Low density cloth preform and methods of manufacturing same
The disclosure describes a low density cloth preform, and apparatuses and methods for manufacturing the same. The low density cloth preform has a lower density than other preforms manufactured using prior apparatuses and methods, thereby rendering the low density cloth preform more amenable to the addition of matrix carbon thereto through the use of less expensive carbon sources and more rapid processes for adding matrix carbon. The apparatuses and methods for manufacturing the low density cloth preform comprise preform needling machines configured and preform needling processes operable to provide a more uniform and lesser needling depth with the result being a preform having a lower density. The preform needling machines utilize foam bases formed from resilient materials having appropriate rebound rates, arrangements of barbed needles in one or more groups and needling stages, and positioning of the barbed needles to minimize deflection of the foam bases and preform material.
1. A method for manufacturing a low density cloth preform, the method comprising the steps of:
receiving cloth preform material atop a foam base that is resilient and has a density and thickness, wherein the cloth preform material has a top surface;
rotating the cloth preform material at a rotational speed along an arcuate path about a vertical axis;
needling the cloth preform material with a plurality of barbed needles depending from a needling board while the cloth preform is present beneath the needling board, wherein prior to needling the top surface has a first elevation and during needling the top surface is deflected downward to an elevation lower than the first elevation; and
after needling, determining a second elevation of the top surface of the cloth preform material at a location along the arcuate path that is distant from the plurality of barbed needles by an arc length;
wherein the foam density, foam base thickness, rotational speed, and arc length are selected to cause the top surface of the cloth preform material to rebound in an upward direction after needling such that the second elevation substantially equals the first elevation by the time the cloth preform material rotates through the arc length.
2. The method of claim 1 , wherein the rotational speed is in the range of 0.75 revolutions per minute to 6.0 revolutions per minute.
3. The method of claim 1 , wherein the foam base has a thickness in the range of 0.75 inches to 3.0 inches.
4. The method of claim 1 , wherein the foam base has a density in the range of 2.5 pounds per cubic foot to 4.5 pounds per cubic foot.
5. The method of claim 1 , wherein the needling board comprises a first portion and a second portion nearest the location where the second elevation of the top surface of the cloth preform material is determined, and wherein all of the barbed needles of the plurality of barbed needles depend from the first portion of the needling board and none of the barbed needles of the plurality of barbed needles depend from the second portion of the needling board.
6. The method of claim 1 , wherein the needling board comprises a first portion and a second portion nearest the location where the second elevation of the top surface of the cloth preform material is determined, and wherein the plurality of barbed needles includes a first plurality of barbed needles secured in the first portion of the needling board and a second plurality of barbed needles secured in the second portion of the needling board, and the first portion of the needling board is separated at a distance from the second portion of the needling board.