A novel thermomechanical model for predicting interfacial stresses in flexible hybrid laminate

Abstract

Triggered by the growing needs for photoelectric conversion and optical interconnections, flexible optoelectronics have recently attracted a surge of interest. Flexible hybrid laminates are promising components of these devices owing to their high performance and flexibility. However, the thermomechanical mismatch of heterostructures usually induces interfacial stresses and resultant failures, particularly for multilayer structures with soft polymeric substrates. The interfacial stresses in flexible laminates remain a challenging matter to be understood distinctly. Herein, the interfacial stresses are investigated via a representative case composed of hard and soft hybrid laminate under nonuniform temperature. By introducing nonuniform shear strain in the thickness direction of bond layer, and nonuniform temperature changes of multilayer simultaneously, a novel analytical model is developed to describe the interfacial stresses with considering adjusted interfacial compliances for the bond layer with varying thicknesses. Our analytical expressions are suitable for different interfacial compliances and a trilinear approximation is verified by the finite element method (FEM) for the adhesive layers with different thicknesses, and comparative analyses were carried out with the existing literatures. The characteristics of the shear stresses are quantitatively illustrated under different temperature variations, elastic moduli and geometrical dimensions. Based on above the vital influencing factors, the mitigating strategies for shear stress are proposed to decrease the interfacial damage. By optimizing key parametric designs, the model and analysis of interfacial stresses could be useful for characterizing the interfacial thermal stress of rigid-flexible films, and enhancing the mechanical stability of heterogeneous multilayers.