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Current gas turbine engines use Yttria-Stabilized Zirconia (YSZ) as the top coat for heat shielding in HP turbines as well as combustors. Unfortunately, YSZ suffers from many drawbacks once the temperature reaches $1200^{\circ }\text{C}$. This limits the long-term application temperature of YSZ, and a few top coat replacements have been suggested and examined. In our study, we make two major changes to the top coat. The first is to use Gadolinium Zirconate (Gd₂Zr₂O₇ or GDZ) which enjoys better thermal properties. The second is to combine it with YSZ in a bilayer configuration, thus, making use of the combined beneficial effects of thermal shielding and mechanical strength of these top coats. In spite of the fact that GDZ/YSZ has been suggested by other authors, no work has been devoted to study the role played by the GDZ–YSZ interphase region, possible interdiffusion, its thermal properties and interphase region strength. In this study, we developed comprehensive atomistic models of the GDZ/YSZ interface using molecular dynamics (MD) with emphasis on thermo-mechanical properties of the GDZ/YSZ interphase region. This allowed us to examine the evolution of the GDZ/YSZ interphase region and compute the interface bond strength with temperature.

The geometrically nonlinear response of sandwich functionally graded cylindrical shells reinforced by orthogonal and/or spiral stiffeners and subjected to axial compressive loads is investigated in this paper. Two types of sandwich functionally graded material models are considered. The formulations are based on the Donnell shell theory considering geometrical nonlinearity and Pasternak’s elastic foundation. The improved Lekhnitskii’s smeared stiffener technique is used to account for the stiffener effects with both mechanical and thermal stresses. The results obtained indicate that the spiral stiffeners have significantly beneficial influences in comparison with orthogonal stiffeners on the nonlinear buckling behavior of shells. The relatively large effects of temperature change, geometrical and material parameters are also demonstrated in the numerical investigations.

In this study, a simple and unified process is established for transient vibration analysis of functionally graded material (FGM) sandwich plates in thermal environment. The temperature field, considered constant in the plane, is distributed along the thickness with uniform, linear and nonlinear profiles. For the material properties, both temperature and position dependence are taken into account. A further refined zigzag plate theory accounting for partitioned transverse displacements and piecewise-continuous in-plane displacements is developed within the framework of Hamilton’s principle including thermal effects. Appropriately and simplicity representation of the deformation states is provided in the governing equations. A spectral analysis technique, namely, method of reverberation ray matrix (MRRM), is employed to calculate the transient vibration responses of FGM sandwich plates with general boundary conditions and arbitrary external loadings. The artificial spring technology and the equivalent wave source vector are introduced to improve the numerical stability and parametric adjustability of MRRM. The accuracy, flexibility and efficiency of the proposed process are discussed using many numerical examples. On this basis, the effects of the boundary parameters, FGM gradient index, core-to-facesheet thickness ratio, thermal properties and external loadings on the transient vibration behaviors of FGM sandwich plates are thoroughly investigated.

In this paper, an edge-based smoothed finite element method (ES-FEM) is further formulated to deal with the thermo-mechanical analysis of composite pressure vessels. In the ES-FEM, the problem domain is first discretized into a set of triangular elements, and the edge-based smoothing domains are further formed along the edges of the triangular meshes. In order to improve the accuracy, the stiffness matrices are calculated using the strain smoothing technique in these smoothing domains. The thermal and mechanical properties are assumed to vary between different layers. The present formulation is straight-forward and no penalty parameters or additional degrees of freedom are used. Several numerical examples are given to demonstrate the effectivity of ES-FEM for thermo-mechanical analysis of composite pressure vessels.

A face-based smoothed finite element method (FS-FEM) is extended to deal with the transient thermal mechanical analyses of composite structures. For this method, the problem domain is first discretized into a set of tetrahedral elements, and the face-based smoothing domains are further formed along the faces of the tetrahedral meshes. The smoothed Galerkin weak form is employed to obtain discretized system equations, and the face-based smoothing domains are used to perform the smoothing operation. After applying these approaches, the numerical integration becomes a simple summation over each smoothing domain. Several composite structures with different kinds of boundary conditions are studied in this paper. Compared with the 4-node tetrahedral FEM, the FS-FEM can achieve much better accuracy and higher convergence when using the same tetrahedral mesh.

A strain-rate-sensitive polyurethane elastomer is numerically investigated to reveal impact behaviors and analyze the inputted strain energy dissipation features with concerned rate dependencies. In view of the amorphous structure of elastomers, a thermo-mechanical model is developed via relating the macro-mechanical behaviors to micro-structural changes through molecular transitions and two distinct flow activations with each possessing a unique activation energy. Under large straining, detangling of molecular chains and networks through sliding is found to produce serious frictional effects resulting in instantaneous heat generation and temperature rise. To incorporate these heat-effected issues, an instantaneous temperature rise is calculated at each macro-level material point to ascertain the localized changes in the associated mechanical response. The overall perspectives of the dynamic mechanical behavior including visco-elastic large deformation, rate dependent yielding, thermal softening, flow at plateau stress, and strain hardening are found well captured. Investigations are extended for the material recoverability and accordingly, strain energy absorptions are clarified. Finally, a power law function is proposed for designing the energy absorption relation to the applied loading rate.