Effects of creep on interfacial stresses of bonded structures

In this work, a survey on the closed form solutions for the prediction of interfacial shear and peeling stresses of bonded structures is first given. And then, comparisons between the closed form solutions, elastic finite element analysis (FEA) and elastic-creep FE results are performed for the bonded structures subjected to thermal loading. To elucidate the creep effects on interfacial stresses, at last, creep damage FE analysis is carried out referring to the K–R damage creep law. Results indicated that both creep and creep-damage analysis will lead to interfacial stress redistribution and thus reduce the shear stress and peeling stress at interface. Creep damage analysis yields the lowest stresses among the linear elastic and elastic creep analysis results. The maximum damage is produced at the edge of the interface where the failure often occurs and is proportional to the modulus ratio of substrate to film. On the other hand, the damage distribution along the interface is very similar to the trend of peeling stress distribution. Compared to the FE results, the existing closed solutions from Mirman et al. [B.A. Mirman, S. Knecht, IEEE Comp. Pack. Manufact. Technol. 13 (1990) 914] and Zhang et al. [X.C. Zhang, B.S. Xu, H.D.Wang, Y.X.Wu, J. Appl. Phys. 100 (2006) 113524]can only give an accurate prediction of the interfacial shear stress but give a rough estimation to the interfacial peeling stress. As far as effects of creep are concerned, the existing closed form solutions based on elastic analysis are inapplicable anymore.