded into the UMAT subroutine,which lays a model foundation for the finite element analysis on the mechanical properties of the twill fabric liner under out-of-plane compression.Based on the mathematical theoretical model of periodic boundary conditions,with the Python scripting interface reserved by the commercial finite element analysis software Abaqus,a Python scripting program for applying periodic boundary conditions to the RVE model of composite materials was written,and then successfully applied to the RVE finite element analysis model of self-lubricating twill fabric liner.The mechanical properties of the self-lubricating twill fabric liner under the test condition are investigated according to the test and evaluation method of the mechanical properties of composite materials.And an improved test method of out-of-plane compression on the twill fabric liner is proposed for the characteristics along the thickness direction of the fabric liner.The damage failure form and mechanical properties of the twill fabric liner under the test condition are obtained,which can provide comparison for the model validation of the numerical analysis and the accuracy of the damage mechanism analysis.Based on the established numerical damage model and method for adding periodic boundary conditions,the damage process to the self-lubricating twill fabric liner RVE outof-plane compression was simulated by the finite element method,and the mechanical response characteristics obtained by numerical simulation were compared with the experimental values to verify the accuracy of the results.The failure model for fabric composites and method for adding periodic boundary conditions established in this paper provide a reference for further research on fabric composites,and provide technical and theoretical support for improving the mechanical properties of fabric composites,especially for self-lubricating fabric liners. |
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