| In this paper, the theoretical analysis is presented to relate the film crack patterns, developed during tensile uniaxial loading of brittle film on ductile substrate, to interface adhesion strength. If the shear stress, developed at the interface due to different deformation properties of two materials with uniaxial loading, exceeds the critical shear strength τ_d, interfacial adhesion is lost by shear breakage of interface bonding. This stress analysis describes the biaxial stress state in near-interface in terms of external strain and crack spacing. With loading the number of parallel cracks increases until the interface separation occurs, and finally no additive film cracks generate. Therefore, the interface shear strength can be estimated from the external strain ε_s and crack spacing λ_s at the onset of saturation through the proposed analysis model. The interface adhesion evaluation of DLC/Al shows the increase by a factor of 1.6 in a 30min Ar-plasma etching compared to no etching. It was found that ε_s increases, conversely λ_s decreases with Ar-plasma etching time, which means that interface adhesion increases. Such strong dependencies of ε_s and λ_s on interface adhesion indicate that the experimentally measured parameters, ε_s and λ_s can be used as a rough estimate of interfacial adhesion in a given system. |
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