Study on the effect of DIC deformation sensor on mechanical property of substrate

• The in-situ loading apparatus that can be combined with optical microscope has been developed.
• The mechanical properties of thin film and its composite structure were studied using MDIC.
• The influence of the thin film as DIC sensor on the measured value of substrate has been presented.
• The application range of thin film as DIC sensor has been concluded.

The thin epoxy film with micro-scale speckle pattern as a digital image correlation (DIC) deformation sensor has been fabricated or transferred on the surface of sample in the previous study. When the thickness of the film cannot be ignored, it may have an influence on the validity of measurement results. And thus, the influence of the thin epoxy film on mechanical properties of substrates should be investigated. In this study, the mechanical behavior of thin film itself and surface strain of composite structure of thin film and substrate were measured using micro digital image correlation (MDIC) method. And theoretical and simulative results were also analyzed. From the comparison analysis of theoretical, simulative and experimental results, it is concluded that when the ratios of Young’s modulus and thickness between the film and substrate are smaller than 13 and 0.5 respectively, the influence from the thin film can be ignored, and thin epoxy film as DIC sensor can be used to measure the deformation of substrate.