Compression resin transfer infusion method

Abstract

To provide a compression resin transfer infusion method.SOLUTION: A dry preform with a thermoplastic veil is placed onto a lower mold die. An injection and cure tool having a sealed cavity holding the dry preform is created. An upper mold die is placed onto the lower mold die. The sealed cavity defines a gap. The gap corresponds to a cavity volume equivalent to an amount of resin to infusion-mold the dry preform. The resin is emitted and injected into the gap of the sealed cavity while the injection and cure tool is maintained at an injection temperature. The upper mold die is lowered to infusion-mold the dry preform to form a resin-injected preform. The resin-injected preform is cured within the injection and cure tool to form a cured composite component. Curing occurs at a curing temperature higher than the injection temperature.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure generally relates to methods for forming composite structures, and more particularly to high rate resin infusion technology.

Background Art

[0002] Composite materials and composite structures including resin-infused carbon fiber laminates are commonly used in applications that require high strength and low weight. For example, in the aerospace industry, composite structures are widely used to form aircraft fuselages, wings, and other components. However, conventional methods and systems for forming composite structures are often time-consuming and labor-intensive, especially in the case of composite structures that combine complementary parts such as fuselage skins and stringers into a single composite structure. Furthermore, to manufacture composite structures at high speed using current aerospace composite manufacturing materials and methods, multiple sets of tools and processing equipment, as well as the factory floor space required to house the equipment, are needed. Therefore, it is difficult and expensive to manufacture high-quality composite structures using aerospace-grade materials to meet performance characteristics at high speed using current manufacturing methods, which limits the manufacturing speed at affordable costs.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, it is desirable to have methods and apparatus that take into account at least some of the problems described above, as well as other possible problems. For example, as is typical in the aerospace industry, it is desirable to present systems and methods for forming composite structures that result in improved manufacturing speed, particularly for composite structures having greater size and complexity.

Means for Solving the Problems

[0004] One embodiment of the present disclosure provides a method of compression resin transfer infusion. A dry preform having a thermoplastic veil is placed on a lower mold. An upper mold is placed on the lower mold to create an infusion and cure tool having a sealed cavity that holds the dry preform. The sealed cavity defines a gap that corresponds to a cavity volume equivalent to the amount of resin for infusion molding the dry preform. While the infusion and cure tool is maintained at an infusion temperature, resin is injected into the gap of the sealed cavity. The upper mold is lowered to infusion mold the dry preform to form a resin-injected preform. To form a cured composite part, the resin-injected preform is cured within the infusion and cure tool, and the curing is performed at a curing temperature higher than the infusion temperature.

[0005] Other embodiments of the present disclosure provide a method of compression resin transfer infusion. While the infusion and cure tool is maintained at an infusion temperature within the range of 130 to 160 °C, resin is injected into the gap of the sealed cavity of the infusion and cure tool. The upper mold of the infusion and cure tool is lowered to inject resin into the dry preform within the sealed cavity to form a resin-injected preform. The temperature of the infusion and cure tool is raised from the infusion temperature to the curing temperature at a ramp rate of 1 to 3 °C / min. To form a cured composite part, the resin-injected preform is cured within the infusion and cure tool, and the curing is performed at a curing temperature within the range of 165 to 190 °C, and the curing temperature is sufficient to expand and melt the thermoplastic veil within the dry preform.

[0006] Yet another embodiment of the present disclosure provides a compression resin transfer infusion method for forming cavitation bubbles in a cured composite part. While the injection and curing tool is maintained at an injection temperature in the range of 130 to 160 °C, resin is injection-molded into the gap of the sealed cavity of the injection and curing tool. To inject resin throughout the thickness of the dry preform in the sealed cavity to form a resin-injected preform, the upper mold of the injection and curing tool is lowered at a mold closing speed of 0.01 to 0.2 inches per minute, and the dry preform includes a thermoplastic veil. The temperature of the injection and curing tool is raised from the injection temperature to the curing temperature. To form the cured composite part, the resin-injected preform is cured within the injection and curing tool, and the curing is performed at a curing temperature in the range of 165 to 190 °C and a curing pressure in the range of 10 to 100 psig. After curing, the temperature of the injection and curing tool is lowered so that cavitation bubbles are generated in the thermoplastic veil when the thermoplastic veil is cooled below its melting temperature.

[0007] The above-described forms and functions can be realized independently in various embodiments of the present disclosure, or may be combined in other embodiments that can be understood with reference to the following description and drawings for further details.

[0008] The characteristics considered to be novel forms of the exemplary embodiments are set forth in the appended claims. However, the exemplary embodiments, as well as their preferred modes of use, further objectives and forms, will be best understood by referring to the following detailed description of the exemplary embodiments of the present disclosure and considering them in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0009]

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MODE FOR CARRYING OUT THE INVENTION

[0010] Referring now to FIG. 1, an explanatory diagram of an aircraft according to an exemplary embodiment is shown. The aircraft 100 has wings 102 and 104 attached to the main body 106. The aircraft 100 includes an engine 108 attached to the wing 102 and an engine 110 attached to the wing 104.

[0011] The main body 106 has a tail section 112. The horizontal stabilizers 114, 116 and the vertical stabilizer 118 are attached to the tail section 112 of the main body 106.

[0012] Aircraft 100 is an example of an aircraft that can have a composite structure formed using a compression resin transfer infusion method. In some exemplary examples, portions of the fuselage 106, wing 102, or wing 104 can include a composite structure formed using a compression resin transfer injection method.

[0013] Referring now to FIG. 2, a block diagram of a manufacturing environment according to an exemplary embodiment is shown. A resin injection and curing tool 202 in the manufacturing environment is used to inject resin 204 into preform 206 and cure the resin-injected preform 208. Compression resin transfer infusion 210 performed using resin injection and curing tool 202 utilizes multiple temperatures.

[0014] The resin injection and curing tool 202 includes an upper mold 218 and a lower mold 216 that are sealed to each other by a seal 222. A sealed cavity 220 exists between the upper mold 218 and the lower mold 216.

[0015] Compression resin transfer infusion 210 includes placing a dry preform 212 having a thermoplastic veil 214 on the lower mold 216 of the resin injection and curing tool 202. The raw material of the dry preform 212 can be formed from any desired type of fiber. In some exemplary examples, the dry preform 212 can have a carbon fiber content of up to 70% by weight. In some exemplary examples, the raw material of the dry preform 212 can include carbon fiber with knitting yarn, carbon fiber with knitting yarn and thermoplastic veil, or carbon fiber with veil. In some exemplary examples, the material of the dry preform 212 can include a carbon fiber-based fabric such as a non-crimp fabric (NCF). In some exemplary examples, the material of the dry preform 212 is a dry multi-axial non-crimp fabric (MA-NCF). In some exemplary examples, the material of the dry preform 212 is a dry unidirectional non-crimp fabric (UD-NCF).

[0016] To create an injection and curing tool 202 having a sealed cavity 220 that holds a dry preform 212, an upper mold 218 is placed over a lower mold 216. The sealed cavity 220 defines a gap 224. The gap 224 corresponds to a cavity volume 226 that is equivalent to the amount of resin 204 for infusion molding the dry preform 212. While the injection and curing tool 202 is maintained at an injection temperature 236, the resin 204 is injected into the gap 224 of the sealed cavity 220 by injection.

[0017] In some exemplary examples, the resin 204 is an epoxy resin. The resin can have a period of latency 205. In some exemplary examples, the resin 204 includes a prepolymerized and degassed epoxy resin having a latency period 205. In some exemplary examples, the resin 204 can include epoxy, cyanate ester, benzoxazine, bismaleimide, polyimide, crosslinkable thermoplastic resin, and in situ polymerizable thermoplastic resin, or combinations thereof. In some exemplary examples, the resin 204 can include, but is not limited to, epoxy / cyanate ester and epoxy / benzoxazine.

[0018] As used herein, the latency period 205 of the resin 204 refers to the time after the components of the resin 204 are mixed until the resin viscosity increases to an unacceptable level. For example, an epoxy resin can be formed by mixing an epoxy component with a curing agent such as an amine. Once mixed, the epoxy resin crosslinks and the viscosity increases. The resin can have a latency period of about 20 minutes to about 1 hour. For example, the resin can have a latency period of about 30 minutes or less.

[0019] To infusion mold the dry preform 212 to form a resin-injected preform 208, the upper mold 218 is lowered. When the upper mold 218 is lowered, the resin 204 is injected into the dry preform 212 throughout the thickness 228 of the dry preform 212.

[0020] Aspects of the injection 232 including a mold closing speed 230, an injection temperature 236, and an injection time 233 are configured to produce a cured composite part 252 having desirable values for rigidity and strength. In some exemplary examples, aspects of the injection 232 including a mold closing speed 230, an injection temperature 236, and an injection time 233 are configured to shorten the processing time of the cured composite part 252. In some exemplary examples, the upper mold 218 is lowered at a mold closing speed 230 of 0.01 - 0.2 inches per minute. In some exemplary examples, the injection temperature 236 is in the range of 130 - 160 °C.

[0021] To form the cured composite part 252, the resin injection preform 208 is cured within the injection and curing tool 202. Curing 260 occurs at a curing temperature 240 that is higher than the injection temperature 236. The curing temperature 240 is sufficient to expand the thermoplastic veil 214 and cause at least one of softening or melting. The thermoplastic veil 214 is at least softened in order to sufficiently bond to the resin 204. In some exemplary examples, the curing temperature 240 is at least the melting temperature 244 of the thermoplastic veil 214.

[0022] The temperature 234 of the injection and curing tool 202 decreases from the curing temperature 240 at a ramp down speed 249 after curing 260. The curing temperature 240 and the ramp down speed 249 are selected to provide a desired bond between the thermoplastic veil 254 and the resin 204 within the cured composite part 252. The curing temperature 240 and the ramp down speed 249 are selected to generate cavitation bubbles 256 in the thermoplastic veil 254 within the cured composite part 252. In some exemplary examples, the cavitation bubbles 256 are an indicator of a desired level of bond between the thermoplastic veil 254 and the resin 204 within the cured composite part 252.

[0023] The other aspects of time, temperature, pressure 242, and curing 260 are controlled to produce a cured composite part 252 having a desired stiffness and strength. In some exemplary examples, curing 260 takes 45 to 180 minutes. In some exemplary examples, the curing temperature 240 is in the range of 165 to 190 °C. In some exemplary examples, the temperature gradient 238 for curing between the injection temperature 236 and the curing temperature 240 has a ramp rate 239 of 1 to 3 °C / min. In some exemplary examples, the difference between the injection temperature 236 and the curing temperature 240 is 40 °C or less. In some exemplary examples, the pressure 242 within the sealed cavity 220 is 10 to 100 psig after the upper mold 218 is lowered, and the pressure 242 is maintained at 10 to 100 psig during curing 260.

[0024] The curing temperature 240 is selected based on the resin 204 and the thermoplastic veil 214. In some exemplary examples, the curing temperature 240 can be a temperature of about 170 °C to about 190 °C. The curing temperature 240 is selected to produce a desired bond between the resin 204 and the thermoplastic veil 214.

[0025] The aspects of injection 232 and curing 260 can be set to maximize the production rate of the resin injection and curing tool 202. The aspects of injection 232 and curing 260 can be set to maximize the production rate of the cured composite part 252.

[0026] The curing time 261 is set to fully cure the preform 206 in the resin injection and curing tool 202. The curing time 261 can be about 45 minutes to about 180 minutes.

[0027] In some exemplary examples, the cured composite part 252 is removed from the injection and curing tool 202 while the injection and curing tool 202 is still hot. In some exemplary examples, the cured composite part 252 is removed from the injection and curing tool 202 while the injection and curing tool 202 is at a temperature 234, the removal temperature 250, within the range of 130 to 160 °C.

[0028] The cured composite part 252 has a sufficient degree of rigidity and strength so that the cured composite part 252 can be safely removed from the resin injection and curing tool 202. The cured composite part 252 is sufficiently cured to maintain its shape without distortion or damage after being removed from the resin injection and curing tool 202. Further, no post-curing is performed on the cured composite part 252 after it is removed from the resin injection and curing tool 202. The cured composite part 252 has sufficient rigidity and strength to meet the desired goals without additional post-curing.

[0029] Each of the injection temperature 236 and the curing temperature 240 is a temperature value having a dispersion of less than ±5°C from the desired value. For example, a temperature of 100°C refers to a temperature maintained between 95°C and 105°C.

[0030] The temperature 234 of the resin injection and curing tool 202 can be maintained / regulated by electrical or resistance heating, induction heating, liquid heating, steam heating, etc. In some embodiments, the mass and heat capacity of the lower mold 216 are configured to prevent large temperature fluctuations due to the external environment or any exothermic or endothermic reaction. For example, the lower mold 216 can include materials such as steel, aluminum, Invar, etc. selected for their high heat capacity. Similarly, the large mass can act as a heat sink to control the exothermic reaction and help maintain a constant temperature by maintaining the temperature during ambient losses.

[0031] The cured composite part 252 includes a desired level of bonding between the cured resin 258 and the thermoplastic veil 254. Due to the temperature gradient 238, the resin 204 can maintain mobility longer and gelate (vitrify) after the thermoplastic veil 214 reaches the melting temperature 244. In some exemplary examples, the thermoplastic veil 214 has a melting temperature 244 that exceeds 170°C. When the thermoplastic veil 214 melts, it expands. After the thermoplastic veil 214 melts, the resin 204 forms a network around the thermoplastic veil 214 while the thermoplastic veil 214 expands, and the resin 204 bonds to the surface of the thermoplastic veil 214.

[0032] When the thermoplastic veil 214 cools back down below the melting temperature 244, the thermoplastic veil 214 attempts to shrink back to its original size. Here, since the thermoplastic veil 214 is bonded to the resin 204, there is no place for the thermoplastic veil 214 to shrink, and cavitation bubbles 256 form at the center of the thermoplastic veil 254.

[0033] In some exemplary examples, at temperatures below the melting temperature 244, such as the injection temperature 236, the resin 204 remains liquid and the thermoplastic veil 214 has its original value of diameter 246. In some exemplary examples, the diameter 246 can have an original value of about 35 μm. At a temperature 234 above the melting temperature 244 of the thermoplastic veil 214, when the thermoplastic veil 214 is softened or melted by the still liquid resin 204, it expands. In some exemplary examples, when the thermoplastic veil 214 is softened or melted, it can expand to have a diameter 246 of about 45 - 50 μm.

[0034] After the resin 204 cures, the thermoplastic veil 214 is fixed to the diameter 246 having the expanded size. When the thermoplastic veil 214 cools below the melting temperature 244, the thermoplastic veil 214 attempts to shrink back to the diameter 246 having its original size. With the outer surface of the thermoplastic veil 214 fixed in place, cavitation bubbles 256 are formed at the center of the thermoplastic veil 254.

[0035] The diagram of the manufacturing environment 200 in FIG. 2 does not imply physical or structural limitations on the manner in which exemplary embodiments may be implemented. Other components may be used in addition to or in place of the illustrated components. Some components may be unnecessary. Also, the blocks are shown to represent some functional components. One or more of these blocks may be combined into different blocks, divided, or combined and then divided when implemented in an exemplary embodiment.

[0036] For example, in some exemplary examples, the resin injection and curing tool 202 can further include a vacuum system (not shown). The vacuum system can be configured to evacuate the gap 224. The vacuum system can create a vacuum in the gap 224 before injecting the resin 204 into the gap 224.

[0037] In some exemplary examples, the curing temperature 240 is less than the melting temperature 244. In some exemplary examples, the curing temperature 240 is sufficient to soften but not melt the thermoplastic veil 214 such that the thermoplastic veil 214 preferably binds to the resin 204.

[0038] Referring now to FIG. 3, a diagram of a temperature chart of the injection temperature and the curing temperature of a high-speed resin injection method according to an exemplary embodiment is shown. The temperature cycle 302 can be used with the resin injection and curing tool 202 of FIG. 2 to form the cured composite part 252 of FIG. 2.

[0039] The temperature chart 300 shows a temperature cycle 302 for the injection and curing of a composite material having a thermoplastic veil. The temperature chart 300 has time 304 as the X-axis and temperature 306 as the Y-axis. In the temperature cycle 302, the injection 308 is performed at the injection temperature 310. In some exemplary examples, the injection temperature 310 is in the range of 130 to 160 °C. After the injection 308, a temperature gradient 312 occurs when the temperature 306 rises to the curing temperature 314. In some exemplary examples, the temperature gradient 312 for curing between the injection temperature 310 and the curing temperature 314 has a ramp rate of 1 to 3 °C / min. In some exemplary examples, the curing temperature 314 is in the range of 165 to 190 °C. In some exemplary examples, the difference between the injection temperature 310 and the curing temperature 314 is 40 °C or less.

[0040] As shown, the curing 316 is performed at the curing temperature 314. In some exemplary examples, the curing 316 takes 45 to 180 minutes. After the curing 316, the temperature gradient 318 lowers the temperature of the composite material.

[0041] The cured composite part is removed at the removal temperature 320. In some exemplary examples, the removal temperature 320 is approximately the same as the injection temperature 310. In some exemplary examples, the removal temperature 320 is in the range of 130 to 160 °C.

[0042] Referring now to FIG. 4, a diagram of a resin injection and curing tool according to an exemplary embodiment is shown. The resin injection and curing tool 400 is a physically implemented version of the resin injection and curing tool 202 of FIG. 2. The temperature cycle 302 can be executed in the resin injection and curing tool 400 to inject and cure the composite preform.

[0043] The resin injection and curing tool 400 includes an upper mold 404 and a lower mold 406 that are sealed to each other by a seal 408. A sealed cavity 410 exists between the upper mold 404 and the lower mold 406. A preform 412 exists on the lower mold 406 within the sealed cavity 410. A gap 416 exists between the preform 412 and the upper mold 404 within the sealed cavity 410. The gap 416 corresponds to a cavity volume that is equivalent to the amount of resin 414 for infusion molding the preform 412. While the injection and curing tool 400 is maintained at the injection temperature, the resin 414 is injection-molded into the gap 416 of the sealed cavity 410.

[0044] The illustrated state 402 is a cross-sectional view of the resin injection and curing tool 400 after the resin 414 has been injection-molded into the sealed cavity 410 formed between the upper mold 404 and the lower mold 406. By lowering the upper mold 404 toward the lower mold 406, the resin 414 is injected into the preform 412.

[0045] During the injection of the resin 414 into the preform 412, the resin injection and curing tool 400 is maintained at the injection temperature. After the resin 414 has been injected into the preform 412, the injected preform is cured. To cure the resin 414 within the preform 412, the resin injection and curing tool 400 is heated from the injection temperature to the curing temperature. In some exemplary examples, the difference between the injection temperature and the curing temperature is up to 40 °C.

[0046] Referring now to FIG. 5, a diagram of the interaction between a thermoplastic veil and resin prior to curing according to an exemplary embodiment is shown. The thermoplastic veil 501 and the resin 502 can be part of the composite structure of the aircraft 100 of FIG. 1. The thermoplastic veil 501 and the resin 502 are diagrams of the thermoplastic veil 214 and the resin 204 of FIG. 2. The thermoplastic veil 501 and the resin 502 can undergo the temperature cycle 302 of FIG. 3. The thermoplastic veil 501 and the resin 502 can be processed by the resin injection and curing tool 400 of FIG. 4.

[0047] In the illustrated state 500, the thermoplastic veil 501 and the resin 502 are at a temperature lower than the melting temperature of the thermoplastic veil 501. In the illustrated state 500, the thermoplastic veil 501 is at an initial size having a first diameter 504. In some exemplary examples, the thermoplastic veil is in the range of about 30 μm to about 40 μm in diameter. In some exemplary examples, the diameter of the thermoplastic veil is about 35 μm.

[0048] Referring now to FIG. 6, a diagram of the interaction between the thermoplastic veil and the resin during curing, according to an exemplary embodiment, is shown. In the illustrated state 600, the thermoplastic veil 501 and the resin 502 are at a curing temperature such as the curing temperature 314 of FIG. 3. In the illustrated state 600, the thermoplastic veil 501 has expanded due to the curing temperature. In the illustrated state 600, the thermoplastic veil 501 has a diameter of 602. In some exemplary examples, the thermoplastic veil 501 can expand by 15% to 45%. In some exemplary examples, the thermoplastic veil 501 expands to have a diameter 602 of about 45 μm to about 50 μm. In some exemplary examples, the thermoplastic veil 501 expands to have a diameter 602 of about 45 μm to about 55 μm.

[0049] Referring now to FIG. 7, a diagram of the interaction between the thermoplastic veil and the resin after curing is shown in accordance with an exemplary embodiment. In the illustrated state 700, the thermoplastic veil 501 and the resin 502 are cooled to below the melting temperature of the thermoplastic veil 501. When the thermoplastic veil 501 cools below the melting temperature, the thermoplastic veil 501 attempts to contract to its original size. In the illustrated state 700, the resin 502 has cured into a network 702, and the thermoplastic veil 501 is now bonded to the resin 502.

[0050] After the resin 502 has cured, the thermoplastic veil 501 is fixed in the expanded size. When the thermoplastic veil 501 is cooled below the melting temperature, the thermoplastic veil 501 attempts to shrink and return to its original size. By bonding the thermoplastic veil 501 to the resin 502, the thermoplastic veil 501 has no place to shrink because cavitation bubbles are generated at the center of the thermoplastic veil. With the outer surface of the thermoplastic veil 501 fixed in place, cavitation bubbles 704 are formed at the center of the thermoplastic veil 501.

[0051] Referring now to FIG. 8, a flowchart of a method of compression resin transfer infusion according to an exemplary embodiment is shown. Method 800 can be performed to form the composite component of the aircraft 100 of FIG. 1. Method 800 can be performed using the resin injection and curing tool 202 of FIG. 2 to form the cured composite component 252. Method 800 can be performed using the temperature cycle 302. Method 800 can be performed using the resin injection and curing tool 400 of FIG. 4. Method 800 can inject and cure the thermoplastic veil 501 and the resin 502 of FIG. 5.

[0052] In method 800, a dry preform having a thermoplastic veil is placed on the lower mold (step 802). In method 800, an upper mold is placed on the lower mold to create an injection and curing tool having a sealed cavity that holds the dry preform, the sealed cavity defining a gap that corresponds to a cavity volume equivalent to the amount of resin for infusion molding the dry preform (step 804). Method 800 injects resin into the gap of the sealed cavity while the injection and curing tool is maintained at the injection temperature (step 806). Method 800 lowers the upper mold to infusion mold the dry preform to form a resin-injected preform (step 808). Method 800 cures the resin-injected preform within the injection and curing tool to form a cured composite component, where the curing is performed at a curing temperature higher than the injection temperature (step 810). Thereafter, method 800 ends.

[0053] In some exemplary examples, the upper mold is lowered at a mold closing speed of 0.01 to 0.2 inches per minute (step 812). In some exemplary examples, the injection temperature is in the range of 130 to 160 °C (step 814). In some exemplary examples, the injection temperature is selected based on the waiting time of the resin.

[0054] In some exemplary examples, the curing temperature is sufficient to expand and melt the thermoplastic veil (step 816). In some exemplary examples, the curing temperature is sufficient to expand and soften the thermoplastic veil. In some exemplary examples, the curing temperature is sufficient to expand the thermoplastic veil by 15% to 45%. In some exemplary examples, the curing temperature exceeds 170 °C.

[0055] In some exemplary examples, method 800 lowers the temperature of the injection and curing tool from the curing temperature at a ramp-down speed after curing, where the curing temperature and the ramp-down speed are selected to generate cavitation bubbles in the thermoplastic veil within the cured composite part (step 818). During curing, the resin forms a network. During curing, the thermoplastic veil binds to the resin. Cavitation bubbles can result from the thermoplastic veil attempting to shrink to its initial size after the thermoplastic veil has bound to the resin network. In some exemplary examples, curing takes 45 to 180 minutes (step 820).

[0056] In some exemplary examples, the curing temperature is in the range of 165 to 190 °C (step 822). In some exemplary examples, the temperature gradient for curing between the injection temperature and the curing temperature has a ramp rate of 1 to 3 °C per minute (step 824). In some exemplary examples, the difference between the injection temperature and the curing temperature is 40 °C or less (step 826).

[0057] In some exemplary examples, method 800 removes the cured composite part from the injection and curing tool (step 828) while the injection and curing tool is at a temperature within the range of 130 - 160°C. In some exemplary examples, the cured composite part is removed from the injection and curing tool at the injection temperature. In some exemplary examples, the cured composite part is removed from the injection and curing tool after ramping down at approximately the same ramp rate as the temperature gradient for curing.

[0058] In some exemplary examples, the cured composite part is removed from the injection and curing tool at approximately the injection temperature. In some exemplary examples, removing the cured composite part during heating will shorten the processing time of the cured composite part. Removing the cured composite part while it is hot will increase the throughput of the injection and curing tool. Removing the cured composite part while it is hot can shorten the pause time between injections of the composite part. Removing the cured composite part while it is hot can reduce the energy used to condition the injection and curing tool for the injection of the next dry preform.

[0059] Referring now to FIG. 9, a flowchart of a method of compression resin transfer infusion according to an exemplary embodiment is shown. Method 900 can be executed to form the composite part of the aircraft 100 of FIG. 1. Method 900 can be executed using the resin injection and curing tool 202 to form the cured composite part 252 of FIG. 2. Method 900 can be executed using the temperature cycle 302. Method 900 can be executed using the resin injection and curing tool 400 of FIG. 4. Method 900 can inject and cure the thermoplastic veil 501 and the resin 502 of FIG. 5.

[0060] Method 900 injects resin into the gap of the sealed cavity of the injection and curing tool (step 902) while the injection and curing tool is maintained at an injection temperature within the range of 130 to 160 °C. Method 900 lowers the upper mold of the injection and curing tool (step 904) to inject resin in a resin waiting time state into the dry preform in the sealed cavity to form a resin-injected preform. Method 900 raises the temperature of the injection and curing tool from the injection temperature to the curing temperature at a desired ramp rate (step 906). Method 900 cures the resin-injected preform in the injection and curing tool to form a cured composite part, where the curing occurs at a curing temperature higher than the injection temperature, and the curing temperature is sufficient to expand and melt the thermoplastic veil in the dry preform and bond the resin to the thermoplastic veil (step 908). Then, method 900 ends.

[0061] In some exemplary examples, the injection temperature is within the range of 130 to 160 °C, the ramp rate is 1 to 3 °C / min, and the curing temperature is within the range of 165 to 190 °C (step 909). In some exemplary examples, the injection of the resin and the lowering of the upper mold are performed within 30 minutes (step 910). The injection time can be selected based on the waiting time.

[0062] In some exemplary examples, the upper mold is lowered at a mold closing speed of 0.01 to 0.2 inches / min (step 912). When the upper mold is lowered, the resin is injected throughout the thickness of the dry preform into the dry preform.

[0063] In some exemplary examples, after the upper mold is lowered, the pressure in the sealed cavity is 10 to 100 psig, and during curing, the pressure is maintained at 10 to 100 psig (step 914). In some exemplary examples, curing takes 45 to 180 minutes (step 916). In some exemplary examples, the difference between the injection temperature and the curing temperature is 40 °C or less (step 918).

[0064] In some exemplary examples, method 900 reduces the temperature of the injection and curing tool from the curing temperature at a ramp-down rate after curing, where the curing temperature and the ramp-down rate are selected to generate cavitation bubbles within the thermoplastic veil in the cured composite part (step 920). The cavitation bubbles are generated when the thermoplastic veil attempts to shrink to its initial diameter after binding to the cured resin.

[0065] In some exemplary examples, method 900 removes the cured composite part from the injection and curing tool while the injection and curing tool is at a temperature within the range of 130 - 160°C (step 922). In some exemplary examples, the cured composite part is removed from the injection and curing tool at approximately the injection temperature. In some exemplary examples, removing the cured composite part during heating will shorten the processing time of the cured composite part. Removing the cured composite part while it is hot will increase the throughput of the injection and curing tool. Removing the cured composite part while it is hot can shorten the pause time between injections of the composite part. Removing the cured composite part while it is hot can reduce the energy used to condition the injection and curing tool for the injection of the next dry preform.

[0066] Referring now to FIG. 10, a flowchart of a method of compression resin transfer infusion for forming cavitation bubbles within a cured composite part, according to an exemplary embodiment, is shown. Method 1000 can be performed to form the composite part of the aircraft 100 of FIG. 1. Method 1000 can be performed using the resin injection and curing tool 202 to form the cured composite part 252 of FIG. 2. Method 1000 can be performed using the temperature cycle 302. Method 1000 can be performed using the resin injection and curing tool 400 of FIG. 4. Method 1000 can inject and cure the thermoplastic veil 501 and the resin 502 of FIG. 5.

[0067] Method 1000 injects resin into the gap of the sealed cavity of the injection and curing tool while the injection and curing tool is maintained at the injection temperature (step 1002). Method 1000 lowers the upper mold of the injection and curing tool to inject resin throughout the thickness of the dry preform in the sealed cavity to form a resin-injected preform, and the dry preform includes a thermoplastic veil (step 1004). Method 1000 raises the temperature of the injection and curing tool from the injection temperature to expand the thermoplastic veil while the thermoplastic veil melts (step 1006). Method 1000 cures the resin-injected preform in the injection and curing tool to form a cured composite part (step 1008). Method 1000 lowers the temperature of the injection and curing tool after curing to shrink the thermoplastic veil in the cured composite part while cooling the thermoplastic veil below its melting temperature, generating cavitation bubbles in the thermoplastic veil (step 1010). Then, method 1000 ends.

[0068] In some exemplary examples, the curing temperature is sufficient to expand and melt the thermoplastic veil in the resin-injected preform (step 1012). In some exemplary examples, the curing temperature is higher than the melting temperature of the thermoplastic veil. In some exemplary examples, the curing temperature is selected such that the thermoplastic veil expands sufficiently to generate cavitation bubbles after the thermoplastic veil cools.

[0069] In some exemplary examples, the injection temperature is in the range of 130 - 160 °C, and curing is performed at a curing temperature in the range of 165 - 190 °C (step 1014). In some exemplary examples, the lowering of the upper mold of the injection and curing tool is performed at a mold closing speed of 0.01 - 0.2 inches per minute (step 1016).

[0070] As used herein, the phrase "at least one of" when used with a list of items means that various combinations of one or more of the listed items may be used and that only one of each item in the list may be required. For example, "at least one of item A, item B, or item C" may include, but is not limited to, item A, item A and item B, or item B. Also, this example may include item A, item B, and item C or item B and item C. Of course, any combination of these items is possible. In another example, "at least one of" may be, for example, two item As, one item B, and ten item Cs, four item Bs and seven item Cs, or other suitable combinations, but is not limited thereto. An item may be a particular object, thing, or category. In other words, "at least one of" means that any combination of items and number of items may be used from the list, but not all of the items in the list are required.

[0071] As used herein, "a number of" when used with respect to items means one or more items.

[0072] Furthermore, all numerical values are values indicated as "about" or "approximately" and take into account experimental errors and variations expected by those skilled in the art. It should be understood that all numerical values and ranges disclosed herein are approximate values and ranges. The terms "about" or "substantially" and "substantially" or "nearly" with respect to an amount or measurement mean that the recited feature, parameter, or value need not be precisely realized. Further, deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limits, and other factors known to those skilled in the art, may occur in an amount that does not preclude the effect sought to be achieved by realizing the feature. As used herein, "about" means within + / - 10% of the recited target value, maximum value, or minimum value.

[0073] Flowcharts and block diagrams in various illustrated embodiments illustrate the architecture, functionality, and operation of some possible implementations of the apparatus and method in the exemplary embodiments. In this regard, each block in the flowchart or block diagram may represent at least one of a module, a segment, a function, or a part of an operation or step.

[0074] In some alternative implementations of the exemplary embodiments, one or more functions described in the blocks may occur out of the order depicted in the figures. For example, in some cases, two blocks shown in succession may be executed substantially simultaneously, depending on the related functions, or may be executed in the reverse order in some cases. Also, in addition to the illustrated blocks of the flowchart or block diagram, other blocks may be added. Some blocks may be optional. For example, steps 812 to 828 may be optional. As another example, steps 910 to 922 may be optional. As a further example, step 1012 may be optional.

[0075] Exemplary embodiments of the present disclosure may be described in relation to the aircraft manufacturing and maintenance inspection method 1100 shown in FIG. 11 and the aircraft 1200 shown in FIG. 12. First, looking at FIG. 11, an explanatory diagram of the aircraft manufacturing and maintenance inspection method in the form of a block diagram according to an exemplary embodiment is shown. During the pre-manufacturing stage, the aircraft manufacturing and maintenance inspection method 1100 may include the specifications and design 1102 and material procurement 1104 of the aircraft 1200 in FIG. 12.

[0076] During manufacturing, the manufacturing 1106 of the components and sub-assemblies of the aircraft 1200 and the system integration 1108 are performed. Thereafter, the aircraft 1200 may go through certification and transportation 1110 in order to be put into service 1112. During service 1112 by the customer, routine maintenance and inspection 1114 of the aircraft 1200 are planned, and the routine maintenance and inspection 1114 may include modifications, reconfigurations, repairs, or other maintenance and inspections.

[0077] Each of the processes of the aircraft manufacturing and maintenance inspection method 1100 may be performed or implemented by a system integrator, a third party, and / or an operator. In these examples, the operator may be a customer. For the purposes of this description, the system integrator may include, but is not limited to, any number of aircraft manufacturers and subcontractors of major systems, and the third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers, and further, the operator may be an airline, a leasing company, an army, a maintenance inspection company, etc.

[0078] Referring now to FIG. 12, an explanatory view of an aircraft that can be the subject of implementation of the exemplary embodiment is shown in the form of a block diagram. In this example, the aircraft 1200 may include a fuselage 1202 produced by the aircraft manufacturing and maintenance inspection method 1100 of FIG. 11 and having a plurality of systems 1204 and an interior 1206. Examples of the system 1204 include one or more of a propulsion system 1208, an electrical system 1210, a hydraulic system 1212, and an environmental system 1214. Any number of other systems may be included.

[0079] In at least one of the stages of the aircraft manufacturing and maintenance inspection method 1100, the devices and methods embodied herein may be used. One or more exemplary embodiments may be manufactured or used during at least one of the manufacturing 1106, system integration 1108, in-flight 1112, or maintenance and inspection 1114 of the components and subassemblies of FIG. 11.

[0080] Exemplary examples provide compression resin transfer infusion. The resin waiting time is the period during which the resin remains liquid and does not start to cure. In some exemplary examples, the resin waiting time is in the range of 20 to 60 minutes. In some exemplary examples, the resin maintains a viscosity of 100 cps or less. In some exemplary examples, the injection temperature of the resin injection and curing tool is in the range of 130 to 160 °C. In some exemplary examples, the mold closing speed at which the upper mold descends towards the lower mold is in the range of 0.01 to 0.2 inches per minute. In some exemplary examples, the pressure within the sealed cavity of the resin injection and curing tool at the end of closing is in the range of 10 to 100 psig.

[0081] The resin injection and curing tool raises the temperature from the injection temperature to the curing temperature. In some exemplary examples, the difference between the injection temperature and the curing temperature is 40 °C or less. In some exemplary examples, the ramp rate from the injection temperature to the curing temperature is in the range of 1 to 3 °C per minute.

[0082] In some exemplary examples, the curing temperature is in the range of 165 to 190 °C. During curing, the pressure within the sealed cavity of the resin injection and curing tool remains at 10 to 100 psig. In some exemplary examples, the curing time is in the range of 45 to 180 minutes.

[0083] In some exemplary examples, the pressure remains at 10 to 100 psig during the temperature rise from the curing temperature to the part removal temperature. In some exemplary examples, the cured composite part is removed from the high-temperature resin injection and curing tool within a temperature range of 130 to 160 °C. No additional post-curing is performed after the cured composite part is removed from the resin injection and curing tool. The cured composite part includes a desired level of bonding between the resin within the preform and the thermoplastic veil.

[0084] Due to the thermal gradient, the resin can maintain its mobility for a longer time and the thermoplastic veil can gelate (vitrify) after reaching its melting temperature. In some examples, the thermoplastic veil melts above 170 °C. When the thermoplastic veil melts, it expands. After the thermoplastic veil melts, the resin forms a network around the expanded veil and binds to the surface of the thermoplastic veil.

[0085] When the thermoplastic veil cools again below its melting temperature, it tries to shrink back to its original size. Here, since the thermoplastic veil is bonded to the resin, there is no place for the thermoplastic veil to shrink, and cavitation bubbles are generated in the center of the thermoplastic veil.

[0086] In some exemplary examples, at temperatures below the melting temperature, the resin is still liquid and the thermoplastic veil is of its original diameter, for example about 35 μm. At temperatures above the melting temperature of the thermoplastic veil, when the thermoplastic veil softens or melts with the resin still in a liquid state, it expands. In some exemplary examples, when the thermoplastic veil softens or melts, it can expand to about 45 - 50 μm.

[0087] After the resin hardens, the thermoplastic veil is fixed at the expanded size. When the thermoplastic veil cools again below its melting temperature, the thermoplastic veil tries to shrink and return to its size. With the outer surface of the thermoplastic veil fixed in place, cavitation bubbles are formed in the center of the thermoplastic veil.

[0088] The description of different exemplary embodiments is presented for purposes of illustration and explanation and is not intended to be exhaustive or limited to the embodiments of the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different exemplary embodiments may provide different features compared to other exemplary embodiments. The selected embodiment or embodiments are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure of the various embodiments with various modifications suitable for the particular use contemplated.

Description of Reference Numerals

[0089] 200 Manufacturing environment 202 Resin injection and curing tool 204 Resin 205 Waiting time 206 Preform 208 Resin-injected preform 210 Compression resin transfer infusion 212 Dry preform 214 Thermoplastic veil 216 Lower mold 218 Upper mold 220 Sealed cavity 222 Seal 224 Gap 226 Cavity volume 228 Thickness 230 Mold closing speed 232 Injection 233 Injection time 234 Temperature 236 Injection temperature 238 Temperature gradient 239 Lamp speed 240 Curing temperature 242 Pressure 244 Melting temperature 246 Diameter 249 Lamp-down speed 250 Withdrawal temperature 252 Cured composite part 254 Thermoplastic Veil 256 Cavitation Bubbles 258 Cured Resin 260 Curing 261 Curing Time 400 Resin Injection and Curing Tool 404 Upper Mold 406 Lower Mold 408 Seal 410 Sealed Cavity 412 Preform 414 Resin 416 Gap 501 Thermoplastic Veil 502 Resin 504 Diameter 602 Diameter 702 Network 704 Cavitation Bubbles

Claims

1. 1. A method (800) for compression resin transfine fusion comprising: Placing (802) a dry preform (212, 412) including a thermoplastic veil (214, 501) on a lower mold (216, 406); placing (804) an upper mold (218, 404) over the lower mold (216, 406) to create an injection and cure tool (202, 400) having a closed cavity (220, 410) for holding the dry preform (212, 412), the closed cavity (220, 410) defining a gap (224, 416), the gap (224, 416) corresponding to a cavity volume (226) corresponding to an amount of resin (204, 414, 502) for infusion molding the dry preform (212, 412); injecting (806) a resin (204, 414, 502) into the gap (224, 416) of the sealed cavity (220, 410) while the injection and curing tool (202, 400) is maintained at an injection temperature (236, 310); lowering (808) the upper mold (218, 404) to infusion mold the dry preform (212, 412) to form a resin infused preform (208); curing (810, 260, 316) the resin infused preform (208) in the infusion and curing tool (202, 400) to form a cured composite part (252), the curing (260, 316) occurring at a curing temperature (240, 314) greater than the infusion temperature (236, 310); The method (800).

2. 10. The method (800) of claim 1, wherein the curing temperature (240, 314) is sufficient to expand and melt (816) the thermoplastic veil (214, 501).

3. 10. The method (800) of claim 1, further comprising the step (818) of decreasing a temperature of the injection and curing tool (202, 400) from the curing temperature (240, 314) at a ramp-down rate (249) after the curing (260, 316), the curing temperature (240, 314) and the ramp-down rate (249) being selected to generate cavitation bubbles (256, 704) within the thermoplastic veil (214, 501) in the cured composite part (252).

4. The method (800) of claim 1, wherein the upper mold (218, 404) is lowered (812) at a closing speed (230) of 0.01 to 0.2 inches per minute.

5. The method (800) of claim 1, wherein the curing (260, 316) takes between 45 and 180 minutes (820).

6. The method (800) of claim 1, wherein the injection temperature (236, 310) is in the range of 130 to 160° C. (814).

7. The method (800) of claim 1, wherein the curing temperature (240, 314) is in the range of 165 to 190°C (822).

8. The method (800) of any preceding claim, wherein a temperature gradient (238, 312) for curing between the injection temperature (236, 310) and the curing temperature (240, 314) has a ramp rate (239) of 1-3° C. / min.

9. 10. The method (800) of claim 1, wherein a difference between the injection temperature (236, 310) and the curing temperature (240, 314) is 40 degrees Celsius or less (826).

10. Removing (828) the cured composite part (252) from the injection and cure tool (202, 400) while the injection and cure tool (202, 400) is at a temperature (234) in the range of 130-160°C.

10. The method of claim 1, further comprising:

11. 1. A method (900) for compression resin transfine fusion comprising: Injecting (902) a resin (204, 414, 502) into a gap (224, 416) of a closed cavity (220, 410) of the injection and curing tool (202, 400) while the injection and curing tool (202, 400) is maintained at an injection temperature (236, 310); lowering (904) an upper mold (218, 404) of the injection and cure tool (202, 400) to infuse the resin (204, 414, 502) into the dry preform (212, 412) in the closed cavity (220, 410) during a resin waiting period to form a resin-infused preform (208); increasing (906) the temperature (234) of the infusion and cure tool (202, 400) from the infusion temperature (236, 310) to a cure temperature (240, 314) at a desired ramp rate; curing (908, 260, 316) the resin infused preform (208) in the infusion and curing tool (202, 400) to form a cured composite part (252), the curing (260, 316) occurring at the curing temperature (240, 314) being greater than the infusion temperature (236, 310), the curing temperature (240, 314) being sufficient to expand and melt a thermoplastic veil (214, 501) in the dry preform (212, 412) and bond the resin to the thermoplastic veil (214, 501); The method (900).

12. The method (900) of claim 11, wherein the injection temperature (236, 310) is in the range of 130-160°C, the ramp rate is 1-3°C / min, and the cure temperature (240, 314) is in the range of 165-190°C.

13. The method (900) of claim 11, wherein the upper mold (218, 404) is lowered (912) at a closing speed (230) of 0.01 to 0.2 inches per minute.

14. The method (900) of claim 11, wherein after the upper mold (218, 404) is lowered, the pressure (242) in the closed cavity (220, 410) is between 10 and 100 psig, and the pressure (242) is maintained (914) between 10 and 100 psig during the curing (260, 316).

15. The method (900) of claim 11, wherein the curing (260, 316) takes between 45 and 180 minutes (916).

16. 12. The method (900) of claim 11, wherein the difference between the injection temperature (236, 310) and the curing temperature (240, 314) is 40 degrees Celsius or less (918).

17. Removing (922) the cured composite part (252) from the injection and cure tool (202, 400) while the injection and cure tool (202, 400) is at a temperature (234) in the range of 130-160°C.

12. The method of claim 11, further comprising:

18. a step (920) of decreasing a temperature (234, 302) of the injection and curing tool (202, 400) from the curing temperature (240, 314) at a ramp-down rate (249) after the curing (260, 316), the curing temperature (240, 314) and the ramp-down rate (249) being selected to generate cavitation bubbles (256, 704) in the thermoplastic veil (214, 501) in the cured composite part (252); 12. The method of claim 11, further comprising:

19. 12. The method (900) of claim 11, wherein the injection of the resin (204, 414, 502) and the lowering of the upper mold (218, 404) occur within 30 minutes (910).

20. 1. A method (1000) of compression resin transfine fusion for forming cavitation bubbles (256, 704) in a cured composite part (252), comprising: Injecting (1002) a resin (204, 414, 502) into a gap (224, 416) of a closed cavity (220, 410) of the injection and curing tool (202, 400) while the injection and curing tool (202, 400) is maintained at an injection temperature (236, 310); lowering (1004) an upper mold (218, 404) of the injection and curing tool (202, 400) to inject the resin (204, 414, 502) into a dry preform (212, 412) in the closed cavity (220, 410) throughout its thickness (228) to form a resin-infused preform (208), the dry preform (212, 412) including a thermoplastic veil (214, 501); increasing (1006) the temperature (234) of the injection and curing tool (202, 400) from the injection temperature (236, 310) to expand the thermoplastic veil while the thermoplastic veil is molten; curing (1008, 260, 316) the resin infused preform (208) in the infusion and cure tool (202, 400) to form a cured composite part (252); reducing (1010) the temperature (234) of the injection and curing tool (202, 400) after the curing (260, 316) to shrink the thermoplastic veil (214, 501) in the cured composite part (252) while cooling the thermoplastic veil (214, 501) below the melting temperature of the thermoplastic veil (214, 501) to generate cavitation bubbles (256, 704) in the thermoplastic veil (214, 501); The method (1000).

21. The method of claim 20, wherein the injection temperature (236, 310) is in the range of 130-160°C and curing is carried out at a curing temperature (240, 314) in the range of 165-190°C.

22. The method of claim 20, wherein the step of lowering (1004) the upper mold (218, 404) of the injection and cure tool (202, 400) is performed at a closing speed (230) of 0.01 to 0.2 inches per minute.

23. 22. The method of claim 21, wherein the curing temperature (240, 314) is sufficient to expand and melt (1012) the thermoplastic veil (214, 501) in the resin infused preform (208).

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