Study Of Viscoelastic Functionally Gradedmaterial Interfacial Region Plane Crack Problem Under Thermal Load

The functionally gradient material is a inhomogeneous composite material with the material parameters changing within the gradient in aspects of composition and structure and can be artificially designed. The material gradient parameter can be described as any continuous function on the space, so that it can be better designed based on function. Functionally gradient material is very dominant compared to traditional composite materials in some aspects such as improving the properties of coating bonding, relieving stress concentration and reducing the residual thermal stress, and has been widely used in many fields. In the field of fracture mechanics, functionally gradient material has a high academic value, because of the arbitrary nature of material gradient parameter also has brought certain difficulties. Scientists have proposed a lot tasks related on viscoelastic mechanics in application process of functional gradient material as thermal protection material. In-depth and systematic research on these tasks, not only enrich the contents of inhomogeneous medium mechanics, but also the research results can provide theoretical guidance for the design and fabrication of functionally gradient materials.At present the latest research results on fracture of viscoelastic functionally graded material was limited to the crack problem of viscoelastic graded material with special function distribution’s material parameters and arbitrary gradient viscoelastic plane crack problem under thermo-mechanical coupling loads. In this paper,the flexibility linear hierarchical model will be introduced to the crack problem of viscoelastic gradient material in order to analyze the crack problems of viscoelastic functionally graded coating. First, we make the mixed boundary value problem into singular integral equation by using Laplace and Fourier integral transform, and then obtain the stress intensity factor through the numerical solution; we analyze the influence of the material gradient parameter on stress intensity factor, also make the proposed model compared with the existing model. The results show that the flexibility linear hierarchical model in the analysis of viscoelastic functionally graded material plane crack is still effective; With regard to the material properties related the case of non coupling function of time and space, conclusion that is similar to the elastic state can be obtained.