Study On The Vibration Characteristic Of Fiber Reinforced Composite Shells Coated With Different Damping Materials

The fiber-reinforced composite shell has excellent mechanical properties because of its good thermal stability and capability on weight reduction and it is widely used in the aeronautics,astronautics,automotive,naval vessel and weapon industry.Currently,there are a large number of such composite thin shell structures,comparing with metal shell,fiber reinforced composite shell has the characteristics of corrosion resistance,insulation and so on.So it is used in many important fields.They are usually in the cantilever boundary condition with one end constraint,such as aeroengine casing,composite drum,composite radome and so on.As their structures become more and more complex and their working environment becomes more and more harsh,their vibration problems become more and more prominent,and they are prone to resonance,fatigue and damage faults.Therefore,it is of great engineering and academic significance to study the vibration characteristics of fiber reinforced composite thin shells(FCTS)coated with different damping materials.On the other hand,fiber reinforced composites have a certain damping capacity,but they do not have strong wear resistance compared with metal cylindrical shells.Therefore,they are often coated with damping materials,which can increase their service life and further reduce their vibration response.When the constrained layer damping is coated on its surface,the nonlinear phenomena will occur at the same time.In order to solve these problems,the vibration characteristics of carbon fiber reinforced resin-based composite thin shells are studied in this paper.The specific research contents are as follows:(1)The fiber reinforced composite thin-walled cylindrical shells(FCTS)under cantilever boundary condition is taken as research object.Based on plate-shell theory,the natural characteristic of FCTS is obtained by using orthogonal polynomial method and beam function method respectively.In addition,the natural characteristic calculation process of two theorical methods is proposed.Meanwhile,the natural characteristic test system is established and the natural frequencies and mode shapes of T300 carbon/epoxy composite thin shell are measured.At last,the natural characteristic results obtained by two theorical methods are compared,and the correctness is verified by comparison with the experimental results.(2)The frequency response characteristics of FCTS under based excitation and the dynamic stiffness of FCTS under impulse excitation are studied.Taking FCTS under cantilever boundary conditions as the research object,the frequency-domain vibration response of the FCTS under the basic excitation is solved based on the multi-level iterative correction technique.At the same time,the half-period sinusoidal signal is used to simulate the impulse excitation load,and the frequency response and dynamic stiffness of FCTS under the impulse excitation are solved by the multi-level correction technique.Subsequently,the vibration response of frequency domain and dynamic stiffness of FCTS under impulse excitation can be obtained by simulating impulse excitation of hammer signal,and their respective vibration response prediction processes are proposed.Finally,the test system of vibration response is built.Taking the T300 carbon fiber/resin composite thin-walled cylindrical shell as the research object,the vibration response of FCTS under based excitation and dynamic stiffness under impulse excitation are tested and obtained respectively.The theoretical prediction results and experimental results are also given,the results are compared and verified.(3)The vibration characteristic of FCTS with hard coating is studied.The natural frequencies,vibration responses and modal loss factors of FCTS with hard coating can be obtained by using beam function method.The above results can be verified by the finite element method.The results show that the accuracy of the mathematical model meets the requirements.Then,the influence of the elastic modulus,loss factor and thickness of the hard coating on the vibration characteristics of the FCTS is discussed,and the rule of using the hard coating to reduce the vibration of the structure is found.(4)The strain energy density function method and the maximum total strain method are used to establish the nonlinear vibration model of FCTS with constrained layer damping that has strain dependence.In addition,the power function fitting technique is used to identify the non-linear stiffness parameters,the non-linear damping parameters and the non-linear fitting parameters in the non-linear vibration model.Then,the specific analysis flow of the non-linear natural frequency and vibration response is proposed,and the non-linear natural frequency and vibration response of the FCTS coated with constrained layer damping are obtained by using the self-compiled MATLAB program.Finally,taking the T300 carbon fiber/resin composite shell coated with constrained layer damping as the research object,the results of its non-linear natural frequency and vibration response are obtained,and the theoretical calculation results are compared with the test results.In this paper,the research further reveals the vibration characteristics of FCTS and FCTS coated with different damping materials.It plays an important role in predicting the vibration damage and fatigue damage of composite structures,as well as in dynamic design,response prediction and performance optimization of structural systems.All of them have important engineering and academic significance.Relevant research results can provide important technical support for the application of composite cylindrical shells in engineering practice.