| With the wide application of composite structures and composite bonded structures in the aerospace industry,the research on the problem of composite bonded structures is becoming more and more extensive.Gluing repair is the primary means of repairing composite materials,including the patching method,the excavation method,and the injection method.The compressive ability of composite fibers is greatly weaker than that of tensile strength.The compression of composite materials is more likely to be destroyed than that of tension,and the literature on the current analytical model of compression is less stretched.Gluing repair is susceptible to the hot and humid environment,which leads to a decrease in the bonding strength.In actual situations,the aircraft is often placed in a hot and humid environment,so the research on the compression mechanical properties of the composite gluing repair structure under the hot and humid environment is very meaningful.In this paper,the compression analysis model of the composite material repairing structure is established,and the analytical ultimate load analysis model of the composite material repairing structure in the hot and humid environment is established.In the two models,the rubber layer only considers the shear deformation,and ignores the shear deformation of the mother board and the patch,assuming that the mother board and the patch are linearly elastic.After the composite material is repaired,the structure may have three failure modes:compression failure of the mother board,compression failure of the patch,and shear failure of the rubber layer.Among them,the first model considers its elastoplastic behavior in the shear failure of the rubber layer.The rubber layer may have four mechanical behaviors:all linear elastic behavior,close to the complete plastic behavior near x=0,near the area near x=d1 Complete plastic behavior,near the full plastic behavior of the region near x=0 and x=d1.The second damp heat model does not consider the elastoplastic behavior of the rubber layer,adopts the linear elastic model for the rubber layer,and considers the influence of damp heat on the mechanical properties of the composite and the wet heat stress generated by the damp heat.The first model can obtain the unknown coefficient in the relation between shear strain and longitudinal position by the corresponding boundary and continuity conditions under different mechanical behaviors of the rubber layer,and then obtain the corresponding ultimate load.The second damp heat model solves the difficulty of directly solving the ultimate load in this mode by introducing the dichotomy method to solve the ultimate load of the repair structure corresponding to the shear failure mode of the rubber layer in the hot and humid environment.Using the method of the second damp heat model and using MATLAB programming,the analytical solution of the compressive ultimate load of the composite repairing structure in the hot and humid environment was calculated,and the compression test of the composite gluing repair structure in the hot and humid environment was carried out.The analytical solution is in good agreement,demonstrating the validity of the second damp heat model.The second damp heat model is used to study the influence of the change of the single repair parameter or the multiple repair parameters on the shear stress maximum and compressive limit load of the structural repair layer of the composite material.The MATLAB programming calculation is used to draw the multi-dimensional surface change map.It embodies the superiority of the analytical model relative to the finite element model and the test method.The result is as follows:the length of the patch and the thickness of the patch increase,the ultimate load increases,and the increasing trend gradually becomes gentle.There is an optimal solution for both;the thickness of the rubber layer increases,and the ultimate load increases.And the increasing trend tends to be flat. |
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