Composite materials are often made by infiltration

that is

by injecting a liquid matrix between packed solid fibers or particles. We give here direct proof that molten copper

slowly infiltrated into a broad spectrum of preforms

displays in initial phases of the process universal scaling and fractal geometric features that are characteristic signatures of percolation-dominated flow. Implications are that the microstructure of infiltrated composite materials can develop over length scales that far exceed the average preform pore size

and that network models are pertinent in the simulation of composite infiltration processing.