Patent ID: 8075827

Claim:
A method of making a variable density preform, comprising: providing a slurry comprising at least one reinforcement particle component, and at least one liquid component; providing a die cavity having at least one inlet opening or orifice and at least one exit opening or orifice defining at least one die cavity flow path therebetween directed toward the exit opening or orifice, the at least one exit opening or orifice 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 flow path of the die cavity to provide for a decreasing pressure gradient along the flow path direction, wherein during said introducing the at least one liquid component exits through the at least one exit orifice while the at least one reinforcement particle component is impeded or blocked from exiting through the at least one exit orifice, to provide for a variable-density preform having a variable density of the at least one particle component, the particle density increasing in a gradient in the at least one flow path direction.