86 T. Kosta and J. O. Mares Jr. Fig. 11.3 Experimental setup illustrating positioning of the sample, loading direction, lighting, and camera Fig. 11.4 Image captured during tensile loading of sample (a) before and (b) after delamination event was conducted to identify a set of appropriate parameter specifications. The parameters of primary interest included step size, noise level, and the interpolation settings. It was determined that the following set of parameters allowed for the greatest performance of the calculation of the strain field: a subset value of 39, noise level of 2.00, step size of 4, Gaussian subset weights, an optimized 8-tap interpolation, a criterion of squared differences, and no low-pass filter, with an incremental correlation and exhaustive search. The DIC software was successful at determining the spatially resolved strain maps as a function of time up to the point of, and shortly after, delamination between the particle and glass inclusion. A series of processed strain results obtained through this analysis is shown in Fig. 11.5. Due to the known capture rate of the camera and the data acquisition rate of the load frame, a common time was established to connect the DIC information to the global load conditions imparted upon the sample. Therefore, the global tensile load and extension of the sample is known at the point of debonding. Additionally, this information coupled with the calculated local strain information near the embedded glass particle and the spatial information of the resulting void structure provide a rich data set of the debonding process. This information can then be used to calibrate and validate modeling and simulation efforts to capture the process of a debonding event. Additionally, the stress state of the binder material can be determined through the known stress-strain relationship of the material.
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