High Strain Gradient Measurements in Notched Laminated Composite Panels by Digital Image Correlation

摘要

Digital Image Correlation (DIC) was used to measure the in-plane strains induced in laminated graphite-epoxy panels containing a central circular hole and loaded in tension. Panels with three different stacking sequences and two hole diameters (0.25 and 0.375 in.) were tested. Measured strains were compared with predictions based on the Savin solution. Reasonable agreement between predicted and measured whole-field strain patterns was achieved. However, it was found that filtering of the DIC strain data, which is performed routinely to reduce noise, can mask the high strain gradients that actually exist near the edge of the hole. It will be shown that stacking sequence of the composite laminate as well as the hole size in addition to the correlation variables such as subset, step, and filter size have direct effect on strain values measured by DIC. In this study, strain measurements from the predictions were used to tune the correlation variables.