Patent Publication Number: US-2022212425-A1

Title: Autoclave system, bladder assembly, and associated method for forming a part

Description:
FIELD 
     This disclosure relates generally to forming composite parts, and more particularly to forming composite parts using an autoclave and a flexible bladder. 
     BACKGROUND 
     Autoclaves provide the heat and pressure necessary to cure composite parts made of curable materials, such as fiber-reinforced polymer materials including catalyzing resins (e.g., epoxies or polyesters). For certain parts with complex shapes, heating some portions of the part, such as internally situated portions, using an autoclave can be difficult due to one or more factors, such as the mass of the part, variable thickness of the part, or variable thickness of the tooling used to form the part. These factors can cause uneven heating of the part, which can lead to lagging temperature gradients in the part, uneven curing of the part, and prolonged cure cycle times. Accordingly, more uniformly and quickly distributing heat to the part during a curing operation in an autoclave is desired. 
     SUMMARY 
     The subject matter of the present application provides examples of an autoclave system, a bladder assembly, and a method of forming parts that overcome the above-discussed shortcomings of prior art techniques. Accordingly, the subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to shortcomings of conventional autoclave systems and methods of curing parts. 
     Disclosed herein is a bladder assembly for forming a part made of a fiber-reinforced polymeric material. The bladder assembly comprises a bladder comprising an interior having a hollow interior channel within the interior of the bladder. The bladder assembly also comprises an intake port fluidically coupled with the interior of the bladder and an exhaust port fluidically coupled with the interior of the bladder. The bladder assembly further comprises a pressure control device fluidically coupled with the exhaust port and configured to control a pressure drop across the interior of the bladder from the intake port to the exhaust port. The preceding subject matter of this paragraph characterizes example 1 of the present disclosure. 
     The bladder comprises a first end portion and a second end portion. The first end portion and the second end portion define opposite ends of the hollow interior channel. The bladder assembly further comprises an intake plug fixed to the first end portion of the bladder. The intake port passes through the intake plug. The bladder assembly further comprises an exhaust plug fixed to the second end portion of the bladder. The exhaust port passes through the exhaust plug. The preceding subject matter of this paragraph characterizes example 2 of the present disclosure, wherein example 2 also includes the subject matter according to example 1, above. 
     The intake port is fluidically coupled with the hollow interior channel of the interior of the bladder. The exhaust port is fluidically coupled with the hollow interior channel of the interior of the bladder. The preceding subject matter of this paragraph characterizes example 3 of the present disclosure, wherein example 3 also includes the subject matter according to example 2, above. 
     The bladder comprises at least an outer layer and an inner layer. The inner layer defines the hollow interior channel. The interior of the bladder has a fluid flow conduit interposed between the outer layer and the inner layer and extending from the first end portion of the bladder to the second end portion of the bladder. The intake port is fluidically coupled with the fluid flow conduit. The exhaust port is fluidically coupled with the fluid flow conduit. The preceding subject matter of this paragraph characterizes example 4 of the present disclosure, wherein example 4 also includes the subject matter according to any one of examples 2 or 3, above. 
     The interior of the bladder has a plurality of fluid flow conduits, spaced apart from each other. The intake port is fluidically coupled with the plurality of fluid flow conduits. The exhaust port is fluidically coupled with the plurality of fluid flow conduits. The preceding subject matter of this paragraph characterizes example 5 of the present disclosure, wherein example 5 also includes the subject matter according to example 4, above. 
     The bladder comprises a first end portion and a second end portion. The first end portion and the second end portion define opposite ends of the hollow interior channel. The bladder assembly further comprises an intake plug fixed to the first end portion of the bladder. The second end portion is closed. The intake port passes through the intake plug. The exhaust port passes through the intake plug. The preceding subject matter of this paragraph characterizes example 6 of the present disclosure, wherein example 6 also includes the subject matter according to example 1, above. 
     The bladder assembly further comprises a tube passing through the hollow interior channel from the first end portion of the bladder toward the second end portion of the bladder. The tube is fluidically coupled with the intake port at the first end portion of the bladder and open to the hollow interior channel proximate the second end portion of the bladder. The preceding subject matter of this paragraph characterizes example 7 of the present disclosure, wherein example 7 also includes the subject matter according to example 6, above. 
     The bladder comprises at least an outer layer and an inner layer. The inner layer defines the hollow interior channel. The interior of the bladder has a fluid flow conduit interposed between the outer layer and the inner layer and extending from the first end portion of the bladder to the second end portion of the bladder. The interior of the bladder has a second fluid flow conduit interposed between the outer layer and the inner layer and extending from the second end portion of the bladder to the first end portion of the bladder. The fluid flow conduit and the second fluid flow conduit are fluidically coupled at the second end portion of the bladder. The intake port is fluidically coupled with the fluid flow conduit. The exhaust port is fluidically coupled with the second fluid flow conduit. The preceding subject matter of this paragraph characterizes example 8 of the present disclosure, wherein example 8 also includes the subject matter according to example 6, above. 
     The fluid flow conduit extends along a first side of the bladder. The second fluid flow conduit extends along a second side of the bladder. The first side is opposite the second side. The preceding subject matter of this paragraph characterizes example 9 of the present disclosure, wherein example 9 also includes the subject matter according to example 8, above. 
     The interior of the bladder has a plurality of fluid flow conduits, spaced apart from each other. The interior of the bladder has a plurality of second fluid flow conduits, spaced apart from each other. Each one of the plurality of fluid flow conduits is fluidically coupled to a corresponding one of the plurality of second fluid flow conduits at the second end portion of the bladder. The intake port is fluidically coupled with the plurality of fluid flow conduits. The exhaust port is fluidically coupled with the plurality of second fluid flow conduits. The preceding subject matter of this paragraph characterizes example 10 of the present disclosure, wherein example 10 also includes the subject matter according to any one of examples 8 or 9, above. 
     The pressure control device is configured to passively control the pressure drop across the interior of the bladder. The preceding subject matter of this paragraph characterizes example 11 of the present disclosure, wherein example 11 also includes the subject matter according to any one of examples 1-10, above. 
     The pressure control device is configured to actively control the pressure drop across the interior of the bladder. The preceding subject matter of this paragraph characterizes example 12 of the present disclosure, wherein example 12 also includes the subject matter according to any one of examples 1-10, above. 
     The bladder assembly further comprises a pressure sensor fluidically coupled with the exhaust port between the exhaust port and the pressure control device. The pressure control device is operably coupled with the pressure sensor. The pressure control device is actuatable in response to feedback from the pressure sensor. The preceding subject matter of this paragraph characterizes example 13 of the present disclosure, wherein example 13 also includes the subject matter according to example 12, above. 
     The pressure control device is further configured to limit the pressure drop across the interior to less than or equal to a pressure-drop percentage threshold. The preceding subject matter of this paragraph characterizes example 14 of the present disclosure, wherein example 14 also includes the subject matter according to any one of examples 1-13, above. 
     The pressure-drop percentage threshold is 5%. The preceding subject matter of this paragraph characterizes example 15 of the present disclosure, wherein example 15 also includes the subject matter according to example 14, above. 
     Also disclosed herein is a system for forming a part made of fiber-reinforced polymeric material. The system comprises an autoclave vessel defining an interior cavity and containing a fluid. The system also comprises a bladder assembly at least partially in the interior cavity of the autoclave vessel. The bladder assembly comprises a bladder comprising an interior through which the fluid is flowable and having a hollow interior channel within the interior of the bladder, an intake port fluidically coupled with the interior of the bladder and open to the interior cavity of the autoclave vessel, an exhaust port fluidically coupled with the interior of the bladder and open to an exterior outside the interior cavity of the autoclave vessel, and a pressure control device fluidically coupled with the exhaust port and configured to control a pressure drop across the interior of the bladder from the intake port to the exhaust port by regulating a flow of the fluid from the interior of the bladder to the exterior. The preceding subject matter of this paragraph characterizes example 16 of the present disclosure. 
     The fluid within the interior cavity of the autoclave vessel has a first pressure, the fluid within interior of the bladder has a second pressure lower than the first pressure, and the fluid in the exterior has a third pressure lower than the second pressure. The preceding subject matter of this paragraph characterizes example 17 of the present disclosure, wherein example 17 also includes the subject matter according to example 16, above. 
     The system further comprises a controller operably coupled with the pressure control device. The controller is configured to compare the second pressure to the first pressure to provide a comparison between the second pressure and the first pressure. The controller is also configured to control actuation of the pressure control device in response to the comparison between the second pressure and the first pressure. The preceding subject matter of this paragraph characterizes example 18 of the present disclosure, wherein example 18 also includes the subject matter according to any one of examples 16 or 17, above. 
     The part comprises a stringer-skin assembly comprising a stringer and a skin. The bladder is interposed between the stringer and the skin. The preceding subject matter of this paragraph characterizes example 19 of the present disclosure, wherein example 19 also includes the subject matter according to any one of examples 16-18, above. 
     The system further comprises a first tool and a second tool between which the bladder is interposed. The first tool has a multi-part construction and comprises a first portion and a second portion. The first portion is adjoined to the second portion along a seam. The bladder is located at the seam such that the bladder is interposed between the seam and the second tool. The preceding subject matter of this paragraph characterizes example 20 of the present disclosure, wherein example 20 also includes the subject matter according to any one of examples 16-19, above. 
     Additionally disclosed herein is a method of forming a part made of fiber-reinforced polymeric material, the method comprises positioning a bladder, comprising an interior having a hollow interior channel, within an interior space of the part, and positioning the part and the bladder within an interior cavity of an autoclave vessel. The method also comprise, while in the interior cavity of the autoclave vessel, shaping the interior space of the part with the bladder. The method further comprises, while shaping the interior space of the part with the bladder, creating a pressure drop across the interior of the bladder, with a pressure control device fluidically coupled with the interior of the bladder and an exterior outside the autoclave vessel to induce flow of a fluid, contained within the autoclave vessel through the interior of the bladder and from the interior of the bladder to the exterior outside the autoclave vessel. The preceding subject matter of this paragraph characterizes example 21 of the present disclosure. 
     The fluid flows into the interior of the bladder from the first end portion of the bladder and flows out of the interior of the bladder to the exterior outside the autoclave vessel from the second end portion of the bladder. The preceding subject matter of this paragraph characterizes example 22 of the present disclosure, wherein example 22 also includes the subject matter according to example 21, above. 
     The fluid flows into the interior of the bladder from the first end portion of the bladder and flows out of the interior of the bladder to the exterior outside the autoclave vessel from the first end portion of the bladder. The preceding subject matter of this paragraph characterizes example 23 of the present disclosure, wherein example 23 also includes the subject matter according to example 21, above. 
     The fluid flows through the interior of the bladder in a first direction from the first end portion of the bladder to the second end portion of the bladder and in a second direction, opposite the first direction, from the second end portion of the bladder to the first end portion of the bladder. The preceding subject matter of this paragraph characterizes example 24 of the present disclosure, wherein example 24 also includes the subject matter according to example 23, above. 
     The fluid flows through the interior of the bladder between an inner layer of the bladder and an outer layer of the bladder. The preceding subject matter of this paragraph characterizes example 25 of the present disclosure, wherein example 25 also includes the subject matter according to any one of examples 21-24, above. 
     The method further comprises comparing the first pressure of the fluid within the autoclave vessel to the second pressure of the fluid within the interior of the bladder to provide a comparison between the first pressure and the second pressure. The method also comprises controlling actuation of the pressure control device, to control the pressure drop across the interior of the bladder, in response to the comparison between the first pressure and the second pressure. The preceding subject matter of this paragraph characterizes example 26 of the present disclosure, wherein example 26 also includes the subject matter according to any one of examples 21-25, above. 
     The described features, structures, advantages, and/or characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more examples, including embodiments and/or implementations. In the following description, numerous specific details are provided to impart a thorough understanding of examples of the subject matter of the present disclosure. One skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced without one or more of the specific features, details, components, materials, and/or methods of a particular example, embodiment, or implementation. In other instances, additional features and advantages may be recognized in certain examples, embodiments, and/or implementations that may not be present in all examples, embodiments, or implementations. Further, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the subject matter of the present disclosure. The features and advantages of the subject matter of the present disclosure will become more fully apparent from the following description and appended claims, or may be learned by the practice of the subject matter as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific examples that are illustrated in the appended drawings. Understanding that these drawings depict only typical examples of the subject matter, they are not therefore to be considered to be limiting of its scope. The subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which: 
         FIG. 1A  is a schematic, cross-sectional, front elevation view of a part manufacturing assembly, according to one or more examples of the present disclosure; 
         FIG. 1B  is a schematic, cross-sectional, front elevation view of a part manufacturing assembly, according to one or more examples of the present disclosure; 
         FIG. 2  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 3  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 4  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 5  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 6  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 7  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 8  is a schematic, cross-sectional, front elevation view of a bladder, taken along the line  8 - 8  of  FIGS. 6 and 7 ; 
         FIG. 9  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 10  is a schematic, cross-sectional, side elevation view of an autoclave system, according to one or more examples of the present disclosure; 
         FIG. 11  is a schematic, cross-sectional, front elevation view of a bladder, taken along the line  11 - 11  of  FIGS. 9 and 10 , according to one or more examples of the present disclosure; 
         FIG. 12  is a schematic flow diagram of a method of forming a part made of fiber-reinforced polymeric material, according to one or more examples of the present disclosure; 
         FIG. 13A  is a schematic, cross-sectional, front elevation view of a bladder, taken along a line similar to the line  8 - 8  of  FIGS. 6 and 7 , according to one or more examples of the present disclosure; and 
         FIG. 13B  is a schematic, cross-sectional, front elevation view of a bladder, taken along a line similar to the line  8 - 8  of  FIGS. 6 and 7 , according to one or more examples of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference throughout this specification to “one example,” “an example,” or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present disclosure. Appearances of the phrases “in one example,” “in an example,” and similar language throughout this specification may, but do not necessarily, all refer to the same example. Similarly, the use of the term “implementation” means an implementation having a particular feature, structure, or characteristic described in connection with one or more examples of the present disclosure, however, absent an express correlation to indicate otherwise, an implementation may be associated with one or more examples. 
     Disclosed herein are various examples of a bladder and bladder assembly that, when used in conjunction with an autoclave, promote uniform heating and curing of parts made of fiber-reinforced polymeric material. The bladder assembly of the present disclosure enables the flow of heated fluid through the bladder, which helps to reduce lagging temperature gradients in parts being cured. A reduction in lagging temperature gradients in parts helps improve cure cycle times. Additionally, enabling the flow of heated fluid through the bladder promotes an accelerated cure in thicker portions of variable-thickness parts. 
     Referring to  FIG. 1A , according to one example, a tooling assembly  102  for forming a part  190  includes a first tool  120  and a second tool  122 . The first tool  120  and the second tool  122  are configured to secure a part  190 , to be made, between the first tool  120  and the second tool  122 . In some examples, the first tool  120  is shaped to define a desired shape of one exterior side of the part  190  and the second tool  122  is shaped to define a desired shape of an opposite side of the part  190 . The first tool  120  and the second tool  122  are made from a stiff, heat-resistant, and thermally conductive material, such as a metal (e.g., Invar) or composite material. The part  190  includes at least two portions that are coupled together to form the part  190 . Moreover, the part  190  further includes an interior space  129  that defines an interior surface of the part  190 . The interior space  129  is defined between the at least two portions of the part  190 . 
     The tooling assembly  102  also includes a bladder  126  positioned within the interior space  129  of the part  190  while the part  190  is formed. The bladder  126  is shaped to define a desired shape of the interior surface of the part  190 . Accordingly, the bladder  126  can have any of various cross-sectional shapes. In the illustrated example, the bladder  126  has a trapezoidal-type cross-sectional shape. However, in other examples, the bladder  126  has another cross-sectional shape, such as square, triangular, circular, ovular, polygonal, and the like. The bladder  126  includes an interior  127 , which includes a hollow interior channel  128  that extends a length of the bladder  126  or into the page in  FIG. 1A . In some examples, a wall defining the bladder  126  has a constant thickness, such that the hollow interior channel  128  has a cross-sectional shape corresponding with the cross-sectional shape of the bladder  126 . In certain examples, the bladder  126  is made of an elastomeric material (e.g. a material exhibiting elastic or rubber-like properties). Accordingly, the bladder  126  is more flexible than the first tool  120  and the second tool  122 . The elastic and flexible nature of the bladder  126  allows the bladder  126  to expand when pressurized and contract with the pressure is removed, which helps to cure the part  190 . Additionally, the elastic and flexible nature of the bladder  126  enables the bladder  126  to be removed from within the interior space  129  after the part  190  is cured. In certain examples, the elastomeric material of the bladder  126  has a hardness of between 50 Shore D and 80 Shore D on the durometer scale. The bladder  126  can also be reinforced with fibers, such as fiberglass. 
     Although the part  190  can be any of various parts, for use with any of various stationary or mobile structures, in the illustrated example, the part  190  is a stringer-skin assembly  125  of an aircraft. More specifically, in the illustrated example, the at least two portions of the part  190  include a stringer  130  and a skin  192 . The skin  192  forms part of the fuselage of the aircraft. The stringer  130  is coupled to an interior side of the skin  192  and helps strengthen the skin  192 . In the illustrated example, the stringer  130  is a hat stringer (e.g., a rounded hat stringer) that includes a hat portion  131  and opposing flange portions  133  extending from the hat portion  131 . The flange portions  133  are affixed directly to the skin  192  such that the interior space  129  of the part  190  is defined as the hollow space between the hat portion  131  of the stringer  130  and the skin  192 . As shown in  FIG. 1A , the stringer  130  and the skin  192  extend lengthwise into the page with the skin  192  also extending circumferentially about an axis parallel to the longitudinal direction of the stringer  130  and the skin  192 . 
     The part  190  is made of fiber-reinforced polymeric material in some examples. The fibers of the fiber-reinforced polymeric material can be continuous fibers made of carbon. According to other examples, the fibers of the fiber-reinforced polymeric material can be made of a material other than carbon, such as glass, and can be continuous or non-continuous. In certain examples, the polymeric material of the fiber-reinforced polymeric material is an epoxy or resin, which in some implementations, is a thermoset or thermoplastic polymeric material (e.g., epoxy or resin). Each one of the at least two portions of the part  190  (e.g., the stringer  130  and the skin  192 ) can be a laminated sheet of multiple layers or plies of a fiber-reinforced polymeric material. 
     The at least two portions of the part  190  are joined together via a bonding together of the polymeric materials of the two portions. Generally, the bonding process includes intermixing the polymeric materials of the at least two portions when in a flowable state and then hardening the polymeric materials to complete the bond. In certain examples where the polymeric materials are thermoset polymeric materials, the part  190  can be laid up with the polymeric materials in an uncured state and then heated at or above a cure temperature of the polymeric materials to cure (e.g., harden) together the polymeric materials. Prior to curing the part  190 , the polymeric materials are in a pliable, malleable, or deformable state. Accordingly, the rigidity of the first tool  120 , the second tool  122 , and bladder  126 , relative to the uncured part  190 , help to maintain a shape of the portions of the part  190  and keep the portions of the part  190  together prior to and during curing (e.g., hardening) of the polymeric materials. 
     In some examples, the first tool  120  is a mandrel or inside mold line tool and the second tool  122  is a caul sheet. The mandrel can be a one-piece or seamless mandrel (e.g., seamless at the stringer  130 ) as shown in  FIG. 1A  (e.g., having a one-piece construction) or a multi-part mandrel with a seam  121  (e.g., having a multi-part construction), between two adjoined portions  120 A- 120 B of the mandrel, at the stringer  130  as shown in  FIG. 1B . In certain examples, such as shown in  FIG. 1B , the bladder  126  is located at the seam  121  between the two adjoined portions  120 A- 120 B of the mandrel. In other words, the bladder  126  extends widthwise from one portion  120 A of the mandrel, across the seam  121  between the adjoined portions  120 A- 120 B, to the other portion  120 B of the mandrel. Put another way, the bladder  126  is interposed between the seam  121  and the second tool  122 . 
     A caul sheet is relatively thin compared to the mandrel. For a part  190  to be cured, heat is transferred to the part  190  through the first tool  120 , the second tool  122 , and the bladder  126 . Because the caul sheet is thin, heat transfer through the second tool  122  may be efficient enough to heat a portion of the part  190  relatively quickly. However, because the mandrel is thicker than the caul sheet, heat transfer through the first tool  120  may be less efficient, thus slowing the heating of other portions of the part  190  and thus slowing the cure process of the part  190  or creating lagging temperature gradients in the part  190 . Alternatively, the part  190  may have a variable thickness that tends to slow the cure process in such thicker portions of the part  190 . 
     Moreover, the mandrel can include heat transfer restrictions in some examples that further slow the transfer of heat through the first tool  120  to the part  190 . For example, as shown in  FIG. 1B , the first tool  120  is a mandrel with a localized thickness increase, such as due to the added robustness of the mandrel at the seam of two adjoining parts of the mandrel. In other words, the first tool  120  of  FIG. 1B  has a thickness t 2  proximate the stringer  130  that is greater than a thickness t 1  of the first tool  120  of  FIG. 1A  at a location proximate the stringer  130 . The thickness t 2 , being greater than the thickness t 1 , increases the thermal mass of the first tool  120  of  FIG. 1B  proximate the stringer  130  compared to the first tool  120  of  FIG. 1A . The increased thermal mass requires more time to reach curing temperatures compared to surrounding portions of the first tool  120 . Accordingly, the increased thermal mass of the first tool  120  of  FIG. 1B  has a tendency to cause lagging temperature gradients in the part  190 , which may result in increased cure cycle times. As is described in more detail below, the bladder  126  is part of bladder assembly  124 , and the bladder assembly  124  enables the flow of heated fluid through the bladder  126 , which helps to reduce lagging temperature gradients in the part  190 . 
     Referring to  FIG. 2 , one example of a system  100  that helps to increase the transfer of heat to the part  190 , for improving cure cycle times of the part  190 , is shown. The system  100  includes an autoclave  110  having an autoclave vessel  112 . Accordingly, the system  100  is considered an autoclave system. The autoclave vessel  112  defines an interior cavity  150 , which is configured to contain the tooling assembly  102  and the part  190  being cured. The interior cavity  150  also contains a fluid  152 , which can be a gas. In certain examples, the fluid  152  is an inert gas. More specifically, according to one example, the fluid  152  is a nitrogen gas. The inert nature of the fluid  152  helps prevent unintended reactions, such as combustion events, within the autoclave vessel  112 . However, in some examples, the fluid  152  is a gas other than an inert gas, such as air, which in some situations would help to retain heat in the autoclave vessel  112 . The fluid  152  is initially supplied to the autoclave vessel  112  from a fluid source (not shown) and can be replenished while the part  190  is cured. 
     The autoclave vessel  112  is hermetically sealable such that the fluid  152  in the interior cavity  150  can be pressurized relative to an exterior  186  of the autoclave vessel  112  outside the interior cavity  150 . Although not shown, the autoclave  110  additionally includes a heater that is operable to heat the fluid  152  contained within the autoclave vessel  112  to temperature at least at a cure temperature of the polymeric materials of the part  190  being formed. More specifically, the fluid  152  within the autoclave vessel  112  is heated by at least one heater to an operational temperature conducive to curing the part  190 . The operational temperature of the fluid  152  is dependent on the curing temperature of the part  190 . According to some examples, the operational temperature of the fluid  152  in the autoclave vessel  112  is at least  350  degrees Fahrenheit, in certain implementations, and at least 400 degrees Fahrenheit, in some implementations. In yet other implementations, the operational temperature of the fluid  152  in the autoclave vessel  112  is as low as 180 degrees and as high as at least 600 degrees Fahrenheit. 
     The fluid  152  can be circulated through the interior cavity  150  and around the tooling assembly  102  and the part  190  by a circulator (not shown). Circulation of the fluid  152  around the tooling assembly  102  and the part  190  helps to accelerate the transfer of heat from the fluid  152  to the tooling assembly  102  via convection by improving the efficiency of the heat transfer process. 
     To further aid in heating and curing the part  190 , the fluid  152  within the autoclave vessel  112  is pressurized to an operational pressure P 1  above atmospheric pressure P 3 . In some examples, the fluid  152  is pressurized to an operation pressure P 1  of at least 90 pounds-per-square-inch (psi). Pressurizing the fluid  152  within the autoclave vessel  112  promotes the transfer of heat to the part  190  and improves the rate at which the part  190  cures. Additionally, pressurizing the fluid  152  in the autoclave vessel  112  helps to compress the part  190 , which promotes a reduction in the voids or air pockets within the laminated features of the part  190 . Pressurization of the fluid  152  can be provided by a pressurized fluid source that introduces pressurized gas into the autoclave vessel  112  prior to curing the part  190 . In some examples, additional pressure is applied to the part  190  during the curing process by isolating the part  190 , relative to the interior cavity  150  of the autoclave vessel  112 , within a hermetically sealed container and pulling pressure from the hermetically sealed container to create vacuum conditions within the hermetically sealed container. 
     As mentioned previously, the autoclave  110  facilitates curing of the uncured polymer of the fiber-reinforced polymer material of the part  190  by heating the uncured polymer up to at least the curing temperature of the polymer. In the case of a thermoset polymer, heating the uncured polymer in this manner results in the hardening of the polymer by cross-linking polymer chains of the polymer. Once hardened via the curing process, the chemical transformation of the polymer is irreversible. For best results, the uncured polymer is uniformly heated to ensure the chemical composition and strength of the cured fiber-reinforced polymer material is consistent throughout the part  190 . 
     The system  100  further includes a bladder assembly  124 , which, when used in conjunction with the autoclave  110 , helps facilitate faster and uniform heating of the uncured fiber-reinforced polymer material of the part  190  by utilizing the bladder  126  to distribute heat to the part  190 . The bladder assembly  124  includes the bladder  126 . Generally, the fluid  152  within the interior cavity  150  of the autoclave vessel  112  is circulated through the interior  127  of the bladder  126 , which helps to distribute heat to less accessible surfaces, such as internal surfaces, of the part  190 , which may not be heated as quickly as more accessible surfaces, such as external surfaces. Accordingly, the bladder assembly  124  is configured to help flow heated and pressurized fluid through the bladder  126  and thus to the internal surfaces of the part  190  to promote faster and more uniform heating of the part  190 . 
     The bladder assembly  124  further includes an intake port  134 , an exhaust port  138 , and a pressure control device  146 . The intake port  134  is fluidically coupled with the interior  127  of the bladder  126 . Likewise, the exhaust port  138  is fluidically coupled with the interior  127  of the bladder  126 . In some examples, the intake port  134  and the exhaust port  138  include a fluid conduit open to the interior  127  of the bladder  126 . According to one example, the intake port  134  and the exhaust port  138  are open to the interior  127  of the bladder  126  by passing through a wall of the bladder  126 . 
     The bladder assembly  124  is positioned at least partially in the interior cavity  150  of the autoclave vessel  112  when curing of the part  190  is performed. In some examples, a substantial portion or an entirety of the bladder assembly  124  is positioned in the interior cavity  150  of the autoclave vessel  112 . In one example, an entirety of the bladder assembly  124 , with the exception of all or a portion of the pressure control device  146 , is positioned within the interior cavity  150 . When positioned in the interior cavity  150  of the autoclave vessel  112 , the intake port  134  is open to and thus fluidically coupled with the interior cavity  150  of the autoclave vessel  112 . Accordingly, the fluid  152  in the interior cavity  150  is free or allowed to enter the interior  127  of the bladder  126  through the intake port  134 . Moreover, the fluid  152 , when in the interior  127  of the bladder  126 , is free or allowed to exit the interior  127  of the bladder  126  through the exhaust port  138 . 
     The pressure control device  146  is fluidically coupled with the exhaust port  138 . Moreover, the pressure control device  146  is configured to control or limit a pressure drop across the interior  127  of the bladder  126 . The pressure drop induces a portion of the fluid  152  in the interior cavity  150  to flow, as indicated by arrows  154 , into the interior  127  of the bladder  126  through the intake port  134 , flow through the interior  127  of the bladder  126 , and flow out of the interior  127  of the bladder  126 . Accordingly, the pressure control device  146  can be considered and defined as a flow control device that is configured to control or regulate the flow of the fluid  152  through the interior  127  of the bladder  126  and from the interior  127  to the exterior  186 . Because the fluid  152  is heated, heat from the fluid  152 , as it flows through the interior  127  of the bladder  126  is more readily transferred to the bladder  126  via conduction and convection than if the fluid  152  in the interior  127  was stagnant or non-flowing. As previously described, heat from the bladder  126  is transferred to the part  190  for curing the part  190 . Therefore, flowing the fluid  152  through the bladder  126 , via the pressure drop, promotes improved heat transfer from the bladder  126  to the part  190 , and thus lower lagging temperature gradients in the part  190  and improved cure cycle times and results. 
     The bladder  126  includes a first end portion  140  and a second end portion  142 . The first end portion  140  and the second end portion  142  define opposite ends of the interior  127 , including the hollow interior channel  128 , of the bladder  126 . In some examples, the bladder  126 , including the hollow interior channel  128 , extends lengthwise from the first end portion  140  to the second end portion  142 . The intake port  134  passes through a wall of the bladder  126  at the first end portion  140 . Accordingly, the bladder  126  includes an intake opening or aperture at the first end portion  140  that at least partially defines the intake port  134 . 
     To facilitate a seal at the first end portion  140 , about the intake opening in the wall of the bladder  126 , the bladder assembly  124  further includes an intake plug  132 . The intake plug  132  is fixed to the first end portion  140  of the bladder  126 . Moreover, the intake plug  132  includes an intake conduit, fluidically open to the interior cavity  150  of the autoclave vessel  112  and to the intake opening in the wall of the bladder  126  that at least partially defines the intake port  134 . In other words, in some examples, the intake port  134  passes through and is defined by the intake opening in the wall of the bladder  126  and the intake conduit formed in the intake plug  132 . The intake plug  132  includes one or more fittings configured to fixedly attach to the first end portion  140  of the bladder  126 . Accordingly, the intake plug  132  has a one-piece monolithic and seamless construction in some examples and a multi-piece construction in other examples. Moreover, the intake plug  132  can be permanently fixedly attached to the bladder  126  or be configured to selectively releasably attach to the bladder  126 . 
     According to some examples, such as shown in  FIGS. 2 and 3 , the bladder assembly  124  also includes an exhaust plug  136  that is fixed to the second end portion  142  of the bladder  126 . In such examples, the exhaust port  138  passes through a wall of the bladder  126  at the second end portion  142 . Accordingly, in the examples shown in  FIGS. 2 and 3 , the bladder  126  includes an exhaust opening or aperture at the second end portion  142  that at least partially defines the exhaust port  138 . The exhaust plug  136  includes an exhaust conduit, fluidically open to the exhaust opening in the wall of the bladder  126 , that at least partially defines the exhaust port  138 , and to the pressure control device  146 . Accordingly, the exhaust conduit in the exhaust plug  136  is not open to the interior cavity  150  of the autoclave vessel  112 , but instead opens to the pressure control device  146 . In the illustrated examples of  FIGS. 2 and 3 , the exhaust port  138  passes through and is defined by the exhaust opening in the wall of the bladder  126  and the exhaust conduit formed in the exhaust plug  136 . The exhaust plug  136  includes one or more fittings configured to fixedly attach to the second end portion  142  of the bladder  126 . Accordingly, the exhaust plug  136  has a one-piece monolithic and seamless construction in some examples and a multi-piece construction in other examples. Moreover, the exhaust plug  136  can be permanently fixedly attached to the bladder  126  or be configured to selectively releasably attach to the bladder  126 . 
     Referring to  FIGS. 2 and 3 , in some examples, the bladder assembly  124  includes an exhaust tube  144  that fluidically couples the exhaust port  138  to the pressure control device  146 . Moreover, the pressure control device  146  is fluidically open, whether directly or indirectly, to an exterior  186  outside the interior cavity  150  of the autoclave vessel  112 . Accordingly, the fluid  152  exiting the interior  127  of the bladder  126  through the exhaust port  138  is expelled into the exterior  186  (e.g., atmosphere), as indicated by a directional arrow  154 , via the exhaust tube  144  and the pressure control device  146 . In certain examples, the pressure control device  146  is located within the interior cavity  150  of the autoclave vessel  112  and is open to the exterior  186  via an extension tube (not shown) coupled to the wall of the autoclave vessel  112 . According to other examples, as shown, the pressure control device  146  is coupled to the wall of the autoclave vessel  112 . In yet alternative examples, the pressure control device  146  is located in the exterior  186  outside the interior cavity  150  and the exhaust tube  144  passes through the wall of the autoclave vessel  112 . 
     The pressure control device  146 , being open to the exterior  186  at the atmospheric pressure P 3  and in fluidic communication with the fluid  152  at the operational pressure P 1 , via the bladder  126 , is configured to control the flow of fluid  152  from the interior cavity  150  and the bladder  126  in a manner that results in a drop of the pressure P 2  of the fluid  152  in the bladder  126  to below the operation pressure P 1  and above the atmospheric pressure P 3 . The drop in pressure from P 1  to P 2  and from P 2  to P 3  facilitates the flow of the fluid  152  through the interior  127  of the bladder  126 . Because the bladder  126  is flexible and hollow, to prevent the collapse of the bladder  126  on itself but to ensure sufficient flow of the fluid  152  through the interior  127 , the pressure control device  146  limits the pressure drop from P 1  to P 2  (i.e., the pressure drop across the interior  127  of the bladder  126 ) to greater than zero, but less than or equal to a pressure-drop percentage threshold. In one example, the pressure-drop percentage threshold is 5%. According to other examples, the pressure-drop percentage threshold is between 2% and 4%. 
     In some examples, as shown in  FIG. 2 , the pressure control device  146  is a passive device configured to passively control the pressure drop across the interior  127  of the bladder  126 . For example, the pressure control device  146  can be a passive pressure control device  147 , such as a passive flow control valve or orifice. The passive flow control valve enables a constant flow rate through the valve independently of pressure changes at the inlet of the valve. The orifice, which can be a fixed-diameter orifice, provides a constant pressure drop across the orifice. Accordingly, the passive pressure control device  147  can be designed to provide a fixed pressure drop across the interior  127  of the bladder  126 . 
     According to other examples, as shown in  FIG. 3 , the pressure control device  146  is an active device configured to actively control the pressure drop across the interior  127  of the bladder  126 . For example, the pressure control device  146  can be an active pressure control device  149 , such as a controllable or adjustable valve or orifice. The active pressure control device  149  enables a variable or adjustable flow rate through the device in response to pressure changes at the inlet of the device. Accordingly, the active pressure control device  149  can be controlled to provide a changing pressure drop or a fixed pressure drop across the interior  127  of the bladder  126 . 
     Referring to  FIG. 3 , in some examples, the bladder assembly  124  additionally includes a pressure sensor  174  that is fluidically coupled with the exhaust port  138  between the exhaust port  138  and the pressure control device  146 . The pressure sensor  174  is configured to sense or detect the pressure P 2  of the fluid  152  exiting the exhaust port  138  before the fluid  152  passes through the pressure control device  146 . In such examples, active control of the pressure drop using the active pressure control device  149  can be dependent on (e.g., actuatable in response to) feedback from the pressure sensor  174 . 
     The system  100  further includes a controller  160  in certain examples. The controller  160  is operably coupled with the pressure sensor  174  and the active pressure control device  149 . The controller  160  is configured to receive feedback from the pressure sensor  174 , such as in the form of electronic signals (e.g., pressure readings) indicative of the pressure P 2  of the fluid  152  sensed by the pressure sensor  174 , and command or control actuation of the active pressure control device  149  to adjust the flow rate through the device in response to the feedback from the pressure sensor  174 . More specifically, in some implementations, the controller  160  compares the pressure readings from the pressure sensor  174  to a predetermined pressure-drop range and controls the active pressure control device  149  to achieve a pressure drop from the pressure P 1  to the pressure P 2  that falls within the predetermined pressure-drop range. The comparison performed by the controller  160  includes receiving data regarding the operational pressure P 1  within the interior cavity  150  of the autoclave vessel  112  and determining a difference between the operational pressure P 1  and the pressure P 2  (as sensed by the pressure sensor  174 ), which is equal to the actual pressure drop across the interior  127  of the bladder  126 . The data regarding the operational pressure P 1  can be obtained from a pressure sensor in pressure sensing communication with the interior cavity  150 . The controller  160  commands the active pressure control device  149  to make flow throughput adjustments to ensure the difference between the operational pressure P 1  and the pressure P 2  stays within the predetermined pressure-drop range. In some examples, the controller  160  further utilizes the atmospheric pressure P 3  to determine the degree of throughput adjustments necessary to achieve a desired pressure drop across the interior  127  of the bladder  126 . 
     In the examples shown in  FIGS. 2 and 3 , the fluid  152  flows through the hollow interior channel  128  of the interior  127  of the bladder  126  from the first end portion  140  to the second end portion  142 . Accordingly, the bladder assembly  124  includes both the intake plug  132  at the first end portion  140  and an exhaust plug  136  at the second end portion  142 . However, in other examples, such as shown in  FIGS. 4, 5, 9, and 10 , the bladder assembly  124  does not include the exhaust plug  136  and the fluid  152  flows through the interior  127  of the bladder  126  in a first direction from the first end portion  140  to the second end portion  142  and is then redirected to flow in a second direction, opposite the first direction, from the second end portion  142  to the first end portion  140 . Moreover, in the examples shown in  FIGS. 4, 5, 9, and 10 , the exhaust port  138  passes through an exhaust conduit formed in the intake plug  132 . Accordingly, the intake plug  132  includes both an intake conduit, which forms a portion of the intake port  134 , and a fluidically separate exhaust conduit, which forms a portion of the exhaust port  138 . The second end portion  142  of the bladder  126  is closed. 
     The bladder assembly  124  of  FIGS. 4, 5, 9, and 10 , having one plug (i.e., the intake plug  132 ) simplifies the construction of the bladder assembly  124 . Moreover, because securing fittings or connections, such as the intake plug  132 , to the bladder  126  can be difficult in certain situations, reducing the number of fittings in the bladder assembly  124  can be advantageous. Additionally, a bladder assembly  124  with only one plug on one end portion of the bladder  126  makes removal of the bladder  126  from the part  190  following curing easier than a bladder assembly  124  with two plugs on corresponding opposite end portions of the bladder  126 . 
     Referring to  FIGS. 4 and 5 , within certain examples, the bladder assembly  124  further includes a tube  180  that facilitates the dual directionality of the flow of the fluid  152 . The tube  180  is hollow and passes through the hollow interior channel  128  from the first end portion  140  of the bladder  126  toward the second end portion  142  of the bladder  126 . The tube  180  is fluidically coupled with the intake port  134  at the first end portion  140  of the bladder  126 . Additionally, the tube  180  terminates before a closed end of the second end portion  142  of the bladder  126 . Therefore, the tube  180  is open to the hollow interior channel  128  proximate the second end portion  142  of the bladder  126 . The tube  180  has a cross-sectional area smaller than the cross-sectional area of the hollow interior channel  128 . In some examples, the tube  180  passes through a central portion of (e.g., is concentric with) the hollow interior channel  128 . Accordingly, in these examples, the hollow interior channel  128  circumscribes (e.g., circumferentially surrounds) the tube  180 . 
     In operation, the pressure drop across the interior  127  of the bladder  126  between the intake port  134  and the exhaust port  138  induces flow of the fluid  152  from the interior cavity  150  of the autoclave vessel  112  into the intake port  134 . From the intake port  134 , the fluid  152  flows through the tube  180  away from the first end portion  140  of the bladder  126  toward the second end portion  142  of the bladder  126 . The fluid  152  then exits the tube  180  into the hollow interior channel  128  proximate the second end portion  142  and, due to the closed end of the bladder  126  at the second end portion  142 , reverses direction back toward the first end portion  140  through the hollow interior channel  128  on the outside of the tube  180 . When back at the first end portion  140 , the fluid  152  exits the hollow interior channel  128  through the exhaust port  138  and ultimately exits the autoclave vessel  112 . As the fluid  152  flows from the second end portion  142  toward the first end portion  140 , heat from the fluid  152  is transferred to the bladder  126 , which is subsequently transferred to the part  190  for curing the part  190 . The control of the pressure drop across the interior  127  of the bladder  126  and the flow of the fluid  152  through the interior  127  of the bladder  126  can be performed passively, as shown in  FIG. 4 , or actively, as shown in  FIG. 5 . As shown, the features for passively and actively controlling the pressure drop and flow of the fluid  152  can be similar to or the same as those shown in and described in associated with  FIGS. 2 and 3 , respectively. 
     As shown in  FIGS. 13A and 13B , instead of the tube  180 , in some examples, to facilitate dual directionality of the flow of the fluid  152  and a single plug, the bladder  126  includes one or more interior walls that divides the hollow interior channel  128  into multiple separate sub-channels. For example, the bladder  126  of  FIGS. 13A and 13B  includes an interior wall  193  that divides the hollow interior channel  128  into an outflow sub-channel  194  and an inflow sub-channel  196 . The outflow sub-channel  194  is fluidically coupled with the intake port  134  and the inflow sub-channel  196  is fluidically coupled with the exhaust port  138 . Accordingly, the fluid  152  flows away from the intake port  134 , into the page in  FIGS. 13A and 13B  (as indicated by an ‘X’), and the fluid  152  flows back, in an opposite direction, toward the exhaust port  138 , out of the page in  FIGS. 13A and 13B  (as indicated by an dot). Although not shown, the interior wall  193  terminates before a closed end of the bladder  126  and the closed end of the bladder  126  redirects the flow of the fluid  152  from the outflow sub-channel  194  to the inflow sub-channel  196 . In one example, as shown in  FIG. 13A , the interior wall  193  is a vertical interior wall and the outflow sub-channel  194  and the inflow sub-channel  196  are on opposite sides of the bladder  126 . In contrast, in another example, as shown in  FIG. 13B , the interior wall  193  is a horizontal interior wall and the outflow sub-channel  194  and the inflow sub-channel  196  are on bottom and top portions of the bladder  126 , respectively. Although a single interior wall and two sub-channels are shown, in other examples, multiple interior walls can be employed to create more than two sub-channels. 
     Referring now to  FIGS. 6-8 , according to some examples, the bladder  126  includes multiple layers that form the wall of the bladder  126 . For example, as shown in  FIG. 8 , the bladder  126  includes an outer layer  170  and an inner layer  172 . The outer layer  170  defines an exterior surface of the bladder  126  and the inner layer  172  defines an interior surface of the bladder  126 . Additionally, the inner layer  172  defines the hollow interior channel  128  of the interior  127  of the bladder  126 . The outer layer  170  and the inner layer  172  are made from the same material in certain examples. Alternatively, in other examples, the outer layer  170  and the inner layer  172  are made from different materials. The outer layer  170  and the inner layer  172  are separately formed and coupled together (e.g., bonded, adhered, fastened, etc.) to form the bladder  126 . Although two layers are shown, the bladder  126  can include more than two layers in some examples. 
     The bladder  126  of  FIGS. 6-8  includes at least one fluid flow conduit  176  interposed between the outer layer  170  and the inner layer  172 . The fluid flow conduit  176  may be defined between a groove formed in the outer layer  170  and the opposing surface of the inner layer  172  (as shown), a groove formed in the inner layer  172  and the opposing surface of the outer layer  170 , or grooves formed in both the inner layer  172  and the outer layer  170 . Additionally, the fluid flow conduit  176  can be located at any of various locations within the bladder  126 , such as a bottom portion  182  of the bladder  126  (as shown), a top portion  184  of the bladder  126 , or one of two side portions of the bladder  126 . Generally, the fluid flow conduit  176  is located at a location of the bladder  126  corresponding with locations on the part  190  that can benefit from the additional heat flowing through the bladder  126 . The fluid flow conduit  176  forms part of the interior  127  of the bladder  126 . Accordingly, as used herein, the interior  127  of the bladder  126  can include the hollow interior channel  128  and a separate one or more fluid flow conduits  176 . 
     In this illustrated example, the fluid flow conduit  176  extends from the first end portion  140  of the bladder  126  to the second end portion  142  of the bladder  126 . At the first end portion  140 , the fluid flow conduit  176  is fluidically coupled with the intake port  134 , which is partially formed through the intake plug  132  fixed to the first end portion  140 , and at the second end portion  142 , the fluid flow conduit  176  is fluidically coupled with the exhaust port  138 , which is partially formed through the exhaust plug  136  fixed to the second end portion  142 . At least one of the intake plug  132  or the exhaust plug  136  includes a vent  198  that passes through the corresponding one or both of the intake plug  132  and the exhaust plug  136  and passes through the wall of the bladder  126 . The vent  198  enables the hollow interior channel  128  to be pressurized to the operational pressure P 1  of the fluid  152  in the interior cavity  150 . 
     In operation, the pressure drop across the interior  127  of the bladder  126  between the intake port  134  and the exhaust port  138  induces flow of the fluid  152  from the interior cavity  150  of the autoclave vessel  112  into the intake port  134 . From the intake port  134 , the fluid  152  flows through the fluid flow conduit  176  away from the first end portion  140  of the bladder  126  toward the second end portion  142  of the bladder  126 . The fluid  152  then exits the fluid flow conduit  176  into the exhaust port  138  and ultimately exits the autoclave vessel  112 . As the fluid  152  flows from the first end portion  140  toward the second end portion  142 , heat from the fluid  152  is transferred to the bladder  126 , which is subsequently transferred to the part  190  for curing the part  190 . The control of the pressure drop across the interior  127  of the bladder  126  (which in this example is a pressure drop across the fluid flow conduit  176 ), and the flow of the fluid  152  through the interior  127  of the bladder  126  can be performed passively, as shown in  FIG. 6 , or actively, as shown in  FIG. 7 . As shown, the features for passively and actively controlling the pressure drop and flow of the fluid  152  can be similar to or the same as those shown in and described in associated with  FIGS. 2 and 3 , respectively. 
     To promote distribution of heat from the bladder  126  to the part  190 , in some examples, the fluid flow conduit  176  can be larger than as shown. Alternatively, to promote distribution of heat from the bladder  126  to the part  190 , in some examples, as shown, the bladder  126  includes a plurality of fluid flow conduits  176  between the outer layer  170  and the inner layer  172  and fluidically coupled with the intake port  134  and the exhaust port  138 . Although the plurality of fluid flow conduits  176  are shown to be concentrated on the bottom portion  182  of the bladder  126 , in other examples, the fluid flow conduits  176  can be concentrated on additional or alternative portions of the bladder  126  (e.g., to transfer heat to targeted portions of the part  190 ) or the fluid flow conduits  176  can be evenly distributed around the bladder  126  (e.g., to promote an even distribution of heat to the part  190 ). 
     Like the bladder  126  of  FIGS. 6-8 , the bladder  126  of  FIGS. 9-11  includes at least one fluid flow conduit  176  interposed between the outer layer  170  and the inner layer  172 . However, unlike the fluid flow conduit  176  of  FIGS. 6-8 , the fluid flow conduit  176  of  FIGS. 9-11  is not fluidically coupled with an exhaust port  138  in an exhaust plug  136 , but rather is fluidically coupled with a second fluid flow conduit  178  that is fluidically coupled with an exhaust port  138  in the intake plug  132 . The fluid flow conduit  176  is considered an inflow conduit and the second fluid flow conduit  178  is considered an outflow conduit. The fluid flow conduit  176  and the second fluid flow conduit  178  together form a continuous fluid flow conduit that extends from the first end portion  140  of the bladder  126  to the second end portion  142  of the bladder  126 , wraps around the closed end of the bladder  126  at the second end portion  142 , and extends from the second end portion  142  back to the first end portion  140 . 
     The fluid flow conduit  176  and the second fluid flow conduit  178  can be located at any of various opposing locations within the bladder  126 . In an example, the fluid flow conduit  176  extends along a first side of the bladder  126 , and the second fluid flow conduit  178  extends along a second side  184  of the bladder  126 . In an example, the first side of the bladder is the bottom portion  182  and the second side of the bladder is top portion  184 . For instance, the fluid flow conduit  176  can be located in the bottom portion  182  of the bladder  126  and the second fluid flow conduit  178  can be located in the top portion  184  of the bladder  126  (as shown). However, these locations can be reversed or the locations can be different, such as opposing side portions. Generally, the fluid flow conduit  176  and the second fluid flow conduit  178  are located at locations of the bladder  126  corresponding with locations on the part  190  that can benefit from the additional heat flowing through the bladder  126 . The fluid flow conduit  176  and the second fluid flow conduit  178  form part of the interior  127  of the bladder  126 . Accordingly, as used herein, the interior  127  of the bladder  126  can include the hollow interior channel  128  and a separate one or more fluid flow conduits  176  and second fluid flow conduits  178 . 
     In operation, the pressure drop across the interior  127  of the bladder  126  between the intake port  134  and the exhaust port  138  induces flow of the fluid  152  from the interior cavity  150  of the autoclave vessel  112  into the intake port  134 . From the intake port  134 , the fluid  152  flows through the fluid flow conduit  176  away from the first end portion  140  of the bladder  126  toward the second end portion  142  of the bladder  126 . The fluid  152  then changes direction and enters the second fluid flow conduit  178 . The fluid  152  flows along the second fluid flow conduit  178  away from the second end portion  142  of the bladder  126  toward the first end portion  140 . From the second end portion  142 , the fluid  152  flows into the exhaust port  138  and then ultimately exits the autoclave vessel  112 . As the fluid  152  flows from the first end portion  140  toward the second end portion  142  and back toward the first end portion  140 , heat from the fluid  152  is transferred to the bladder  126 , which is subsequently transferred to the part  190  for curing the part  190 . The control of the pressure drop across the interior  127  of the bladder  126  (which in this example is a pressure drop across the fluid flow conduit  176  and the second fluid flow conduit  178 ), and the flow of the fluid  152  through the interior  127  of the bladder  126  can be performed passively, as shown in  FIG. 9 , or actively, as shown in  FIG. 10 . As shown, the features for passively and actively controlling the pressure drop and flow of the fluid  152  can be similar to or the same as those shown in and described in associated with  FIGS. 2 and 3 , respectively. 
     To promote distribution of heat from the bladder  126  to the part  190 , in some examples, the fluid flow conduit  176  and the second fluid flow conduit  178  can be larger than as shown. Alternatively, to promote distribution of heat from the bladder  126  to the part  190 , in some examples, as shown, the bladder  126  includes a plurality of fluid flow conduits  176 , spaced apart from each other, and second fluid flow conduits  178 , spaced apart from each other, between the outer layer  170  and the inner layer  172  and fluidically coupled with the intake port  134  and the exhaust port  138 . Although the plurality of fluid flow conduits  176  and the second fluid flow conduits  178  are shown to be concentrated on the bottom portion  182  and the top portion  184  of the bladder  126 , respectively, in other examples, the fluid flow conduits  176  and the second fluid flow conduits  178  can be concentrated on additional or alternative portions of the bladder  126  (e.g., to transfer heat to targeted portions of the part  190 ) or the fluid flow conduits  176  and the second fluid flow conduits  178  can be evenly distributed around the bladder  126  (e.g., to promote an even distribution of heat to the part  190 ). 
     Referring to  FIG. 12 , one example of a method  200 , which summarizes the method of forming the part  190  using the bladder assembly  124  and autoclave  110  of the system  100  as described throughout the above disclosure, is shown. The method  200  includes (block  202 ) positioning the bladder  126  within the interior space  129  of the part  190  and (block  204 ) positioning the part  190  and the bladder  126  within the interior cavity  150  of the autoclave vessel  112 . The method  200  also includes (block  206 ), while in the interior cavity  150  of the autoclave vessel  112 , shaping the interior space  129  of the part  190  with the bladder  126 . The method further includes (block  208 ), while shaping the interior space  129  of the part  190  with the bladder  126 , creating a pressure drop across the interior  127  of the bladder  126 , with the pressure control device  146  fluidically coupled with the interior  127  of the bladder  126  and the exterior  186  outside the autoclave vessel  112 , to induce flow of the fluid  152 , contained within the autoclave vessel  112 , through the interior  127  of the bladder  126  and from the interior  127  of the bladder  126  to the exterior  186  outside the autoclave vessel  112 . 
     In some examples of the method  200 , the fluid  152  flows into the interior  127  of the bladder  126  from the first end portion  140  of the bladder  126  and flows out of the interior  127  of the bladder  126  to the exterior  186  outside the autoclave vessel  112  from the second end portion  142  of the bladder  126 . 
     In yet other examples of the method  200 , the fluid  152  flows into the interior  127  of the bladder  126  from the first end portion  140  of the bladder  126  and flows out of the interior  127  of the bladder  126  to the exterior  186  outside the autoclave vessel  112  from the first end portion  140  of the bladder  126 . The fluid  152  can flow through the interior  127  of the bladder  126  in a first direction from the first end portion  140  of the bladder  126  to the second end portion  142  of the bladder  126  and in a second direction, opposite the first direction, from the second end portion  142  of the bladder  126  to the first end portion  140  of the bladder  126 . 
     According to some examples of the method  200 , the fluid  152  flows through the interior  127  of the bladder  126  between an inner layer  172  of the bladder  126  and an outer layer of the bladder  170 . 
     In certain examples, the method  200  further includes comparing the first pressure P 1  of the fluid  152  within the autoclave vessel  112  to the second pressure P 2  of the fluid  152  within the interior  127  of the bladder  126  to provide a comparison between the first pressure P 1  and the second pressure P 2 . The method  200  can also include controlling actuation of the pressure control device  146 , to control the pressure drop across the interior  127  of the bladder  126 , in response to the comparison between the first pressure P 1  and the second pressure P 2 . 
     Within examples, the method  200  can involve using the disclosed bladder assembly  124  to create the pressure drop across the interior  127  of the bladder  126  to induce flow of the fluid  152 , contained within the autoclave vessel  112 , through the interior  127  of the bladder  126  and from the interior  127  of the bladder  126  to the exterior  186  outside the autoclave vessel  112 . For instance, the method  200  can involve using the bladder assembly  124  illustrated in any of  FIG. 2, 3, 4, 5, 6, 7, 9 , or  10  to create the pressure drop to induce the flow of fluid  152 . Further, within examples, the bladder  126  of method  200  can be the bladder  126  illustrated in any of  FIGS. 1A-11, 13A, and 13B . 
     In the above description, certain terms may be used such as “up,” “down,” “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” “over,” “under” and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same object. Further, the terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise. Further, the term “plurality” can be defined as “at least two.” 
     Additionally, instances in this specification where one element is “coupled” to another element can include direct and indirect coupling. Direct coupling can be defined as one element coupled to and in some contact with another element. Indirect coupling can be defined as coupling between two elements not in direct contact with each other, but having one or more additional elements between the coupled elements. Further, as used herein, securing one element to another element can include direct securing and indirect securing. Additionally, as used herein, “adjacent” does not necessarily denote contact. For example, one element can be adjacent another element without being in contact with that element. 
     As used herein, the phrase “at least one of”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of” means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination. 
     Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, e.g., a “second” item does not require or preclude the existence of, e.g., a “first” or lower-numbered item, and/or, e.g., a “third” or higher-numbered item. 
     As used herein, a system, apparatus, structure, article, element, component, or hardware “configured to” perform a specified function is indeed capable of performing the specified function without any alteration, rather than merely having potential to perform the specified function after further modification. In other words, the system, apparatus, structure, article, element, component, or hardware “configured to” perform a specified function is specifically selected, created, implemented, utilized, programmed, and/or designed for the purpose of performing the specified function. As used herein, “configured to” denotes existing characteristics of a system, apparatus, structure, article, element, component, or hardware which enable the system, apparatus, structure, article, element, component, or hardware to perform the specified function without further modification. For purposes of this disclosure, a system, apparatus, structure, article, element, component, or hardware described as being “configured to” perform a particular function may additionally or alternatively be described as being “adapted to” and/or as being “operative to” perform that function. 
     The schematic flow chart diagrams included herein are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of one example of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Although various arrow types and line types may be employed in the flow chart diagrams, they are understood not to limit the scope of the corresponding method. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. 
     The present subject matter may be embodied in other specific forms without departing from its spirit or essential characteristics. The described examples are to be considered in all respects only as illustrative and not restrictive. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.