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WO2018167741A1 - Molding assembly for high temperature composite articles using low temperature inflatable mandrels - Google Patents

Molding assembly for high temperature composite articles using low temperature inflatable mandrels Download PDF

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Publication number
WO2018167741A1
WO2018167741A1 PCT/IB2018/052060 IB2018052060W WO2018167741A1 WO 2018167741 A1 WO2018167741 A1 WO 2018167741A1 IB 2018052060 W IB2018052060 W IB 2018052060W WO 2018167741 A1 WO2018167741 A1 WO 2018167741A1
Authority
WO
WIPO (PCT)
Prior art keywords
mandrel
mold form
bladder
conduit
cooling
Prior art date
Application number
PCT/IB2018/052060
Other languages
French (fr)
Inventor
Robert Michael DAVIES
Original Assignee
Davies Robert Michael
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Davies Robert Michael filed Critical Davies Robert Michael
Publication of WO2018167741A1 publication Critical patent/WO2018167741A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
    • B29C33/48—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling
    • B29C33/50—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling elastic or flexible
    • B29C33/505—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling elastic or flexible cores or mandrels, e.g. inflatable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/02—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means
    • B29C33/04—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means using liquids, gas or steam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/02—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means
    • B29C33/04—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means using liquids, gas or steam
    • B29C33/046—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means using liquids, gas or steam using gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/44—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
    • B29C51/26—Component parts, details or accessories; Auxiliary operations
    • B29C51/28—Component parts, details or accessories; Auxiliary operations for applying pressure through the wall of an inflated bag or diaphragm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
    • B29C51/26—Component parts, details or accessories; Auxiliary operations
    • B29C51/42—Heating or cooling
    • B29C51/427—Cooling of the material with a fluid blast
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/06—Fibrous reinforcements only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2101/00—Use of unspecified macromolecular compounds as moulding material
    • B29K2101/10—Thermosetting resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2101/00—Use of unspecified macromolecular compounds as moulding material
    • B29K2101/12—Thermoplastic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B29K2105/08—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts of continuous length, e.g. cords, rovings, mats, fabrics, strands or yarns
    • B29K2105/0809—Fabrics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B29K2105/12—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts of short lengths, e.g. chopped filaments, staple fibres or bristles

Definitions

  • the present invention relates generally to a method for molding hollow composite plastic articles using inflatable mandrels where the process temperature is greater than the service temperature or the melting temperature of the inflatable mandrel or the seal features and components used to maintain gas pressure throughout the process.
  • the composite material is an amalgamation of resin and either woven or braided fibers from materials such as carbon or glass.
  • the mandrel sometime referred to as a bladder, is inflated with gas pressure to force the composite material against the exterior mold surface.
  • the pressure exerted pushes the resin and fibers into an intimate, low void, relationship known as consolidation in the composite making art.
  • the pressure is maintained until the article reaches the end of the process defined by the desired temperature, and timed profile.
  • Molds typically have at least two parts. The parts mate with each other along what is known in the industry as a parting line. When in the closed condition, a cavity is defined by the space between the two parts. This cavity area represents space in which the product is to be molded from a re-formable material such as polymer resin composite.
  • the molding of plastics and plastic composites generally require the mold to be heated and cooled to facilitate the molding process and conditions.
  • the dominant systems used today for thermal cycling of molds use water, steam, or oil circulation or electric resistance heaters such as cartridge heaters.
  • the heat applied to the mold is also applied to the mandrel and fittings connecting it to the pressure source, gas or hydraulic.
  • the high temperatures required to mold many materials exceed the working temperatures of the gas fittings and the mandrel requiring the use of expensive high temperature materials, such as silicone rubber or polytetrafluoroethylene film.
  • the use of the costlier high temperature materials for the inflation mandrel excludes this desirable composite part making method for many applications.
  • the present invention is a molding assembly for high temperature composite articles using low temperature inflatable mandrels.
  • the present invention utilizes a heat exchanger to maintain the temperature of the inexpensive mandrel to decrease the overall operating cost of producing the hollow composite article within a molding assembly.
  • FIG. 1 is a perspective view of the mold assembly, wherein the at least one inflation adapter is a pair of inflation adapters.
  • FIG. 2 is a cross-sectional view of the mold assembly along a sagittal plane of the mold assembly, wherein the at least one inflation adapter is a pair of inflation adapters.
  • FIG. 3 is a flow chart detailing the general steps for the method of use for the mold assembly.
  • FIG. 4 is a flow chart detailing the steps for the method of use for the mold assembly, wherein an external pressure is applied to the first mold form and the second mold form as the mandrel bladder is pressurized.
  • FIG. 5 is a flow chart detailing the steps for the method of use for the mold assembly, wherein the mandrel bladder is pressurized with a hot nonreactive gas.
  • FIG. 6 is a flow chart detailing the steps for the method of use for the mold assembly, wherein the at least one inflation adapter is a pair of inflation adapters.
  • the present invention is a molding assembly for high temperature composite articles using low temperature inflatable mandrels.
  • the present invention reduces the operating cost for producing composite articles using inexpensive inflatable mandrels.
  • the present invention utilizes a heat exchanger to maintain the temperature of the inexpensive mandrel to decrease the overall operating cost of producing the hollow composite article within a molding assembly.
  • the molding assembly comprises a first mold form 1, a second mold form 2, at least one inflation adapter 3, and a mandrel bladder 4.
  • the first mold form 1 and the second mold form 2 delineate the exterior shape for a composite article that will be produced from a thermoforming compound, while the mandrel bladder 4 defines the interior shape of the composite article.
  • the thermoforming compound is selected from the group consisting of thermoplastics, thermoset resins, composite fibers, and combinations thereof.
  • Thermoplastics are polymers that become malleable when heated, allowing the thermoplastic to be molded into the composite article.
  • the thermoset resins are polymers that undergo a curing process when exposed to heat to produce the composite article.
  • the composite fibers provide structural strength to reinforce the composite article and are made from materials such as carbon fiber or glass.
  • the at least one inflation adapter 3 allows for the inflation of the mandrel bladder 4.
  • the at least one inflation adapter 3 seals the first mold form 1 and second mold form 2 to prevent the molten thermoforming compound from being expelled from the mold assembly, as the mandrel bladder 4 is inflated, and forces the molten thermoforming compound to wet out the composite fibers, wherein the thermoforming compound is a mixture comprising the composite fibers.
  • the first mold form 1 and the second mold form 2 each comprises a molding recess 7 that corresponds to the exterior shape of the composite article.
  • the molding recess 7 of the first mold form 1 is adjacently positioned to the molding recess 7 of the second mold form 2 to delineate a mold cavity 5 between the first mold form 1 and the second mold form 2.
  • the first mold form 1 is removably fastened to the second mold form 2 to allow for the extraction of the composite article.
  • the at least one inflation adapter 3 allows for the inflation or deflation of the mandrel bladder 4.
  • Each inflation adapter 3 comprises an adapter base 8, a mandrel conduit 9, and a cooling conduit 10.
  • the adapter base 8 is adjacently connected to the first mold and the second mold form 2 to secure the at least one inflation adapter 3 to the first mold form 1 and the second mold form 2.
  • the mandrel conduit 9 is a tube or pipe to allow for a stream of pressurized nonreactive gas to pass through to inflate and deflate the mandrel bladder 4.
  • the nonreactive gas helps to preserve the mandrel bladder 4 at high temperatures over an extended duration.
  • the nonreactive gas is preferred to be air;
  • the nonreactive gas may include helium, nitrogen, or any other inert gases that does not adversely react with the mandrel bladder 4, the thermoforming compound, or the composite article.
  • the mandrel conduit 9 traverses through the adapter base 8.
  • the mandrel bladder 4 defines the interior profile of the composite article. The thickness of the composite article is dependent on the inflated diameter of the mandrel bladder 4.
  • the mandrel bladder 4 is preferred to be made from a material that is non-permeable to gas and has sufficient diameter to match the inner perimeter dimension of the mold cavity 5, as shown in FIG. 2. The thickness of the mandrel bladder 4 is sufficient to apply force without rupturing.
  • the mandrel bladder 4 is positioned within the mold cavity 5.
  • the mandrel bladder 4 is sealably pressed between the first mold form 1 and the mandrel conduit 9. Similarly, the mandrel bladder 4 is sealably pressed between the second mold form 2 and the mandrel conduit 9. In this configuration, the first mold form 1, the second mold form 2, and the mandrel bladder 4 delineate a sealed composite volume within the mold cavity 5.
  • the mandrel bladder 4 is in fluid communication with the mandrel conduit 9 to allow for the mandrel bladder 4 to be inflated or deflated within the mold cavity 5. Inflating the mandrel bladder 4 presses the fluidal thermoforming compound against the first mold form 1 and the second mold form 2 to produce the composite article.
  • the thermoforming compound is heated through the first mold form 1 and the second mold form 2 to liquify the thermoforming compound, allowing the thermoforming compound to take the shape of the mold cavity 5 between the first mold form 1, the second mold form 2, and the mandrel bladder 4.
  • the cooling conduit 10 allows for heat transfer within the at least one inflation adapter 3 to maintain the integrity of the mandrel bladder 4 adjacent to the first mold form 1 and the second mold form 2. If the integrity of the mandrel bladder 4 was compromised, the gas within the mandrel bladder 4 would escape and compromise the ability of the mandrel bladder 4 to apply pressure to the composite article.
  • the cooling conduit 10 traverses into the adapter base 8 and the cooling conduit 10 is positioned adjacent to the mandrel bladder 4 to transfer heat away from the mandrel bladder 4 in order to maintain the structural integrity of the mandrel bladder 4.
  • each inflation adapter 3 further comprises a mandrel seal 11 and a seal receiving aperture 12, detailed in FIG. 2.
  • the mandrel seal 11 is a removable stopper that applies pressure onto the mandrel bladder 4 to maintain a hermetic seal to allow for the inflation of the mandrel.
  • the seal receiving aperture 12 receives the mandrel seal 11.
  • the seal receiving aperture 12 traverses through the adapter base 8 to allow the mandrel seal 11 to interface with the mandrel bladder 4.
  • the mandrel bladder is positioned within the seal receiving aperture 12.
  • the mandrel seal 11 is positioned within the seal receiving aperture 12.
  • the mandrel bladder 4 is sealably pressed between the first mold form 1 and the mandrel conduit 9 through the mandrel seal 11.
  • the mandrel conduit 9 hermetically traverses through the mandrel seal 11. This configuration allows for the mandrel conduit 9 and the mandrel seal 11 to be modular with the mold assembly, such that the mandrel conduit 9 or the mandrel seal 11 is able to be easily replaced if either fail.
  • the cooling conduit 10 comprises a cooling inlet 13, a cooling outlet 14, and a cooling pipe 15, shown in FIG. 1.
  • the cooling inlet 13 is adjacently and externally connected to the adapter base 8.
  • the cooling outlet 14 is adjacently connected to the adapter base 8.
  • the cooling pipe 15 is positioned around the mandrel bladder 4, or more specifically, around the seal receiving aperture 12, within the adapter base 8.
  • the cooling inlet 13 is in fluid communication with the cooling outlet 14 through the cooling pipe 15.
  • This configuration of the cooling conduit 10 allows for a coolant stream to pass from the cooling inlet 13, through the cooling pipe 15, and out from the cooling outlet 14.
  • the coolant steam absorbs heat from the first mold form 1 and the second mold form 2 to prevent the mandrel bladder 4 from degrading local to the mandrel conduit 9 due to the temperatures used to melt the thermoforming compound.
  • the at least one inflation adapter 3 is a pair of inflation adapters 6, shown in FIG. 1 and FIG. 2.
  • Each of the pair of inflation adapters 6 is oppositely positioned to the other about the first mold form 1 and the second mold form 2.
  • the pair of inflation adapters 6 allow the mandrel bladder 4 to be pressurized through each inflation adapter 3.
  • the pressure of the mandrel bladder 4 on the fluidal molten thermoforming compound is able to be distributed more evenly within the fiber composite, as the mandrel bladder 4 expands more uniformly.
  • the pair of inflation adapters 6 allows for the production of tubular or hollow composite articles within the mold assembly.
  • the method of use of the mold assembly requires a thermoforming compound, and a coolant source [Step A]. Initially, the molding cavity, external to the mandrel bladder 4, is filled with the thermoforming compound [Step B]. The first mold form 1 and the second mold form 2 are then heated until the
  • thermoforming compound is fluid [Step C] .
  • the at least one inflation adapter 3 is cooled, simultaneous to step C, by flowing a coolant stream from the coolant source through the cooling conduit 10 [Step D].
  • the coolant source is preferred to be cold water; however, any fluid such as air or oil may be substituted to maintain the temperature of the at least one inflation adapter 3.
  • the fluidal thermoforming compound is then pressed preform against the first mold form 1 and the second mold form 2 by pressurizing the mandrel bladder 4 through the mandrel conduit 9 [Step E] .
  • the pressure within the mandrel bladder 4 is maintained through a valve or regulator connected to the mandrel conduit 9.
  • the fluidal thermoforming compound is then cured into a composite article by cooling the molding assembly [Step F].
  • the composite article is removed from the molded assembly, by separating the first mold form 1 and the second mold form 2 [Step G]. Further in accordance to the preferred embodiment for the method of use for the molding assembly, external pressure is applied onto the first mold form 1 and the second mold form 2 during Step E, detailed in FIG. 4. By applying external pressure, the first mold form 1 and the second mold form 2 will not separate from each other due to the pressure exerted by the mandrel bladder 4.
  • the mandrel bladder 4 is pressurized with a hot nonreactive gas, during Step E, detailed in FIG. 5.
  • a hot nonreactive gas By pressurizing the mandrel bladder 4 with the hot nonreactive gas, the thermoforming compound is heated from both sides within the mold cavity 5. The thermoforming compound transitions more consistently into a fluid throughout the fiber composite and mold cavity 5 to have a more uniform consistency throughout the composite article.
  • the hot nonreactive gas is then exchanged with a cooler nonreactive gas within the mandrel bladder 4, during Step F, to cool the fluid thermoforming compound adjacent to the mandrel bladder 4. Similar to heating, the thermoforming compound transitions more consistently into the composite article throughout the mold cavity 5 to have a more uniform consistency throughout the composite article.
  • the mandrel bladder 4 is evenly inflated through the pair of inflation adapters 6, during Step E, in accordance to FIG. 6.
  • the pair of inflation adapters 6 is cooled by flowing a coolant stream from the coolant source through each corresponding cooling conduits, during Step D, to maintain the integrity of the mandrel bladder 4 adj acent to each mandrel conduit 9.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

A molding assembly for high temperature composite articles utilizes low temperature inflatable mandrels to produce composite articles from a thermoforming compound. The molding assembly includes a first mold form, a second mold form, at least one inflation adapter, and a mandrel bladder. The first mold form and the second mold form each comprise a molding recess to mold the thermoforming compound as the thermoforming compound is heated. The mandrel bladder is pressurized to inflate and press the thermoforming compound against the first mold form and the second mold form. Each inflation adapter comprises a mandrel conduit and a cooling conduit. The mandrel conduit allows for the inflation and deflation of the mandrel bladder. The cooling conduit allows for a stream of coolant to flow adjacent to the mandrel bladder to prevent structural degradation of the mandrel bladder from the temperatures necessary to transition the thermoforming compound into a fluid.

Description

Molding Assembly for High Temperature Composite Articles Using Low Temperature Inflatable Mandrels
The current application claims a priority to the U.S. Provisional Patent application serial number 62/470,769 filed on March 13, 2017.
FIELD OF THE INVENTION The present invention relates generally to a method for molding hollow composite plastic articles using inflatable mandrels where the process temperature is greater than the service temperature or the melting temperature of the inflatable mandrel or the seal features and components used to maintain gas pressure throughout the process.
BACKGROUND OF THE INVENTION
Many hollow composite articles are molded using an external mold with an inflatable mandrel on the inside of the composite material to be molded. The composite material is an amalgamation of resin and either woven or braided fibers from materials such as carbon or glass. The mandrel, sometime referred to as a bladder, is inflated with gas pressure to force the composite material against the exterior mold surface. The pressure exerted pushes the resin and fibers into an intimate, low void, relationship known as consolidation in the composite making art. The pressure is maintained until the article reaches the end of the process defined by the desired temperature, and timed profile. Molds typically have at least two parts. The parts mate with each other along what is known in the industry as a parting line. When in the closed condition, a cavity is defined by the space between the two parts. This cavity area represents space in which the product is to be molded from a re-formable material such as polymer resin composite.
The molding of plastics and plastic composites generally require the mold to be heated and cooled to facilitate the molding process and conditions. The dominant systems used today for thermal cycling of molds use water, steam, or oil circulation or electric resistance heaters such as cartridge heaters. The heat applied to the mold is also applied to the mandrel and fittings connecting it to the pressure source, gas or hydraulic. The high temperatures required to mold many materials exceed the working temperatures of the gas fittings and the mandrel requiring the use of expensive high temperature materials, such as silicone rubber or polytetrafluoroethylene film. The use of the costlier high temperature materials for the inflation mandrel excludes this desirable composite part making method for many applications.
Therefore, it is an object of the present invention to utilize cost effective inflatable mandrels of low melting temperature resins, such as polypropylene or nylon, to produce hollow composite articles requiring process temperatures greater than the melting temperature of the bladder material. The present invention is a molding assembly for high temperature composite articles using low temperature inflatable mandrels. The present invention utilizes a heat exchanger to maintain the temperature of the inexpensive mandrel to decrease the overall operating cost of producing the hollow composite article within a molding assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the mold assembly, wherein the at least one inflation adapter is a pair of inflation adapters.
FIG. 2 is a cross-sectional view of the mold assembly along a sagittal plane of the mold assembly, wherein the at least one inflation adapter is a pair of inflation adapters.
FIG. 3 is a flow chart detailing the general steps for the method of use for the mold assembly.
FIG. 4 is a flow chart detailing the steps for the method of use for the mold assembly, wherein an external pressure is applied to the first mold form and the second mold form as the mandrel bladder is pressurized.
FIG. 5 is a flow chart detailing the steps for the method of use for the mold assembly, wherein the mandrel bladder is pressurized with a hot nonreactive gas. FIG. 6 is a flow chart detailing the steps for the method of use for the mold assembly, wherein the at least one inflation adapter is a pair of inflation adapters.
DETAIL DESCRIPTIONS OF THE INVENTION
All illustrations of the drawings are for the purpose of describing selected versions of the present invention and are not intended to limit the scope of the present invention.
The present invention is a molding assembly for high temperature composite articles using low temperature inflatable mandrels. The present invention reduces the operating cost for producing composite articles using inexpensive inflatable mandrels. The present invention utilizes a heat exchanger to maintain the temperature of the inexpensive mandrel to decrease the overall operating cost of producing the hollow composite article within a molding assembly.
In accordance to FIG. 1, the molding assembly comprises a first mold form 1, a second mold form 2, at least one inflation adapter 3, and a mandrel bladder 4. The first mold form 1 and the second mold form 2 delineate the exterior shape for a composite article that will be produced from a thermoforming compound, while the mandrel bladder 4 defines the interior shape of the composite article. The thermoforming compound is selected from the group consisting of thermoplastics, thermoset resins, composite fibers, and combinations thereof. Thermoplastics are polymers that become malleable when heated, allowing the thermoplastic to be molded into the composite article. The thermoset resins are polymers that undergo a curing process when exposed to heat to produce the composite article. The composite fibers provide structural strength to reinforce the composite article and are made from materials such as carbon fiber or glass. The at least one inflation adapter 3 allows for the inflation of the mandrel bladder 4. In addition, the at least one inflation adapter 3 seals the first mold form 1 and second mold form 2 to prevent the molten thermoforming compound from being expelled from the mold assembly, as the mandrel bladder 4 is inflated, and forces the molten thermoforming compound to wet out the composite fibers, wherein the thermoforming compound is a mixture comprising the composite fibers. The first mold form 1 and the second mold form 2 each comprises a molding recess 7 that corresponds to the exterior shape of the composite article. The molding recess 7 of the first mold form 1 is adjacently positioned to the molding recess 7 of the second mold form 2 to delineate a mold cavity 5 between the first mold form 1 and the second mold form 2. The first mold form 1 is removably fastened to the second mold form 2 to allow for the extraction of the composite article.
The at least one inflation adapter 3 allows for the inflation or deflation of the mandrel bladder 4. Each inflation adapter 3 comprises an adapter base 8, a mandrel conduit 9, and a cooling conduit 10. The adapter base 8 is adjacently connected to the first mold and the second mold form 2 to secure the at least one inflation adapter 3 to the first mold form 1 and the second mold form 2. The mandrel conduit 9 is a tube or pipe to allow for a stream of pressurized nonreactive gas to pass through to inflate and deflate the mandrel bladder 4. The nonreactive gas helps to preserve the mandrel bladder 4 at high temperatures over an extended duration. The nonreactive gas is preferred to be air;
however, the nonreactive gas may include helium, nitrogen, or any other inert gases that does not adversely react with the mandrel bladder 4, the thermoforming compound, or the composite article. The mandrel conduit 9 traverses through the adapter base 8. The mandrel bladder 4 defines the interior profile of the composite article. The thickness of the composite article is dependent on the inflated diameter of the mandrel bladder 4. The mandrel bladder 4 is preferred to be made from a material that is non-permeable to gas and has sufficient diameter to match the inner perimeter dimension of the mold cavity 5, as shown in FIG. 2. The thickness of the mandrel bladder 4 is sufficient to apply force without rupturing. The mandrel bladder 4 is positioned within the mold cavity 5. The mandrel bladder 4 is sealably pressed between the first mold form 1 and the mandrel conduit 9. Similarly, the mandrel bladder 4 is sealably pressed between the second mold form 2 and the mandrel conduit 9. In this configuration, the first mold form 1, the second mold form 2, and the mandrel bladder 4 delineate a sealed composite volume within the mold cavity 5. The mandrel bladder 4 is in fluid communication with the mandrel conduit 9 to allow for the mandrel bladder 4 to be inflated or deflated within the mold cavity 5. Inflating the mandrel bladder 4 presses the fluidal thermoforming compound against the first mold form 1 and the second mold form 2 to produce the composite article. The thermoforming compound is heated through the first mold form 1 and the second mold form 2 to liquify the thermoforming compound, allowing the thermoforming compound to take the shape of the mold cavity 5 between the first mold form 1, the second mold form 2, and the mandrel bladder 4. The cooling conduit 10 allows for heat transfer within the at least one inflation adapter 3 to maintain the integrity of the mandrel bladder 4 adjacent to the first mold form 1 and the second mold form 2. If the integrity of the mandrel bladder 4 was compromised, the gas within the mandrel bladder 4 would escape and compromise the ability of the mandrel bladder 4 to apply pressure to the composite article. The cooling conduit 10 traverses into the adapter base 8 and the cooling conduit 10 is positioned adjacent to the mandrel bladder 4 to transfer heat away from the mandrel bladder 4 in order to maintain the structural integrity of the mandrel bladder 4.
More specifically, each inflation adapter 3 further comprises a mandrel seal 11 and a seal receiving aperture 12, detailed in FIG. 2. The mandrel seal 11 is a removable stopper that applies pressure onto the mandrel bladder 4 to maintain a hermetic seal to allow for the inflation of the mandrel. The seal receiving aperture 12 receives the mandrel seal 11. The seal receiving aperture 12 traverses through the adapter base 8 to allow the mandrel seal 11 to interface with the mandrel bladder 4. The mandrel bladder is positioned within the seal receiving aperture 12. The mandrel seal 11 is positioned within the seal receiving aperture 12. The mandrel bladder 4 is sealably pressed between the first mold form 1 and the mandrel conduit 9 through the mandrel seal 11. The mandrel conduit 9 hermetically traverses through the mandrel seal 11. This configuration allows for the mandrel conduit 9 and the mandrel seal 11 to be modular with the mold assembly, such that the mandrel conduit 9 or the mandrel seal 11 is able to be easily replaced if either fail.
Further in accordance to the preferred embodiment of the mold assembly, the cooling conduit 10 comprises a cooling inlet 13, a cooling outlet 14, and a cooling pipe 15, shown in FIG. 1. The cooling inlet 13 is adjacently and externally connected to the adapter base 8. The cooling outlet 14 is adjacently connected to the adapter base 8. The cooling pipe 15 is positioned around the mandrel bladder 4, or more specifically, around the seal receiving aperture 12, within the adapter base 8. The cooling inlet 13 is in fluid communication with the cooling outlet 14 through the cooling pipe 15. This configuration of the cooling conduit 10 allows for a coolant stream to pass from the cooling inlet 13, through the cooling pipe 15, and out from the cooling outlet 14. The coolant steam absorbs heat from the first mold form 1 and the second mold form 2 to prevent the mandrel bladder 4 from degrading local to the mandrel conduit 9 due to the temperatures used to melt the thermoforming compound.
In some embodiments of the present invention, the at least one inflation adapter 3 is a pair of inflation adapters 6, shown in FIG. 1 and FIG. 2. Each of the pair of inflation adapters 6 is oppositely positioned to the other about the first mold form 1 and the second mold form 2. The pair of inflation adapters 6 allow the mandrel bladder 4 to be pressurized through each inflation adapter 3. The pressure of the mandrel bladder 4 on the fluidal molten thermoforming compound is able to be distributed more evenly within the fiber composite, as the mandrel bladder 4 expands more uniformly. Further, the pair of inflation adapters 6 allows for the production of tubular or hollow composite articles within the mold assembly.
In accordance to FIG. 3, the method of use of the mold assembly requires a thermoforming compound, and a coolant source [Step A]. Initially, the molding cavity, external to the mandrel bladder 4, is filled with the thermoforming compound [Step B]. The first mold form 1 and the second mold form 2 are then heated until the
thermoforming compound is fluid [Step C] . The at least one inflation adapter 3 is cooled, simultaneous to step C, by flowing a coolant stream from the coolant source through the cooling conduit 10 [Step D]. The coolant source is preferred to be cold water; however, any fluid such as air or oil may be substituted to maintain the temperature of the at least one inflation adapter 3. The fluidal thermoforming compound is then pressed preform against the first mold form 1 and the second mold form 2 by pressurizing the mandrel bladder 4 through the mandrel conduit 9 [Step E] . The pressure within the mandrel bladder 4 is maintained through a valve or regulator connected to the mandrel conduit 9. The fluidal thermoforming compound is then cured into a composite article by cooling the molding assembly [Step F]. Finally, the composite article is removed from the molded assembly, by separating the first mold form 1 and the second mold form 2 [Step G]. Further in accordance to the preferred embodiment for the method of use for the molding assembly, external pressure is applied onto the first mold form 1 and the second mold form 2 during Step E, detailed in FIG. 4. By applying external pressure, the first mold form 1 and the second mold form 2 will not separate from each other due to the pressure exerted by the mandrel bladder 4.
Further in accordance to the preferred method of use for the mold assembly, the mandrel bladder 4 is pressurized with a hot nonreactive gas, during Step E, detailed in FIG. 5. By pressurizing the mandrel bladder 4 with the hot nonreactive gas, the thermoforming compound is heated from both sides within the mold cavity 5. The thermoforming compound transitions more consistently into a fluid throughout the fiber composite and mold cavity 5 to have a more uniform consistency throughout the composite article. The hot nonreactive gas is then exchanged with a cooler nonreactive gas within the mandrel bladder 4, during Step F, to cool the fluid thermoforming compound adjacent to the mandrel bladder 4. Similar to heating, the thermoforming compound transitions more consistently into the composite article throughout the mold cavity 5 to have a more uniform consistency throughout the composite article.
For embodiments of the mold assembly wherein the at least one pair of inflation adapters 6 is implemented, the mandrel bladder 4 is evenly inflated through the pair of inflation adapters 6, during Step E, in accordance to FIG. 6. By evenly inflating the mandrel bladder 4, the resulting composite article has a more consistent thickness. The pair of inflation adapters 6 is cooled by flowing a coolant stream from the coolant source through each corresponding cooling conduits, during Step D, to maintain the integrity of the mandrel bladder 4 adj acent to each mandrel conduit 9.
Although the invention has been explained in relation to its preferred
embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.

Claims

What is claimed is:
1. A molding assembly for high temperature composite articles using low
temperature inflatable mandrels comprises:
a first mold form;
a second mold form;
an at least one inflation adapter;
a mandrel bladder;
the first mold form and the second mold form each comprise a molding recess;
each inflation adapter comprises an adapter base, a mandrel conduit, and a cooling conduit;
the molding recess of the first mold form being adjacently positioned to the molding recess of the second mold form, delineating a mold cavity;
the first mold form being removably fastened to the second mold form; the adapter base being adjacently connected to the first mold form and the second mold form;
the mandrel bladder being positioned within the mold cavity; the mandrel conduit traversing through the adapter base; the mandrel bladder being sealably pressed between the first mold form and the mandrel conduit;
the mandrel bladder being sealably pressed between the second mold form and the mandrel conduit;
the mandrel bladder being in fluid communication with the mandrel conduit;
the cooling conduit traversing into the adapter base; and
the cooling conduit being positioned adjacent to the mandrel bladder.
2. The molding assembly for high temperature composite articles using low
temperature inflatable mandrels, as claimed in claim 1, comprises:
each inflation adapter further comprises a mandrel seal, and a seal receiving aperture; the seal receiving aperture traversing through the adapter base;
the mandrel seal being positioned into the seal receiving aperture;
the mandrel bladder being sealably pressed between the first mold form and the mandrel conduit through the mandrel seal;
the mandrel bladder being sealably pressed between the second mold form and the mandrel conduit through the mandrel seal; and
the mandrel conduit hermetically traversing through the mandrel seal.
The molding assembly for high temperature composite articles using low temperature inflatable mandrels, as claimed in claim 1, comprises:
the cooling conduit comprises a cooling inlet, a cooling outlet, and a cooling pipe;
the cooling inlet being adjacently and externally connected to the adapter base;
the cooling outlet being adjacently connected to the adapter base;
the cooling pipe being positioned around the seal receiving aperture, within the adapter base; and
the cooling inlet being in fluid communication with the cooling outlet through the cooling pipe.
The molding assembly for high temperature composite articles using low temperature inflatable mandrels, as claimed in claim 1, comprises:
the at least one inflation adapter being a pair of inflation adapters; and each of the pair of inflation adapters being oppositely positioned the other about the first mold form and the second mold form.
A method of use for the molding assembly, as claimed in claim 1 , comprises the steps of:
(A) providing a thermoforming compound, and a coolant source;
(B) filling the molding cavity with the thermoforming compound and fiber composite preform; (C) heating the first mold form and the second mold form until the thermoforming compound is fluid;
(D) cooling the at least one inflation adapter by flowing a coolant stream from the coolant source through the cooling conduit;
(E) pressing the fluidal thermoforming compound against the first mold form and the second mold form by pressurizing the mandrel bladder through the mandrel conduit;
(F) curing the fluidal thermoforming compound into a composite article by cooling the molding assembly; and
(G) removing the composite article form the mold assembly, by separating the first mold form and the second mold form.
The method of use for the molding assembly, as claimed in claim 5, comprises the step of:
applying external pressure onto the first mold form and the second mold form during Step E.
The method of use for the molding assembly, as claimed in claim 5, comprises the step of:
depressurizing the mandrel bladder after Step F.
The method of use for the molding assembly, as claimed in claim 5, comprises the step of:
pressurizing the mandrel bladder with a hot nonreactive gas during Step E.
The method of use for the molding assembly, as claimed in claim 8, comprises the step of:
exchanging the hot nonreactive with a cooler nonreactive within the mandrel bladder during Step F.
10. The method of use for the molding assembly, as claimed in claim 5, comprises the step of:
wherein the at least one inflation adapter is a pair of inflation adapters; and evenly inflating the mandrel bladder through the pair of inflation adapters during Step E.
11. The method of use for the molding assembly, as claimed in claim 10, comprises the step of:
cooling the pair of inflation adapters by flowing a coolant stream from the coolant source through each corresponding cooling conduit during Step D.
12. The molding assembly for high temperature composite articles using low
temperature inflatable mandrels, as claimed in claim 5, wherein the
thermoforming compound is selected from the group consisting of thermoplastics, thermoset resins, composite fibers, and combinations thereof.
PCT/IB2018/052060 2017-03-13 2018-03-26 Molding assembly for high temperature composite articles using low temperature inflatable mandrels WO2018167741A1 (en)

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