Mechanical characterization at nanometric scale for heterogeneous graphite–salt phase change materials with a statistical approach

A statistical indentation analysis of a series of phase change graphite–salt composite materials for latent heat thermal energy storage applications was investigated using instrumented indentation technique with the aim of isolate the mechanical influence of each phase. This method employs the instrumented indentation technique to extract the in situ hardness and Young's modulus properties of individual components without the need to observe the residual imprints for heterogeneous materials. This approach relies on a large array of imprints (around 1000 indentations performed at 200 nm of indentation depth) and the statistical analysis of the resulting data. A statistical study by a Cumulative Distribution Function fit and Gaussian simulated distributions showed that the mechanical properties for each compound can be isolated when the indentation depth is much lower than the size of the secondary phases.