Reconstructing the fractal dimension of granular aggregates from light intensity spectra.

There has been growing interest in using the fractal dimension to study the hierarchical structures of soft materials after realising that fractality is an important property of natural and engineered materials. This work presents a method to quantify the internal architecture and the space-filling capacity of granular fractal aggregates by reconstructing the three-dimensional capacity dimension from their two-dimensional optical projections. Use is made of the light intensity of the two-dimensional aggregate images to describe the aggregate surface asperities (quantified by the perimeter-based fractal dimension) and the internal architecture (quantified by the capacity dimension) within a mathematical framework. This method was tested on control aggregates of diffusion-limited (DLA), cluster-cluster (CCA) and self-correlated (SCA) types, stereolithographically-fabricated aggregates, and experimentally-acquired natural sedimentary aggregates. Statistics of the reconstructed capacity dimension featured correlation coefficients R ≥ 98%, residuals NRMSE ≤ 10% and percent errors PE ≤ 4% as compared to controls, and improved earlier approaches by up to 50%.