Nonlinear Analysis Of Carbon Nanotube Reinforced Composite Laminated Structure With Negative Poisson's Ratio

Carbon nanotubes,is a popular advanced material,which has attracted more attention due to its excellent performance in many construction works.The use of carbon nanotube reinforced composite(CNTRC)as structural elements(e.g.,beams,plates)can both develop high-performance components and improve enhance the service life of structural elements under extreme environments.Due to the potential applications of CNTRCs in many fields such as aeronautical,petrochemical and marine industries,it is important to study the nonlinear behavior of these structures under different loading scenarios.In addition,negative Poisson's ratio(NPR)materials and structures also shown excellent performance in many fields such as aerospace defence and sport equipments.CNTRCs have strong anisotropy with a ratio of two in-plane Young's moduli over 40,which makes them ideal for the design of laminated structures with NPR.In this study,based on classical lamination theory,two types of FG-CNTRC with NPR are designed by taking CNTRC as an example and combining the concept of functionally graded(FG)materials.At the same time,the concept of NPR is extended to hybrid laminated structure composed of fiber reinforced composite(FRC)and CNTRC.The effect of NPR can improve the impact and fracture resistance of CNTRC laminates,so that it can show the advantages of higher ratio of strength to light during the service.In this thesis,the study of the nonlinear bending,vibration,and dynamic response of the laminated structure with NPR is carried out.The nonlinear governing equations of the laminated beams and plates are given by combining Reddy's high order shear deformation theory and von Kármán's large deflection theory.The theoretical solution for the nonlinear bending and vibration of the laminated structure is obtained by using a two-step perturbation method.The numerical solution for the dynamic response of these structures is obtained via introducing the fourth-order Runge Kutta(RK4)method.The main findings and conclusions of the crrent work are as follows:Taking the FRC/CNTRC hybrid structures with NPR for instance,the effects of different types of CNT distribution,temperature fields,and elastic foundations the on bending and vibration characteristics are examined.Meanwhile,the FRC/CNTRC hybrid structure with a positive Poisson's ratio(PPR)is adopted as a reference.The sensitivity of the NPR and PPR structure to the changes of environment conditions are discussed.For the dynamic response problem,the effects of the CNT distribution,dynamic loading sceneries,and viscoelastic foundations on the dynamic behavior of the FGCNTRC with NPR is discussed in detail.The effective Poisson's ratio(EPR)-deflection curve of FG-CNTRC structures is also presented.It is obvious that the value of ERP first shows a downward trend and then moves upward smoothly with the increasing deflection.In addition,different types of CNT distribution have significant effects on the mechanical behavior of the laminated structure with NPR.The FG-? beam and FG-X showed an excellent performance in the bending and dynamic responses.As for the nonlinear vibration,the FG-X beams exhibit satisfatory performance.The theoretical results also indicate that FG-X distribution can improve the mechanical behavior of laminated plates.A laminated structure with NPR is designed for the first time by using CNTRC.The symmetric and antisymmetirc laminated structures with NPR are presented.The concept of NPR is extended to a hybrid FRC/CNTRC structure.This not only promotes the application of FG-CNTRC structure but also provides new ideas for the design of the structure with NPR.The parametric analysis of FG-CNTRC and hybrid structures with NPR are greatly helpful to understanding for engineering design.