Patent Publication Number: US-2020282669-A1

Title: Caul plate with feature for separating from composite part

Description:
FIELD 
     The disclosure relates to the field of composite parts, and in particular, to caul plates for composite parts. 
     BACKGROUND 
     Aircraft parts, such as wing components, often comprise composite parts made by a resin infusion process in which a stack of porous material (known as a preform) is filled with a liquid resin. After infusion, the resin matrix is cured to solidify the combined material into a unified rigid composite. The result is a cost-effective way of manufacturing structural materials that exhibit enhanced physical characteristics (e.g., strong, lightweight, resistive to harsh environments, etc.) useful for high-performance applications such as aerospace. 
     Composite fabrication systems often use caul plates during fabrication to shape the preform and provide a smooth, aerodynamic surface on the finished part. However, caul plates are difficult to separate from the finished part without damaging the part. Caul plates are typically flat and featureless, and often get resin build up around its edge from the fabrication process. Current techniques for removing the caul plate thus include prying, lifting, twisting, hammering, and pulling with fingertips. Due to the force needed to dislodge the caul plate from the composite part, these techniques pose safety and ergonomic issues and create a risk of delaminating or causing other types of damage to the part. 
     SUMMARY 
     Embodiments described herein provide a caul plate having an integrated feature for removing the caul plate from a composite part. The feature may comprise a groove, hole, or member configured to receive a lateral mechanical force for release and removal of the caul plate from a composite part, such as a stringer of an aircraft. For instance, a groove in the top surface of the caul plate may enable a tool head to apply sufficient lateral force for dislodging the caul plate in a sliding motion without rotating the caul plate upwards during removal. The feature therefore provides a technical benefit in enabling the caul plate to slide off the composite part without causing delamination or damage to the composite part. 
     One embodiment is an apparatus including a caul plate for forming a composite part. The caul plate includes a body that includes a lower surface which faces the composite part, and an upper surface that is opposite to the lower surface. The caul plate also includes a groove in the upper surface to accept a tool to slide the caul plate laterally from the composite part. 
     One embodiment is a method of using a caul plate to fabricate a composite part. The method includes machining a groove into an upper surface of the caul plate sized to receive a head of a tool, positioning a lower surface of the caul plate on top of a preform, and curing the preform into the composite part. The method also includes inserting the tool into the groove in the upper surface of the caul plate, and removing the caul plate from the composite part by actuating the tool laterally to slide the caul plate off the composite part. 
     Another embodiment is an apparatus including a caul plate for a composite part. The caul plate includes a body that includes a lower surface which faces the composite part, and an upper surface that is opposite to the lower surface, a structural member protruding from the upper surface, and a hole in the structural member to receive a tool to slide the caul plate laterally from the composite part. 
     Other illustrative embodiments (e.g., methods and computer-readable media relating to the foregoing embodiments) may be described below. The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the present disclosure are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings. 
         FIG. 1  is a perspective exploded view of a composite fabrication system in an illustrative embodiment. 
         FIG. 2  is a perspective view of a caul plate in an illustrative embodiment 
         FIG. 3  is a perspective view of a caul plate coupled with a tool in an illustrative embodiment. 
         FIG. 4  is a perspective view of a caul plate in another illustrative embodiment. 
         FIG. 5  is a block diagram of a composite fabrication system in an illustrative embodiment. 
         FIG. 6  is a flowchart illustrating a method for fabricating a composite part via the use of a caul plate with an integral channel in an illustrative embodiment. 
     
    
    
     DESCRIPTION 
     The figures and the following description illustrate specific illustrative embodiments of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within the scope of the disclosure. Furthermore, any examples described herein are intended to aid in understanding the principles of the disclosure, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the disclosure is not limited to the specific embodiments or examples described below, but by the claims and their equivalents. 
       FIG. 1  is a perspective exploded view of a composite fabrication system  100  in an illustrative embodiment. The composite fabrication system  100  is configured to manufacture composite structures, such as a composite part of an aircraft. In doing so, the composite fabrication system  100  applies heat and pressure to infuse a resin into a preform  110 . After the resin is infused, the composite fabrication systems  100  cures the preform  110  into a hardened structure, creating the desired composite part. 
     Generally, the composite fabrication system  100  includes a tool mandrel  120 , a caul plate  130 , a vacuum bag  140 , and one or more pressure source(s)  150 . The preform  110  may include layers or plies of fibers, such as carbon fibers or fiberglass fibers, that are laid-up on the tool mandrel  120  and placed under the caul plate  130 . The tool mandrel  120  (sometimes referred to as a mandrel, mold tool, or forming tool) thus provides a base or surface which supports the preform  110 , and may form an Inner Mold Line (IML) for the preform  110 . The caul plate  130  defines a surface shape for the other side of the preform  110 , and may form an Outer Mold Line (OML) for the preform  110 . 
     The vacuum bag  140  seals to the tool mandrel  120  via sealing tape  162 , and encloses the preform  110  to form a chamber. The pressure source  150  (e.g., vacuum pump) creates a pressure differential in the chamber to draw resin into the preform  110 . After the preform  110  is sufficiently infused with the resin, the preform  110  may be cured with a curing temperature and pressure to form the composite part. 
     In current fabrication systems, the caul plate is difficult to remove from the composite part without causing damage to the composite part. Caul plates are typically flat and featureless, and therefore are removed from the part after cure by prying edges of the caul plate upward (e.g., in the z-direction) with fingertips. Unfortunately, this prying movement can cause edges of the caul plate to damage the composite part. 
     The composite fabrication system  100  and the caul plate  130  are therefore enhanced with a groove  160  in the caul plate  130  configured to receive a tool for sliding the caul plate  130  laterally from the composite part. The groove  160  is an indentation in an upper surface  132 , or bag side, of the caul plate  130  sized to accept the end or head of the tool. The upper surface  132  is opposite to a lower surface  134 , or part side, which faces the composite part. The groove  160  provides in a technical benefit in enabling the caul plate  130  to be gripped at the upper surface  132  for sliding the lower surface  134  of the caul plate  130  laterally off the composite part. Advantageously, the lower surface  134  of the caul plate  130  need not be rotated upward during removal. The groove  160  thus enables the caul plate  130  to be removed from the composite part without any risk of damage to the composite part. 
     Although the caul plate  130  is shown and described with respect to the composite fabrication system  100 , it will be appreciated that the caul plate  130  may be used in any number of alternative composite fabrication processes and resin distribution systems, including pre-preg processes where the fiber material is pre-impregnated with resin. In such instances, the resin may be at room temperature for a period of time before initiating the cure process. Additionally, the composite fabrication system  100  may include various consumable items not shown for ease of illustration, such as a peel ply, vacuum lines, breathers, etc., that may be removed and disposed after demold. Additional examples of components not shown include a resin distribution medium having a permeable membrane to enable the resin to flow and distribute into the preform  110 . It will also be appreciated that alternative types and configurations of components, such as additional vacuum bags and alternative types of sealing members, are also possible. 
       FIG. 2  is a perspective view of the caul plate  130  in an illustrative embodiment. As shown in  FIG. 2 , the caul plate  130  includes a body  230 , which is shaped to a desired contour for a composite part. For example, the body  230  may be shaped flat, curved along one dimension, curved along multiple dimensions (e.g., in a complex contour), etc. 
     The body  230  includes the lower surface  134  which faces the composite part, and the upper surface  132  that is opposite to the lower surface  134 . The lower surface  134  conforms against the preform and defines a contour for the preform (e.g., an Outer Mold Line (OML), while the upper surface  132  does not. The lower surface  134  may define an aerodynamically smooth surface contour (e.g., a contour having surface or finish that results in a roughness of less than two hundred and fifty μinch Ra). 
     The body  230  may be shaped from a rigid or flexible sheet of material having a thickness T. For instance, caul plate  130  may be made from any suitable rigid material, such as steel, aluminum, etc. In some embodiments, the caul plate  130  is made from an elastically deformable shape memory material, such as spring steel. In still further embodiments, caul plate  130  may itself be made of a composite material. 
     The groove  160  is an indentation in the upper surface  132  configured to mechanically couple the caul plate  130  with a tool for movement in a lateral direction (e.g., in the x-y plane). The groove  160  includes a floor  262  and walls  264  having a shape to receive a head of the tool. The floor  262  is sunken into the upper surface  132  for a distance less than the thickness T of the body  230 . The groove  160  therefore does not affect the lower surface  134  for shaping the composite part. The walls  264  transfer a lateral force of the tool to the caul plate  130 . As described in greater detail below, the groove  160 , including the floor  262  and the walls  264 , may have a shape that matches or corresponds with a shape of a head of a tool. 
       FIG. 3  is a perspective view of the caul plate  130  coupled with a tool  350  in an illustrative embodiment. The tool  350  includes a head  352  to fit in the groove  160 , and a shank  354  attached to the head  352  to pull the caul plate  130  laterally (e.g., in the x-y plane). The head  352  couples with the upper surface  132  of the caul plate  130  by inserting the head  352  perpendicularly (e.g., in the z-direction) into the groove  160 . The walls  264  (not shown in  FIG. 3 ) of the groove  160  may be sized with a height and shaped with a perimeter that corresponds with the head  352  to minimize potential for slippage when pulling the tool  350  in the groove  160 . 
     In some embodiments, the groove  160  is machined in the upper surface  132  at a location near an edge of the caul plate  130  for coupling and pulling the tool  350  from that edge. For example, the caul plate  130  may include a tapered edge  332  where the upper surface  132  declines toward the composite part toward its end. The groove  160  may be disposed partially or entirely in a region of the tapered edge  332 , as indicated by the dashed line in  FIG. 3 . Accordingly, the tool  350  couples and pulls from the tapered edge  332  of the upper surface  132 , as indicated by the arrow in  FIG. 3 . The tool  350  may be actuated by a manual force gripping the shank  354 . Alternatively, the shank  354  may couple with machinery for actuating the tool  350 . 
     It will be appreciated that the tool  350  and the groove  160  shown in  FIGS. 2-3  are examples for purposes of illustration and that alternative corresponding shapes and sizes thereof are possible. For example, the tool  350  may include a flange lock nut as the head  352  and a wrench as the shank  354 . Alternatively or additionally, the tool  350  may include a block, pin, or plug as the head  352 , and the groove  160  may comprise a corresponding hole indentation to fit the head  352 . In another example, the tool  350  may comprise a slide hammer. 
       FIG. 4  is a perspective view of a caul plate  400  in another illustrative embodiment. The caul plate  400  includes a body  430  having a lower surface  434  which faces the composite part, and an upper surface  432  that is opposite to the lower surface  434 . Additionally, as shown by this example, the body  430  is U-shaped or horse shoe shaped with side members  442 - 444  and a base member  446  forming the structure. The body  430  also includes a structural member  450  protruding from the upper surface  432 . In some embodiments, the structural member  450  includes a male pad-up/block feature attached to the upper surface  432  and configured to receive a lateral force for removing the caul plate  400  from the composite part. The structural member  450  may be integrated with the body  430  of the caul plate  400 . The structural member  450  may be formed of a rigid material and/or a same material as that of the body  430 . 
     Alternatively or additionally, as shown in  FIG. 4 , the structural member  450  may comprise a fin protruding vertically from the base member  446  to align with a stringer of an aircraft. The structural member  450 , or fin, may include a hole  460  through its structure to receive a tool  350  to slide the caul plate  400  laterally from the composite part. For example, the tool  350  may include a hook or pin to insert through the hole  460  to pull the caul plate  400  laterally. Thus, the caul plate  400  of this example, including a U-shaped body and fin, is configured to shape a composite part comprising a stringer of an aircraft. Like the caul plate  130  described in  FIGS. 1-4 , the caul plate  400  may be used in any number of composite fabrication processes and resin distribution systems, and may comprise alternative shapes, location/configuration of structural member, hole, etc. 
       FIG. 5  is a block diagram of a composite fabrication system  500  in an illustrative embodiment. As shown in  FIG. 5 , the caul plate  130  is disposed above the composite part  510 . The composite part  510  is formed by applying pressure with the pressure source  150  coupled with a port  542  in the vacuum bag  140  to draw resin from a resin reservoir  520  via a resin distribution medium  530 . During infusion/cure of the composite part  510 , the groove  160  in the caul plate  130  faces the vacuum bag  140  but is advantageously sunken in the upper surface  132  and therefore does not risk puncturing the vacuum bag  140 . 
     After infusion/cure of the composite part  510 , the vacuum bag  140  is removed and the tool  350  couples to the caul plate  130  with the head  352  situated in the groove  160 . The shank  354  is pushed or pulled with a lateral force  550  to slide the caul plate  130  off the composite part  510 . The caul plate  130  is thus removed from the composite part  510  without damaging the composite part  510 . Alternatively or additionally, the upper surface  132  may include a structural member and hole for coupling with the lateral force  550 . 
       FIG. 6  is a flowchart illustrating a method  600  for fabricating a composite part via the use of the caul plate  130  enhanced with the groove  160  in an illustrative embodiment. The steps of the method  600  are described with reference to the caul plate  130  of  FIGS. 1-4 , but those skilled in the art will appreciate that method  600  may be performed in other systems and alternative caul plates as desired. The steps of the flowcharts described herein are not all inclusive and may include other steps not shown. The steps described herein may also be performed in an alternative order. 
     In step  602 , the groove  160  is machined into the upper surface  132  of the caul plate  130  to receive the head  352  of the tool  350 . Alternatively, a structural member  450  may be attached to the upper surface  132  and/or a hole  460  machined through the structural member  450  to receive an end of the tool  350 . 
     In step  604 , the lower surface  134  of the caul plate  130  is positioned on top of the preform  110 . In step  606 , the preform  110  is cured to form the composite part  510 . In step  608 , the tool  350  is inserted into the groove  160  in the upper surface  132  of the caul plate  130 . Alternatively, the tool  350  is inserted through the hole  460  of the structural member  450 . In step  610 , the caul plate  130  is removed from the composite part  510  by actuating the tool  350  laterally to slide the caul plate  130  off the composite part  510 . 
     The method  600  provides a substantial benefit over prior techniques because caul plate  130  may be removed without lifting or prying, thereby avoiding damage to the composite part  510 . The use of the caul plate  130  improves labor in removing the caul plate  130 , and reduces overall cost of fabricating composite parts fabricated by reducing instances of scrapping parts due to damage imparted to the composite part during removal. 
     Although specific embodiments are described herein, the scope of the disclosure is not limited to those specific embodiments. The scope of the disclosure is defined by the following claims and any equivalents thereof.