Nonlinear Analysis of Matrix Cracked Hybrid Laminated Structures Made of Advanced Composite Materials

Author:Fan Yin

Supervisor:wang hai


Degree Year:2016





A hybrid laminated structure containing both carbon nanotube reinforced composite(CNTRC)and fiber reinforced composite(FRC)is presented in this paper.Due to the limitation of preparation,adding CNTRC to traditional FRC structure is a feasible plan in the engineering application.Because CNTRC can be functionally graded(FG)in the direction of thickness,for this reason,the mechanical properties and design performance of hybrid laminated structure may be improved further.It can be expected that this advanced composite hybrid structure has a widely potential application in major aeras,such as areonatics and astronautics.Mesoscopic damage is presented in the interior of composite structure in the service.When the structure is subjected to tensile、bending or fatige load,it is easy to produce the inner matrix cracks.The presence of matrix cracking which is invisible is usually at the earlier stage in the service period of the structure.The stiffness of structure can be significantly influenced by matrix cracking,which makes a further influence on the nonlinear mechanical behaviors of structure.Hence,it is of importance that the mechanical properties of structure should be revalued after matrix cracking arising and the results of revaluation may be referenced for the maintenance and damage tolerance of structure.This paper mainly investigates nonlinear dynamic,nonlinear bending,postbuckling,thermally postbuckled vibration and nonlinear low-velocity impact response of matrix-cracked hybrid laminated structure resting on an elastic foundation.In the frame work of von-Karame nonlinearity,the equilibrium equations of beam or plate are established based on classical theory or Reddy’s higher-order shear deformation theory and solved by a two-step perturbation method.In the analysis of nonlinear dynamics and nonlinear low-velocity impact,a Runge-Kutta numerical method is used to compute second order ordinary differential equations.In the constitutive relation of beam or plate,the effect of matrix cracks can be introduced by shear-lag model(SLM),self-consistent model(SCM)and elasticity theory model(ETM).SLM and SCM are modified herein to be suitable in the structural analysis.For the sake of simulating the process of contact between impactor and functionally graded structure accurately,Hertz contact model is also refined for the analysis of nonlinear low-velocity impact.The FG distribution of CNTRC does affect the mechanical properties of structure dramaticly.Based on existing FG in a CNTRC single layer,two kinds of FG distributions which are both symmetric according to the middle plane for laminated structure.Numerical results show that FG-1 distibution can improve the mechanical behaviors of structure,which may be helpful for pratical engineering application.Based on the theortical analysis,numerous C++ analytical programs are developed to carry out parametric study on hybrid laminated structure.The volume fraction of carbon nantube(CNT)in a CNTRC layer,temperature fild and elastic foundation are mainly considered.In the analysis of nonlinear dynamics and nonlinear low-velocity impact,the initial velocity of impactor and damping effect are also taken into account.In the nonlinear bending and thermal postbuckling of hybrid laminated beam,piezoelectirc fiber reinforced composite(PFRC)is included into the beam and the effect of electric field can be considered,consequently.A large amount of numerical results are presented for the first time.These results can be compared and benchmarked by others in the future.The results obtained by parametric study can be helpful to understanding the nonlinear behaviors of such structure,which may guide the application of the structure in engineering.