Variable-density preforms

Provided are novel devices and methods for making a variable density preform, the methods comprising obtaining a slurry comprising a reinforcement particle component and a liquid component; obtaining a die cavity having at least one inlet opening and at least one exit opening defining at least one die cavity flow path therebetween directed toward the exit opening, the at least one exit opening suitably sized or configured to provide for exit of the at least one liquid component while impeding or blocking exit of the at least one reinforcement particle component; and introducing the slurry under pressure, and for a sufficient time period, through the inlet orifice into the die cavity flow path to provide for a decreasing pressure gradient along the flow path direction, to provide for a variable density of the at least one particle component, the particle density increasing in the at least one flow path direction.