Strain measurement of particle-reinforced composites at the microscale: An approach towards concurrent characterization of strain and microstructure

The mechanical behavior of particle-reinforced composites is largely determined by the interaction between the reinforcing particles and matrix. Although conventional digital image correlation (DIC) allows accurate measurements of strain at microscale, it usually requires preparation of synthetic pattern on the sample surface, which would affect the observation of reinforcing particles. An approach is proposed in this work that relies solely on the reinforcing particles as DIC pattern, thereby enabling concurrent microstructure observation and strain measurement. The main idea of the approach is that only the regions of high gray level contrast shall be correlated. The approach has been tested against the benchmarks taken from the images of rigidly translated and rotated sample, and the influence of image magnification has been discussed in detail. The approach has also been applied to actual tensile test and yielded qualitatively similar results as the conventional DIC approach.