The evolution of macroscopic material closed filaments in a time-periodic chaotic 2D flow is simulated for cases with large, small, and very small islands of regular motion using an algorithm that preserves spatial continuity. The length of the stretched filament increases much faster than predicted by the Liapunov exponent. In chaotic regions, the filament asymptotically evolves into a self-similar structure with permanent spatial nonuniformities in density. Filament densities and local length scales corresponding to different times are described by families of frequency distributions with invariant shape that can be collapsed onto a single curve by means of a simple scaling.