Influence of Temperature Dependent Properties on Tunneling Cracks in Multi‐Layer Polymer Thin Films

Tunneling cracks severely compromise the mechanical integrity of multi‐layer polymer thin films on stiff substrates. Although previous models assume a constant elastic modulus, this study characterizes four candidate thermoset polymers. Their elastic modulus (), coefficient of thermal expansion (CTE), and glass transition temperature () are modeled as temperature‐dependent properties across both rubbery and glassy states. Due to a significant CTE mismatch with the stiff substrate, cooling below induces severe tensile thermal stresses. A thermo‐mechanical model is developed to analyze these accumulated stresses and calculate the strain energy release rate (G) and crack opening displacement (COD) of tunneling cracks. Results demonstrate that G and COD are significantly influenced by the properties of both the cracked layer and adjacent layers, highlighting critical inter‐layer interactions. A parametric study examines how variations in , and CTE influence G. This research provides a framework for evaluating the mechanical performance of functionalized multi‐layer thin film polymers.