Analysis Of Failure Behavior Of Viscoelastic Material-based Interfacial Structure

Failure of interfacial structure composed of metal shell and solid propellant is one of important forms of engine failure. External loading such as mechanical loading, temperature loading and chemical loading, and viscoelastic behavior of solid propellant which is a typical viscoelastic material play a significant role in interfacial failure. In this paper, viscoelastic properties of solid propellant are taken into consideration to investigate interfacial structural failure based on critical J-integral theory and cohesive laws, respectively. The related details are illustrated as follows:Firstly, J-integral of pre-crack of numerical model are evaluated based on J-integral under varied temperatures and tension velocity. Interfacial strength acquired from paper and stress value of model are compared to identify critical J-integral under different conditions. The relationships between critical J-integral and temperature and tension velocity are then deduced which are adopted as failure criterion of interfacial structure under specific condition.Secondly, a cohesive model is proposed in which cohesive element is used to model adhesive layer combining metal shell with solid propellant. Interfacial failure, therefore, can be achieved under various temperature and tension velocity. A critical crack propagation velocity is applied to distinguish whether interfacial failure happens or not. Then damage dissipation energy and failure area are extracted from the model to get critical energy release rate. The relationships between critical energy release rate and temperature and tension velocity are regarded as failure criterion for assessing interfacial structure under specific condition.The two failures criterion mentioned above are relationship between critical energy release rate and temperature and tension velocity which are obtained from different theories. Therefore, comparison of the two criterions can lead to a relatively more accurate, or safe law which is more practical.Finally, based cohesive model mentioned above, cohesive elements are also inserted into solid propellant to model its failure. This paper gives deep sight into the problem whether crack propagates along interface or inside solid propellant under different conditions.