Buckling Behavior Of Thick Walled Cylindrical Shells With Advanced Functionally Graded Materials

Functional gradient materials(FGMs)have been widely used in many high-tech fields since their introduction.This is mainly due to its continuously changing physical properties and mechanical properties.From the original traditional ceramic metal functional gradient materials to today's advanced carbon nanotubes and graphene gradient-enhanced metal-based materials,or from a single-use development to a variety of uses,have shown the advanced nature and importance of functionally graded materials.The cylindrical shell is a common structure widely used in various fields,and its main failure mode is buckling failure.Therefore,it is of great value to study the buckling behavior of advanced functionally graded cylindrical shells.Based on Reddy's high-order shear deformation theory,this paper establishes the basic equation of the thick-walled cylindrical shell structure,and then uses the theoretical solution method to solve the basic equations.Firstly,the buckling behavior of FRP coated CFRP cylindrical shells under compression and thermal loading was studied.Based on the Micromechanical model and the Voigt model,respectively,the CFRP layer and the inner and outer surfaces of the FGM coating at the center of the shell are described.Considering that epoxy resin matrix is a brittle material,micro cracks are inevitable during production or use.Therefore,damage variables were introduced to describe the CFRP layer damage.The Galerkin method is used to solve the buckling solution of a cylindrical shell under a simple supported boundary.The effects of various parameters such as geometric parameters,number of fiber layers,laminate stacking sequence,fiber layer angle,damage variable,functionally graded material properties,carbon fiber content and temperature field on the buckling results were discussed in detail.It was found that more attention should be paid to the influence of fiber layer angle and micro-crack damage in practical applications.Secondly,the buckling behavior of porous graphene gradient-reinforced cylindrical shells under external pressure was studied.The characteristics of porous graphene reinforced metal matrix composites were described based on the Halpin-Tsai micro mechanical model.In order to obtain more accurate results,the variational method was used to obtain the buckling solution of the cylindrical shell under the fixed boundary.The influence of the geometric parameters of cylindrical shells,three pore distributions,three GPL distributions,porosity and GPL mass fraction on the critical buckling stress is discussed in detail.