Preferential curing technique in compression molding of fiber reinforced composites

Abstract

A molding process that involves applying heat ( 17 ) to a mold billet ( 12 ) located in a mold cavity ( 11 ) defined by steel inserts ( 15 ). A layer ( 19 ) of material having a low thermal conductivity of 1-2 BTU/hour/square foot/inch/F° at 450° F. is positioned contiguously to at least one of the inserts ( 15 ) so that a portion ( 13 ) of the mold billet ( 12 ) in the vicinity of the low thermal conductivity material layer ( 19 ) remains cooler than portions of the mold billet that are remote from the layer of material ( 19 ). Also, a mold apparatus comprising a mold cavity ( 11 ) defined by steel inserts ( 1 5 ) wherein each of the inserts ( 15 ) rests on a bed ( 19 ) of low thermal conductivity material which is comprised of 38-48 weight-% calcium carbonate, 27-38 weight-% polymerized unsaturated polyester resin, and 20-30 weight-% fiberglass. The mold billet ( 12 ) may be configured in the shape of an aircraft landing system brake disc preform ( 33 ).

1 - 13 . (canceled) 
     
     
         14 . A system comprising:
 an annular mold cavity including an inner diameter and an outer diameter, wherein a portion of the annular mold cavity is defined by a steel insert;   a heat source configured to heat a mold billet in the mold cavity, wherein the annular mold cavity is configured to receive the mold billet in the form of an annular carbon fiber-reinforced phenolic matrix composite disc; and   a layer of calcium carbonate-filled fiberglass-reinforced plastic material that has a thermal conductivity of 1-2 BTU/hour/square foot/inch/° F. at 450 ° F. positioned between the steel insert and the heat source, wherein the layer of calcium carbonate-filled fiberglass-reinforced plastic material is positioned relative to the mold cavity such that heat transfer from the heat source into the mold billet through a bottom surface of the mold cavity is greater than heat transfer from the heat source into the steel insert.   
     
     
         15 . The system of  claim 14 , further comprising the annular carbon fiber-reinforced phenolic matrix composite disc. 
     
     
         16 . The system of  claim 15 , wherein the annular carbon fiber-reinforced phenolic matrix composite disc comprises an aircraft landing system brake disc. 
     
     
         17 . The system of  claim 14 , wherein the layer of calcium carbonate-filled fiberglass-reinforced plastic material is configured such that portions of the mold billet adjacent at least one of the inner diameter or the outer diameter of the annular mold cavity are prevented from being subjected to accelerated heating and curing relative to portions of the mold billet adjacent to the bottom surface of the mold cavity to permit volatile materials generated within the annular carbon fiber-reinforced phenolic matrix composite disc by application of heat and pressure thereto to escape through portions of the mold billet adjacent the at least one of the inner diameter or the outer diameter of the annular disc defined during a breath cycle of the process. 
     
     
         18 . The system of  claim 14 , wherein the apparatus is configured such that the temperature of the steel insert, when the heat source heats the mold billet in the mold cavity, is approximately 5° C. lower than the temperature that it would reach in an otherwise identical process in which the layer of calcium carbonate-filled fiberglass-reinforced plastic material was not located between the heat source and the steel insert. 
     
     
         19 . The system of  claim 14 , wherein the layer of calcium carbonate-filled fiberglass-reinforced plastic material comprises a board comprised of 38-48 weight percent calcium carbonate, 27-38 weight percent polymerized unsaturated polyester resin, and 20-30 weight percent fiberglass. 
     
     
         20 . The system of  claim 19 , wherein the board defines a thickness of approximately 0.5 inches. 
     
     
         21 . The system of  claim 14 , wherein the mold cavity is configured in the shape of an aircraft landing system brake disc, wherein the layer of calcium carbonate-filled fiberglass-reinforced plastic material comprises an annular board 0.5 inches in thickness having a width approximately equal to the width of the annular brake disc preform.