In-situ compression clamp for composite single-side notch test piece and test method

Abstract

The invention relates to the technical field of mechanical evaluation of composite materials, and discloses an in-situ compression clamp and a test method for a single-side notch test piece of a composite material, the in-situ compression clamp comprises an upper base and a lower base, and the upper base and the lower base are respectively clamped by two clamping blocks on a testing machine; the movable clamping assembly comprises two movable pieces and two clamping pieces, the two movable pieces are arranged on the opposite sides of the upper base and the lower base respectively, the two clamping pieces are arranged on the two movable pieces respectively, a test piece is clamped between the two clamping pieces, and the test piece moves in the X-axis direction and the Y-axis direction through the movable pieces; and the guide piece capable of being quickly mounted and dismounted is arranged between the upper base and the lower base, is used for realizing alignment of the upper base and the lower base, and is configured to be capable of quickly dismounting the guide piece when the test piece is scanned. The X-ray optical path is prevented from being shielded, meanwhile, it is guaranteed that the characterization area of the in-situ test piece is within the X-ray view field range during X-CT scanning, and the in-situ test piece scanning device is suitable for in-situ test pieces of different sizes.

Description

Technical Field

[0001] The invention relates to the technical field of composite material mechanical evaluation, and in particular to an in-situ compression fixture and a test method for a composite material single-side notch specimen. Background Art

[0002] Carbon fiber reinforced resin-based composite materials have the advantages of high specific strength, high specific stiffness, integral molding and designability, and are currently one of the most widely used lightweight materials. With the advent of new high-strength and high-modulus carbon fibers such as T1100 and M40X, the research direction of the third-generation composite materials is high strength, high modulus, and high toughness to meet the performance requirements of composite materials that need to frequently withstand bending loads when used in aerospace and other fields. When a composite material is subjected to a bending load, stresses of different natures will be generated in various parts of the material: tensile stress on one side and compressive stress on the other side. Therefore, the compression performance as a "short board" limits the application and development of carbon fiber resin-based composite materials. Improving the compression strength has become an important direction for the third-generation composite materials. It is the current research focus and hotspot of carbon fiber resin-based composite materials and has important research and application value.

[0003] When conducting quasi-static compression and compression-compression fatigue tests, the composite material compression test fixture in the ASTM standard usually uses a guide shaft to connect the upper and lower parts. The following significant problems exist in the single-sided notch specimen fixture of resin-based composite materials used for X-CT in-situ compression testing: (1) How to ensure that the fixture does not block the X-ray light path during the 360° rotation of the single-sided notch in-situ specimen. (2) How to ensure that the characterization area of ​​the in-situ specimen is within the X-ray field of view during X-CT scanning. (3) How to improve the versatility of the fixture for in-situ specimens of different sizes.

[0004] Therefore, there is an urgent need for an in-situ compression fixture and test method for composite material single-side notch specimens to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide an in-situ compression fixture and a test method for a composite material single-edge notch specimen, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides an in-situ compression fixture for a composite material single-side notched specimen, comprising:

[0007] An upper base and a lower base, wherein the upper base and the lower base are clamped by two clamping blocks on the testing machine respectively;

[0008] A mobile clamping assembly, comprising two moving parts and two clamping parts, wherein the two moving parts are respectively arranged on opposite sides of the upper base and the lower base, and the two clamping parts are respectively arranged on the two moving parts, a test piece is clamped between the two clamping parts, and the test piece is moved in the X-axis and Y-axis directions through the moving parts;

[0009] A guide member is disposed between the upper base and the lower base, and is used to achieve alignment between the upper base and the lower base, and is configured to remove the guide member when scanning the test piece.

[0010] According to an in-situ compression fixture for composite material single-edge notched specimen provided by the present invention, the moving part comprises:

[0011] An X-axis moving platform is arranged on the upper base and the lower base to perform X-axis movement;

[0012] A Y-axis moving platform, arranged on the upper base and the lower base for Y-axis movement;

[0013] Two driving members are respectively arranged on the upper base, the lower base and the X-axis moving platform, and the two driving members are used to drive the X-axis moving platform and the Y-axis moving platform respectively.

[0014] According to an in-situ compression fixture for a composite material single-edge notch specimen provided by the present invention, the driving component includes: a U-shaped plate, which is installed on the upper base, the lower base, and the X-axis moving platform by a plurality of first bolts, a motor is fixedly connected inside the U-shaped plate, a first gear is fixedly connected to the output shaft of the motor, a threaded rod is threadedly connected to the X-axis moving platform and the Y-axis moving platform, one end of the threaded rod is fixedly connected to the second gear, and the first gear is meshed with the second gear.

[0015] According to an in-situ compression fixture for a composite material single-edge notched specimen provided by the present invention, the clamping member comprises:

[0016] A first clamping plate is fixedly connected to the Y-axis moving platform, a second clamping plate is slidably connected to the first clamping plate, and one end of the test piece is clamped by the first clamping plate and the second clamping plate.

[0017] According to an in-situ compression fixture for composite material single-edge notch specimen provided by the present invention, a plurality of second bolts are arranged on the first clamping plate, and one end of the second bolt passes through the first clamping plate and is threadedly connected to the second clamping plate.

[0018] According to an in-situ compression fixture for a composite material single-edge notch specimen provided by the present invention, the guide member comprises: two guide rods, the bottom end of the guide rod is fixedly connected to a push rod, a symmetrical ball table slider and a second spring are sleeved on the push rod, the two ends of the second spring are respectively in contact with the push rod and the bottom end of the symmetrical ball table slider, grooves are respectively provided on both sides of the top end of the lower base, a pressure rod is slidably connected in the groove via a first spring, the push rod and the symmetrical ball table slider are respectively adapted to the pressure rod, through holes are provided at both ends of the upper base, and the other end of the guide rod extends out of the upper base through the through holes.

[0019] According to the in-situ compression fixture for composite material single-edge notch specimen provided by the present invention, the number of the second bolts is four and they are distributed in an array.

[0020] According to an in-situ compression fixture for a composite single-edge notched specimen provided by the present invention, composite reinforcement sheets are fixedly connected to two clamping surfaces at both ends of the specimen, and the composite reinforcement sheets are in contact with the first clamping plate and the second clamping plate.

[0021] According to an in-situ compression fixture for composite material single-edge notch specimen provided by the present invention, the top end of the upper base and the bottom end of the lower base are both fixedly connected with a column, and the testing machine clamps the column.

[0022] A test method for a single-edge notched specimen of a resin-based composite material comprises the following steps:

[0023] Installing the test piece between the two clamping members;

[0024] The position of the test piece is adjusted by the two movable members so that the test piece is within the field of view of the X-CT;

[0025] The guide is pressed down again and can then be quickly pulled out to perform an X-CT scan on the test piece.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] The present invention provides an in-situ compression fixture and test method for composite material single-sided notch specimens. The clamping block on the test machine clamps the upper base and the lower base. The clamping position is adjusted by adjusting the distance between the upper base and the lower base. During the adjustment process, a guide member that can be quickly installed and removed is used to ensure the stability of the docking. After the adjustment, the test piece is clamped by a set clamping member. After clamping, the position of the test piece is adjusted by a set moving member. After the adjustment is completed, the guide member is quickly removed to conduct the test. This application avoids blocking the X-ray optical path, while ensuring that the characterization area of ​​the in-situ test piece is within the X-ray field of view during X-CT scanning, and is suitable for in-situ test pieces of different sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor:

[0029] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 It is an exploded view of the clamp of the present invention;

[0031] Figure 3 It is a schematic diagram of the structure of the clamping member of the present invention;

[0032] Figure 4 It is a schematic diagram of the structure of the moving part of the present invention;

[0033] Figure 5 It is a side view of the driving member of the present invention;

[0034] Figure 6 This is a schematic diagram of the guide rod that can be quickly installed and removed according to the present invention;

[0035] Among them, 1. upper base; 2. lower base; 3. test piece; 4. X-axis moving platform; 5. Y-axis moving platform; 6. U-shaped plate; 7. first bolt; 8. motor; 9. first gear; 10. threaded rod; 11. second gear; 12. first clamping plate; 13. second clamping plate; 14. second bolt; 15. guide rod; 16. composite material reinforcement plate; 17. column; 18. push rod; 19. symmetrical ball table slider; 20. first spring; 21. pressure rod; 22. second spring. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Reference Figure 1-Figure 6 The present invention provides an in-situ compression fixture for composite material single-side notch specimen, comprising:

[0039] The upper base 1 and the lower base 2 are clamped by two clamping blocks on the testing machine respectively;

[0040] The mobile clamping assembly includes two moving parts and two clamping parts. The two moving parts are respectively arranged on opposite sides of the upper base 1 and the lower base 2. The two clamping parts are respectively arranged on the two moving parts. The test piece 3 is clamped between the two clamping parts. The test piece 3 is moved in the X-axis and Y-axis directions by the moving parts.

[0041] The guide member is disposed between the upper base 1 and the lower base 2 to achieve the alignment of the upper base 1 and the lower base 2 and is configured to be removed when scanning the test piece 3 .

[0042] In one embodiment of the present invention, the clamping block on the test machine clamps the upper base 1 and the lower base 2, and the clamping position is adjusted by adjusting the distance between the upper base 1 and the lower base 2. During the adjustment process, the stability of the docking is ensured by the guide member that can be quickly installed and removed. After the adjustment, the test piece 3 is clamped by the clamping member, and the position of the test piece 3 is adjusted by the movable member after clamping. After the adjustment, the guide member is quickly removed to conduct the test. This application avoids blocking the X-ray optical path, and at the same time ensures that the characterization area of ​​the in-situ test piece is within the X-ray field of view during X-CT scanning, and is suitable for in-situ test pieces of different sizes.

[0043] As an optional embodiment, the moving member includes: an X-axis moving platform 4, which is arranged on the upper base 1 and the lower base 2 to perform X-axis movement;

[0044] A Y-axis moving platform 5 is arranged on the upper base 1 and the lower base 2 to move along the Y-axis;

[0045] The two driving members are respectively arranged on the upper base 1, the lower base 2 and the X-axis moving platform 4, and the two driving members are used to drive the X-axis moving platform 4 and the Y-axis moving platform 5 respectively.

[0046] In one embodiment of the present invention, the X-axis moving platform 4 and the Y-axis moving platform 5 are controlled by a provided driving member, thereby achieving adjustment of the position of the test piece 3 .

[0047] As an optional embodiment, the driving member includes: a U-shaped plate 6, which is installed on the upper base 1, the lower base 2, and the X-axis moving platform 4 by a plurality of first bolts 7, a motor 8 is fixedly connected inside the U-shaped plate 6, a first gear 9 is fixedly connected to the output shaft of the motor 8, a threaded rod 10 is threadedly connected to the X-axis moving platform 4 and the Y-axis moving platform 5, a second gear 11 is fixedly connected to one end of the threaded rod 10, and the first gear 9 is meshed with the second gear 11.

[0048] In one embodiment of the present invention, a motor 8 is provided to drive the first gear 9 to rotate, and the first gear 9 drives the meshing second gear 11 to rotate. When the second gear 11 rotates, it drives the connected threaded rod 10 to rotate. When the threaded rod 10 rotates, it drives the threadedly connected X-axis mobile platform 4 and Y-axis mobile platform 5 to move, thereby realizing the control of the X-axis mobile platform 4 and the Y-axis mobile platform 5.

[0049] As an optional embodiment, the clamping member includes: a first clamping plate 12, fixedly connected to the Y-axis moving platform 5, a second clamping plate 13 slidably connected to the first clamping plate 12, and one end of the test piece 3 is clamped by the first clamping plate 12 and the second clamping plate 13.

[0050] In one embodiment of the present invention, the test piece 3 is clamped by the first clamping plate 12 and the second clamping plate 13 .

[0051] As an optional implementation, a plurality of second bolts 14 are provided on the first clamping plate 12 , and one end of the second bolt 14 passes through the first clamping plate 12 and is threadedly connected to the second clamping plate 13 .

[0052] In one embodiment of the present invention, the distance between the first clamping plate 12 and the second clamping plate 13 is adjusted by screwing the second bolt 14 , so as to achieve stable clamping of the test piece 3 .

[0053] As an optional embodiment, the guide member includes: two guide rods 15, the bottom end of the guide rod 15 is fixedly connected to a push rod 18, a symmetrical ball table slider 19 and a second spring 22 are sleeved on the push rod 18, the two ends of the second spring 22 are respectively in contact with the bottom ends of the push rod 18 and the symmetrical ball table slider 19, grooves are respectively provided on both sides of the top of the lower base 2, a pressure rod 21 is slidably connected in the groove through a first spring 20, the push rod 18 and the symmetrical ball table slider 19 are respectively adapted to the pressure rod 21, through holes are provided at both ends of the upper base 1, and the other end of the guide rod 15 extends out of the upper base 1 through the through hole.

[0054] In one embodiment of the present invention, the clamping block of the testing machine clamps the upper base 1 and the lower base 2, and the distance between the upper and lower clamps is slowly shortened, while ensuring that the two guide rods 15 accurately pass through the through hole of the upper base 1. After adjusting to a suitable distance, in order to ensure that the X-rays are not blocked during X-CT scanning, the two guide rods 15 are quickly disassembled after the clamp assembly is completed.

[0055] As an optional implementation, the number of the second bolts 14 is four and they are distributed in an array.

[0056] In one embodiment of the present invention, the number of the second bolts 14 is four. During installation, the four second bolts 14 are lightly tightened in sequence, and the four second bolts 14 are tightened in sequence using a torque wrench according to the diagonal tightening principle, so that the clamping section of the test piece 3 is evenly stressed.

[0057] As an optional implementation, composite material reinforcement sheets 16 are fixedly connected to the two clamping surfaces at both ends of the test piece 3 , and the composite material reinforcement sheets 16 are in contact with the first clamping plate 12 and the second clamping plate 13 .

[0058] In one embodiment of the present invention, the composite material reinforcement sheet 16 is firstly adhered to both sides of the clamping section of the test piece 3 by using an adhesive, and then cured at a certain temperature and pressure. The specific composite material is preferably a glass fiber resin-based composite material.

[0059] As an optional implementation, a column 17 is fixedly connected to the top end of the upper base 1 and the bottom end of the lower base 2 , and the testing machine clamps the column 17 .

[0060] In one embodiment of the present invention, the clamping block of the testing machine is used to clamp the column 17 on the upper base 1 and the lower base 2 .

[0061] A test method for a single-edge notched specimen of a resin-based composite material comprises the following steps:

[0062] Install the test piece 3 between the two clamps;

[0063] The position of the test piece 3 is adjusted by two movable parts so that the test piece 3 is within the field of view of the X-CT;

[0064] The guide piece is pressed down again and can then be quickly pulled out to perform an X-CT scan on the test piece 3.

[0065] Specifically, 692-3K epoxy resin is used as the matrix, 24K-T300 carbon fiber is used as the reinforcement, and the vacuum-assisted resin transfer molding process is used to prepare the carbon fiber resin-based composite material. The compression displacement rate is 0.03mm / min. During the test, several displacement holding points of the test piece are set for X-CT scanning, and the test temperature is 100℃. To carry out the processing of the test piece, the geometric dimensions of the test piece, the fiber laying angle, and the sequence are designed first. The vacuum-assisted resin transfer molding process is used to prepare the carbon fiber reinforced resin-based composite material. The fiber cloth is laid in the mold according to the design requirements. The air in the mold is extracted using a vacuum pump to form a vacuum environment. The resin is injected into the mold through the injection port. The resin is cured in the mold. After the curing is completed, the vacuum is released, and then the component is taken out of the mold. The in-situ compression test piece of the resin-based composite material is processed by CNC machining technology.

[0066] Use adhesive to stick the glass fiber resin-based composite material reinforcement sheet 16 on both sides of the clamping section of the test piece 3 and cure it at a certain temperature and pressure. Clamp the lower base 2 with the lower clamp block of the testing machine, connect the two guide rods 15 to the lower base 2, clamp the upper base 1 with the upper clamp block of the testing machine, and slowly shorten the distance between the upper and lower clamps while ensuring that the two guide rods 15 accurately pass through the through holes of the upper base 1. After adjusting to the appropriate distance, clamp the test piece 3.

[0067] To ensure that the X-rays are not blocked during X-CT scanning, the two guide rods 15 are taken out from above the upper base 1 after the fixture is assembled; after the in-situ test machine is installed, the scanning parameters are set and the X-rays are turned on; the X and Y positions of the test piece are controlled by computer software to ensure that the characterization area is within the X-CT field of view.

[0068] Conduct in-situ compression or compression-compression fatigue tests on the single-sided notch structure of the resin-based composite material used for X-CT; if the ambient temperature needs to be changed, ensure that the temperature in the high-temperature furnace meets the test requirements through the temperature controller, set the load controller to force hold, and when the thermocouple displays that the temperature reaches the set temperature, keep warm for 1 hour and start the test; apply the corresponding load conditions through the in-situ testing machine load controller. When the single-sided notch structure of the carbon fiber resin-based composite material reaches the set load conditions, set the load controller to displacement hold, and carry out X-CT scanning. The test ends when the structure fails or reaches the specified life.

[0069] The present invention provides an in-situ compression fixture and test method for a composite material single-sided notch specimen, which ensures that the fixture does not block the light path during the 360° rotation of the single-sided notch in-situ test specimen, and ensures that the characterization area of ​​the in-situ test specimen is within the X-ray field of view during X-CT scanning. At the same time, the stability, versatility and cost control of the fixture are greatly improved compared with the existing technology, laying a solid experimental foundation for the exploration of the strength and fatigue performance of resin-based composite materials.

[0070] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0071] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An in-situ compression fixture for composite material single-side notch specimens, characterized in that: include: An upper base (1) and a lower base (2), wherein the upper base (1) and the lower base (2) are respectively clamped by two clamping blocks on a testing machine; A mobile clamping assembly, comprising two mobile parts and two clamping parts, wherein the two mobile parts are respectively arranged on opposite sides of the upper base (1) and the lower base (2), and the two clamping parts are respectively arranged on the two mobile parts, a test piece (3) is clamped between the two clamping parts, and the test piece (3) is moved in the X-axis and Y-axis directions by the mobile parts; A guide member is arranged between the upper base (1) and the lower base (2) and is used to achieve alignment between the upper base (1) and the lower base (2), and is configured to be removed when scanning the test piece (3).

2. The in-situ compression fixture for composite material single-edge notch specimen according to claim 1, characterized in that: The moving part comprises: An X-axis moving platform (4) is arranged on the upper base (1) and the lower base (2) to perform X-axis movement; A Y-axis moving platform (5) is arranged on the upper base (1) and the lower base (2) to perform Y-axis movement; Two driving members are respectively arranged on the upper base (1), the lower base (2) and the X-axis movable platform (4), and the two driving members are used to drive the X-axis movable platform (4) and the Y-axis movable platform (5) respectively.

3. The in-situ compression fixture for composite material single-edge notch specimen according to claim 2, characterized in that: The driving member comprises: a U-shaped plate (6) which is mounted on the upper base (1), the lower base (2) and the X-axis movable platform (4) by means of a plurality of first bolts (7); a motor (8) is fixedly connected inside the U-shaped plate (6); a first gear (9) is fixedly connected to the output shaft of the motor (8); a threaded rod (10) is threadedly connected to the X-axis movable platform (4) and the Y-axis movable platform (5); one end of the threaded rod (10) is fixedly connected to a second gear (11); the first gear (9) is meshed with the second gear (11).

4. The in-situ compression fixture for composite material single-edge notched specimen according to claim 2, characterized in that: The clamping member comprises: A first clamping plate (12) is fixedly connected to the Y-axis movable platform (5); a second clamping plate (13) is slidably connected to the first clamping plate (12); one end of the test piece (3) is clamped by the first clamping plate (12) and the second clamping plate (13).

5. The in-situ compression fixture for composite material single-edge notched specimen according to claim 4, characterized in that: A plurality of second bolts (14) are arranged on the first clamping plate (12), and one end of the second bolt (14) passes through the first clamping plate (12) and is threadedly connected to the second clamping plate (13).

6. The in-situ compression fixture for composite material single-edge notched specimen according to claim 1, characterized in that: The guide member comprises: two guide rods (15), the bottom end of the guide rod (15) is fixedly connected with a push rod (18), the push rod (18) is sleeved with a symmetrical ball table slider (19) and a second spring (22), the two ends of the second spring (22) are respectively in contact with the push rod (18) and the bottom end of the symmetrical ball table slider (19), the top of the lower base (2) is respectively provided with grooves on both sides, a pressure rod (21) is slidably connected in the groove via a first spring (20), the push rod (18) and the symmetrical ball table slider (19) are respectively matched with the pressure rod (21), and the two ends of the upper base (1) are both provided with through holes, and the other end of the guide rod (15) protrudes out of the upper base (1) through the through holes.

7. The in-situ compression fixture for composite material single-edge notched specimen according to claim 5, characterized in that: The number of the second bolts (14) is four and they are distributed in an array.

8. The in-situ compression fixture for composite material single-edge notched specimen according to claim 4, characterized in that: Composite material reinforcement sheets (16) are fixedly connected to the two clamping surfaces at both ends of the test piece (3), and the composite material reinforcement sheets (16) are in contact with the first clamping plate (12) and the second clamping plate (13).

9. The in-situ compression fixture for composite material single-edge notched specimen according to claim 1, characterized in that: The top end of the upper base (1) and the bottom end of the lower base (2) are both fixedly connected with a column (17), and the testing machine clamps the column (17).

10. A test method for a single-edge notched specimen of a resin-based composite material, applicable to the in-situ compression fixture for a single-edge notched specimen of a composite material as claimed in claim 1, characterized in that: The following steps are involved: Installing the test piece (3) between the two clamping pieces; The position of the test piece (3) is adjusted by the two movable members so that the test piece (3) is located within the X-CT field of view; The guide piece is pressed down again and then quickly pulled out to perform an X-CT scan on the test piece (3).

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