Fragmentation as an aggregation process

Abstract

When severely impacted, a cohesive object deforms and eventually breaks into fragments. Cohesion forces keeping the material together and momentum driving the fragmentation couple through a complicated process involving crack propagation on a deforming substrate, so that a comprehensive scenario for the build-up of the full fragment size distribution of broken objects is still lacking. We use necklaces of cohesive particles (magnetized spheres) as an experimental model of a one-dimensional material, which we expand radially in an impulsive way. Exploring in real time the intermediate state where the particles are no longer in contact, but still in interaction as they separate, we demonstrate that the final fragments result from the self-assembly of individual particles and that their size distribution converges to a stable self-similar distribution whose parameters, interpreted from first principles, depend on the expansion and cohesion strengths.