Session: 01-01-01: General Topics of Aerospace Structures 1

Paper Number: 162184

162184 - Analytical Modeling of Multi-Layered Structures With Creep Effects 

Multi-layered structures consisting of thin layers mounted on a substrate or clamped between two plates, such as thermal barrier coatings, actuators, optical thin films and solid oxide fuel cells (SOFCs), are widely used in various industries.

The electrochemical performance degradation observed in a multi-layer structure is largely attributed to irreversible creep deformations. Such creep deformations can disrupt the original mechanical and electrochemical states in the structure, potentially leading to localized electrochemical failures, increased contact resistance, and gas leakage.

In a multi-cell structure, the deformation experienced by a unit cell is influenced by the manufacturing process, component assembly within the repeating unit, and position of the cell in the structure. Additionally, since many multi-layer structures operate at high temperatures, creep-induced stress relief can cause localized and uneven permanent deformations in individual cells and their associated components. As these deformations accumulate over time, they can lead to performance deterioration or even failure in the cell and structure. Therefore, identifying the parameters related to creep is crucial for studying failure mechanisms. However, studies on the creep behavior of these layered structures remains limited, especially for the creep effect on interfacial stresses. Most existing models were developed to analyze multi-layered structures under pure bending induced solely by thermal loads. In addition, these models do not have the capability to evaluate interfacial stresses between layers, which are crucial for the design process and for identifying potential failure regions. Moreover, the majority of these existing models are restricted to a specific number of layers.

In the current study, a new analytical model built on an extended Euler-Bernoulli beam theory is developed for perfectly-bonded multilayer structures, which incorporates the effects of Poisson's ratio and creep. The model is capable of analyzing multi-layered structures with an arbitrary number of layers of dissimilar materials subjected to general thermal and mechanical loads. The newly developed model can effectively predict stress relaxation and interfacial stresses in multi-layered structures. The model is validated by comparing with finite element simulation results obtained using COMSOL Multiphysics and other data from existing studies. This work extends our earlier studies on multi-layered structures without considering creep effects [1,2].

References

[1] Shaat, M., Gao, X.-L., Battentier, A. and Massue, N. (2024). New analytical model for multi-layered composite plates with imperfect interfaces under thermomechanical loading. Acta Mech. 235, 7083–7120.

[2] Shaat, M., Gao, X.-L., Li, K. and Littlefield, A. G. (2023). New analytical model for thermomechanical responses of multi-layered structures with imperfect interfaces. Acta Mech. 234, 5779–5818.

Presenting Author: Xin-Lin Gao Southern Methodist University

Presenting Author Biography: Dr. Xin-Lin Gao is currently a professor of mechanical engineering at Southern Methodist University. He is a fellow of ASME and a past chair of the aerospace division of ASME.