Manufacturing method of composite material test specimens and composite material test specimens

Abstract

This disclosure relates to a method for manufacturing a composite material test specimen and the composite material test specimen itself. The method includes: determining a design scheme for the composite material test specimen, the design scheme including the layup location and in-plane location of designed wrinkle defects, and the designed porosity of the composite material test specimen; obtaining buckled fiber bundles corresponding to the shape and size of the designed wrinkle defects; laying prepreg layer by layer on a tooling according to the design scheme to form a laminated blank, wherein the buckled fiber bundles are positioned at the corresponding layup location and in-plane location in the laminated blank according to the layup location and in-plane location of the designed wrinkle defects; encapsulating the laminated blank and curing the encapsulated laminated blank according to the designed porosity of the composite material test specimen; and obtaining the composite material test specimen by demolding after curing. This disclosure enables controllable wrinkle defects and porosity defects in the composite material test specimen.

Description

Technical Field

[0001] This disclosure relates to the field of testing, and in particular to a method for manufacturing composite material test specimens and composite material test specimens. Background Technology

[0002] In the production, processing, and application of composite materials, two types of problems have a crucial impact on the degradation of material performance. One is defects generated during manufacturing, and the other is damage caused during processing and use. Porosity and wrinkles are among the most common defects in composite materials, significantly affecting compressive strength and fatigue life. Wrinkles can be caused by a variety of factors, such as mismatched thermal expansion coefficients of the fiber, matrix, and mold materials, improper control of curing temperature and pressure, errors in layup contour and position accuracy, and improper layup sequence. Porosity is usually caused by resin moisture absorption or insufficient pressure. Summary of the Invention

[0003] The inventors discovered through research that in practical engineering, the formation of wrinkles often leads to insufficient curing pressure on the curved surfaces of the layup, resulting in accompanying porosity defects. To study the relationship between wrinkles and porosity defects on the performance of composite parts, especially the correlation between the two types of defects when they coexist, it is necessary to simultaneously and controllably manufacture both types of defects at different content levels.

[0004] In view of this, the present disclosure provides a method for manufacturing composite material test specimens and a composite material test specimen, which can realize controllable wrinkle defects and porosity defects in composite material test specimens.

[0005] In one aspect of this disclosure, a method for manufacturing a composite material test specimen is provided, comprising:

[0006] Determine the design scheme of the composite material test specimen, the design scheme including the layup location and in-plane location of the design wrinkle defects and the design porosity of the composite material test specimen;

[0007] Obtain the buckled fiber bundles corresponding to the shape and size of the designed wrinkle defects;

[0008] According to the design scheme, the prepreg is laid layer by layer on the tooling to form a laminated blank. The buckled fiber bundles are set in the laminated blank at the corresponding lay-up position and in-plane position according to the lay-up position and in-plane position of the designed wrinkle defects.

[0009] The laminated blank is encapsulated, and the encapsulated laminated blank is cured according to the design porosity of the composite material test piece.

[0010] After curing, composite material test specimens are obtained by demolding.

[0011] In some embodiments, the step of obtaining the bent fiber bundle includes:

[0012] Multiple fibers are pultruded into a fiber bundle with a preset length, preset diameter, and preset buckling state through a fiber pultrusion process.

[0013] In some embodiments, the plurality of fibers are 3K carbon fiber filaments with a diameter of 0.28 mm or 12K carbon fiber filaments with a diameter of 0.56 mm.

[0014] In some embodiments, the step of obtaining the bent fiber bundle includes:

[0015] Obtain a metal wire with a preset length, preset diameter, and preset buckling state.

[0016] In some embodiments, the preset buckling state includes a preset buckling angle and a preset number of bucklings.

[0017] In some embodiments, the buckling angle is at least one of 5°, 10°, and 20°.

[0018] In some embodiments, the step of positioning the buckled fiber bundles at corresponding layup and in-plane positions in the laminated preform includes:

[0019] After laying prepreg layer by layer on the tooling, corresponding to the number of layers where the designed wrinkle defect is located, the buckled fiber bundle is placed on the prepreg of the current layer, and the in-plane position of the buckled fiber bundle in the current layer is consistent with the in-plane position of the designed wrinkle defect.

[0020] In some embodiments, the method of manufacturing composite specimens further includes, when the buckled fiber bundles are disposed on the prepreg of the current layup:

[0021] The buckled fiber bundles are secured on the prepreg of the current layup using accessible pressure-sensitive tape.

[0022] In some embodiments, the step of curing the encapsulated laminated preform includes:

[0023] The encapsulated laminated blank is evacuated to a first preset vacuum level P. V0 ;

[0024] The encapsulated laminated blank is placed in an autoclave, and the vacuum degree of the encapsulated laminated blank, as well as the internal pressure and internal temperature of the autoclave, are adjusted to complete the curing process.

[0025] The step of adjusting the internal temperature of the autoclave includes:

[0026] At an initial time t0, the internal temperature of the autoclave is increased from the initial temperature T0 to a first preset temperature value T1 at a preset heating rate, and then maintained for a preset time t. L Maintain the first preset temperature value T1, and then reduce the temperature from the first preset temperature value T1 to a temperature lower than the second preset temperature value T2 at a preset cooling rate.

[0027] The steps for adjusting the internal pressure of the autoclave include:

[0028] At the initial time t0, the internal pressure of the autoclave is increased from the initial pressure P0 to the first preset pressure value P1, and the first preset pressure value P1 is maintained until the internal temperature of the autoclave drops to the second preset temperature value T2, at which point the internal pressure of the autoclave is released.

[0029] The steps for adjusting the vacuum level of the packaged stack blank include:

[0030] At the initial time t0, the vacuum level of the packaged stack blank is reduced from the first preset vacuum level value P. V0 The pressure decreases, and at time t1, when the internal pressure of the autoclave rises from the initial pressure P0 to a second preset pressure value P2 that is less than the first preset pressure value P1, the vacuum degree of the encapsulated laminate blank reaches the second preset vacuum degree value P. V1 The second preset vacuum value P V1 Less than the first preset vacuum value P V0 .

[0031] In some embodiments, the design porosity of the composite material specimen is less than 1%, and the first preset vacuum value P V0 The first preset pressure value P1 is 7 bar, which is -1.0 bar.

[0032] In some embodiments, the composite material test specimen has a design porosity greater than 1% and less than 3%, and the first preset vacuum value P V0 The value is -0.6 bar, and the first preset pressure value P1 is 2 bar.

[0033] In some embodiments, the second preset pressure value P2 is 1 bar, and the second preset vacuum value P V1 The preset temperature is -0.2 bar, the first preset temperature value T1 is 175-185℃, the second preset temperature value T2 is 60℃, and the preset duration t is... L The time is 115-125 min, the preset heating rate is 1-2℃ / min, and the preset cooling rate is 2-5℃ / min.

[0034] According to one aspect of this disclosure, a composite material test specimen is provided, formed using the aforementioned composite material test specimen manufacturing method.

[0035] Therefore, according to the embodiments of this disclosure, based on the design scheme of the composite material test specimen, the layup position and in-plane position of the designed wrinkle defect are arranged in the prepreg during the layup of the prepreg, and the buckled fiber bundles corresponding to the shape and size of the designed wrinkle defect are respectively placed in the layup position and in-plane position of the prepreg. Then the prepreg is encapsulated, and the encapsulated prepreg is cured according to the design porosity of the composite material test specimen, thereby obtaining a composite material test specimen with controllable wrinkle defects and porosity defects, so as to meet the performance research requirements of the composite material part when these two types of defects coexist. Attached Figure Description

[0036] The accompanying drawings, which form part of this specification, illustrate embodiments of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0037] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein:

[0038] Figure 1 This is a schematic flowchart of some embodiments of the method for manufacturing composite material test specimens according to the present disclosure;

[0039] Figure 2 This is a schematic diagram of a method for manufacturing composite test specimens according to the present disclosure, in which bent fiber bundles are provided in a prepreg.

[0040] Figure 3 This is a schematic diagram of the structure and dimensional parameters of the buckled fiber bundle used in the embodiments of the composite material test specimen manufacturing method of this disclosure;

[0041] Figure 4 This is a schematic diagram showing the change of process parameters over time during the curing process according to an embodiment of the composite material test specimen manufacturing method disclosed herein.

[0042] It should be understood that the dimensions of the various parts shown in the accompanying drawings are not drawn to actual scale. Furthermore, the same or similar reference numerals denote the same or similar components. Detailed Implementation

[0043] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The descriptions of the exemplary embodiments are merely illustrative and are in no way intended to limit the present disclosure or its application or use. The present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided so that the present disclosure will be thorough and complete, and will fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless specifically stated otherwise, the relative arrangement of components and steps, the composition of materials, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0044] The terms "first," "second," and similar words used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Words such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well. Terms such as "above," "below," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, this relative positional relationship may also change accordingly.

[0045] In this disclosure, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0046] All terms used in this disclosure (including technical or scientific terms) have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary, such as a dictionary, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0047] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0048] Before formally describing the various embodiments of this disclosure, several technical terms involved in the technical content of this disclosure will be defined.

[0049] Composite Material: A new material formed by optimizing and combining material components with different properties using material preparation techniques, such as resin-based composite materials.

[0050] Defect: Any abnormal condition that has been confirmed in a composite material product.

[0051] Wrinkles: wavy bending deformations within a composite material.

[0052] Porosity: The percentage of the total volume of pores smaller than a certain size in a composite material to the total volume of the composite material in its natural state.

[0053] Non-destructive inspection (NDI) is a technique that uses the attenuation and reflection characteristics of defects in composite materials to detect the location, size, shape, and other features of defects.

[0054] Defect tolerance: For defects in composite materials that are difficult to detect by non-destructive testing techniques, their impact on the performance of the composite material must be considered. Composite material design must consider that performance requirements can still be met even when the most unfavorable combination of undetectable defects exists. This is called defect tolerance.

[0055] Figure 1 This is a schematic flowchart illustrating some embodiments of the method for manufacturing composite material test specimens according to this disclosure. (See reference) Figure 1 In some embodiments, the method for manufacturing composite material test specimens includes:

[0056] Step S1: Determine the design scheme of the composite material test specimen, the design scheme including the layup location and in-plane location of the design wrinkle defects and the design porosity of the composite material test specimen;

[0057] Step S2: Obtain the buckled fiber bundles corresponding to the shape and size of the designed wrinkle defects;

[0058] Step S3: According to the design scheme, the prepreg is laid layer by layer on the tooling to form a laminated blank, wherein the buckled fiber bundles are set in the laminated blank at the corresponding lay-up position and in-plane position according to the lay-up position and in-plane position of the designed wrinkle defects.

[0059] Step S4: Encapsulate the laminated blank and cure the encapsulated laminated blank according to the design porosity of the composite material test piece;

[0060] Step S5: After curing, obtain the composite material test piece by demolding.

[0061] This embodiment, based on the design scheme of the composite material test specimen, specifies the layup and in-plane locations of the designed wrinkle defects. During the prepreg layup, buckled fiber bundles corresponding to the shape and size of the designed wrinkle defects are placed in the laminated blank at the layup and in-plane locations corresponding to the designed wrinkle defects, respectively. The laminated blank is then encapsulated and cured according to the designed porosity of the composite material test specimen. This produces a composite material test specimen with controllable wrinkle and porosity defects, suitable for non-destructive testing research and defect tolerance design. This satisfies the performance research requirements of composite material parts when these two types of defects are coupled, thereby solving problems such as unclear mechanisms of the influence of coupled defects on performance and unavailable experimental data in engineering. Furthermore, this method effectively reduces the manufacturing cost of test specimens and improves the efficiency of test block production.

[0062] In step S1, a suitable test specimen design scheme can be selected based on the defects in the composite material to be studied. To study composite material test specimens exhibiting the coupling of wrinkle defects and porosity defects, various test specimen design schemes with different parameters for wrinkle and porosity defects can be designed to manufacture different test specimens that meet various testing requirements. In the design scheme, the layup location and in-plane location of the designed wrinkle defects, as well as the designed porosity of the composite material test specimen, can be pre-designed.

[0063] The location of the designed wrinkle defect in the ply refers to which layer the designed wrinkle defect is in among multiple plies. This ply location is not limited to a single layer but can include multiple layers, such as the 7th and 12th layers. The in-plane location of the designed wrinkle defect refers to its specific position within its layer, such as the starting and ending coordinates determined by the coordinate system of the layer plane. The design porosity of the composite specimen refers to the required porosity value or range within the final composite specimen.

[0064] In step S2, a buckled fiber bundle corresponding to the shape and size of the designed wrinkle defect is obtained based on the relevant structural parameters of the designed wrinkle defect in the determined design scheme. This buckled fiber bundle can be manufactured in-house or purchased from other manufacturers. The acquisition operation in step S2 can be performed according to the design scheme in step S1.

[0065] Figure 2 This is a schematic diagram of a prepreg containing bent fiber bundles according to an embodiment of the composite material test specimen manufacturing method disclosed herein. Figure 3 This is a schematic diagram of the structure and dimensional parameters of the buckled fiber bundle used in the embodiments of the composite material test specimen manufacturing method disclosed herein.

[0066] refer to Figure 3In some embodiments, the step of obtaining the bent fiber bundle 20 includes: pultruding multiple fiber filaments into a fiber bundle with a preset length, preset diameter, and preset buckling state using a fiber pultrusion process. For example, pultruding 0.28mm diameter 3K carbon fiber filaments or 0.56mm diameter 12K carbon fiber filaments into a 300mm long fiber bundle with a certain buckling angle using a fiber pultrusion process, wherein the diameter and number of buckles of the fiber bundle can be adjusted as needed.

[0067] exist Figure 3 In this context, the length L of the fiber bundle can be defined as the straight-line distance between the two ends of the buckled fiber bundle 20 in its natural state. The preset buckling state may include a preset buckling angle α and a preset number of buckles. The buckling angle can be defined as the maximum angle between the corrugations included in the fiber bundle and the centerline of the entire buckled fiber bundle 20, with reference to the centerline. This value can be taken from at least one of 5°, 10°, and 20°. The number of buckles can be defined as the number of corrugations included in the fiber bundle.

[0068] Designers can precisely control the wrinkle angle, orientation, coverage, and porosity of the manufactured test specimen by designing various parameters of the buckled fiber bundle 20. Furthermore, the entire buckled fiber bundle lies on the same plane to form planar buckling wrinkle defects.

[0069] In some other embodiments, the step of obtaining the buckled fiber bundle 20 may also include obtaining a metal wire having a preset length, preset diameter, and preset buckling state. The metal wire, like carbon fiber, has a certain stiffness and is not easily deformed by resin flow during the curing process after setting, thus affecting the controllability of various parameters of the wrinkle defect.

[0070] In step S3, the prepreg is laid layer by layer on the tooling according to the design scheme to form a laminated blank with multiple layups 10. To position the buckled fiber bundles 20 appropriately, refer to... Figure 2 The number of lay-up layers corresponding to the location of the designed wrinkle defect can be stacked layer by layer on the tooling (e.g., ...). Figure 2 After the prepreg of the Nth layer shown, the buckled fiber bundle 20 is placed on the prepreg of the current layup, and the in-plane position of the buckled fiber bundle 20 in the current layup is consistent with the in-plane position of the designed wrinkle defect.

[0071] To prevent the buckled fiber bundle 20 from shifting due to resin flow during curing, the step of placing the buckled fiber bundle 20 on the prepreg of the current layup may further include: securing the buckled fiber bundle 20 on the prepreg of the current layup using a contactable pressure-sensitive tape 30. For example, the ends of the buckled fiber bundle 20 may be secured to the layup allowance area using a contactable pressure-sensitive tape 30.

[0072] In step S4, a vacuum bag can be used to encapsulate the laminated blank, and the curing process conditions are set according to the designed porosity of the composite material test specimen during the curing process. Changing the curing process conditions can obtain porosity in different ranges in the test specimen. For example, the porosity of the final obtained test specimen can be changed by adjusting the vacuum degree of the encapsulation and the pressure in the autoclave.

[0073] Figure 4 This is a schematic diagram illustrating the changes in process parameters over time during the curing process according to an embodiment of the composite material test specimen manufacturing method of this disclosure. (Reference) Figure 4 The step of curing the encapsulated stacked blank in step S4 includes: evacuating the encapsulated stacked blank to a first preset vacuum level P. V0 The encapsulated laminated blank is placed inside an autoclave, and the vacuum degree of the encapsulated laminated blank, as well as the internal pressure and internal temperature of the autoclave, are adjusted to complete the curing process.

[0074] In this process, the step of adjusting the internal temperature of the autoclave includes: at an initial time t0, raising the internal temperature of the autoclave from the initial temperature T0 to a first preset temperature value T1 at a preset heating rate, and for a preset time t... L The temperature is maintained at the first preset temperature value T1, and then the temperature is reduced from the first preset temperature value T1 to a temperature lower than the second preset temperature value T2 at a preset cooling rate.

[0075] The step of adjusting the internal pressure of the autoclave includes: at the initial time t0, increasing the internal pressure of the autoclave from the initial pressure P0 to a first preset pressure value P1, and maintaining the first preset pressure value P1 until the internal temperature of the autoclave drops to the second preset temperature value T2, and then releasing the internal pressure of the autoclave.

[0076] The step of adjusting the vacuum degree of the packaged stack blank includes: at the initial time t0, adjusting the vacuum degree of the packaged stack blank from the first preset vacuum degree value P. V0 The pressure decreases, and at time t1, when the internal pressure of the autoclave rises from the initial pressure P0 to a second preset pressure value P2 that is less than the first preset pressure value P1, the vacuum degree of the encapsulated laminate blank reaches the second preset vacuum degree value P. V1 The second preset vacuum value P V1 Less than the first preset vacuum value P V0 .

[0077] In this embodiment, the porosity of the test specimen is accurately controlled by adjusting the vacuum pressure after encapsulation, as well as the temperature and pressure parameters within the heating chamber. The porosity control principle is as follows: by reducing the vacuum level, the saturated vapor pressure of hygroscopic moisture and other volatile substances in the prepreg layer is increased, thereby increasing the temperature at which they vaporize and escape. Before the prepreg reaches its lowest viscosity state, a significant amount of moisture and volatile substances remain in a non-gaseous state within the layer. After the prepreg reaches its lowest viscosity state, the gas escape channels are gradually closed. At this point, the reduced curing pressure is lower than the saturated vapor pressure of moisture and volatile substances at the corresponding temperature. The moisture and volatile substances in the prepreg layer vaporize under high temperature and lower pressure and cannot escape, forming pores. The porosity can be adjusted by regulating the vacuum level and curing pressure.

[0078] To obtain composite material test specimens with a designed porosity of less than 1%, the first preset vacuum value P can be set. V0 The first preset pressure value P1 is 7 bar, and the first preset vacuum value P is -1.0 bar. To obtain composite material test specimens with a design porosity greater than 1% and less than 3%, the first preset vacuum value P can be adjusted. V0 The first preset pressure value P1 is 2 bar, and the second preset vacuum value P2 is -0.6 bar. Other process conditions may include: the second preset pressure value P2 is 1 bar, and the second preset vacuum value P1 is -0.6 bar. V1 The preset temperature is -0.2 bar, the first preset temperature value T1 is 175-185℃, the second preset temperature value T2 is 60℃, and the preset duration t is... L The time is 115-125 min, the preset heating rate is 1-2℃ / min, and the preset cooling rate is 2-5℃ / min.

[0079] In step S5, after curing, the test specimen is demolded to obtain a composite material test specimen with designed porosity and designed wrinkle defects. The molded specimen can then be processed into corresponding test specimen sizes according to different performance testing standards, and the impact of defect coupling on performance can then be studied.

[0080] Based on the various embodiments of the above-described composite material test specimen manufacturing method, this disclosure also provides a composite material test specimen formed using the above-described composite material test specimen manufacturing method embodiments. This test specimen can meet the research requirements on the influence of the coupling of different morphologies of wrinkle defects and different percentage contents of pore defects on performance and non-destructive testing signal characteristics, thereby facilitating the formulation of more reasonable defect tolerance and testing standards.

[0081] The following is a specific example illustrating the manufacturing process of composite material test specimens that conform to in-plane and out-of-plane wrinkle coupling defects with different percentages of porosity and different angles:

[0082] 1. Test specimen design: [0] 20 For the layup, the test specimen size was designed to be 300mm×300mm, and folds of 5°, 10° and 20° were designed at the middle 9, 10 and 11 layers of the test specimen.

[0083] 2. Manufacturing of in-plane buckling defects: 0.28mm (3K carbon fiber tow pultrusion) or 0.56mm (12K carbon fiber tow pultrusion) fiber bundles are pultruded into fiber bundles with a certain buckling angle and a length of 300mm through fiber pultrusion molding process. The length, diameter and buckling state (including buckling angle, number of buckles, etc.) of the fiber bundle can be adjusted as needed.

[0084] 3. Test specimen placement: Lay the prepreg on the flat fixture in the layup sequence and place the crimped fiber bundles in the corresponding layup. To prevent the crimped fiber bundles from shifting due to resin flow during curing, they can be fixed in place in the layup position with accessible pressure-sensitive tape in the layup allowance area.

[0085] 4. Packaging: The obtained stacked blanks are packed into vacuum bags to achieve packaging.

[0086] 5. Curing: The vacuum bag containing the laminated preform is placed in an autoclave for curing. Test pieces with different porosity contents are obtained by changing the curing process parameters. For the IM7 / M91 material system, the curing process conditions corresponding to two porosities are given below:

[0087] (1) To obtain a porosity of <1%, the curing process is as follows:

[0088] The encapsulated stacked blank is subjected to vacuum treatment to achieve a vacuum level of -1.0 bar;

[0089] The autoclave is pressurized from atmospheric pressure to 7 bar. During the pressurization process, the vacuum degree of the encapsulated laminate blank is reduced, so that when the pressure in the autoclave drops to 1 bar, the vacuum degree is reduced to -0.2 bar.

[0090] While adjusting the pressure of the autoclave, the temperature of the autoclave is also raised to 180℃±5℃ at a heating rate of 1-2℃ / min, and then held at 180℃±5℃ for (120±5)min, and then lowered from that temperature at a cooling rate of 2-5℃ / min.

[0091] Release the pressure in the autoclave when the temperature reaches below 60°C.

[0092] (2) To obtain a porosity >1% and <3%, the curing process is as follows:

[0093] The encapsulated stacked blank is subjected to vacuum treatment to achieve a vacuum level of -0.6 bar;

[0094] The autoclave is pressurized from atmospheric pressure to 2 bar. During the pressurization process, the vacuum degree of the encapsulated laminate blank is reduced, so that when the pressure in the autoclave drops to 1 bar, the vacuum degree is reduced to -0.2 bar.

[0095] While adjusting the pressure of the autoclave, the temperature of the autoclave is also raised to 180℃±5℃ at a heating rate of 1-2℃ / min, and then held at 180℃±5℃ for (120±5)min, and then lowered from that temperature at a cooling rate of 2-5℃ / min.

[0096] Release the pressure in the autoclave when the temperature reaches below 60°C.

[0097] 6. Demolding: After curing, demold the test piece to obtain a test piece with designed wrinkles and defects containing the designed porosity.

[0098] 7. Performance Testing: The 300mm×300mm pore and wrinkle coupling test specimens are processed into corresponding test specimen sizes according to different performance testing standards to study the impact of defect coupling on performance. Common tensile test specimen sizes are 250×325mm, and compression test specimen sizes are 140x12mm. The 300x300mm size of this test specimen can meet the corresponding processing requirements.

[0099] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0100] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A method for manufacturing a composite material test specimen, comprising: Determine the design scheme of the composite material test specimen, the design scheme including the layup location and in-plane location of the design wrinkle defects and the design porosity of the composite material test specimen; Obtain the buckled fiber bundles corresponding to the shape and size of the designed wrinkle defects; According to the design scheme, the prepreg is laid layer by layer on the tooling to form a laminated blank. The buckled fiber bundles are set in the laminated blank at the corresponding lay-up position and in-plane position according to the lay-up position and in-plane position of the designed wrinkle defects. The laminated blank is encapsulated, and the encapsulated laminated blank is cured according to the design porosity of the composite material test piece. After curing, composite material test specimens are obtained by demolding. The steps for obtaining the bent fiber bundles include: Multiple fibers are pultruded into a fiber bundle with a preset length, preset diameter, and preset buckling state through a fiber pultrusion process.

2. The method for manufacturing composite material test specimens according to claim 1, wherein, The multiple fibers are either 3K carbon fiber filaments with a diameter of 0.28 mm or 12K carbon fiber filaments with a diameter of 0.56 mm.

3. The method for manufacturing composite material test specimens according to claim 1, wherein, The steps for obtaining bent fiber bundles include: Obtain a metal wire with a preset length, preset diameter, and preset buckling state.

4. The method for manufacturing composite material test specimens according to claim 1 or 3, wherein, The preset buckling state includes a preset buckling angle and a preset buckling number.

5. The method for manufacturing composite material test specimens according to claim 4, wherein, The buckling angle is at least one of 5°, 10° and 20°.

6. The method for manufacturing composite material test specimens according to claim 1, wherein, The step of positioning the buckled fiber bundles at the corresponding layup and in-plane positions in the laminated blank includes: After laying prepreg layer by layer on the tooling, corresponding to the number of layers where the designed wrinkle defect is located, the buckled fiber bundle is placed on the prepreg of the current layer, and the in-plane position of the buckled fiber bundle in the current layer is consistent with the in-plane position of the designed wrinkle defect.

7. The method for manufacturing composite material test specimens according to claim 6, wherein, When placing the buckled fiber bundles on the prepreg of the current layup, the method further includes: The buckled fiber bundles are secured on the prepreg of the current layup using accessible pressure-sensitive tape.

8. The method for manufacturing composite material test specimens according to claim 1, wherein, The steps for curing the encapsulated laminate preform include: The encapsulated laminated blank is evacuated to a first preset vacuum level P. V0 ; The encapsulated laminated blank is placed in an autoclave, and the vacuum degree of the encapsulated laminated blank, as well as the internal pressure and internal temperature of the autoclave, are adjusted to complete the curing process. The step of adjusting the internal temperature of the autoclave includes: At an initial time t0, the internal temperature of the autoclave is increased from the initial temperature T0 to a first preset temperature value T1 at a preset heating rate, and then maintained for a preset time t. L Maintain the first preset temperature value T1, and then reduce the temperature from the first preset temperature value T1 to a temperature lower than the second preset temperature value T2 at a preset cooling rate. The steps for adjusting the internal pressure of the autoclave include: At the initial time t0, the internal pressure of the autoclave is increased from the initial pressure P0 to the first preset pressure value P1, and the first preset pressure value P1 is maintained until the internal temperature of the autoclave drops to the second preset temperature value T2, at which point the internal pressure of the autoclave is released. The steps for adjusting the vacuum level of the packaged stack blank include: At the initial time t0, the vacuum level of the packaged stack blank is reduced from the first preset vacuum level value P. V0 The pressure decreases, and at time t1, when the internal pressure of the autoclave rises from the initial pressure P0 to a second preset pressure value P2 that is less than the first preset pressure value P1, the vacuum degree of the encapsulated laminate blank reaches the second preset vacuum degree value P. V1 The second preset vacuum value P V1 Less than the first preset vacuum value P V0 .

9. The method for manufacturing composite material test specimens according to claim 8, wherein, The designed porosity of the composite material test specimen is less than 1%, and the first preset vacuum value P V0 The first preset pressure value P1 is 7 bar, which is -1.0 bar.

10. The method for manufacturing composite material test specimens according to claim 8, wherein, The composite material test specimen has a designed porosity greater than 1% and less than 3%, and the first preset vacuum value P V0 The value is -0.6 bar, and the first preset pressure value P1 is 2 bar.

11. The method for manufacturing composite material test specimens according to any one of claims 8 to 10, wherein, The second preset pressure value P2 is 1 bar, and the second preset vacuum value P V1 The preset temperature is -0.2 bar, the first preset temperature value T1 is 175~185℃, the second preset temperature value T2 is 60℃, and the preset duration t is... L The time is 115~125 min, the preset heating rate is 1~2℃ / min, and the preset cooling rate is 2~5℃ / min.

12. A composite material test specimen, formed using the composite material test specimen manufacturing method according to any one of claims 1 to 11.

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