Study On The Refined Calculation Method For Layered Structures With Application

Orthotropic and transversely isotropic layered structures are the most common in engineering,such as composite laminates,honeycomb sandwich,piezoelectric devices and chip structures.Because most layered str uctures are characterized by thin single layer thickness and are affected by the interface effect between layers,the mechanical behaviors among layers in the layered structures under load influence and coupling each other,and finally a complex and difficult to solve elastic field is formed in structure.For the multi-field coupling problem of piezoelectric devices,in addition to the above difficulties,the coupling effect of the coupling field should be further considered,which further increases the com plexity of the problem.However,if the full-field solution,or even the coupling field,of the layered structure and the failure prediction of the material can be obtained,the influence of various structural parameters on the mechanical response of the m aterial can be systematically studied,so as to further optimize the structural design.Based on the above background,this thesis carries out the following four aspects of work:First of all,the single layer plate is the basic element of the layered stru cture,the study of the single layer plate is the fou ndation of the further study of the multi-layer structure.So here for two-dimensional orthotropic single layer plate and three-dimensional transversely isotropic single layer plate,respectively,based on two-dimensional general solution of orthotropic ma terials and three-dimensional general solution of transversely isotropic material,new harmonic function is constructed for the normal concentrated force and tangential force load,then the Green’s function solutions of elastic field under concentrated force loading with different direction are proposed.Based on the Green’s function solution,the stress distribution characteristics of the two plates are analyzed comprehensively,and the stress solutions of the two plates under the common distributed forces are obtained based on the superposition principle.Secondly,on the basis of obtaining the Green’s function solutions of two-dimensional orthotropic plates,a new harmonic function for two-dimensional orthotropic sandwich structures is constructed,and th e Green’s function solutions of the elastic fields under the normal and tangential concentrated forces are obtained.Based on the solution of Green’s function,the stress distribution characteristics of two-dimensional orthotropic sandwich structures under concentrated loads are analyzed.Furthermore,the stress distribution characteristics of the composite bonding layer with different lay-up combinations are analyzed and refined in detail.In addition,the influence of material parameters and thickness of interlayer on interfacial stress of sandwich structure is studied by adjusting parameters.These results can be directly used to analyze the material selection of layered structures and the fine design of their strength.In addition,based on the obtained Green’s function solution of 2D orthotropic sandwich structure,the Green’s function solution of 2D orthotropic sandwich structure is further extended to 2D orthotropic piezoelectric sandwich structure,and the Green’s function solution of the coupling field of piezoelectric plate buried in non-piezoelectric dielectric material under concentrated load is obtained.Based on the analysis of parameters,the influences of the substrate material and the thickn ess of piezoelectric plate on the interface stress tr ansfer and the potential difference between the interfaces are studied,and the suggestions for the design and material selection of piezoelectric devices are given according to the above results.Finally,composite structure is one of the most common layered structure,its component is the typical orthotropic materials.After studying the Green’s function solution,the strength analysis can be implemented.However,because of the failure of the composite material is complicated,usually multiple failure mo des occur simultaneously and influence each other,the key for refined analysis of composite structure is an accurate and robust failure criterion.Based on this,a hybrid method based on artificial neural network algorithm and computational meso-mechanics is proposed for failure prediction of unidirectional carbon fiber composites u nder multi-axial loads.