Particulate field distributions in centrifugally cast composites

A method for casting an object in a mold from a composite material, comprising the steps of:

• (a) at least partially filling the mold with a mixture of a first material that is a liquid and a second material that is a solid, one of said first material and said second material having a greater density than the other;
• (b) rotating the mold about an axis of rotation for a time interval, said rotating producing a centrifugal force that tends to cause said one of the first material and the second material to move away from said axis of rotation, creating a greater concentration of said one of the first material and the second material nearer a periphery of the mold than adjacent to the axis of rotation in an extended gradient distribution that produces desired material enhancements in a predetermined portion of the casting without an abrupt transition in the concentration of said one of the first material and the second material;
• and
• (c) causing the mixture to solidify into a composite material having a shape defined by the mold so that the second material remains in the extended gradient non-homogeneous distribution pattern in the composite comprising the casting.

A method for producing a composite material having a particulate reinforcement, said composite material having a relatively high mass compared to that of the particulate reinforcement, comprising the steps of:

• (a) in a mold, providing a mixture of a first material comprising particles and a second material comprising a liquid, said liquid having a greater density than said particles;
• (b) rotating the mold about an axis of rotation for a time interval, said rotating producing a centrifugal force that tends to cause the second material to move towards a periphery of the mold, creating a greater concentration of the second material nearer the periphery of the mold than adjacent to the axis of rotation and a greater concentration of the first material adjacent to said axis of rotation;
• (c) causing the mixture to solidify into a shape defined by the mold, said shape comprising the composite material having a non-homogeneous distribution of the first material and the second material;
• (d) extracting the shape from the mold;
• and
• (e) removing a portion of the shape disposed around the rotational axis, leaving a remainder of the composite material, said portion having a greater concentration of the first material than the remainder and having a substantially greater tensile strength than said remainder.

A method for producing a composite material having a particulate reinforcement, said composite material having a relatively low mass compared to that of the particulate reinforcement, comprising the steps of:

• (a) in a mold, providing a mixture of a first material comprising a liquid and a second material comprising particles, said particles having a greater density than said liquid;
• (b) rotating the mold about an axis of rotation for a time interval, said rotating producing a centrifugal force that tends to cause the second material to move towards a periphery of the mold, creating a greater concentration of the second material nearer the periphery of the mold than adjacent to the axis of rotation;
• (c) causing the mixture to solidify into a shape defined by the mold, said shape comprising the composite material having a non-homogeneous distribution of the first material and the second material;
• (d) extracting the shape from the mold;
• and
• (e) removing a portion of the shape disposed around the rotational axis, leaving a remainder of the composite material, said remainder having a greater concentration of the second material than the portion removed and having a substantially greater tensile strength than said portion.

A method for producing a composite material having a relatively higher particulate reinforcement than that of an initial composite material, comprising the steps of:

• (a) in a mold, providing the initial composite material in a liquid state;
• (b) rotating the mold about an axis of rotation for a time interval, said rotating producing a centrifugal force that tends to cause the particulate reinforcement to become more concentrated adjacent a periphery of the mold than about the axis of rotation;
• (c) causing the composite material to solidify into a shape defined by the mold;
• (d) extracting the shape from the mold;
• and
• (e) removing a portion of the shape adjacent the axis of rotation, leaving a remainder that comprises the composite material having the higher particulate reinforcement than the initial composite material.

A method for increasing a concentration of a reinforcing component relative to a base component in a composite material, where said composite material initially has a first concentration of the reinforcing component, said reinforcing component having a substantially greater density than said base component, comprising the steps of:

• (a) causing the composite material to be in a fluid state within a container;
• (b) rotating the container about an axis of rotation for a time interval, said step of rotating developing a centrifugal force tending to move the reinforcing component away from said axis of rotation generally toward a periphery of the container, creating a region adjacent to the axis of rotation in which the relative concentration of the reinforcing component is much less than said first concentration, and also creating a region nearer the periphery of the container in which the concentration of the reinforcing component is much greater than said first concentration, said region of greater concentration of the reinforcing component exhibiting a substantially homogeneous distribution of the reinforcing component at a second concentration;
• (d) stopping the rotation of the container and solidifying said composite material;
• and
• (e) removing and discarding said region adjacent to the axis of rotation, so that a remainder of the composite exhibits the second concentration of said reinforcing component.