Composite spar removable mandrel

Abstract

A mandrel for use in manufacturing a spar having a spar cavity is provided including a first component, a second component, and a center component. The first component is configured to define at least an interior first surface of the spar cavity. The second component is configured to define at least an interior second surface of the spar cavity and form a space between the first and second components. The second component has a second side arranged in contact with a first side of the first component. The center component is arranged within the space to separate the first and second components and to engage at least a portion of each of the first and second components to retain the first and second components in a desired position.

What is claimed is: 
     
         1 . A mandrel for use in manufacturing a spar having a spar cavity, the mandrel comprising:
 a first component configured to define at least an interior first surface of the spar cavity;   a second component configured to define at least an interior second surface of the spar cavity and forming a space between the first and second components, the second component having a second side arranged in contact with a first side of the first component; and   a center component arranged within the space to separate the first and second components and to engage at least a portion of each of the first and second components to retain the first and second components in a desired position.   
     
     
         2 . The mandrel according to  claim 1 , wherein at least one of the first component, second component, and center component is formed via an additive manufacturing process. 
     
     
         3 . The mandrel according to either  claim 1  or  2 , wherein at least one of the first component, second component, and center component is formed from a thermal plastic material. 
     
     
         4 . The mandrel according to any of the preceding claims, wherein the first component, second component, and center component are removably coupled to one another using keyway grooves and/or magnets. 
     
     
         5 . The mandrel according to any of  claims 1 - 4 , wherein an exterior of the mandrel is shrink wrapped such that the mandrel has a shape complementary to an inner mold line of the spar. 
     
     
         6 . The mandrel according to any of  claims 1 - 5 , wherein a cross-section of the mandrel varies over a length of the mandrel. 
     
     
         7 . The mandrel according to  claims 1 - 6 , wherein at least one of the first component, second component, and center component is formed from a plurality of connected segments. 
     
     
         8 . A method of constructing a mandrel including a plurality of components, the mandrel being generally complementary to a spar cavity of a spar, comprising:
 connecting a first component and a second component to form a central space there between; and   inserting a center component within the central space such that the center component retains the first component and second component in a desired position forming an outer surface of the mandrel which corresponds to an inner surface of the spar cavity.   
     
     
         9 . The method according to  claim 8 , wherein the connecting the first component and second component comprises magnetically coupling the first and second components. 
     
     
         10 . The method according to either of  claims 8 , wherein connecting the first component and second component comprises interlocking the first and second components using complementary keyway grooves. 
     
     
         11 . The method according to any of the preceding claims, wherein inserting the center component further comprises interlocking a portion of the center component with the first and second components. 
     
     
         12 . The method according to any of  claims 8 - 11 , wherein connecting the first and second components and inserting the central component forms a first segment of the mandrel, the method further comprising:
 forming a second segment by connecting a third component and a fourth component to form another central space there between;   inserting another center component within the another central space such that the another center component retains the third component and fourth component in a desired position forming another outer surface of the mandrel which corresponds to another inner surface of the spar cavity; and   connecting the formed first segment and second segment of the mandrel.   
     
     
         13 . The method according to any of  claims 8 - 12 , further comprising forming at least one of the first component, second component, and center component using a plastic material via an additive manufacturing method. 
     
     
         14 . The method according to any of  claims 8 - 13 , further comprising applying a layer of shrink wrap about the outer surface of the mandrel. 
     
     
         15 . The method according to any of  claims 8 - 14 , further comprising applying a bagging material about the shrink wrap, the bagging material being configured to apply a pressure to the inner surface of the spar cavity. 
     
     
         16 . A method of constructing a spar having a spar cavity for a rotor blade, comprising:
 assembling a mandrel, the mandrel including:
 a first component configured to define at least an interior first surface of the spar cavity; 
 a second component configured to define at least an interior second surface of the spar cavity and forming a space between the first and second components, the second component having a second side arranged in contact with a first side of the first component; 
 a center component arranged within the space to separate the first and second components and to engage at least a portion of each of the first and second components to retain the first and second components in a desired position; 
 a layer of shrink wrap arranged about an exterior of the first and second component; and 
 a layer of bagging material arranged over the layer of shrink wrap; 
   layering multiple plies of material about at least a portion of an exterior of the mandrel;   installing the mandrel in a final curing mold;   applying a pressure to at least one of the interior first surface and the interior second surface of the spar;   removing the mandrel from a center of layered plies by individually removing the first, second, and center components; and   curing the layers of plies.   
     
     
         17 . The method according to  claim 16 , wherein removing the mandrel includes the steps of:
 removing the center component of the mandrel; and   removing each of the first component and second component individually.   
     
     
         18 . The method according to either of  claims 16  or  17 , wherein the layered plies have varying fiber orientations relative to the mandrel. 
     
     
         19 . The method according to any of the preceding claims, wherein the layered plies are cured using a vacuum.