Study On Bonding Properties Of Composite Shell/Insulation Interface Of The Rocket Motor

In the process of launch and vertical storage,the solid rocket motor will be subjected to the axial load,and the shear stress on its bonding interface will be more obvious.The debonding of any interface will threaten the structural integrity of the solid rocket motor and thus affecting the normal operation of the solid rocket motor.To investigate the mechanical properties of the carbon fiber/nitrile rubber interface of solid rocket motor,the bonding characteristics of the interface under load are analyzed through the interface mechanical tests and finite element simulation methods,and the models characterizing the mechanical characteristics of the carbon fiber/nitrile rubber interface are established to simulate the actual working conditions of the solid rocket motor in this paper.The main research contents of this present paper include the following items:(1)Experimental research on the mechanical properties for the carbon fiber/nitrile rubber interfaceAccording to the characteristics of the carbon fiber and nitrile rubber materials and relevant test standards,taking the carbon fiber/nitrile rubber interface as the object,the debonding test and creep test of carbon fiber/nitrile rubber interface at model II were carried out with the single lap specimens.The load-displacement curves of the interface were obtained in the debonding test at model II,and the crack propagation process of the specimens was recorded.The test data were processed by the methods of fracture mechanics,and the bonding shear strength and fracture energy of the carbon fiber/nitrile rubber interface were obtained.The creep strain-time curves of the interface were obtained by the shear creep test.After data processing,the creep parameters of the carbon fiber/nitrile rubber interface were obtained.The data obtained from the tests will provide the interface mechanical parameters for the construction of the carbon fiber/nitrile rubber interface mechanical constitutive model.(2)Construction of fracture constitutive model for the carbon fiber/nitrile rubber interfaceIn order to describe the debonding characteristics of the carbon fiber/nitrile rubber interface,the cohesive models were studied,and the applicability of the cohesive models were compared and analyzed through the numerical simulation results of the commercial finite element software ABAQUS.Based on the characteristics of classical cohesive models and the change trend of the test curves,a new cohesive rule suitable for characterizing the carbon fiber/nitrile rubber interface is proposed.In addition,due to the limitations of the test methods,there are some errors in the test results.An inversion identification method combining the test and numerical simulation was introduced to further obtain the more accurate constitutive model of the carbon fiber/nitrile rubber interface at mode II fracture,and the reliability of the model was verified by the comparison between the test results and the simulation prediction results.(3)Construction of creep constitutive model for carbon fiber/nitrile rubber interfaceAccording to the stress correlation of the carbon fiber/nitrile rubber interface in creep,the time hardening models were used to study the creep characteristics of the interface.Combined with the fitting effects of the models,the accuracies of every time hardening model in describing the interfacial creep of the carbon fiber/nitrile rubber interface were compared,and the interfacial creep process was simulated in the software ABAQUS to verify the correctness of the time hardening model theory.The results show that the creep constitutive model constructed by the generalized time hardening model has a higher fitting accuracy than other models,which can better characterize the creep mechanical properties of the carbon fiber/nitrile rubber interface,and can also be better suitable for the prediction of the interface creep.(4)Study on bonding interface performance of solid rocket motor under launch overload and vertical storageIn view of the characteristics of solid rocket motor bear the combined action of axial overload and gas internal pressure during ignition and launch and the axial gravity load during vertical storage,the solid rocket motor models under launch and vertical storage were established by methods of numerical simulation and the mechanical properties of the carbon fiber/nitrile rubber interface of the solid rocket motor under launch and vertical storage were studied by finite element analysis.Finally,by changing the length and diameter of the solid rocket motor,the effect of length diameter ratio on the bonding properties of the carbon fiber/nitrile rubber interface was studied.