Method for embedding reinforcing fibers in thermoplastic resins

Abstract

A method of embedding reinforcing fibers in a thermoplastic resin is disclosed. The method includes providing a sealed cavity enclosing the stack and defined by the first and second metal members and a seal. The laminate includes at least one thermoplastic resin layer including a thermoplastic resin and at least one reinforcing fiber layer including reinforcing fibers. The method further includes subjecting the sealed cavity to a vacuum to form a vacuum sealed cavity, thereby applying an impregnation pressure on the stack. The method further includes heating the stack to an impregnation temperature of the thermoplastic resin to form a heated thermoplastic resin while maintaining a seal temperature of the seal below the impregnation temperature. The method further includes impregnating the heated thermoplastic resin into the reinforcing fibers to form a heated composite. The method further includes cooling the heated composite material to form a thermoplastic composite material.

Description

Technical Field

[0001] The present disclosure relates to a method for embedding reinforcing fibers into a thermoplastic resin. The method can be used for impregnation while protecting seals used in the method from excessive thermal degradation. Background Art

[0002] Polymer materials (e.g., thermoplastic materials) can be formed into articles. The polymer material can be a polymer matrix composite material including reinforcing fibers. Non-limiting examples of articles formed from polymer materials include decorative items, exterior automotive parts (e.g., hoods, fenders, trunk lids, roofs, bumpers, and instrument panels), structural automotive parts (e.g., seats, bumper beams, fenders, cargo floors, pickup truck cargo boxes, and box liners), interior automotive parts (e.g., decorative panels), building products, consumer products (e.g., sporting goods and appliances), and medical products and components. Summary of the invention

[0003] In one embodiment, a method for embedding reinforcing fibers in a thermoplastic resin is disclosed. The method includes providing a sealed cavity defined by a first metal member and a second metal member and a seal, the sealed cavity enclosing a plystack. The stack includes at least one thermoplastic resin layer (ply) including a thermoplastic resin and at least one reinforcing fiber layer including reinforcing fibers. The method also includes subjecting the sealed cavity to a vacuum to form a vacuum sealed cavity, thereby applying an impregnation pressure on the stack. The impregnation pressure can be increased by external pressure (e.g., by mechanical or external means). The method also includes heating the stack to an impregnation temperature of the thermoplastic resin to form a heated thermoplastic resin, while maintaining the seal temperature of the seal below the impregnation temperature of the thermoplastic resin. The method also includes impregnating the heated thermoplastic resin into the reinforcing fibers to form a heated composite material. The method also includes cooling the heated composite material to form a thermoplastic composite material. The heating step may include multiple vacuum cavities in an oven. The seal may be an inflatable tube, an airbag, or a portion.

[0004] The heating step may include heating the vacuum chamber to an impregnation temperature above the glass transition temperature of the thermoplastic resin to achieve a temperature greater than 25 cm according to ISO 1133-1. 3 / 10 minutes and a melt volume rate measured using a test temperature equal to the impregnation temperature using a 2.16 kg nominal load. The heating step can reduce the dynamic viscosity of the heated thermoplastic resin to less than 1000 Pa-s, and in some embodiments less than 500 Pa-s, according to ISO6721-10, when measured at an angular frequency of 0.01 rad / s. The ideal impregnation temperature varies depending on the specific resin. In polyolefins and copolyesters, the ideal impregnation temperature can exceed 270°C, and in some embodiments can exceed 290°C. The heating step can include heating multiple vacuum sealed cavities in an oven.

[0005] The first metal component and the second metal component can be a first rigid metal component and a second rigid metal component, respectively. The first metal component and the second metal component include a first flat surface and a second flat surface, respectively. The subjecting step includes subjecting the sealed cavity to a vacuum to form a vacuum cavity, the vacuum cavity having a support area under vacuum, applying an impregnation pressure on a surface area of ​​the stack that is smaller than the support area under vacuum to produce a strengthening effect caused by a ratio of the support area under vacuum to the surface area of ​​the stack that is greater than 1. The vacuum can produce a pressure differential of 0.1 to 1 bar between the vacuum cavity and the area outside the vacuum cavity, and the average impregnation pressure can be proportional to the ratio multiplied by the pressure differential. The deflection of the overhanging area of ​​the sealed cavity during the subjecting step is supported by one or more support structures at some point during the process.

[0006] The heating step may include heating the stack to an infusion temperature of the thermoplastic resin to form a heated thermoplastic resin while maintaining a seal temperature of the seal below a seal temperature limit of the seal. The infusion temperature of the thermoplastic resin may exceed the temperature limit of the seal. The infusion temperature may be 280°C or higher and the seal temperature may be 260°C or lower. The maintaining step may be performed using active cooling. The maintaining step may be performed using passive cooling. The temperature difference between the infusion temperature and the seal temperature may be at least 5°C.

[0007] At least one thermoplastic resin layer can include a nonwoven fabric of spunbond fibers, melt-blown fibers, needle-punched fibers, wet-laid fibers or air-laid fibers. At least one thermoplastic resin layer can include at least one thermoplastic film. Non-limiting examples of thermoplastic resins include polyolefins, polyamides, polyesters and copolyesters. At least one reinforcing fiber layer can include a woven fabric, a non-crimp fabric, a non-woven fabric or a binder-stabilized fabric. Reinforcing fibers can include glass fiber, carbon fiber, mineral fiber, organic fiber, natural fiber or a combination thereof.

[0008] The impregnation temperature may be greater than a thermogravimetric analysis (TGA) onset temperature of at least one thermoplastic resin layer in air using a heating rate of 0.1° C. / min.

[0009] The infusion step may include infusing a heated thermoplastic resin into the reinforcing fibers to form a heated composite material resulting from a 20% to 80% reduction in height between the first metal member and the second metal member.

[0010] At least one thermoplastic resin layer includes a first thermoplastic resin layer and a second thermoplastic resin layer. At least one reinforcing fiber layer may include a first reinforcing fiber layer and a second reinforcing fiber layer. The laminate may include at least three alternating layers, at least three alternating layers including at least one reinforcing fiber layer and at least one thermoplastic resin layer. The laminate may include a metal layer. In one embodiment, the top layer and the bottom layer may be metal, thereby increasing the stiffness or wear resistance or shielding quality of the thermoplastic composite material while preventing the laminate from adhering to the component. At least one thermoplastic resin layer may be a polyolefin, polyester, copolyester or polyamide family. The laminate may include at least one metal layer.

[0011] The method may further comprise: maintaining at the immersion temperature for a holding period. The holding period may be 1 to 60 minutes.

[0012] The subjecting step may include increasing the applied vacuum during the heating step.After the cooling cycle, the vacuum chamber may be subjected to a positive gas pressure to open the vacuum chamber and separate the thermoplastic composite material from one or both of the first component and the second component, thereby removing the thermoplastic composite material from the chamber.

[0013] In another embodiment, a method for embedding reinforcing fibers in a thermoplastic resin is disclosed. The method includes: providing a sealed cavity defined by a first metal member and a second metal member and a seal, the sealed cavity enclosing a thermoplastic prepreg partially impregnated with reinforcing fibers with a thermoplastic resin. The method also includes: subjecting the sealed cavity to a vacuum to form a vacuum cavity, thereby applying an impregnation pressure on the thermoplastic prepreg. The method also includes: heating the thermoplastic prepreg to an impregnation temperature of the thermoplastic resin to form a heated thermoplastic resin, while maintaining a seal temperature of the seal below the impregnation temperature of the thermoplastic resin. The method also includes: impregnating the heated thermoplastic resin into the reinforcing fibers to form a heated composite material. The method also includes: cooling the heated composite material to form a thermoplastic composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A top view of the cavity of the closed stack is depicted.

[0015] Figure 2 Depicts the Figure 1 The line 2-2 is intercepted Figure 1 A cross-sectional view of the cavity and stack.

[0016] Figure 3 Depicted is a top view of a cavity enclosing a stack including a core material.

[0017] Figure 4 Depicts the Figure 1 4-4 interception Figure 3 A cross-sectional view of a cavity and a stack including a core material.

[0018] Figure 5A Depicted are a partial cross-sectional view and a partial end view of a bellows seal.

[0019] Figure 5B Depicted are partial cross-sectional and partial end views of an alternative bellows seal.

[0020] Figure 6 A partial cross-sectional view and a partial end view of an inflatable seal are depicted.

[0021] Figure 7 A perspective view of a stent supporting a lumen is depicted.

[0022] Figure 8 Depicts the oven Figure 7 A stereogram of the bracket. DETAILED DESCRIPTION

[0023] As required, detailed embodiments of the present invention are disclosed herein, however, it should be understood that the disclosed embodiments are merely examples of the present invention that may be specifically implemented in various alternative forms. The drawings are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein are not to be interpreted as limiting, but are merely to be interpreted as a representative basis for teaching those skilled in the art to adopt the present invention differently.

[0024] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The drawings are not necessarily to scale; some features may be exaggerated or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein are not to be interpreted as limitations, but are merely to be interpreted as a representational basis for teaching those skilled in the art to adopt the embodiments differently. As will be understood by those of ordinary skill in the art, the various features illustrated and described with reference to any one of the figures may be combined with the features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combination of the illustrated features provides representative embodiments of typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be desirable for specific applications or implementations.

[0025] As used herein, the terms "substantially," "generally," or "approximately" mean that the amount or value in question may be a specified specific value or some other value in its vicinity. It may be implied that the specified specific value is modified by the term "approximately." The term "approximately," which represents a value, is intended to represent a range within ±5% of that value. As an example, the phrase "approximately 100" represents a range of 100 ± 5 (i.e., a range of 95 to 105). The term "substantially" may modify a value or relative property disclosed or claimed in the present disclosure. In this case, "substantially" may represent that the value or relative property it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of that value or relative property.

[0026] Integer ranges can include all intervening integers. For example, an integer range of 1 to 10 includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, a range of 1 to 100 includes 1, 2, 3, 4, ..., 97, 98, 99, and 100. Intervening numbers that are increments of the difference between the upper and lower limits divided by 10 (or a number of the magnitude of 10) can be considered as alternative upper or lower limits. For example, if the range is 1.1 to 2.1, the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 can be selected as lower or upper limits.

[0027] Fiber reinforced thermoplastic composites can generally include thermoplastic resins and reinforcing fibers. In many cases, resins and reinforcing fibers have different characteristics, so that when these components are combined, the resulting fiber reinforced composite has a characteristic between resin and reinforcing fibers. For example, resins can have relatively low strength, but can have relatively high elongation characteristics, and reinforcing fibers can have relatively high strength, but may be relatively brittle. The parts obtained by the composite material can have a strength greater than the resin, while also being relatively tougher than the reinforcing fibers.

[0028] Thermoplastic composite sheets are intermediate material forms in which reinforcing fibers are pre-impregnated with a matrix resin and manufactured into sheet form for further conversion into parts. Common terms used for such materials include: glass mat thermoplastics (GMT), which typically include chopped randomly oriented reinforcing fibers, also described as nonwoven fabrics sometimes combined with continuous reinforcing fibers in woven or stitched fabric form; organic sheets, which typically refer to sheets constructed from continuous reinforcing fibers in woven or stitched fabric form; tape-based laminates, which are produced using unidirectional (UD) continuous fiber composite tapes, which are typically assembled into multi-layer forms with customized fiber orientations in the individual layers; and thermoplastic prepregs, which are terms borrowed from the thermoset composite industry and are loosely applied to refer to pre-impregnated intermediate composite forms.

[0029] The term prepreg is generally applied to an intermediate material form of monomeric and prepolymeric thermosetting resins that partially or completely impregnates the reinforcing fibers in the form of continuous UD or fabric and maintains its flexibility until cured. Thermosetting resins generally exhibit rheological behavior that is significantly different from that of already polymerized thermoplastic resins, especially in their ability to reach very low viscosities at temperatures well below their curing temperature, after which they undergo an irreversible polymerization process, usually initiated by light or heat, usually in conjunction with a catalyst, to become a rigid polymer.

[0030] Thermoplastic composite sheets are usually produced in large quantities using a variety of methods. Both GMT and organic sheet forms are usually produced using a double belt press (DBP), in which a combination of reinforcing fibers in fabric form is combined with a thermoplastic resin delivered directly from a film die as a melt. The stack is continuously delivered to the DBP from a supplementary fabric roll. The DBP operates at a certain speed, which is controlled by the thickness of the laminate to be produced, the applied thermoplastic resin, the temperature and pressure of the belt, the permeability of the fabric, and the time to achieve sufficient impregnation levels. Usually these DBPs represent a significant investment, which can only be justified by significant demand and continuous operation, and usually prevents the end users of these products from integrating this process into their own operations. In addition, the investment and cost of operation require considerable pressure to accelerate impregnation and maximize production. Moreover, the width of the production line is a limiting factor and cannot be expanded beyond its original width. Larger sizes of interest (such as two (2) meters) are currently not available on the market, and thicknesses above a few millimeters are impractical for cost-effective production. Since it is impractical to operate such a line under vacuum conditions, the raw materials are exposed to ambient conditions such as air which may cause oxidation, thereby limiting the temperature to which a particular resin can be heated.

[0031] An alternative batch method for producing composite sheets is a type of stack molding in which individual stacks of resin in film form are assembled with fabrics of reinforcing fibers of specific sizes and placed between plates or stamping plates within a press. Typically, this process is designed to accommodate multiple stacks simultaneously by providing multiple stamping plates. Pressure is applied to the stack by the press and heat is applied by the stamping plates or heated housing. Although a vacuum can be applied to ambient conditions throughout the housing, the pressure is only generated by the press and the economy of the process requires higher pressures to accelerate impregnation. Larger sheet sizes result in press tonnage and cost. Higher thicknesses significantly reduce production volume and increase costs.

[0032] Melt impregnation of UD tapes provides another means of producing composite sheets, which pultrudes fibers in the form of continuous rovings, yarns or tows through a die through which heated thermoplastic resin is applied and impregnated into the fibers and cooled. These tapes are then assembled into multilayer laminates and consolidated by various means. Consolidation is a term used to transform layers or sheets of already pre-impregnated thermoplastic composite sheets into solid laminates. Various means include DBP, autoclaves (vacuum bagging) and hot presses. The capital investment for the entire conversion process is huge and exceeds the ability of most customers of such composite sheets to adopt internally.

[0033] In view of the above, there is a need for the ability of a converter of composite sheets to cost effectively produce its own sheets, regardless of sheet size and thickness.One or more methods disclosed herein separate the impregnation process from the expensive equipment used by other processes to apply pressure.

[0034] Impregnation is a process that requires time, temperature and pressure. One or more methods disclosed herein show that, as long as sufficient impregnation time and temperature are given to achieve sufficiently low viscosity, vacuum can be used alone to generate sufficient pressure to produce thermoplastic composite sheets. The process currently used to impregnate reinforcing fabrics with thermoplastic resins can use equipment (e.g., hydraulic press, DBP or autoclave) representing expensive capital investment. One or more methods disclosed herein utilize vacuum alone between two components to form a pressure for impregnation. Since the pressure formed is relatively low (e.g., 0.1 to 2 bar), the lower viscosity of the resin is achieved at relatively high processing temperatures (e.g., 250°C or higher), which cannot be used in some conventional processes because higher processing temperatures may cause oxidation of resins such as polypropylene. Conventional processes operated under higher pressures from external sources such as double belt presses, hydraulic presses or autoclaves may cause excessive resin flow at such low viscosity, thereby causing the position of the reinforcing fibers to be disturbed by the resin washing, or causing the resin to flow excessively from the laminate.

[0035] One or more methods disclosed herein can provide a relatively low-cost process to batch process multiple stacks in an oven in a closed support under vacuum, the support including a support for supporting the stack. Batch processing can perform impregnation on all supported stacks in a relatively short period of time (e.g., 30 minutes to 3 hours). Batch processing provides the ability to produce composite sheets using reinforcing fibers in larger forms than provided using existing infrastructure and systems and in smaller volumes than using traditional capital-intensive process economies.

[0036] Due to one or more reasons, conventional vacuum bagging processes cannot achieve one or more results of one or more methods disclosed herein. Conventional vacuum bagging processes can be used to form parts by curing thermosetting resins that are not fully polymerized. Low viscosity liquids can be infused into dry stacks of reinforcing fibers at a temperature lower than the final glass transition temperature of the cured resin, and the reinforcing fibers are applied to a mold with a part shape under a sealed flexible member (also referred to as a film or bag) to which a vacuum is applied and then cured under heating. Prepregs in which the reinforcing fibers have been partially or completely impregnated with thermosetting resins can be applied to a mold with a part shape under a sealing film, and consolidated and heated under a pressure differential until cured. Any subsequent impregnation is reduced as the viscosity of the thermosetting resin is heated to below the glass transition temperature of the cured polymer. One or more impregnation methods described herein are carried out at a temperature higher than the glass transition temperature of the polymer.

[0037] The curing process of conventional vacuum bagging process is not reversible like thermosetting resin. Therefore, conventional vacuum bagging process is not used to make composite sheets that can be subsequently formed into shaped parts. Vacuum bagging uses elevated temperature, which reduces viscosity and then immediately cures by polymerization of thermosetting resin. Polymerization makes thermosetting resin become irreversible rigid state. In the case of reversible reduction of viscosity without curing, vacuum bagging does not use elevated temperature. The elevated temperature used in vacuum bagging process is within the normal processing window of thermosetting resin. Vacuum bagging process is not used with highly elevated temperature to achieve low viscosity for impregnation. Conventional vacuum bagging applies three-dimensional mold (e.g., rigid tool surface) and flexible film. Vacuum bagging process does not use a pair of planar rigid surfaces to produce intermediate forms. Vacuum bagging uses prepreg, in which fiber reinforcement material is partially or completely impregnated with resin before vacuum bagging process. Vacuum bagging is not used with single layer of resin and dry reinforcing fiber. When vacuum bagging is applied, the strengthening effect from vacuum alone cannot be achieved because the film cannot support the pressure difference and collapses on the material or relative surface. Instead, the resulting pressure on the material is exactly the pressure difference created between the vacuum and ambient conditions. The higher pressure is simply the result of increasing the ambient pressure via the autoclave.

[0038] Due to one or more reasons, conventional thermoplastic film stacking cannot achieve one or more results of one or more methods disclosed herein. Conventional thermoplastic film stacking combines the layers of resin and reinforcing fabric between two unsealed heated embossing plates or double belt presses open to the atmosphere. The only vacuum formed can be outside the heated embossing plate. Moreover, the pressure generated by the system only comes from the pressure applied to the embossing plate. In the matching mold process, the higher pressure generated is the product of the press used by the matching mold. In the lamination process, under the heat and pressure of the double belt press in continuous operation, the layer of resin in the form of melt, film or powder is combined with the layer of reinforcing fabric. This process cannot separate the resin from atmospheric oxygen, thereby operating at relatively low temperatures and relatively high pressures due to higher viscosity.

[0039] As disclosed herein, a method for embedding reinforcing fibers in a thermoplastic resin is disclosed. The method includes the following steps: providing a sealed cavity defined by a first metal member and a second metal member and a seal, the sealed cavity enclosing a stack. The stack includes at least one thermoplastic resin layer including a thermoplastic resin and at least one reinforcing fiber layer including reinforcing fibers. The method also includes: subjecting the cavity to a vacuum to form a vacuum cavity, thereby applying an impregnation pressure on the stack. The method also includes: heating the stack to an impregnation temperature of the thermoplastic resin to form a heated thermoplastic resin, while maintaining the seal temperature of the seal below the impregnation temperature of the thermoplastic resin. The method also includes: impregnating the heated thermoplastic resin into the reinforcing fibers to form a heated composite material (e.g., a heated composite sheet). The method also includes: cooling the heated composite material to form a thermoplastic composite material. Demolding or separation of the thermoplastic composite material may include introducing a positive gas pressure into the vacuum sealed cavity to reverse the pressure difference and separate the two members from the thermoplastic composite material. The thermoplastic composite material may be a thermoplastic composite sheet. The thermoplastic composite sheet may be a flat or planar sheet. However, the thermoplastic composite sheet may include slight curvatures and / or minor geometries to accommodate functional and / or aesthetic design features.

[0040] Figure 1 and Figure 2A cavity 10 of a closed stack 12 is depicted. The cavity 10 includes a first member 14 formed by a first rigid planar member, a second member 16 formed by a second rigid planar member, and a seal 18 formed by a sealing material. The second member 16 may have a larger perimeter than the first member 14 to form a ledge configured to facilitate mechanical gripping and movement of the cavity 10. Non-limiting examples of sealing materials include suction cups, elastomers, rubbers, compressible materials, foams, bellows, and inflatable shapes. The seal 18 may be adhesively applied to the first member 14 or the second member 16. The first member 14 includes an inner skin 20, an outer skin 22, and a core 24 extending between the inner skin 20 and the outer skin 22. The inner skin 20 and the outer skin 22 may be formed of a metal material. The core 24 may be formed of a honeycomb core. The second member 16 includes an inner skin 26, an outer skin 28, and a core 30 extending between the inner skin 26 and the outer skin 28. The inner skin 26 and the outer skin 28 may be formed of a metal material. The core material 30 may be formed of a honeycomb core material. The component skin may be formed of a metal material (e.g., steel, aluminum, or a nickel-iron alloy such as Invar). The component core may be formed of a honeycomb core material (e.g., steel, aluminum, or a nickel-iron alloy such as Invar). The core materials 24 and 30 are configured to reduce the heat used to increase the temperature of the first component 14 and the second component 16 relative to the first component 14 and the second component 16 formed of a single sheet of metal or glass material. As disclosed alternatively, the first component and the second component may be formed of a single sheet of metal material, wherein the component has a thickness smaller than the first component and the second component having the core material. The component skin may have a thickness of 0.5 to 5 millimeters. The component core may have a thickness of 5 to 100 millimeters. The total thickness of the component may be 5 millimeters to more than 100 millimeters. The laminate 12 may have a width of 0.1 to 5.0 meters. The laminate 12 may have a length of 0.1 to 5.0 meters. The laminate 12 may have a thickness of 0.25 to 100 millimeters.

[0041] like Figure 2 As shown, the laminate 12 includes five (5) layers 12A and four (4) layers 12B, which are thermoplastic resin layers formed by thermoplastic resin and reinforcing fiber layers formed by reinforcing fibers, respectively. The total number of total layers can be 2 to more than 400 layers. More than one layer of thermoplastic resin or reinforcing fiber can be arranged between adjacent reinforcing fiber layers or thermoplastic layers. The layering sequence can be one thermoplastic resin layer, two reinforcing fiber layers, one thermoplastic resin layer, two reinforcing fiber layers, and so on.

[0042] The thermoplastic resin layer may include a nonwoven fabric. The nonwoven fabric may be a spunbond fiber, a meltblown fiber, a needle-punched fiber, a wet-laid fiber, or an air-laid fiber. Spunbond fibers can be produced using a continuous process of spinning fibers and dispersing the spun fibers (e.g., via an airflow) into a mesh deflector and onto a belt. Meltblown fibers can be produced by blowing a heated polymer coming out of an orifice into a fine fiber bundle via hot, high-speed air. Spunbond and meltblown forms can operate over a wider melt flow range (e.g., greater than 10cc / 10 minutes) than film forms, which typically require a higher melt strength in order to process into a film. Resins with higher melt flows typically exhibit poorer melt strength or require special formulations that increase costs. Since resins with higher melt flows also exhibit lower viscosity, they are more conducive to impregnation, especially at relatively low pressures as described in one or more methods disclosed herein. Needle-punched fibers can be produced by a fiber web (e.g., a carded web) that is repeatedly penetrated by fine needles and then bonded together by fiber entanglement. Wet-laid fibers can be produced by suspending staple fibers, optionally mixed with viscose and / or wood pulp to form a water-fiber / pulp dispersion that is continuously deposited on a forming wire. Air-laid fibers can be produced by forming a fiber web by mixing fibers with air to form a uniform air-fiber mixture, which is then deposited on a moving, air-permeable belt or wire.

[0043] The thermoplastic resin layer can be formed by a thermoplastic film. The reinforcing layer can include a woven fabric, a non-flex fabric, a non-woven fabric or a fabric stabilized by an adhesive. The reinforcing layer can include glass fiber, carbon fiber, mineral fiber, organic fiber, natural fiber or a combination thereof. The thickness of each thermoplastic resin layer can be 0.01 to 1.0 millimeter. The thickness of each reinforcing layer can be 0.01 to 1.0 millimeter.

[0044] The individual layers of the laminate 12 can be cut and laid up on a cutting table. Once laid up, the laminate 12 can be placed on the inner skin 26 of the second member 16 before or after the seal 18 is placed on the inner skin 26 of the second member 16. After the laminate 12 and the seal 18 are placed on the inner skin 26 of the second member 16, the first member 14 is placed thereon so that the inner skin 20 of the first member 14 contacts the seal 18 and the laminate 12, thereby forming the cavity 10. Once the cavity 10 is formed, the width of the seal 18 can be 5 to 100 millimeters, depending on the seal profile, the sealing method, and the height of the laminate. Once the cavity 10 is formed, the height of the seal 18 can be 0.25 to 100 millimeters. Once the cavity 10 is formed, the thickness of the laminate 12 can be 0.25 to 100 millimeters.

[0045] like Figure 1As shown, stack 12 has stack perimeter 32, seal 18 has inner perimeter 34 and outer perimeter 36, and first component 14 and second component 16 have component perimeter 38. Seal 18 is located inwardly of component perimeter 38 of cavity 10 and has an inward dimension.

[0046] like Figure 1 As shown, the stack perimeter 32 is smaller than the inner perimeter 34 of the seal 18 to form a gap area therebetween. The gap area accommodates the perimeter increase from the stack perimeter 32 to the perimeter of the thermoplastic composite during the embedding of the reinforcing fibers into the thermoplastic resin and the bulging of the seal 18 during the embedding process, which reduces the inner perimeter 34 of the seal 18 and increases the outer perimeter 36 of the seal 18. Alternatively, a seal (such as a bellows seal or an inflatable seal) that does not bulge during the process but undergoes some other structural changes to accommodate height changes can be used. The gap area before embedding is constructed so that the gap area is not eliminated after embedding to avoid contact between the edge area of ​​the thermoplastic composite and the seal 18. This contact may cause the thermoplastic composite to adhere to the seal 18 at the edge, thereby making the edge unusable. The unusable edge is trimmed as waste. Moreover, this situation may make the seal 18 unusable. Prior to embedding, the gap region may be minimized to produce a uniform thickness of the thermoplastic composite while avoiding contact between the thermoplastic composite and the seal 18. The gap region may cause the first member 14 and / or the second member 16 to overhang because the gap region is not supported by the stack 12. The overhang or overhang may cause a lack of uniformity in the thickness of the thermoplastic composite. Such lack of uniformity in the edge region may be discarded when uniformity in the thickness of the composite is desired. The support structure 42 may be located in the gap region between the stack 12 and the seal 18, or located outside the seal 18, or located within the seal, such as Figure 6 As shown. The height of the support structure 42 can be positioned at about (e.g., slightly less than or slightly greater than) the target final thickness of the impregnated stack. The support structure 42 is configured to help minimize the overhang effect by reducing the length of the overhang (e.g., a few millimeters to less than one millimeter), thereby reducing waste. The support structure 42 can be formed of a metal material such as aluminum.

[0047] The cavity 10 also includes a vacuum port 40 configured to receive a vacuum line (not shown). The vacuum port 40 may include an inner shoulder for receiving an end of the vacuum line to create suction therebetween when a vacuum is applied within the vacuum line. Demolding or separation of the thermoplastic composite may include introducing positive air pressure into the vacuum sealed cavity through the vacuum port 40 to reverse the pressure differential and separate the two components from the thermoplastic composite. Figure 7 and Figure 8 Describe the vacuum line in more detail.

[0048] Figure 3 and Figure 4 A cavity 50 is depicted enclosing a stack 52. The cavity 50 includes a first member 54 formed by a first rigid planar member, a second member 56 formed by a second rigid planar member, and a seal 58 formed by a sealing material. The seal 58 may be suitable for stacks, such as stacks 52 including a core material 52C, because the seal does not have to be compressed as much as it is for stacks formed only by alternating layers without a core material. The seal 58 may have a compression factor in the range of 1% to 30%, while the bellows seal and / or the inflatable seal may have a compression factor in the range of 1% to 80%. The compression factor indicates the amount of compression as a percentage of the uncompressed height. The support structure 62 has a height of approximately (e.g., slightly less than or slightly greater than) the target final thickness of the impregnated stack. The first member 54 and the second member 56 may be formed by a single sheet of material such as metal, glass (e.g., transparent glass) or ceramic. The single sheet of metal material may be constructed by machining on one side to optimize quality and performance, and may have internal channels for heating and cooling. Alternatively, the first and second components may also be constructed from multiple plates into which internal heating / cooling channels are stamped, machined or etched and assembled using diffusion bonding or brazing. The total thickness of the components may be from 5 mm to 100 mm.

[0049] like Figure 4 As shown, the stack includes an upper alternating layer 52A and a lower alternating layer 52B and a core material 52C extending therebetween. The core material 52C may be formed of a honeycomb or foam core material (e.g., metal, thermoplastic, paper, or thermosetting plastic). Each of the upper alternating layer 52A and the lower alternating layer 52B includes at least one thermoplastic resin layer formed of a thermoplastic resin and at least one reinforcing fiber layer formed of reinforcing fibers (e.g., glass fibers). The stack may also include an adhesive layer against the core material. One of the at least one thermoplastic resin layer of the upper alternating layer 52A may contact the first member 54, and one of the at least one thermoplastic resin layer of the lower alternating layer 52B may contact the second member 56. The chamber 50 also includes a vacuum port 60 configured to receive a vacuum line.

[0050] Figure 5AA cross-sectional view of a seal 100 is depicted. The seal 100 extends between a first member 104 and a second member 106 and around a cavity 108 within the perimeter of the first member 104 and the second member 106. The first flat portion 110 or the second flat portion 112 of the seal 100 may be adhesively fixed to the first member 104 or the second member 106, respectively. The angled portion 102 extends between the first flat portion 110 and the second flat portion 112 and includes a bellows 114 that contributes to the structural integrity of the seal to maintain functionality under an applied pressure differential. The angled portion 102 is configured to flex from an uncompressed state to an initial compressed state when the cavity 108 is subjected to a vacuum to form a vacuum-sealed cavity, and flex to a final compressed state once the thermoplastic resin layer is fully impregnated into the reinforcing fiber layer. The bellows 114 is configured to provide structural strength to the seal 100. The seal 100 is configured to compress its height at a compression factor (e.g., 1% to 80%).

[0051] Figure 5B A cross-sectional view of a seal 150 is depicted. The seal 150 extends between a first member 154 and a second member 156 and around a cavity 158 within the perimeter of the first member 154 and the second member 156. The first flat portion 160 or the second flat portion 162 of the seal 150 may be adhesively secured to the first member 154 or the second member 156, respectively. An angled portion 164 extends between the first flat portion 160 and the second flat portion 162 and includes a bellows 166. The angled portion 164 is configured to flex from an uncompressed state to an initial compressed state when the cavity 158 is subjected to a vacuum to form a vacuum-tight cavity, and to flex to a final compressed state once the thermoplastic resin layer is fully impregnated into the reinforcing fiber layer. The bellows 166 is configured to strengthen and reinforce the seal 150. The seal 150 is configured to compress its height at a compression factor (e.g., 1% to 80%).

[0052] Figure 6A partial cross-sectional view and a partial end view of an inflatable seal 170 are depicted. The seal 170 extends between a first member 172 and a second member 174 and around a cavity 178 within the perimeter of the first member 172 and the second member 174. The seal 170 includes an arched portion 176 configured to contact the first member 172. The arched portion 176 terminates at a first flange 180 and a second flange 182 extending inwardly into a sealed cavity 184. In another alternative, the first flange and the second flange may extend outwardly from the sealed cavity 184. A support structure 186 is positioned within the cavity 184. The support structure 186 includes a first notch 188 and a second notch 190, which are configured to receive the first flange 180 and the second flange 182, respectively. The bottom surface of the support structure 186 may be adhesively or mechanically fixed to the second member 174. The first flange 180 and the second flange 182 may be adhesively or mechanically fixed to the second member 174 and / or the support structure 186. The height of the support structure 186 can be positioned at approximately (e.g., slightly less than or slightly greater than) the target final thickness of the impregnated stack. The support structure 186 is configured to help minimize the overhang effect identified herein, thereby reducing thickness variations at the edges of the stack and reducing waste. Port 192 is configured to introduce pressurized gas (e.g., 0.1 to 5 bar) into the sealing cavity 184. The sealing cavity 184 is configured to compress to form an initial compressed state against the initial height of the stack when the cavity 178 is subjected to a vacuum, and to compress to a final compressed state once the thermoplastic resin layer is fully impregnated into the reinforcing fiber layers of the stack. The seal 170 is configured to compress its height with a compression factor (e.g., 1% to 80%).

[0053] Figure 7 A stent 200 is depicted with a cavity 202 supported by a support 204. The stent 200 includes a left side 206 and a right side 208, a top 210, and a bottom 212. The stent 200 may be formed of a metallic material (e.g., steel or aluminum). Figure 7 As shown, there are seven (7) supports 204 configured to support seven (7) chambers 202. The number of supports can be from 1 to 200. One or both of the left side 206 and the right side 208 can include a panel with an opening configured to receive a vacuum line therethrough. The height of each opening can be from 25 to 250 millimeters. The support 200 can be supported on casters 214 that are configured to easily transport the support 200 after the support 200 is loaded with chambers 202, each chamber containing a stack. The width and length of the support 200 can be sized to accommodate the width and length of the chambers supported therein. The height of the support 200 can be sized to accommodate the chambers 202 supported by the supports 204 of the support 200. The height can be from 1.0 to 15.0 feet.

[0054] Figure 8The rack 200 is depicted being placed in the oven 220 through an opening 222 defined by the oven 220. Once the rack 200 is placed in the oven 220, the door 224 is configured to rotate from an open position to a closed position. The oven 220 includes a left side panel 226 and a right side panel 228 and an upper panel 230 extending therebetween. The right side panel 228 includes an aperture 232 that is configured to receive a vacuum line 234 therethrough. The distal end of the vacuum line 234 is configured to attach to a vacuum port 236 of the chamber 202. The width, length, and height of the oven 220 can be sized to accommodate the width, length, and height of the rack 200.

[0055] After the support 200 is placed in the oven 220, the vacuum line 234 is connected to the vacuum port 236 of the sealed cavity 202, and a vacuum can be applied between two rigid planar members to apply an impregnation pressure on each laminate. The vacuum produces a pressure difference between the vacuum sealed cavity and the area outside the vacuum sealed cavity. The pressure difference can be 0.1 to 1.0 bar. The support area of ​​the member can include an overhanging area outside the laminate, and when subjected to the pressure difference of the vacuum, the overhanging area can maintain its planar geometry. The rigidity of the member can make the local deformation of the member surface under the load in contact with the laminate less than 1mm, and the deflection of any overhanging area is less than 10mm. In some embodiments, the local deformation of the member surface in contact with the laminate is less than 0.050mm. In other embodiments, the deflection of any overhanging area of ​​the member is less than 5mm. During this process, when the gap between the upper member and the lower member is reduced due to the resin layer being impregnated into the fiber layer, the support structure can be used to control and / or offset the deflection of the overhanging area and the deformation of the member adjacent to the perimeter of the laminate. Such a support structure may not engage with the member until the stack approaches its final thickness. The self-supporting overhanging area outside the stack subjected to the pressure difference of the vacuum can contribute additional load to the stack, thereby increasing the impregnation pressure by more than the size of the pressure difference. The ratio of the support area under vacuum (e.g., the area of ​​the stack including the stack support member and the self-supporting overhanging area outside the stack) (e.g., the perimeter inside the inner perimeter of the seal, where the perimeter is projected on a flat plane) to the surface area of ​​the stack (e.g., the upper or lower surface of the stack) can be greater than or equal to 1. The average impregnation pressure is proportional to this ratio multiplied by the pressure difference. Due to the local deformation of the member under the load across the stack and into any overhanging area that may exist, the impregnation pressure across the stack can be variable. Therefore, in some embodiments, the term average impregnation pressure is used. When the stack is positioned between two rigid planar members, the pressure difference causes the pressure applied directly to the stack. If the area of ​​the stack is equal to the support area under vacuum between the two members, the pressure applied to the stack is the same as the pressure difference achieved by the vacuum. However, if the area of ​​the stack is smaller than the support area under vacuum, the pressure applied directly to the stack is intensified and is higher than the pressure differential.

[0056] In one or more methods disclosed herein, in addition to the static weight of the top member, vacuum is the only source of impregnation pressure (e.g., no mechanical or external pressure means are applied to the stack). However, these disclosed methods do not exclude increasing the impregnation pressure by external pressure (e.g., by mechanical or external means). For example, the impregnation pressure can be increased by applying a weight (e.g., a 1000-pound steel block) on the top of the member and / or by using a fixture to open and close the member. Since the member may be heavy (e.g., 100 kilograms) for a relatively large area, a fixture system can be used to open and close the cavity generated by the member to load the stack and unload the thermoplastic composite material. The fixture can apply a relatively small force on the stack. In one or more methods, vacuum can be the main source of impregnation pressure without excluding other sources of impregnation pressure (e.g., by mechanical or external means). The heated stamping plate can be configured to locally apply heat to the metal member by conduction to increase the impregnation pressure.

[0057] The method may further include increasing the vacuum level during the heating step.In one or more methods disclosed herein, the layup is heated to an infusion temperature to infuse the heated thermoplastic resin into the reinforcing fibers to form a heated composite material while maintaining a seal temperature of the seal below the infusion temperature of the thermoplastic resin.

[0058] In addition to removing trapped air within the layup, the vacuum also facilitates heating the thermoplastic resin in the layup above its normal processing temperature when processed under ambient conditions because the vacuum removes oxygen from the sealed environment, thereby mitigating or preventing oxidation. This allows the embedding process to heat the thermoplastic resin to temperatures significantly higher than would otherwise be practical, in order to reduce the viscosity of the resin to a level where the resin can penetrate the fibers at the relatively low pressures achieved by the vacuum.

[0059] The heating step may be accomplished by placing the sealed cavity in an oven or alternatively by heating integrated into the cavity member to heat the stack. Such integrated heating may include electrical heating elements or internal channels through which steam or a heating fluid (such as oil) is pumped to heat the individual stacks. The step of heating the stack may be performed by an external hot plate or a stamping plate that applies heat directly to the metal member by conduction. Other non-limiting methods of heating the stack may include infrared heating of the metal member.

[0060] The heating step may include maintaining the seal temperature of the seal below the impregnation temperature of the thermoplastic resin during the heating step (e.g., one or more heating cycles) to protect the seal from degradation and reduction in life. The seal may be formed of a thermosetting or thermoplastic material. These seal materials cannot withstand relatively high impregnation temperatures in repeated heating / impregnation cycles. The seal material may have a seal temperature limit, and if the limit is exceeded by heating the seal to the impregnation temperature, the seal may be degraded or its normal life may be reduced. One or more properties of the seal (e.g., shear strength, compressive strength, or tensile strength) may degrade at the impregnation temperature, rendering the seal inoperative. Exceeding the seal temperature may also significantly or substantially reduce the normal life of the seal. Life may refer to the number of heating cycles in which the seal is used. A substantial reduction in life may be measured as a percentage reduction in life. The percentage reduction in life can be at least any one of the following percentages or a range of any two of the following percentages: 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0%. The substantial reduction in life can be measured in a reduction in useful cycles. The number of reductions in useful cycles can be at least any one of the following numbers or a range of any two of the following numbers: 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and 200.

[0061] Maintaining the seal temperature below the seal temperature limit and / or the impregnation temperature of the thermoplastic resin can be achieved by actively cooling and / or passively cooling the seal during the heating step. In the case where the seal is exposed to the same heating environment (e.g., in an oven) as for heating the stack, active cooling can be utilized. As an example of active cooling, a cooling medium can flow adjacent to the inner and / or outer sides of a solid or hollow seal (e.g., seals 18, 58, 100, 150, and / or 176). As another additional or alternative example of active cooling, a cooling medium can flow through the conduit of a solid seal or the cavity of a hollow seal (e.g., through a port 192 communicated with seal 170). For example, an internal passage can be configured to facilitate active cooling of the seal during the heating step. Passive cooling can be used to separate or isolate the seal from the heating environment for heating the stack. A non-limiting example of passive cooling is to cool the seal by ambient convection. Another non-limiting example is to isolate the seal from the heating environment using a thermal insulation material. Passive cooling can be applied to situations where local heating is applied to the system just above and / or just below the stack by conduction heating. In one or more embodiments, the temperature difference between the stack material and the seal is sufficient to provide sufficient impregnation of the stack while protecting the seal from thermal degradation and premature end of life. For example, the temperature difference can be any one of the following temperatures or within the range of any two of the temperatures: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20°C. As another example, the impregnation temperature (e.g., the temperature of the stack material) can reach 275°C or higher, while the seal temperature can be maintained at 270°C or lower. As yet another example, the impregnation temperature can reach 280°C or higher, while the seal temperature can be maintained at 260°C or lower. Active and passive technologies can be combined to create a protective environment for the seal.

[0062] The heating step can reduce the dynamic viscosity of the heated thermoplastic resin to less than 1000 Pa-s, and in some embodiments less than 500 Pa-s, when measured at an angular frequency of 0.01 rad / s, according to ISO 6721-10. The heating step includes heating the vacuum sealed cavity to an impregnation temperature so as to reduce the dynamic viscosity of the heated thermoplastic resin to less than 1000 Pa-s, and in some embodiments less than 500 Pa-s, according to ISO 1133-1. 3 The heated thermoplastic resin is impregnated at a melt volume rate measured using a 2.16 kg nominal load at a test temperature equal to the impregnation temperature for 10 minutes. The impregnation temperature may be greater than a thermogravimetric analysis (TGA) starting temperature of at least one thermoplastic resin layer in air using a heating rate of 0.1°C / minute. The embedding process may also include maintaining a holding period (e.g., 1 to 20 minutes) at the impregnation temperature.

[0063] By separating the process from the expensive equipment required to apply pressure, the economic dependence on the time of the process is significantly reduced, thereby allowing a wider time window to promote impregnation at lower pressures. The system for implementing the process includes a vacuum pump and a method for heating the laminate sealed in the plate under vacuum, heating the material to the desired impregnation temperature and maintaining the material at the temperature for the desired residence time to facilitate impregnation. Subsequently, the impregnated heated thermoplastic sheet can be cooled. Another benefit of an embodiment of the process is that a plurality of such cavities can be staged in a common oven in a batch process that can produce 2 to 100 sheets simultaneously, thereby obtaining a relatively high production volume with a very moderate capital investment.

[0064] The components of the system described herein may be actuated by a controller. The controller may include a processor, which may be any suitable processing device or processing device group, such as but not limited to a microprocessor, a microcontroller-based platform, an integrated circuit, one or more field programmable gate arrays (FPGAs) and / or one or more application-specific integrated circuits (ASICs). The memory may communicate with the controller. The memory may be a volatile memory (e.g., a RAM including nonvolatile RAM, magnetic RAM, ferroelectric RAM, etc.), a nonvolatile memory (e.g., a disk memory, a flash memory, an EPROM, an EEPROM, a nonvolatile solid-state memory based on a memristor, etc.), an unchangeable memory (e.g., an EPROM), a read-only memory and / or a high-capacity storage device (e.g., a hard disk drive, a solid-state drive, etc.). In some examples, the memory may include a variety of memories, particularly volatile memories and nonvolatile memories. The memory may be a computer-readable medium, on which one or more groups of instructions may be embedded, such as software for operating the method disclosed herein. The instruction may specifically implement one or more of the methods or logics described herein. For example, the instruction may reside completely or at least partially in any one or more of the memory, the computer-readable medium and / or in the controller during the execution of the instruction.

[0065] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the present invention. On the contrary, the words used in the specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the present invention. In addition, the features of the various embodiments may be combined to form other embodiments of the present invention.

Claims

1. A method for embedding reinforcing fibers in a thermoplastic resin, the method comprising: providing a sealed cavity defined by the first and second metal members and a seal, the sealed cavity enclosing a stack including at least one thermoplastic resin layer including the thermoplastic resin and at least one reinforcing fiber layer including the reinforcing fibers; subjecting the sealed cavity to a vacuum to form a vacuum cavity, thereby applying an impregnation pressure on the stack; heating the stack to an infusion temperature of the thermoplastic resin to form a heated thermoplastic resin while maintaining a seal temperature of the seal below the infusion temperature of the thermoplastic resin; infusing the heated thermoplastic resin into the reinforcing fibers to form a heated composite material; as well as The heated composite material is cooled to form a thermoplastic composite material.

2. The method according to claim 1, wherein: The heating step comprises: heating the vacuum chamber to the impregnation temperature above the glass transition temperature of the thermoplastic resin so as to be greater than 25 cm when measured according to ISO 1133-1 using a test temperature equal to the impregnation temperature and a nominal load of 2.16 kg. 3 The heated thermoplastic resin is impregnated at a melt volume rate of / 10 minutes.

3. The method according to claim 1, wherein: The first metal component and the second metal component are respectively a first rigid metal component and a second rigid metal component.

4. The method according to claim 1, wherein: The subjecting step includes subjecting the sealed cavity to a vacuum to form a vacuum cavity having a support area under vacuum, applying the impregnation pressure over a surface area of ​​the stack that is less than the support area under vacuum to produce a strengthening effect caused by a ratio of the support area under vacuum to the surface area of ​​the stack that is greater than 1.

5. The method according to claim 1, wherein: The first metal component and the second metal component include a first planar surface and a second planar surface, respectively.

6. The method according to claim 1, wherein: The heating step includes heating the stack to the infusion temperature of the thermoplastic resin to form the heated thermoplastic resin while maintaining the seal temperature of the seal below a seal temperature limit of the seal.

7. The method according to claim 1, wherein: The impregnation temperature of the thermoplastic resin exceeds a temperature limit of the seal.

8. The method according to claim 1, wherein: The vacuum generates a pressure difference of 0.1 to 1 bar between the vacuum chamber and a region outside the vacuum chamber, and the average impregnation pressure is proportional to the ratio multiplied by the pressure difference.

9. The method according to claim 1, wherein: The immersion temperature is 275° C. or higher, and the seal temperature is 270° C. or lower.

10. The method according to claim 1, wherein: The maintaining step is performed using active cooling.

11. The method according to claim 1, wherein: The maintaining step is performed using passive cooling.

12. The method according to claim 1, wherein: The temperature difference between the immersion temperature and the seal temperature is at least 5°C.

13. The method according to claim 1, wherein: The at least one thermoplastic resin layer comprises a nonwoven fabric of spunbond fibers, meltblown fibers, needlepunched fibers, wet-laid fibers or air-laid fibers.

14. The method according to claim 1, wherein: The at least one thermoplastic resin layer includes at least one thermoplastic film.

15. The method according to claim 1, wherein: The at least one reinforcing fiber layer comprises a woven fabric, a non-crimp fabric, a non-woven fabric, or an adhesive-stabilized fabric.

16. The method according to claim 1, wherein: The reinforcing fibers include glass fibers, carbon fibers, mineral fibers, organic fibers, natural fibers or a combination thereof.

17. The method according to claim 1, wherein: The immersion temperature is greater than a thermogravimetric analysis (TGA) onset temperature of the at least one thermoplastic resin layer in air using a heating rate of 0.1° C. / min.

18. The method according to claim 1, wherein: The impregnating step includes infusing the heated thermoplastic resin into the reinforcing fibers to form a heated composite material resulting from a 20% to 80% reduction in height between the first metal member and the second metal member.

19. The method according to claim 1, wherein: The at least one thermoplastic resin layer includes a first thermoplastic resin layer and a second thermoplastic resin layer.

20. The method according to claim 1, wherein: The at least one reinforcing fiber layer includes a first reinforcing fiber layer and a second reinforcing fiber layer.

21. The method according to claim 1, wherein: The laminate comprises at least three alternating layers comprising the at least one layer of reinforcing fibers and the at least one layer of thermoplastic resin.

22. The method of claim 1, further comprising: The immersion temperature is maintained for a holding period of 1 to 60 minutes.

23. The method according to claim 1, wherein: The impregnation pressure is increased by external pressure.

24. The method according to claim 1, wherein: The heating step includes heating the plurality of vacuum chambers in an oven.

25. The method of claim 1, wherein: Deflection of the overhanging region of the sealed cavity during the subjecting step is supported at some point during the process by one or more support structures.

26. The method of claim 1, wherein: The seal is an inflatable tube, bladder or portion.

27. The method of claim 1, wherein: The layer stack comprises at least one metal layer.

28. The method of claim 1, wherein: The subjecting step includes increasing the applied vacuum during the heating step.

29. The method of claim 1, wherein: After the cooling cycle, the vacuum chamber is subjected to positive gas pressure to open the vacuum chamber and separate the thermoplastic composite material from one or both of the first and second metal components, thereby removing the thermoplastic composite material from the chamber.

30. A method of embedding reinforcing fibers in a thermoplastic resin, the method comprising: providing a sealed cavity defined by the first and second metal members and a seal, the sealed cavity enclosing a thermoplastic prepreg partially impregnating the reinforcing fibers with the thermoplastic resin; subjecting the sealed cavity to a vacuum to form a vacuum cavity, thereby exerting an impregnation pressure on the thermoplastic prepreg; heating the thermoplastic prepreg to an infusion temperature of the thermoplastic resin to form a heated thermoplastic resin while maintaining a seal temperature of the seal below the infusion temperature of the thermoplastic resin; infusing the heated thermoplastic resin into the reinforcing fibers to form a heated composite material; as well as The heated composite material is cooled to form a thermoplastic composite material.

Images