A high-temperature multi-purpose test tool for ceramic matrix composite

Abstract

A kind of ceramic matrix composite high-temperature vacuum environment multipurpose test tool, upper clamp tool, lower clamp tool and the sample between upper clamp tool and lower clamp tool;Upper clamp tool, from top to bottom, including upper connecting seat, upper connecting rod and upper pressure head assembly, lower clamp tool from top to bottom, including lower pressure head assembly, lower connecting rod and lower connecting seat.This application adopts high-temperature ceramic material design, solves the problem of high-temperature alloy 800 degrees Celsius above strength sharp decline and thermal deformation, and simplifies the structure and is reliable;Using adjusting gasket and clamping block clamping structure, avoid local stress concentration, and the centering of sample load can be adjusted;In the aspect of maintenance, only need to replace chuck parts, save cost;Without changing chuck, high-temperature interlaminar shear test can also be carried out, more convenient and efficient.

Description

Technical Field

[0001] This invention relates to the field of materials engineering experiments, specifically to a high-temperature shear testing fixture for ceramic matrix composites, which can be used in a high-temperature vacuum environment for high-temperature compression performance testing and high-temperature interlaminar shear performance testing. Background Technology

[0002] Ceramic matrix composites, as a novel type of composite material, are compounds with ceramic materials as the matrix and ceramic fibers, whiskers, particles, etc., as reinforcements. These materials maintain good mechanical properties even at high temperatures and play an important role in defense industries such as aerospace and nuclear power. Therefore, it is necessary to conduct high-temperature compression and high-temperature interlaminar shear mechanical property tests on various ceramic matrix composites at high-temperature environments (above 800℃) to obtain accurate mechanical property data, thereby guiding the structural design of ceramic matrix composites. When conducting high-temperature compression and high-temperature interlaminar shear tests, one end of the plate-shaped workpiece needs to be fixed and clamped, and a set pressure load needs to be applied to the other end.

[0003] Chinese invention patent CN 110977825 B discloses "a combined high-temperature compression clamp", which includes symmetrically arranged upper and lower compression clamps; the upper compression clamp includes, from top to bottom, an upper connecting rod, an upper pressure rod, and an upper pressure head connected coaxially in sequence, and the upper connecting rod and the upper pressure rod have through holes through which a first connecting screw for connecting the upper connecting rod and the upper pressure rod passes; the lower compression clamp includes, from bottom to top, a lower connecting rod, a lower pressure rod, and a lower pressure head connected coaxially in sequence, and the lower connecting rod and the lower pressure rod have through holes through which a second connecting screw for connecting the lower connecting rod and the lower pressure rod passes; the upper and lower pressure heads are used to clamp the test sample; the upper and lower connecting rods and the first and second connecting screws are made of metal materials, and the upper and lower pressure rods and the upper and lower pressure heads are made of carbon-carbon or carbon-ceramic materials.

[0004] Existing technologies employ overly simplistic structures that fail to account for potential issues during high-temperature testing, such as chuck loosening, deformation, or even damage. Such conditions lead to test failure and unreliable results. Furthermore, replacement requires replacing the entire device, resulting in high costs. Alternatively, the simple clamping structure neglects the possibility of abnormal sample loading due to misalignment of the upper and lower loading mechanisms, affecting test accuracy. Additionally, the use of carbon-carbon or carbon-ceramic materials for clamps results in low strength, fragility, and low rigidity, unsuitable for testing high-strength ceramic matrix composites. Moreover, the strength of carbon fiber clamps decreases significantly after oxidation, and graphite matrices are highly susceptible to oxidation and burn-out at high temperatures. Extremely high sealing requirements exist during testing; any leaks can lead to instantaneous damage and significantly increase operating costs.

[0005] Therefore, how to improve the experimental equipment, avoid the deformation and damage of the chuck under high temperature environment, improve the convenience of equipment replacement, and improve the adaptability of the chuck so that it can be used for high temperature compression tests and high temperature interlaminar shear tests without replacing the chuck has become a technical problem that needs to be solved in the current technology. Summary of the Invention

[0006] The purpose of this invention is to propose a multi-purpose fixture for testing the high-temperature compression / interlaminar shear properties of ceramic matrix composites in a vacuum environment. This fixture can adapt to high-temperature environments, ensuring uniform heating of the entire sample and further improving testing accuracy. The structure, which uses adjusting shims in conjunction with clamping blocks for fixation and indenter end face loading, can achieve close clamping of samples with dimensional errors, avoiding local stress concentration. At the same time, the centering of the load on the sample is adjustable, preventing abnormal loads from affecting the test results.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A multi-purpose high-temperature vacuum environment testing fixture for ceramic matrix composites, capable of being used for compressive strength and interlaminar shear strength tests, is characterized by:

[0009] Upper fixture, lower fixture, and sample piece located between the upper fixture and lower fixture;

[0010] The upper clamping fixture, from top to bottom, includes an upper connecting seat, an upper connecting rod, and an upper pressure head assembly.

[0011] The lower part of the upper connecting seat is fixedly connected to the upper connecting rod;

[0012] The upper connecting rod is connected to the upper connecting seat and the upper pressure head assembly, respectively.

[0013] The upper pressure head assembly is connected to the upper connecting rod at its upper part and the sample piece is fixed at its lower part by clamping.

[0014] The lower fixture tooling, from top to bottom, includes a lower pressure head assembly, a lower connecting rod, and a lower connecting seat;

[0015] The lower pressure head assembly has a sample piece fixed by clamping at the upper part and is connected to the upper connecting rod at the lower part.

[0016] The lower connecting rod is fixedly connected to the lower pressure head assembly 23 and the lower connecting seat, respectively.

[0017] The lower connecting seat is connected to the lower connecting rod.

[0018] Optionally, the upper pressure head assembly includes: an upper pressure head connecting seat, an upper pressure head, an upper pressure head stop, an upper pressure head adjusting shim, and an upper pressure head fixing sleeve;

[0019] The upper pressure head fixing sleeve is circular with threads on the inner side and a step at the bottom to fix the upper pressure head and the upper pressure head stop;

[0020] The upper pressure head and the upper pressure head stop are symmetrically arranged on both sides of the sample clamping section plane. The upper pressure head has a cylindrical outer periphery at the top and a semi-cylindrical shape at the bottom. The semi-cylindrical shape has a groove to vertically place the sample.

[0021] The upper pressure head stop is semi-cylindrical and cooperates with the lower part of the upper pressure head to clamp the two sides of the clamping end of the sample piece. An upper pressure head adjusting shim is placed between the sample piece and the upper pressure head stop to achieve stable centering and clamping of the sample piece.

[0022] The upper part of the upper pressure head connecting seat has a protrusion and the lower part is cylindrical. It is threadedly engaged with the upper pressure head fixing sleeve, thereby pressing the upper pressure head and the upper pressure head stop against the upper pressure head fixing sleeve to form the upper pressure head assembly.

[0023] Optionally, the end face of the upper pressure head is a large-radius spherical convex surface, and the bottom of the upper pressure head connecting seat is a concave surface, with the two fitting together. This structural design ensures axial alignment of the test loading force and avoids eccentricity.

[0024] Optionally, the upper part of the upper pressure head connecting seat has a pin connecting hole, and the upper connecting rod has a circular pin mounting hole. When the upper pressure head assembly is installed in the upper connecting rod, the upper pressure head fixing pin fixes the upper connecting rod and the upper pressure head connecting seat.

[0025] Optionally, the pressure head assembly includes: a pressure head connecting seat, a pressure head, a pressure head stop, and a pressure head adjusting shim.

[0026] The lower pressure head connecting seat is embedded in the lower connecting rod.

[0027] The pressure head and the pressure head stop are symmetrically arranged on both sides of the plane of the sample clamping section.

[0028] The upper part of the pressure head is cylindrical, and the lower part is semi-cylindrical. The semi-cylindrical part has a groove to vertically place the sample piece.

[0029] The lower pressure head stop is semi-cylindrical and cooperates with the lower part of the lower pressure head, thereby clamping the two sides of the sample clamping end on the vertical surface. A lower pressure head adjusting shim is placed between the sample and the lower pressure head stop.

[0030] After the pressure head and the pressure head stop are engaged, they form a cylindrical shape. The pressure head connecting seat has a stepped circular hole structure to fix the engaged pressure head and pressure head stop.

[0031] Optionally, the upper connecting seat has a threaded hole inside, and the top of the upper connecting rod has a bolt mounting hole. The upper part of the upper connecting rod is embedded in the upper connecting seat and is fixedly connected to the upper connecting seat by an upper connecting rod fixing screw passing through the bolt mounting hole of the upper connecting rod.

[0032] Optionally, the upper part of the upper pressure head connecting seat has a pin connecting hole, and the upper connecting rod has a circular pin mounting hole. When the upper pressure head assembly is installed in the upper connecting rod, the upper pressure head fixing pin fixes the upper connecting rod and the upper pressure head connecting seat.

[0033] Optionally, the lower connecting seat has a threaded hole inside, and the bottom of the lower connecting rod has a bolt mounting hole. The lower part of the lower connecting rod is embedded in the lower connecting seat and is fixedly connected to the lower connecting seat by a lower connecting rod fixing screw passing through the bolt mounting hole of the lower connecting rod.

[0034] Optionally, the top of the upper connecting seat and the lower part of the lower connecting seat have threaded structures to connect the fixture to the loading mechanism of the testing machine, respectively.

[0035] Optionally, the upper pressure head and the lower pressure head are made of high-temperature resistant ceramic material, and the upper connecting rod and the lower connecting rod are made of high-temperature resistant ceramic matrix composite material or high-temperature molybdenum-lanthanum alloy material.

[0036] The present invention has the following advantages:

[0037] 1. The upper and lower pressure head assemblies are designed with high-temperature ceramic materials, which can maintain strength and not deform under test environment of 800 to 1800 degrees Celsius. This solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0038] 2. The upper and lower pressure head connecting rod assembly is designed with high-temperature ceramic composite material and high-temperature molybdenum-lanthanum alloy. It can maintain its strength and not deform under the test environment of 800 to 1400 degrees Celsius. It solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0039] 3. The structure of adjusting shims and clamping blocks can achieve close clamping of samples with dimensional errors, avoid local stress concentration, and adjust the centering of the load on the sample to avoid abnormal loads affecting the test results.

[0040] 4. The separate design and connection design of the chuck assembly ensure a certain level of accuracy in the current test, while in terms of maintenance, only the chuck parts need to be replaced, saving costs;

[0041] 5. High-temperature ceramic composite material clamps are used to hold the specimens. Since the clamps are not sensitive to high-temperature deformation and the clamping structure of the adjusting shims is fixed, they will not have a significant impact on the test results.

[0042] 6. In addition to high-temperature compression tests, this device can also perform high-temperature interlaminar shear tests without changing the clamps, making it more convenient and efficient. Attached Figure Description

[0043] Figure 1 , Figure 2 These are views of two different specimens used in specific embodiments of the present invention;

[0044] Figure 3 This is a front view of the test fixture according to a specific embodiment of the present invention;

[0045] Figure 4 This is a cross-sectional view of the test fixture according to a specific embodiment of the present invention;

[0046] Figure 5 This is a perspective view of the test fixture according to a specific embodiment of the present invention;

[0047] Figure 6 This is an exploded view of the upper clamping fixture according to a specific embodiment of the present invention;

[0048] Figure 7 This is a cross-sectional view of the upper clamping fixture according to a specific embodiment of the present invention;

[0049] Figure 8 This is a cross-sectional view of the upper pressure head assembly according to a specific embodiment of the present invention;

[0050] Figure 9 This is a perspective view of the upper pressure head assembly according to a specific embodiment of the present invention;

[0051] Figure 10 This is a perspective view of the upper pressure head according to a specific embodiment of the present invention;

[0052] Figure 11 This is a front view of the upper pressure head according to a specific embodiment of the present invention.

[0053] Figure 12 This is a perspective view of the upper pressure head stop block according to a specific embodiment of the present invention;

[0054] Figure 13 This is a view of the upper pressure head adjusting shim according to a specific embodiment of the present invention;

[0055] Figure 14 This is a cross-sectional view of the upper pressure head connecting seat according to a specific embodiment of the present invention;

[0056] Figure 15This is a perspective view of the upper pressure head connector according to a specific embodiment of the present invention;

[0057] Figure 16 This is a perspective view of the upper pressure head fixing sleeve according to a specific embodiment of the present invention;

[0058] Figure 17 This is a cross-sectional view of the upper connecting rod according to a specific embodiment of the present invention;

[0059] Figure 18 This is a perspective view of the upper connecting rod according to a specific embodiment of the present invention;

[0060] Figure 19 This is a cross-sectional view of the upper connecting seat according to a specific embodiment of the present invention;

[0061] Figure 20 This is an exploded view of the lower fixture tooling according to a specific embodiment of the present invention;

[0062] Figure 21 This is a perspective view of the lower clamping fixture according to a specific embodiment of the present invention;

[0063] Figure 22 This is a cross-sectional view of the lower clamping fixture according to a specific embodiment of the present invention;

[0064] Figure 23 This is a cross-sectional view of the pressure head assembly according to a specific embodiment of the present invention;

[0065] Figure 24 This is a perspective view of the pressure head assembly according to a specific embodiment of the present invention;

[0066] Figure 25 This is a perspective view of the pressure head stop block according to a specific embodiment of the present invention.

[0067] The technical features referred to by the reference numerals in the figure are as follows:

[0068] 11. Upper connecting seat; 12. Upper connecting rod; 13. Upper pressure head assembly; 14. Upper connecting rod fixing screw; 15. Upper pressure head fixing pin; 16. Upper pressure head connecting seat; 17. Upper pressure head; 18. Upper pressure head stop; 19. Upper pressure head adjusting shim; 10. Upper pressure head fixing sleeve; 2. Sample piece; 21. Lower connecting seat; 22. Lower connecting rod; 23. Lower pressure head assembly; 24. Lower pressure head connecting seat; 25. Lower pressure head; 26. Lower pressure head stop; 27. Lower pressure head adjusting shim; 28. Lower connecting rod fixing screw; 3. Sample piece. Detailed Implementation

[0069] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0070] The invention features: the upper and lower pressure heads and the upper and lower connecting rods are designed with materials suitable for high temperatures, ensuring that the strength does not decrease or deform under high-temperature testing conditions; the upper and lower pressure heads adopt a modular, separate design, which can be connected by a certain structure, ensuring the accuracy of the test and facilitating maintenance by only replacing the pressure head parts, thus saving costs; the use of adjusting shims in conjunction with clamping blocks allows for close clamping of samples with dimensional errors, avoiding local stress concentration, and the centering of the sample under load is adjustable; the separate pressure head design and the baffle connection design ensure a certain level of test accuracy, while only the clamping blocks need to be replaced according to changes in the size of the test specimen or for maintenance, thus saving costs.

[0071] A method for testing the compressive strength mechanical properties of ceramic matrix composites in a high-temperature vacuum environment is needed, as there is a lack of relevant domestic testing methods and standards. This study draws on the International Organization for Standardization (ISO) standard 14544-2013, which describes the determination of compressive properties of ceramic composites at high temperatures in fine ceramics (advanced ceramics, advanced process ceramics). The test specimen is designed as follows: Figure 1 As shown, the specific requirements are as follows:

[0072] 1) Traditional high-temperature composite material compression performance testing uses cylindrical specimens. However, cylindrical specimens for ceramic matrix composites are difficult to prepare, so a flat plate specimen design is adopted.

[0073] 2) The test specimen is prone to damage at the loading positions at both ends, so it is designed as a flat dumbbell shape to ensure that the failure position is in the middle of the specimen. The thickness is not less than 2mm, and the total length is related to the fixture system and furnace.

[0074] 3) Both ends are clamping loading sections, which are relatively wide, with a width of not less than 10mm, and are symmetrical on both sides;

[0075] 4) The middle section is the test section, which is relatively narrow. The width is designed to be no less than 8mm and the length l is no less than 15mm.

[0076] 5) The test section and the bearing section adopt a rounded transition to avoid stress concentration failure during the test;

[0077] 6) The specific design dimensions for each part of the failure are determined through simulation calculation and analysis to ensure that the specimen fails in the test section during the test.

[0078] For high-temperature interlaminar shear tests, there is a lack of relevant domestic testing methods and standards for the mechanical properties of interlaminar shear strength of ceramic matrix composites in high-temperature vacuum environments. Therefore, this study references the standard test method for interlaminar shear strength of 1D and 2D continuous fiber reinforced advanced ceramics at high temperatures (standard number: ASTM C1425-19) in the United States, and designs the test specimen as follows: Figure 2 The specific requirements are as follows:

[0079] 1) The sample is designed as a flat plate with a thickness of 6 mm and a total length of 30 mm;

[0080] 2) The width is 10mm;

[0081] 3) The middle section is the test section, with a length of 6mm. The groove depth at both ends of the test section is h / 2 to ensure that the failure location is in the middle of the sample.

[0082] See Figures 3-25 The structure and installation process of the ceramic matrix composite high-temperature vacuum environment shear test fixture of the present invention will be described separately.

[0083] See Figures 3-5 The multi-purpose testing fixture for high temperature vacuum environment of ceramic matrix composites includes: upper fixture 1, lower fixture 2, and sample 3 located between upper fixture 1 and lower fixture 2.

[0084] The upper clamping fixture 1 includes, from top to bottom, an upper connecting seat 11, an upper connecting rod 12, and an upper pressure head assembly 13. In the high-temperature test, the entire upper pressure head assembly 13 and most of the upper connecting rod 12 are located in the high-temperature zone inside the high-temperature environment chamber, while the upper connecting seat 11, the mounting base of the upper connecting rod 12, is located outside the high-temperature environment chamber and is only affected by thermal radiation temperature.

[0085] During the test, the entire sample 3 was placed in a high-temperature environment chamber, in a designed high-temperature (800-1500 degrees Celsius) air environment, i.e., the dotted line part; the upper and lower fixtures were mostly placed in the high-temperature environment chamber, in a designed high-temperature (800-1500 degrees Celsius) air environment; the upper and lower fixtures were each designed with tie rod parts, which were connected to the conventional loading mechanism of the testing machine through the tie rod parts, and the tie rods and tie rod joints were outside the high-temperature environment chamber.

[0086] See Figure 7 The lower part of the upper connecting seat 11 is fixedly connected to the upper connecting rod 12, and the top end has a threaded structure to connect the clamp to the loading mechanism of the testing machine.

[0087] The upper connecting rod 12 is connected to the upper connecting seat 11 and the upper pressure head assembly 13 respectively;

[0088] See Figure 8The upper pressure head assembly 13 is connected to the upper connecting rod 12 at its upper part and the lower part is used to fix the sample 3 by clamping. The sample can be as follows: Figure 2 The sample shown.

[0089] In an optional embodiment, the upper connecting seat 11 has a threaded hole inside, and the top of the upper connecting rod 12 has a bolt mounting hole. The upper part of the upper connecting rod 12 is embedded in the upper connecting seat 11 and is fixedly connected to the upper connecting seat 11 by an upper connecting rod fixing screw 14 passing through the bolt mounting hole of the upper connecting rod 12.

[0090] Specifically, the upper pressure head assembly 13 includes: an upper pressure head connecting seat 16, an upper pressure head 17, an upper pressure head stop 18, an upper pressure head adjusting shim 19, and an upper pressure head fixing sleeve 10;

[0091] The upper pressure head fixing sleeve 10 is circular, with threads on the inner side and a step at the bottom to fix the upper pressure head 17 and the upper pressure head stop 18.

[0092] The upper pressure head 17 and the upper pressure head stop 18 are made of high-temperature and high-strength ceramic materials and are symmetrically arranged on both sides of the plane of the clamping section of the sample 3.

[0093] The upper pressure head 17 has a cylindrical outer periphery at the top and a semi-cylindrical shape at the bottom. The semi-cylindrical shape has a groove to vertically place the sample piece 3.

[0094] The upper pressure head stop 18 is semi-cylindrical and cooperates with the lower part of the upper pressure head 17 to clamp the two sides of the clamping end of the sample piece. An upper pressure head adjusting shim 19 is placed between the sample piece 3 and the upper pressure head stop 18 to achieve stable clamping of the sample piece and avoid tilting and abnormal damage to the sample piece during the test.

[0095] After the upper pressure head 17 and the upper pressure head stop 18 are engaged, they form a step shape and are thus fixed in the upper pressure head fixing sleeve 10;

[0096] The upper pressure head connecting seat 16 has a protrusion on the upper part and a cylindrical shape on the lower part. It is threadedly engaged with the upper pressure head fixing sleeve 10, thereby pressing the upper pressure head 17 and the upper pressure head stop 18 against the upper pressure head fixing sleeve 10 to form the upper pressure head assembly 13.

[0097] Furthermore, common Figure 11 , Figure 14 The end face of the upper pressure head 17 is a large-radius spherical convex surface, and the bottom of the upper pressure head connecting seat 16 is a concave surface. The two cooperate with each other, which is conducive to the automatic centering of load transmission along the axial direction.

[0098] In another optional embodiment, the upper part of the upper pressure head connecting seat 16 has a pin connecting hole, and the upper connecting rod 12 has a circular pin mounting hole. When the upper pressure head assembly 13 is installed in the upper connecting rod 12, the upper pressure head fixing pin 15 fixes the upper connecting rod 12 and the upper pressure head connecting seat 16, and transmits pressure load through end face contact.

[0099] In this invention, the upper pressure head fixing sleeve 10 and the upper pressure head connecting seat 16 are made of high-temperature resistant ceramic composite materials such as carbon / silicon carbide or high-temperature alloy materials such as molybdenum-lanthanum alloy; the upper connecting rod 12, the upper pressure head 17 and the upper pressure head stop 18 are made of high-temperature and high-strength ceramic materials such as silicon-based multi-component composite ceramics; the upper pressure head adjusting shim 19 is made of high-temperature semi-flexible materials such as high-temperature flexible graphite; and the upper connecting seat 11 and the upper pressure head fixing pin 15 are made of high-temperature alloys such as nickel-based high-temperature alloys.

[0100] See Figure 20-22 The lower fixture tooling includes, from top to bottom, a lower pressure head assembly 23, a lower connecting rod 22, and a lower connecting seat 21. During the high-temperature test, the entire lower pressure head assembly 23 and most of the lower connecting rod 22 are located in the high-temperature zone inside the high-temperature environment chamber, while the mounting base of the lower connecting rod 22, the lower connecting seat 21, is located outside the high-temperature environment chamber and is only affected by thermal radiation temperature.

[0101] The lower pressure head assembly 23 has the sample piece 3 fixed in place by clamping at the upper part and is connected to the upper connecting rod 12 at the lower part.

[0102] The lower connecting rod 22 is fixedly connected to the lower pressure head assembly 23 and the lower connecting seat 21 respectively. For example, it is connected and cooperated with the lower pressure head assembly 23 through a circular step structure, and the pressure load is transmitted through the end face contact cooperation.

[0103] The lower connecting seat 21 is connected to the lower connecting rod 22. The lower part has a threaded structure, and the fixture is connected to the loading mechanism of the testing machine through the threaded structure.

[0104] See Figure 20 The lower connecting seat 21 has a threaded hole inside, and the bottom of the lower connecting rod 22 has a bolt mounting hole. The lower part of the lower connecting rod 22 is embedded in the lower connecting seat 21 and is fixedly connected to the lower connecting seat 21 by the lower connecting rod fixing screw 28 passing through the bolt mounting hole of the lower connecting rod 22.

[0105] Specifically, the pressure head assembly 23 includes: a pressure head connecting seat 24, a pressure head 25, a pressure head stop 26, and a pressure head adjusting shim 27.

[0106] The lower pressure head connecting seat 24 is embedded in the lower connecting rod 22.

[0107] The pressure head 25 and the pressure head stop 26 are made of high-temperature and high-strength ceramic material and are symmetrically arranged on both sides of the clamping section plane of the sample 3.

[0108] The upper part of the pressure head 25 is cylindrical, and the lower part is semi-cylindrical. The semi-cylindrical part has a groove to vertically place the sample piece 3.

[0109] The pressure head stop 26 is semi-cylindrical and cooperates with the lower part of the pressure head 25 to clamp the two sides of the clamping end of the sample piece. The pressure head adjusting shim 27 is placed between the sample piece 3 and the pressure head stop 26 to achieve stable centering and clamping of the sample piece, and to avoid tilting and abnormal damage to the sample piece during the test.

[0110] After the pressure head 25 and the pressure head stop 26 are engaged, they form a cylindrical shape. The pressure head connecting seat 24 has a stepped circular hole structure to fix the engaged pressure head 25 and pressure head stop 26. The end face of the pressure head connecting seat is in contact with the end face of the pressure head and transmits pressure.

[0111] Unlike the upper pressure head assembly 13, the lower clamping fixture presses the sample 3 upwards. Therefore, the lower pressure head assembly 23 is simpler than the upper pressure head assembly 13, and there is no need for the upper pressure head and the upper pressure head connecting seat to be fitted in a concave-convex manner. If both the upper and lower pressure heads are fitted in the above manner, it is easy to cause instability.

[0112] In this invention, the lower pressure head connecting seat 24 is made of high-temperature resistant ceramic composite materials such as carbon / silicon carbide or high-temperature alloy materials such as molybdenum-lanthanum alloy; the lower connecting rod 22, the lower pressure head 25, and the lower pressure head stop 26 are made of high-temperature and high-strength ceramic materials such as silicon-based multi-component composite ceramics; and the lower pressure head adjusting shim 27 is made of high-temperature semi-flexible materials such as high-temperature flexible graphite. The lower connecting seat 21 and the lower connecting rod fixing screw 28 are made of high-temperature alloys such as nickel-based high-temperature alloys.

[0113] The following describes how to install the test fixture of the present invention and conduct tests.

[0114] (1) Installation of upper clamp

[0115] 1) Place the ceramic matrix composite compression performance test specimen (or interlaminar shear performance test specimen) into the slotted position of the upper indenter of the upper clamp, with its end face closely fitting the corresponding position of the indenter. One side of the clamping section plane should fit with the upper indenter, and the other side should fit with the adjusting shim. Control the centering of the test specimen by adjusting the thickness of the shim. Clamp the test specimen by the upper indenter stop.

[0116] 2) Fix the upper pressure head, upper pressure head stop, and adjusting shims to the upper pressure head connecting seat using the upper pressure head fixing sleeve, and adjust for alignment. The upper pressure head connecting seat transmits the pressure load to the upper pressure head through a spherical fit, and finally to the end face of the specimen.

[0117] 3) The upper pressure head connector is fitted with the upper connecting rod via a stepped structure and secured with a pin. The pressure load is transmitted to the upper pressure head connector through the end face of the connecting rod.

[0118] 4) The other end of the upper connecting rod is connected to the upper connecting rod connecting seat through a stepped structure and is connected by screws.

[0119] 5) The upper connecting rod connecting seat is connected to the loading mechanism of the testing machine through its top thread structure.

[0120] (2) Installation of the lower clamp

[0121] 1) Place the ceramic matrix composite compression performance specimen (or interlaminar shear performance specimen) into the slotted position of the lower clamping head, with its end face closely fitting the corresponding position of the clamping head. One side of the clamping section plane should fit with the lower clamping head, and the other side should fit with the adjusting shim. Control the centering of the specimen by adjusting the thickness of the shim. Clamp the specimen with the lower clamping head stop.

[0122] 2) The lower indenter, lower indenter block, and adjusting shims for holding the specimen are fixed to the lower indenter connecting seat using a stepped structure, and then aligned. The upper indenter connecting seat transmits the pressure load to the upper indenter through a spherical fit, and finally to the end face of the specimen.

[0123] 3) The lower pressure head connector is fitted with the upper connecting rod via a stepped structure. The pressure load is transmitted to the upper pressure head connector through the end face of the connecting rod.

[0124] 4) The other end of the lower connecting rod is connected to the lower connecting rod connecting seat through a stepped structure and is connected by screws.

[0125] 5) The lower connecting rod connecting seat is connected to the loading mechanism of the testing machine through its top thread structure.

[0126] The present invention has the following advantages:

[0127] 1. The upper and lower pressure head assemblies are designed with high-temperature ceramic composite materials, which can maintain strength and not deform under test environment of 800 to 1800 degrees Celsius. This solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0128] 2. The upper and lower pressure head connecting rod assembly is designed with high-temperature ceramic composite material and high-temperature molybdenum-lanthanum alloy. It can maintain its strength and not deform under the test environment of 800 to 1400 degrees Celsius. It solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0129] 3. The structure of adjusting shims and clamping blocks can achieve close clamping of samples with dimensional errors, avoid local stress concentration, and adjust the centering of the load on the sample to avoid abnormal loads affecting the test results.

[0130] 4. The separate design and connection design of the chuck assembly ensure a certain level of accuracy in the current test, while in terms of maintenance, only the chuck parts need to be replaced, saving costs;

[0131] 5. The specimen is held by high-temperature ceramic composite material clamps. Since the clamps are not sensitive to high-temperature deformation and the self-locking anti-loosening clamping structure is fixed, it will not have a significant impact on the test results.

[0132] 6. In addition to high-temperature compression tests, this device can also perform high-temperature interlaminar shear tests without changing the clamps, making it more convenient and efficient.

[0133] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A multi-purpose testing fixture for high-temperature vacuum environment of ceramic matrix composites, capable of being used for compressive strength and interlaminar shear strength tests, characterized in that: Upper fixture, lower fixture, and sample piece located between the upper fixture and lower fixture; The upper clamping fixture, from top to bottom, includes an upper connecting seat, an upper connecting rod, and an upper pressure head assembly. The lower part of the upper connecting seat is fixedly connected to the upper connecting rod; The upper connecting rod is connected to the upper connecting seat and the upper pressure head assembly, respectively. The upper pressure head assembly is connected to the upper connecting rod at its upper part and the sample piece is fixed at its lower part by clamping. The lower fixture tooling, from top to bottom, includes a lower pressure head assembly, a lower connecting rod, and a lower connecting seat; The lower pressure head assembly has a sample piece fixed by clamping at the upper part and is connected to the upper connecting rod at the lower part. The lower connecting rod is fixedly connected to the lower pressure head assembly 23 and the lower connecting seat, respectively. The lower connecting seat is connected to the lower connecting rod. The upper pressure head assembly includes: an upper pressure head connecting seat, an upper pressure head, an upper pressure head stop, an upper pressure head adjusting shim, and an upper pressure head fixing sleeve; The upper pressure head fixing sleeve is circular with threads on the inner side and a step at the bottom to fix the upper pressure head and the upper pressure head stop; The upper pressure head and the upper pressure head stop are symmetrically arranged on both sides of the sample clamping section plane. The upper pressure head has a cylindrical outer periphery at the top and a semi-cylindrical shape at the bottom. The semi-cylindrical shape has a groove to vertically place the sample. The upper pressure head stop is semi-cylindrical and cooperates with the lower part of the upper pressure head to clamp the two sides of the clamping end of the sample piece. An upper pressure head adjusting shim is placed between the sample piece and the upper pressure head stop to achieve stable centering and clamping of the sample piece. The upper part of the upper pressure head connecting seat has a protrusion and the lower part is cylindrical. It is threadedly engaged with the upper pressure head fixing sleeve, thereby pressing the upper pressure head and the upper pressure head stop against the upper pressure head fixing sleeve to form the upper pressure head assembly. The pressure head assembly includes: a pressure head connector, a pressure head, a pressure head stop, and a pressure head adjusting shim. The lower pressure head connecting seat is embedded in the lower connecting rod. The pressure head and the pressure head stop are symmetrically arranged on both sides of the plane of the sample clamping section. The upper part of the pressure head is cylindrical, and the lower part is semi-cylindrical. The semi-cylindrical part has a groove to vertically place the sample piece. The lower pressure head stop is semi-cylindrical and cooperates with the lower part of the lower pressure head, thereby clamping the two sides of the sample clamping end on the vertical surface. A lower pressure head adjusting shim is placed between the sample and the lower pressure head stop. After the pressure head and the pressure head stop are engaged, they form a cylindrical shape. The pressure head connecting seat has a stepped circular hole structure to fix the engaged pressure head and pressure head stop.

2. The multi-purpose testing fixture according to claim 1, characterized in that: The end face of the upper pressure head is a large-radius spherical convex surface, and the bottom of the upper pressure head connecting seat is a concave surface, and the two cooperate with each other.

3. The multi-purpose testing fixture according to claim 1, characterized in that: The upper part of the upper pressure head connecting seat has a pin connection hole, and the upper connecting rod has a circular pin mounting hole. When the upper pressure head assembly is installed in the upper connecting rod, the upper pressure head fixing pin fixes the upper connecting rod and the upper pressure head connecting seat.

4. The multi-purpose testing fixture according to claim 1, characterized in that: The upper connecting seat has a threaded hole inside, and the top of the upper connecting rod has a bolt mounting hole. The upper part of the upper connecting rod is embedded in the upper connecting seat and is fixedly connected to the upper connecting seat by an upper connecting rod fixing screw passing through the bolt mounting hole of the upper connecting rod.

5. The multi-purpose testing fixture according to claim 1, characterized in that: The upper part of the upper pressure head connecting seat has a pin connection hole, and the upper connecting rod has a circular pin mounting hole. When the upper pressure head assembly is installed in the upper connecting rod, the upper pressure head fixing pin fixes the upper connecting rod and the upper pressure head connecting seat.

6. The multi-purpose testing fixture according to claim 1, characterized in that: The lower connecting seat has a threaded hole inside, and the bottom of the lower connecting rod has a bolt mounting hole. The lower part of the lower connecting rod is embedded in the lower connecting seat and is fixedly connected to the lower connecting seat by a lower connecting rod fixing screw passing through the bolt mounting hole of the lower connecting rod.

7. The multi-purpose testing fixture according to claim 1, characterized in that: The top of the upper connecting seat and the lower part of the lower connecting seat have threaded structures to connect the fixture tooling to the loading mechanism of the testing machine, respectively.

8. The multi-purpose testing fixture according to claim 1, characterized in that: The upper pressure head and the lower pressure head are made of high-temperature resistant ceramic material, and the upper connecting rod and the lower connecting rod are made of high-temperature resistant ceramic matrix composite material or high-temperature multiphase alloy material.

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