Method of seamlessly bagging composite parts

Abstract

A method and system for manufacturing composite parts free of wrinkles and mark-offs from bagging compression. The method can include placing composite material around a rigid mandrel and sealing opposing end of an elastomeric hollow membrane within a rigid external vessel. Then the method can include inflating the hollow membrane from a natural state to an inflated state. In the natural state, the hollow membrane can have a cross-section smaller than the cross section of the rigid mandrel with the composite material thereon. The method can then include inserting the rigid mandrel and the composite material into the membrane while it is in the inflated state, followed by releasing the membrane from the inflated state to naturally contract toward its natural state. Then the method can include heating the composite material to a cure temperature while the composite material is compressed by the membrane.

1 . A composite curing system comprising:
 a rigid mandrel having a maximum cross-sectional size, wherein the rigid mandrel is configured for placement of composite material thereon;   a rigid external vessel having a minimum cross-sectional size that is larger than the maximum cross-sectional size of the rigid mandrel such that the rigid mandrel fits within the rigid external vessel; and   a hollow membrane made of elastomeric material and having two opposing ends at which two opposing openings are formed, wherein the hollow membrane is located within and sealed to the rigid external vessel at or proximate to the two opposing ends of the hollow membrane, wherein the hollow membrane is axially stretchable from a first configuration in a natural state to a second configuration achieved by pulling opposing ends of the hollow membrane in opposite directions axially, wherein a cross-section of the hollow membrane in the natural state is larger than a cross-section of the hollow membrane in the second configuration and the cross-section of the hollow membrane in the second configuration corresponds to the rigid mandrel and with the composite material thereon.   
     
     
         2 . The composite curing system of  claim 1 , further comprising two plugs insertable into the rigid external vessel and the two opposing ends of the hollow membrane. 
     
     
         3 . The composite curing system of  claim 2 , wherein the two plugs are tapered toward and abut against or attach to the rigid mandrel, centering and holding the rigid mandrel within the rigid external vessel. 
     
     
         4 . The composite curing system of  claim 1 , wherein the rigid external vessel is an autoclave having at least one vacuum port and configured to provide at least one of heat and pressure during curing of the composite material on the rigid mandrel. 
     
     
         5 . The composite curing system of  claim 1 , further comprising the composite material, wherein when the hollow membrane is axially stretched to the second configuration, the hollow membrane compresses the composite material between the hollow membrane and the rigid mandrel. 
     
     
         6 . The composite curing system of  claim 5 , wherein the composite material is wrapped around the rigid mandrel. 
     
     
         7 . The composite curing system of  claim 1 , wherein the rigid mandrel is made of an electrically conductive material. 
     
     
         8 . The composite curing system of  claim 1 , wherein the hollow membrane is secured in the second configuration. 
     
     
         9 . The composite curing system of  claim 1 , further comprising mechanical tooling configured for clamping onto the two opposing ends of the hollow membrane and pulling from either or both of the two opposing ends in an axial direction. 
     
     
         10 . A composite curing system comprising:
 composite material;   a rigid mandrel having a maximum cross-sectional size, wherein the composite material is placed on the rigid mandrel;   a rigid external vessel having a minimum cross-sectional size that is larger than the maximum cross-sectional size of the rigid mandrel with the composite material thereon such that the rigid mandrel and the composite material fit within the rigid external vessel; and   a hollow membrane made of elastomeric material and having two opposing ends at which two opposing openings are formed, wherein the hollow membrane is located within and sealed to the rigid external vessel at or proximate to the two opposing ends of the hollow membrane, wherein the hollow membrane is axially stretchable from a first configuration in a natural state to a second configuration achieved by pulling opposing ends of the hollow membrane in opposite directions axially, wherein a cross-section of the hollow membrane in the natural state is larger than a cross-section of the hollow membrane in the second configuration and the cross-section of the hollow membrane in the second configuration is small enough to cause the hollow membrane to provide pressure against the composite material in a direction toward the rigid mandrel.   
     
     
         11 . The composite curing system of  claim 10 , further comprising two plugs insertable into the rigid external vessel and the two opposing ends of the hollow membrane. 
     
     
         12 . The composite curing system of  claim 11 , wherein the two plugs are tapered toward and abut against or attach to the rigid mandrel, centering and holding the rigid mandrel within the rigid external vessel. 
     
     
         13 . The composite curing system of  claim 10 , wherein the rigid external vessel is an oven or an autoclave configured to provide heat for curing of the composite material on the rigid mandrel. 
     
     
         14 . The composite curing system of  claim 10 , wherein the rigid mandrel is made of a conductive material. 
     
     
         15 . The composite curing system of  claim 14 , further comprising a heat source providing joule heating to the conductive material of the rigid mandrel for curing of the composite material. 
     
     
         16 . The composite curing system of  claim 10 , wherein the hollow membrane is secured in the second configuration. 
     
     
         17 . The composite curing system of  claim 10 , further comprising mechanical tooling configured for clamping onto the two opposing ends of the hollow membrane and pulling from either or both of the two opposing ends in an axial direction. 
     
     
         18 . The composite curing system of  claim 10 , wherein the composite material includes a composite skin co-cured or fused to at least one composite substructure, wherein the rigid mandrel includes divots or indents sized and shaped to receive and properly position the at least one composite substructure relative to the composite skin. 
     
     
         19 . A composite curing system comprising:
 composite material;   a rigid mandrel having a maximum cross-sectional size, wherein the composite material is placed on the rigid mandrel;   a hollow membrane made of elastomeric material and having two opposing ends, wherein the hollow membrane is positioned around the composite material and the rigid mandrel, wherein the hollow membrane is axially stretchable from a first configuration in a natural state to a second configuration achieved by pulling opposing ends of the hollow membrane in opposite directions axially, wherein a cross-section of the hollow membrane in the natural state is larger than a cross-section of the composite material and the rigid mandrel and also larger than a cross-section of the hollow membrane in the second configuration, wherein the cross-section of the hollow membrane in the second configuration is small enough to cause the hollow membrane to provide pressure against the composite material in a direction toward the rigid mandrel;   mechanical tooling clamped onto the two opposing ends of the hollow membrane and actuatable to pull from either or both of the two opposing ends in an axial direction into the second configuration, thereby compressing the composite material against the rigid mandrel with the hollow membrane; and   a heat source proving sufficient heat for curing the composite material.   
     
     
         20 . The composite curing system of  claim 19 , wherein the heat source is:
 a rigid external vessel having a minimum cross-sectional size that is larger than the maximum cross-sectional size of the rigid mandrel with the composite material thereon, with the rigid mandrel and the composite material placed within the rigid external vessel, wherein the rigid external vessel is an autoclave, or   the rigid mandrel, wherein the rigid mandrel is made of a conductive material and is configured to connect to a source of electricity, thereby providing joule heat to the conductive material of the rigid mandrel.