Mass distribution and geometry of a crumpled ball

We use X-ray CT scanning to resolve in 3-dimensions the conformation of aluminum sheets with diameters L=7cm to 10cm and thickness T=25 microns, crumpled into spheres with diameters D=1.2cm to 1.5cm. The linear resolution of the reconstructed images is less than 6 microns/voxel. Measurements were made on spheres with average volume fractions, $\phi $ ranging from 0.06 to 0.11. The mass is not homogeneously distributed in the volume: when averaged over several samples, the volume fraction $\phi $(L/D) is found to increase with radius so that the sphere is densest at its surface. The radial dependence of volume fraction appears to be independent of average volume fraction and diameter, D. We also report preliminary measurements of the distribution of curvature in the sphere.