Method and system for curing composites and related microcrack resistant composites

Abstract

To provide a method and a system for curing a composite material and a related microcrack resistant composite material.SOLUTION: A method for curing a composite material, including a thermosetting resin, a reinforcing material, and a thermoplastic additive which has a melt initiation temperature, includes heating the composite material so as to increase the resin temperature of the thermosetting resin and, during the heating, controlling the resin temperature so that the resin temperature exceeds the melt initiation temperature before the thermosetting resin reaches a curing degree of 98%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This application relates to the curing of composites such as carbon fiber reinforced plastics, and in particular to the curing of thermoplastic-toughened thermoset polymer-matrix composites. [Background technology]

[0002] Fiber-reinforced thermosetting polymer matrix composites, such as carbon fiber-reinforced plastics, tend to exhibit high strength at relatively low weight, and therefore are commonly used in a variety of applications (e.g., structural applications) throughout the aerospace industry, as well as in other industries (e.g., automotive and marine).

[0003] It has been known for some time that fiber-reinforced thermosetting polymer matrix composites can be strengthened by incorporating various thermoplastic additives within them. For example, interlayers containing thermoplastic filaments have been incorporated between reinforcing layers of carbon fiber reinforced material to increase the strength of the resulting fiber-reinforced thermosetting polymer matrix composite.

[0004] During the thermosetting cycle, the expansion and contraction of the components within the composite changes the stresses applied across the material, which can lead to microcracking. Such microcracking tends to occur within the thermosetting polymer matrix, particularly at the interfaces between the resin and the reinforcing materials, and between the resin and the thermoplastic additives.

[0005] Accordingly, research and development efforts by those skilled in the art continue to focus on the curing of composites. Summary of the Invention

[0006] A method is disclosed for curing a composite comprising a thermosetting resin, a reinforcing material, and a thermoplastic additive, the thermoplastic additive having an onset melting temperature.

[0007] In one embodiment, the method of the present disclosure includes heating the composite to increase the resin temperature of the thermosetting resin, and controlling the resin temperature during the heating so that the resin temperature exceeds a melting initiation temperature before the thermosetting resin reaches about 100 percent cure.

[0008] In another embodiment, the method of the present disclosure includes heating the composite to increase the resin temperature of the thermosetting resin, and controlling the resin temperature during the heating step such that the resin temperature exceeds a melting initiation temperature before the thermosetting resin reaches 98 percent cure.

[0009] In another embodiment, a method of the present disclosure includes the following steps: (1) placing a preform including a reinforcing material and a thermoplastic additive in an oven; (2) injecting a thermosetting resin into the preform to produce a resin-infused preform; (3) heating the resin-infused preform to increase the resin temperature of the thermosetting resin; and (4) controlling the resin temperature during the heating such that the resin temperature exceeds a melting initiation temperature while the thermosetting resin has a degree of cure of between about 5 percent and about 85 percent.

[0010] Also disclosed is a system for curing a composite including a thermosetting resin, a reinforcing material, and a thermoplastic additive, wherein the thermosetting resin has a resin temperature and the thermoplastic additive has a melting onset temperature.

[0011] In one embodiment, a system of the present disclosure includes an oven having an oven temperature, a first temperature sensor positioned to detect the oven temperature, a tool positioned within the oven, the tool defining a tool surface for supporting a composite thereon, a vacuum bag coupled to the tool to define an injection space between the vacuum bag and the tool, a resin source fluidly coupled to the injection space to supply a thermosetting resin to the injection space, a second temperature sensor positioned to detect a resin temperature of the thermosetting resin in the injection space, and a controller in communication with the first temperature sensor, the second temperature sensor, and the oven, wherein the controller controls the resin temperature of the thermosetting resin in the injection space to exceed a melting initiation temperature during curing of the composite before the thermosetting resin reaches approximately 85 percent cure.

[0012] Crack resistant composites produced using the methods and systems of the present disclosure are also disclosed.

[0013] The disclosed methods and systems for curing composites and related microcrack resistant composites will become apparent from the following detailed description, the accompanying drawings, and the appended claims. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a flow diagram illustrating one embodiment of a method for curing a composite material of the present disclosure. [Figure 2] 2 is a schematic cross-sectional view of a composite that can be produced using the method of FIG. 1. [Figure 3] 2 is a graphical representation (temperature and extent of cure versus time) of a thermal cure cycle not performed according to the method of FIG. 1. [Figure 4] 2 is a graphical representation (temperature and extent of cure versus time) of an exemplary thermal cure cycle carried out according to the method of FIG. 1. [Figure 5] 2 is a graphical representation (temperature and extent of cure versus time) of another exemplary thermal cure cycle carried out according to the method of FIG. 1. [Figure 6] 2 is a graphical representation (temperature and extent of cure versus time) of another exemplary thermal cure cycle carried out according to the method of FIG. 1. [Figure 7] 2 is a graphical representation (temperature and extent of cure versus time) of yet another exemplary thermal cure cycle carried out according to the method of FIG. 1. [Figure 8] FIG. 2 is a flow diagram depicting another embodiment of a method for curing a composite of the present disclosure. [Figure 9] 1 is a schematic representation of one embodiment of a system for curing composites of the present disclosure. [Figure 10] FIG. 1 is a flow diagram of an aircraft production and service method. [Figure 11] FIG. 1 is a block diagram of an aircraft. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following detailed description refers to the accompanying drawings, which illustrate specific embodiments of the present invention. Other examples having different structures and processes are also within the scope of the present disclosure. Like reference numbers may represent the same elements or components in different drawings.

[0016] Referring to FIG. 1, a flow diagram illustrating one embodiment of a method 100 of the present disclosure for curing a composite 10 (FIG. 2) is shown. As shown in FIG. 2, the composite 10 may include a thermosetting resin 12, a reinforcing material 14, and a thermoplastic additive 16. The thermosetting resin 12 is heated to a resin temperature (T R The thermoplastic additive 16 has a melting onset temperature (T eim As used herein, the melting onset temperature (T eim ) means the extrapolated melting onset temperature as specified in accordance with ASTM D3418.

[0017] As indicated at block 110, the method 100 determines the resin temperature (TR 9. Heating (block 110) may include heating the composite 10 to enhance the thermal conductivity of the composite 10. Heating (block 110) may be performed by placing the composite 10 in an interior space 304 of an oven 302, such as the oven 302 shown in FIG.

[0018] As indicated at block 120, the method 100 begins by heating the thermoset resin 12 to a degree of cure (D) of approximately 100 percent (i.e., 98 percent or greater). C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R 9. The controlling (block 120) may be performed during heating (block 110), such as by a controller, such as controller 350 shown in FIG.

[0019] In one particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches approximately 85 percent degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches approximately 80 percent degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches approximately 75 percent degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (TR ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches approximately 70 percent degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches approximately 60 percent degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches approximately 50 percent degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches a degree of cure (D) of approximately 40 percent. C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches a degree of cure (D) of approximately 30 percent. C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In yet another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches a degree of cure (D) of approximately 20 percent. C ) before reaching the melt temperature (T R) is the melting temperature (T eim ) so that the melt temperature (T R ) may be controlled.

[0020] Resin temperature (T R ) (block 120) is controlled to maintain the thermosetting resin 12 at approximately 1 percent degree of cure (D C ) is reached, the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In one particular example, controlling the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches a degree of cure (D) of approximately 5 percent. C ) is reached, the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In yet another particular embodiment, the resin temperature (T R ) (block 120) is controlled to ensure that the thermosetting resin 12 reaches a degree of cure (D) of approximately 10 percent. C ) is reached, the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R ) may be controlled.

[0021] Resin temperature (T R ) (block 120) ensures that the thermosetting resin 12 reaches a degree of cure (D) between about 5 percent and about 80 percent. C ) while the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R In one particular example, controlling the resin temperature (T R ) (block 120) ensures that the thermosetting resin 12 reaches a degree of cure (D) between about 10 percent and about 70 percent. C ) while the melt temperature (T R ) is the melting temperature (Teim ) so that the melt temperature (T R In another particular embodiment, the resin temperature (T R ) (block 120) ensures that the thermosetting resin 12 reaches a degree of cure (D) between about 20 percent and about 60 percent. C ) while the melt temperature (T R ) is the melting temperature (T eim ) so that the melt temperature (T R ) may be controlled.

[0022] The resin temperature (T R Heating the composite 10 (block 110) to increase the resin temperature (T R ) to the maximum curing temperature (T M ) in one particular embodiment, heating (block 110) may include heating the composite 10 to a melting onset temperature (T eim ) at least 5 degrees Celsius higher than the maximum curing temperature (T M In another particular embodiment, the heating (block 110) includes heating the material to a melting initiation temperature (T eim ) at least 10 degrees Celsius higher than the maximum curing temperature (T M In another particular embodiment, the heating (block 110) includes heating the composite 10 to a melting initiation temperature (T eim ) at least 15 degrees Celsius higher than the maximum curing temperature (T M In yet another particular embodiment, the heating (block 110) includes heating the material to a melting initiation temperature (T eim ) at least 20 degrees Celsius higher than the maximum curing temperature (T M ) heating.

[0023] Referring to Figure 2, a composite 10 is shown that may be manufactured according to the method 100 of Figure 1. The composite 10 may include a thermosetting resin 12, a reinforcing material 14, and a thermoplastic additive 16. The reinforcing material 14 may include at least two plies 18, 20. Optionally, the thermoplastic additive 16 may be disposed between the two plies 18, 20.

[0024] In one particular embodiment, the thermosetting resin 12 may be (or may include) an epoxy. However, other thermosetting resins 12 are contemplated and their use would not depart from the scope of the present disclosure. Non-limiting examples of other suitable thermosetting resins 12 include polyurethanes, polyester resins, benzoxazines, polyimides, and bismaleimides.

[0025] In one particular embodiment, the reinforcing material 14 may be (or may include) carbon fiber. However, other reinforcing materials are contemplated, and their use as the reinforcing material 14 would not depart from the scope of the present disclosure. Non-limiting examples of other suitable reinforcing materials 14 include thermoset fibers, carbon nanotubes, glass fibers, ceramic fibers, and metal fibers.

[0026] The thermoplastic additive 16 may be an interlayer, a veil, a mass of fibers / filaments, a film / sheet, a fabric (woven or nonwoven), etc., and may be incorporated into the composite 10 for the purpose of reinforcing the composite 10. Compositionally, the thermoplastic additive 16 may be (or may include) a thermoplastic polymer. Examples of thermoplastic polymers that may be used in or as the thermoplastic additive 16 include, but are not limited to, polyamide, polyetheretherketone, polyetherketone, polyester, polyethersulfone, polyimide, polyurethane, polyolefin, polyethylene, polypropylene, polymethylpentene, polybutene-1, acrylic, poly(methyl methacrylate), and / or nylon.

[0027] The thermoplastic additive 16 has a range of melting onset temperatures (T eimIn one particular embodiment, the thermoplastic additive 16 may have a melting onset temperature (T eim ) may be at a temperature of at least about 150 degrees Celsius. In another particular embodiment, the melting onset temperature (T eim ) may be between about 160 degrees Celsius and about 190 degrees Celsius. In yet another particular embodiment, the melting onset temperature (T eim ) may be at a temperature between about 170 degrees Celsius and about 180 degrees Celsius.

[0028] In one particular embodiment, the method 100 may include the reinforcement material 14 and thermoplastic additive 16 configured as a preform 50 (as shown in FIG. 9 ) and may further include injecting the thermosetting resin 12 into the preform 50 (block 220 of FIG. 8 ).

[0029] At this point, one skilled in the art will appreciate that the method 100 may result in a cured composite 10. The cured composite 10 may be a useful article, such as a part for a vehicle (e.g., an aircraft).

[0030] 8, another embodiment of a method 200 for curing a composite 10 of the present disclosure is shown. As indicated at block 210, the method 200 may begin with placing a preform 50 into an oven 302. The preform 50 may include a reinforcing material 14 and a thermoplastic additive 16. The preform 50 may be substantially free of a thermoset resin 12 (i.e., the preform 50 may be a dry preform).

[0031] At block 220, the method 200 may further include injecting a thermosetting resin 12 into the preform 50 to produce a resin-infused preform 50'. The infusion of the thermosetting resin 12 (block 220) may be performed using a system such as the system 300 shown in FIG.

[0032] At block 230, the method 200 determines the resin temperature (T R9. The method may further include heating the thermosetting resin 12 and the resin-infused preform 50' to enhance the thermal conductivity of the resin-infused preform 50'. The heating (block 230) may be performed by placing the preform 50 in an oven 302, as shown in FIG.

[0033] At block 240, the method 200 begins by determining whether the thermoset resin 12 is between about 5 percent and 85 percent cured (D C ) or before the thermosetting resin 12 reaches about 100 percent (i.e., 98 percent or greater) degree of cure (D C ) before reaching the melt temperature (T R ) is the melting temperature (T eim ) of the thermosetting resin 12. R 9. The controlling (block 240) may be performed during heating (block 230), such as by a controller 350 shown in FIG.

[0034] Referring to Figure 9, a schematic representation of one embodiment of a system 300 for curing the composite 10 of the present disclosure is shown. The system 300 includes an oven temperature (T O ) oven 302, oven temperature (T O a first temperature sensor (S T1 ), and a tool 306 disposed within the oven 302 defining a tool surface 308 for supporting the composite 10 thereon.

[0035] The system 300 may further include a vacuum bag 310 coupled to the tool 306 to define an injection space 312 between the tool 306 and the vacuum bag 310. A resin source 314 may be fluidly coupled (e.g., by a fluid line 316) to the injection space 312 to supply the thermosetting resin 12 to the injection space 312. A second temperature sensor (S T2 ) is the resin temperature (T R ) may be arranged to detect

[0036] The system 300 includes a first temperature sensor (S T1 ), the second temperature sensor (S T2 ) and the oven 302. The controller 350 may control whether the thermoset resin 12 reaches a degree of cure (D) of between about 5 percent and 85 percent during curing of the composite 10. C ) or before the thermosetting resin 12 reaches about 100 percent (i.e., 98 percent or greater) degree of cure (D C ) of the thermosetting resin 12 in the injection space 312. R ) is the melting temperature (T eim ) of the thermosetting resin 12 in the injection space 312. R ) can be controlled.

[0037] System 300 may be configured or modified in various ways without departing from the scope of the present disclosure. In one embodiment, controller 350 controls oven temperature (T O ) of the thermosetting resin 12 in the injection space 312. R ) in the injection space 312. In another embodiment, the system 300 may be configured such that the controller 350 further controls the flow rate of the thermosetting resin 12 from the resin source 314 to the injection space 312. In another embodiment, the system 300 may be configured such that the controller 350 further controls the flow rate of the thermosetting resin 12 from the resin source 314 to the injection space 312. T2 ) is the resin temperature (T R ) indirectly. In another embodiment, system 300 may be configured to include flow media 320 disposed within injection volume 312 to facilitate dispersion of the resin. In yet another embodiment, system 300 may be configured such that preform 50 is disposed on tool surface 308 of tool 306, where preform 50 includes reinforcing material 14 and thermoplastic additive 16.

[0038] Example Comparative Example Referring to Figure 3, there is shown a graphical representation (temperature and extent of cure versus time) of a thermal cure cycle not performed according to the method of the present disclosure. The experiment was performed by exposing Thermoplastic Additive #1 to Cure Cycle #1. Thermoplastic Additive #1 is a polyamide.

[0039] Cure cycle #1 is performed to achieve a degree of cure (D) of approximately 100 percent (i.e., greater than 98 percent). C ), then allowing the sample to cool and be removed from the oven. The samples were then subjected to a microcracking test, and the example used in FIG. 3 failed the microcracking test.

[0040] The microcracking test involved standard thermal humidity cycling of the laminate between high and low temperatures for a large number of cycles combined with cyclic humidity conditions. The test was performed in an environmental chamber. The chamber temperature, laminate temperature, and chamber humidity were recorded during the test. The presence of microcracking was identified by optical microscopy of a cross section cut from the laminate upon completion of the microcracking test. The test was successful when there were no systematic, detrimental, or propagating cracks. Typically, this meant that there were no apparent cracks at the end of the test.

[0041] The graphical representation in Figure 3 represents the degree of cure (D C ) before reaching the melting onset temperature (T eim ) (within the range of about 2 degrees Celsius to about 5 degrees Celsius). eim ) was determined according to ASTM D3418. C ) was measured using computer modeling based on a resin model constructed from actual differential scanning calorimetry (DSC) testing of the resin.

[0042] Example 1 Referring to Figure 4, there is shown a graphical representation (temperature and extent of cure versus time) of one exemplary thermal cure cycle carried out in accordance with the method of the present disclosure. The experiment was carried out by exposing thermoplastic additive #1 to cure cycle #2.

[0043] Cure cycle #2 is performed to achieve a degree of cure (D) of approximately 100 percent (i.e., greater than 98 percent). C ), then allowing the sample to cool and be removed from the oven. The samples were then subjected to a microcracking test, and the example used in FIG. 4 passed the microcracking test. The graphical representation in FIG. 4 shows that Thermoplastic Additive #1 exceeded its melting onset temperature (T) of 185 degrees Celsius before reaching a degree of cure of 100 percent (i.e., 98 percent or greater). eim ) (approximately 6 degrees Celsius to approximately 12 degrees Celsius). C ) is the temperature at which the thermoplastic additive #1 begins to melt (T eim ) was 69 percent.

[0044] Example 2 Referring to Figure 5, there is shown a graphical representation (temperature and extent of cure versus time) of another exemplary thermal cure cycle carried out in accordance with the method of the present disclosure. This experiment was carried out by exposing thermoplastic additive #2 to cure cycle #1. Thermoplastic additive #2 is a polyamide.

[0045] After Cure Cycle #1 was completed, the sample was subjected to the microcracking test and passed. The graphical representation in Figure 5 shows the degree of cure (D) of 100 percent (i.e., 98 percent or greater). C ) before reaching the melting onset temperature (T eim ) (about 12 degrees Celsius to about 18 degrees Celsius). C ) is the temperature at which thermoplastic additive #2 begins to melt (T eim ) was 14 percent.

[0046] Example 3 Referring to Figure 6, there is shown a graphical representation (temperature and extent of cure versus time) of another exemplary thermal cure cycle carried out in accordance with the method of the present disclosure. This experiment was carried out by exposing thermoplastic additive #3 to cure cycle #1. Thermoplastic additive #3 is a polyamide.

[0047] After Cure Cycle #1 was completed, the sample was subjected to a microcracking test and passed. The graphical representation in Figure 6 shows that Thermoplastic Additive #3 reaches a melting onset temperature (T) of 162 degrees Celsius before reaching 100 percent (i.e., greater than 98 percent) degree of cure. eim ) (from about 16 degrees Celsius to about 22 degrees Celsius). C ) is the temperature at which thermoplastic additive #3 begins to melt (T eim ) was 11 percent.

[0048] Example 4 7, there is shown a graphical representation (temperature and extent of cure versus time) of yet another exemplary thermal cure cycle carried out in accordance with the method of the present disclosure. This experiment was carried out by exposing thermoplastic additive #4 to cure cycle #1. Thermoplastic additive #4 is a polyamide.

[0049] After Cure Cycle #1 was completed, the sample was subjected to the microcracking test and passed. The graphical representation in Figure 7 shows that Thermoplastic Additive #4 reaches a melting onset temperature (T) of 171 degrees Celsius before reaching 100 percent (i.e., greater than 98 percent) degree of cure. eim ) (about 8 degrees Celsius to about 12 degrees Celsius). C ) is the temperature at which thermoplastic additive #4 begins to melt (T eim ) was 0.16.

[0050] Considering the data presented in Figures 3-7 together, it is clear that 100 percent (i.e., 98 percent or greater) degree of cure (D C) before the thermoplastic additive reaches the melting point (T eim ), microcracking was significantly reduced (e.g., no microcracking). At this point, one skilled in the art will appreciate that various cure cycles and thermoplastic additives can be used to achieve these conditions without departing from the scope of the present disclosure.

[0051] Embodiments of the disclosure may be described in the context of an aircraft manufacturing and service method 1100, as shown in FIG. 10 , and an aircraft 1102, as shown in FIG. 11 . The aircraft manufacturing and service method 1100 may include, during a pre-production phase, specification and design 1104 of the aircraft 1102 and material procurement 1106. During production, component / subassembly manufacturing 1108 and system integration 1110 of the aircraft 1102 occurs. The aircraft 1102 may then undergo certification and delivery 1112 and be placed into service 1114. While operated by a customer, the aircraft 1102 is scheduled for routine maintenance and service 1116, which may include modification, reconfiguration, refurbishment, etc.

[0052] Each process of method 1100 may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this specification, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors, a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers, and an operator may be an airline, a leasing company, a military organization, a service organization, etc.

[0053] 11 , an aircraft 1102 produced by exemplary method 1100 may include an airframe 1118 having a number of systems 1120 and an interior 1122. Examples of the number of systems 1120 may include one or more of a propulsion system 1124, an electrical system 1126, a hydraulic system 1128, and an environmental system 1130. Any number of other systems may also be included.

[0054] The disclosed methods and systems may be employed during any one or more stages of aircraft manufacturing and service method 1100. As one example, components or subassemblies corresponding to component / subassembly manufacturing 1108, system integration 1110, and / or maintenance and service 1116 may be assembled using the disclosed methods and systems. As another example, an airframe 1118 may be constructed using the disclosed methods and systems. Also, one or more example apparatuses, methodologies, or combinations thereof may be utilized in component / subassembly manufacturing 1108 and / or system integration 1110, for example, by substantially streamlining the assembly of the aircraft 1102, such as the airframe 1118 and / or interior 1122, or reducing the cost of the aircraft 1102. Similarly, one or more of the example systems, methodologies, or combinations thereof may be utilized during the operational life of the aircraft 1102, for example, but not limited to, maintenance and service 1116.

[0055] Aspects of the disclosed embodiments may be implemented in software, hardware, firmware, or a combination thereof. Various elements of the system, either individually or in combination, may be implemented as a computer program product tangibly embodied in a machine-readable storage device for execution by a processor. Various steps of the embodiments may be performed by a computer processor executing a program tangibly embodied on a computer-readable medium to perform functions by operating on inputs and generating outputs. The computer-readable medium may be, for example, a memory, e.g., a compact disc, or a portable medium such as a flash drive, by which a computer program embodying aspects of the present disclosure may be loaded into a computer.

[0056] The methods and systems described above are described in the context of aircraft. However, those skilled in the art will clearly understand that the methods and systems of the present disclosure are suitable for a variety of applications, and the present disclosure is not limited to aircraft manufacturing applications. For example, the methods and systems of the present disclosure may be implemented in various types of vehicles, including, for example, helicopters, passenger ships, automobiles, marine products (boats, motor vessels, etc.), etc. Non-vehicle applications are also contemplated.

[0057] Additionally, while the foregoing description has described methods and systems for curing composites and related microcrack resistant composites as enabling the manufacture of aircraft parts in the aviation industry in compliance with various regulations (e.g., civil, military, etc.), it is contemplated that the methods and systems of the present disclosure may be implemented to facilitate the manufacture of parts in any industry in accordance with applicable industry standards. Particular methods and systems may be selected and tailored depending on the particular application.

[0058] The present disclosure further includes embodiments according to the following clauses: Article 1. A method (100) for curing a composite (10) comprising a thermosetting resin (12), a reinforcing material (14), and a thermoplastic additive (16), the thermoplastic additive (16) having a melting onset temperature (T eim ), and the method (100) comprises: The resin temperature (T R heating (110) the composite (10) to increase During the heating (110), the thermosetting resin (12) is heated to a degree of cure (D) of 98 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R ) controlling (120). Article 2. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 85 percent of the thermosetting resin (12).C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 3. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 80 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 4. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 75 percent of the thermosetting resin (12). C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 5. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 70 percent of the thermosetting resin (12). C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 6. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 60 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 7. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 50 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 8. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 40 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 9. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 30 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 10. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 20 percent. C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 11. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 1 percent. C ) is reached, the resin temperature (TR ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 12. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 5 percent. C ) is reached, the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 13. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of about 10 percent. C ) is reached, the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 14. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of between about 5 percent and about 80 percent of the thermosetting resin (12). C ) while the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R 2. The method (100) according to claim 1, comprising controlling Article 15. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of between about 10 percent and about 70 percent of the thermosetting resin (12). C ) while the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R2. The method (100) according to claim 1, comprising controlling Article 16. 10. The method (100) of claim 1, wherein the thermosetting resin (12) comprises an epoxy. Article 17. 10. The method (100) of claim 1, wherein the reinforcing material (14) comprises carbon fiber. Article 18. 2. The method (100) of claim 1, wherein the reinforcing material (14) comprises at least two plies (18, 20), and the thermoplastic additive (16) is disposed between the two plies (18, 20). Article 19. 10. The method of claim 1, wherein the thermoplastic additive comprises a member selected from the group consisting of polyamide, polyetheretherketone, polyetherketone, polyester, polyethersulfone, polyimide, polyurethane, polyolefin, polyethylene, polypropylene, polymethylpentene, polybutene-1, acrylic, poly(methyl methacrylate), nylon, and combinations thereof. Article 20. The melting start temperature (T eim 2. The method (100) of claim 1, wherein the temperature is between about 160 degrees Celsius and about 190 degrees Celsius. Article 21. 10. The method (100) of claim 1, wherein the reinforcing material (14) and the thermoplastic additive (16) comprise a preform (50), and the method (100) further comprises injecting (220) the thermosetting resin (12) into the preform (50). Article 22. The resin temperature (T R Heating (110) the composite (10) to increase the resin temperature (T R ) to the maximum curing temperature (T M ), and heating the composite to the maximum cure temperature (T M ) is the melting initiation temperature (T eim ) at least 5 degrees Celsius higher than the temperature of the air temperature (100) of the method according to clause 1. Article 23. The resin temperature (T R Heating (110) the composite (10) to increase the resin temperature (T R ) to the maximum curing temperature (T M ), and heating the composite to the maximum cure temperature (T M ) is the melting initiation temperature (T eim ) at least 10 degrees Celsius higher than the temperature (100) of the method according to clause 1. Article 24. 10. A cured composite (10) produced by the method (100) described in clause 1. Article 25. A method (200) for curing a composite (10) comprising a thermosetting resin (12) comprising an epoxy, a reinforcing material (14) comprising carbon fiber, and a thermoplastic additive (16), the thermoplastic additive (16) having an onset of melting temperature (T) between about 160 degrees Celsius and about 190 degrees Celsius. eim ), and the method (200) comprises: placing (210) a preform (50) including the reinforcing material (14) and the thermosetting resin (16) in an oven (302); injecting (220) the thermosetting resin (12) into the preform (50) to produce a resin-infused preform (50'); The resin temperature (T R heating (230) the resin-infused preform (50') to enhance During the heating (230), the thermosetting resin (12) reaches a degree of cure (D) of between about 5 percent and about 85 percent. C ) while the resin temperature (T R ) is the melting initiation temperature (T eim ) so that the resin temperature (T R ) controlling (240). Article 26. A system (300) for curing a composite (10) comprising a thermosetting resin (12), a reinforcing material (14), and a thermoplastic additive (16), wherein the thermosetting resin (12) is heated to a resin temperature (T R ), and the thermoplastic additive (16) has a melting onset temperature (T eim ), and the system (300) comprises: Oven temperature (T O an oven (302) having a The oven temperature (T O a first temperature sensor (S T1 ), a tool (306) disposed within the oven (302), the tool (306) defining a tool surface (308) for supporting the composite (10) thereon; a vacuum bag (310) coupled to the tool (306) to define an injection space (312) between the vacuum bag (310) and the tool (306); a resin source (314) fluidly coupled to the injection space (312) for supplying the thermosetting resin (12) to the injection space (312); The resin temperature (T R A second temperature sensor (S) is arranged to sense T2 ),and The first temperature sensor (S T1 ), the second temperature sensor (S T2 ), and a controller (350) in communication with the oven (302), the controller (350) configured to adjust the thermosetting resin (12) to about 85 percent degree of cure (D ) during curing of the composite (10). C ) of the thermosetting resin (12) in the injection space (312) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim The resin temperature (T ) of the thermosetting resin (12) in the injection space (312) is increased to exceed the resin temperature (T R ) controlling the system (300). Article 27. The controller (350) controls the oven temperature (T O ) of the thermosetting resin (12) in the injection space (312) by at least partially controlling the resin temperature (T R ) the system (300) according to clause 26. Article 28. 27. The system (300) of clause 26, wherein the controller (350) further controls a flow rate of the thermosetting resin (12) from the resin source (314) to the injection space (312). Article 29. The second temperature sensor (S T2 ) is the resin temperature (T R ) indirectly detecting the system (300) according to clause 26. Article 30. 27. The system (300) of clause 26, further comprising a flow medium (320) disposed within the injection space (312). Article 31. 27. The system (300) of claim 26, further comprising a preform (50) disposed on the tool surface (308) of the tool (306), the preform (50) including the reinforcing material (14) and the thermoplastic additive (16).

[0059] While various embodiments of the disclosed methods and systems for curing composites and related microcrack-resistant composites have been shown and described, modifications may occur to those skilled in the art upon reading this specification, and the present application includes such modifications and is limited only by the scope of the claims.

Claims

1. A method (100) for curing a composite (10) comprising a thermosetting resin (12), a reinforcing material (14), and a thermoplastic additive (16), wherein the thermoplastic additive (16) has an onset of melting temperature (T eim ) and the method (100) comprises: placing a preform (50) comprising said reinforcing material (14) and said thermoplastic additive (16) in an oven (302); injecting the thermosetting resin (12) into the preform (50) in an injection space (312) to obtain a resin-infused preform (50'); The resin temperature (T R heating (110) the resin-infused preform (50') using the oven (302) to enhance During the heating (110), detecting a resin temperature (TR) of the thermosetting resin (12) in the injection space (312) using a second temperature sensor (ST2) disposed in communication with the injection space (312) and detecting an oven temperature (TO) in the oven (302) using a first temperature sensor (ST1) disposed in communication with the oven (302); and During the heating (110), based on the detection, after the thermosetting resin (12) reaches a 5 percent degree of cure (DC), and after the thermosetting resin (12) reaches an 85 percent degree of cure (D C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so as to exceed the resin temperature (T R ) to prevent the formation of microcracks in the thermoset resin (12).

2. The resin temperature (T R ) is controlled (120) to achieve a degree of cure (D) of 75 percent of the thermosetting resin (12). C ) before reaching the resin temperature (T R ) is the melting initiation temperature (T eim ) so as to exceed the resin temperature (T R 10. The method of claim 1, further comprising:

3. The method (100) of claim 1 or 2, wherein the thermosetting resin (12) comprises an epoxy.

4. The method (100) of any one of claims 1 to 3, wherein the reinforcing material (14) comprises carbon fiber.

5. 5. The method (100) of any one of claims 1 to 4, wherein the reinforcing material (14) comprises at least two plies (18, 20), and the thermoplastic additive (16) is disposed between the two plies (18, 20).

6. The resin temperature (T R Heating (110) the composite (10) to increase the resin temperature (T R ) to the maximum curing temperature (T M ), and heating the composite to a maximum cure temperature (T M ) is the melting initiation temperature (T eim 6. The method (100) of claim 1, wherein the temperature is at least 5 degrees Celsius higher than the reference temperature.

7. A method (100) according to any one of claims 1 to 5, wherein heating (110) the composite (10) to increase the resin temperature (TR) of the thermosetting resin (12) comprises heating the composite to increase the resin temperature (TR) to a maximum cure temperature (TM), wherein the maximum cure temperature (TM) is at least 10 degrees Celsius higher than the melting onset temperature (T eim ).

8. The method (100) of claim 1, wherein controlling (120) the resin temperature (TR) comprises controlling the resin temperature (TR) such that the resin temperature (TR) exceeds the melting initiation temperature (T eim ) before the thermosetting resin (12) reaches 60 percent degree of cure (DC).

9. A method (100) described in any one of claims 1 to 8, wherein the melting initiation temperature (T eim ) of the thermoplastic additive (16) is a temperature (T eim ) between 160 degrees Celsius and 190 degrees Celsius.

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