Ceramic matrix composite out-of-plane tensile test piece, tool and test method

Abstract

A ceramic matrix composite out-of-plane tensile test piece comprises a first tensile plane and a second tensile plane, the first tensile plane and the second tensile plane are located on the two sides of the ceramic matrix composite out-of-plane tensile test piece in the thickness direction, and a plurality of parallel bonding grooves are formed in the first tensile plane and the second tensile plane respectively. The bonding grooves in the first stretching plane and the second stretching plane are perpendicular to each other. The test piece can realize out-of-plane stretching with higher load, and the mechanical property of the ceramic matrix composite material in the out-of-plane direction is effectively evaluated. The invention further provides a ceramic matrix composite out-of-plane stretching tool and a testing method.

Description

Technical Field

[0001] The invention belongs to the field of material performance characterization, and in particular relates to an out-of-plane tensile test piece of a ceramic-based composite material, a tool and a testing method. Background Art

[0002] Ceramic matrix composites (CMC) have excellent properties such as high temperature resistance, corrosion resistance, light weight and high strength, and have broad application prospects in aerospace hot end structural components. Affected by the characteristics of CMC materials themselves, the size, structure, manufacturing process and other factors of CMC parts have a significant impact on their mechanical properties. Furthermore, CMC materials often have a certain anisotropy, which makes the conventional mechanical properties test using standard specimens poor in characterizing the performance of CMC material parts. In engineering practice, CMC materials are mostly used to manufacture thin-walled structures. It is difficult to use conventional methods to test mechanical properties in the out-of-plane direction, which makes it difficult to measure the out-of-plane tensile properties of CMC materials. Some schemes use bonding to bond and fix sheet CMC test pieces between loading devices for tensile testing, but the strength of CMC materials is relatively high, and it is often the case that the CMC test pieces are intact but the bonding surface is torn. At the same time, not all CMC materials can find high-strength adhesives that are suitable for them. The lack of characterization methods is not conducive to the accurate prediction of the mechanical properties and service life of CMC parts, nor is it conducive to the popularization of CMC materials. Summary of the invention

[0003] The purpose of the present invention is to provide a ceramic matrix composite material out-of-plane tensile test piece, which can accurately measure the mechanical properties of the ceramic matrix composite material in the out-of-plane direction. The present invention also provides a ceramic matrix composite material out-of-plane tensile tool and test method.

[0004] According to an embodiment of one aspect of the present invention, there is provided a ceramic-based composite material out-of-plane tensile test piece, the test piece comprising a first tensile plane and a second tensile plane, the first tensile plane and the second tensile plane being located on both sides of the ceramic-based composite material out-of-plane tensile test piece in a thickness direction, a plurality of parallel bonding grooves being respectively arranged on the first tensile plane and the second tensile plane, the bonding grooves in the first tensile plane and the second tensile plane being perpendicular to each other.

[0005] By setting up the bonding groove, the bonding area of ​​the end face of the test piece during the tensile test can be increased. The adhesive in the bonding groove can withstand additional shear stress to improve the bonding strength of the end face of the test piece, so that the failure fracture during the tensile process occurs in the out-of-plane direction, thereby accurately reflecting the out-of-plane tensile strength of the CMC material.

[0006] Furthermore, the depth of each bonding groove is 1 / 3-2 / 5 of the thickness of the ceramic matrix composite material out-of-plane tensile test piece. When the bonding groove is too shallow, the shear stress borne by the adhesive in the bonding groove is insufficient, and fracture is likely to occur on the bonding surface; when the bonding groove is too deep, the distance between the bottom of the bonding groove on the first tensile plane and the second tensile plane is too small, stress is concentrated, and the out-of-plane tensile strength of the CMC material cannot be correctly reflected.

[0007] Furthermore, 4 to 8 bonding grooves are arranged at equal intervals in the first stretching plane and the second stretching plane, respectively. The bonding grooves arranged at equal intervals can evenly distribute the load in the plane of the test piece.

[0008] Furthermore, the width of the bonding groove is configured to be 0.5 mm-1 mm. If the width of the bonding groove is too narrow, it will be difficult to bond with the tooling, and if the width of the bonding groove is too wide, it will easily lead to cracking and failure between the grooves during the tensile test.

[0009] Furthermore, the ceramic matrix composite material out-of-plane tensile test piece is configured as a rectangular piece with a side length of 15mm-20mm and a thickness of 3mm-5mm. The test piece area is sufficiently large to provide sufficient bonding force; if the thickness is too small, it is difficult to measure, and if the thickness is too large, invalid data is easily generated.

[0010] Furthermore, the depth of the bonding groove near the edge is greater than that of the bonding groove far from the edge. Load concentration is prone to occur in the area near the edge, and setting a bonding groove with a larger depth is conducive to eliminating load concentration, thereby reducing the edge effect of the bonding layer in the edge area during tensile loading, avoiding the bonding layer in the edge area from cracking first during the stretching process due to stress concentration, improving the overall tensile strength of the bonding layer, and ultimately further improving the success rate of the test.

[0011] Furthermore, the ceramic matrix composite material out-of-plane tensile test piece is manufactured using a fiber preform, and the fiber preform is configured as a stack of multiple layers of two-dimensional fiber materials along the thickness direction, and the thickness of a single layer in the stack does not exceed 0.5 mm.

[0012] According to another embodiment of the present invention, there is provided a ceramic matrix composite material out-of-plane tensile tooling, which is used to test the ceramic matrix composite material out-of-plane tensile test piece in any of the aforementioned embodiments, and the tooling includes two loading blocks, the loading blocks include a concave bonding surface, and the bonding surface is provided with a convex bonding edge, and the bonding edges on the bonding surfaces of the two loading blocks are respectively matched with the bonding grooves of the first tensile plane and the second tensile plane of the ceramic matrix composite material out-of-plane tensile test piece. Through the bonding edge and the side wall surface of the concave bonding surface, the loading block can be bonded to the test piece with a larger bonding area, and the tensile load is shared by the shear stress on the bonding edge, thereby causing the fracture to occur inside the CMC test piece.

[0013] Furthermore, it also includes a universal joint loading chain, the two loading blocks are respectively connected to the universal joint loading chain, and the universal joint loading chain provides a loading fixed position for the tensile test. The universal joint loading chain is convenient for fixing and loading the tensile load.

[0014] According to another embodiment of the present invention, there is provided a method for testing an out-of-plane tensile test of a ceramic matrix composite material, the method comprising the following steps: providing an out-of-plane tensile test piece of a ceramic matrix composite material in any of the aforementioned embodiments; providing an out-of-plane tensile tooling for a ceramic matrix composite material in any of the aforementioned embodiments, and bonding the bonding surfaces of the tooling loading block to the first tensile plane and the second tensile plane of the test piece respectively; applying an out-of-plane tensile load to the out-of-plane tensile test piece of the ceramic matrix composite material through the loading block until the out-of-plane tensile test piece of the ceramic matrix composite material breaks and fails in the out-of-plane direction. This method can effectively improve the success rate of the out-of-plane tensile test of CMC materials and accurately measure the out-of-plane tensile performance data of CMC materials.

[0015] Furthermore, the method preferably performs multiple tests, and the sample data whose fracture surface does not pass through the bonding groove is taken as the effective test data. If there is a bonding groove on the fracture surface, it means that the area of ​​the CMC test piece that bears the load when it fails is smaller than the total area of ​​the test piece, and the fracture behavior of the section where the bonding groove is located may be different from the normal fracture behavior of the CMC test piece, which may lead to errors in the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of an out-of-plane tensile test piece of a ceramic matrix composite material in one embodiment;

[0017] Figure 2a This is a schematic diagram of the structure of a loading block of an out-of-plane stretching tool for ceramic-based composite materials in one embodiment;

[0018] Figure 2b It is a schematic diagram of the cross-sectional structure of the AA section of the loading block of the out-of-plane stretching tooling for ceramic matrix composite materials in one embodiment;

[0019] Figure 3 This is a schematic diagram of the out-of-plane stretching tooling structure of a ceramic matrix composite material in one embodiment;

[0020] Figure 4a This is a schematic diagram of the installation position of the test piece in the out-of-plane tensile test of the ceramic matrix composite material in one embodiment;

[0021] Figure 4b for Figure 4a Schematic diagram of the local enlarged structure of area B in the middle.

[0022] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of simplicity, the above drawings only schematically illustrate the structures related to the technical features of the present invention, and do not strictly illustrate the entire structure and all details according to the actual proportion. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0024] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0025] In the description of this article, unless otherwise clearly specified and limited, the technical terms "installed", "connected", "connected" and the like should be understood in a broad sense, which can be a movable connection, a fixed connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0026] In the description of this document, terms indicating orientation or positional relationships, such as "up", "down", "left", "right", "horizontal", "vertical", "height", "length", and "width", are intended to accurately describe the embodiments and simplify the description, but are not intended to limit the parts or structures involved to have a specific orientation, be installed or operate in a specific orientation, and should not be construed as a limitation on the embodiments in this document.

[0027] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0028] Since thin sheet structures are difficult to clamp, existing ceramic matrix composite (CMC) out-of-plane tensile performance tests are usually conducted by bonding thin sheet CMC test pieces to a tensile device. Since CMC materials generally have high mechanical properties, bonding for tensile testing requires that the bonding force provided by the adhesive is not less than the strength of the CMC material in the out-of-plane direction. This results in many scenarios where the appropriate adhesive cannot be obtained for the CMC out-of-plane tensile test, and tearing along the bonding surface occurs during the test, resulting in test failure and no valid test data can be measured. The lack of out-of-plane tensile performance data restricts the structural design and practical application of CMC materials.

[0029] In order to solve the above problems, an embodiment of one aspect of the present invention provides a ceramic matrix composite material out-of-plane tensile test piece 1, the test piece structure is as follows: Figure 1 As shown, it includes a first stretching plane 11 and a second stretching plane 12, the first stretching plane 11 and the second stretching plane 12 are respectively located on both sides of the thickness direction of the test piece, and are respectively evenly provided with a plurality of bonding grooves 13a, 13b, 14a, 14b. The bonding grooves 13a, 13b, 14a, 14b are configured as a rectangular groove that passes through the test piece in the plane, and the bottom of the groove is processed to be flat or set to have a chamfer. Among them, the bonding grooves 13a and 13b located on the first stretching plane 11 are parallel to each other, and the bonding grooves 14a and 14b located on the second stretching plane 12 are parallel to each other, and 13a, 13b and 14a, 14b are perpendicular to each other. The setting of the bonding groove can increase the bonding area of ​​the test piece, provide higher bonding force under the same cross-sectional area, and further make full use of the strength of the adhesive by the way that the adhesive bears part of the shear stress.

[0030] In a preferred embodiment, the depth of the bonding grooves 13a, 13b, 14a, and 14b is configured to be 1 / 3-2 / 5 of the total thickness of the test piece, and the width is configured to be 0.5mm-1mm. When the depth of the bonding groove is too shallow, the bonding strength is insufficient; and when the bonding groove is too deep, the integrity of the test piece will be divided and destroyed by the bonding groove, and the spacing between the bottoms of the bonding grooves located on the first bonding surface 11 and the second bonding surface 12 is too small, and the bonding grooves themselves are prone to become stress concentration areas, inducing CMC failure. Therefore, the spacing between the bottoms of the bonding grooves on the two tensile planes should be at least 20% of the thickness of the test piece.

[0031] In a preferred embodiment, the test piece 1 is configured as a rectangular piece with a side length of 15mm-20mm and a thickness of 3mm-5mm. The shape and size of the CMC test piece should meet the actual engineering application. If the thickness is too thin, it is difficult to process the bonding groove that meets the requirements, while if the thickness is too large, the randomness of the fracture in the tensile test will increase, resulting in an increase in invalid data.

[0032] In a preferred embodiment, on the first stretching plane 11 and the second stretching plane 12 of the test piece 1, the depths of the bonding grooves 13b and 14b close to the edge are respectively greater than the depths of the bonding grooves 13a and 14a away from the edge, the depths of the bonding grooves 13a and 14a are 1 / 3 of the thickness of the test piece 1, and the depths of the bonding grooves 13b and 14b are 2 / 5 of the thickness of the test piece 1, thereby reducing the edge effect of the bonding layer in the edge area during tensile loading, avoiding the bonding layer in the edge area from cracking first during the stretching process due to stress concentration, improving the overall tensile strength of the bonding layer and ultimately further improving the success rate of the test.

[0033] In other embodiments, according to differences in the structure and size of the test piece 1, the number of adhesive grooves set on each stretching plane can be 4 to 8.

[0034] In some preferred embodiments, the test piece 1 is manufactured using a fiber preform, and the fiber preform is configured as a stack of multiple layers of two-dimensional fiber materials along the thickness direction, and the thickness of a single layer in the stack does not exceed 0.5 mm.

[0035] According to another embodiment of the present invention, a ceramic matrix composite material out-of-plane stretching tool is provided for testing the test piece 1 in any of the above embodiments, such as Figure 2a As shown, the tooling includes a metal loading block 2, one side of which is provided with a concave bonding surface 21, the size of which matches the test piece 1, and a raised bonding edge 22 is provided on the bonding surface 21. The tooling includes two metal loading blocks 2, and the bonding edges on the bonding surfaces 21 of the two metal loading blocks 2 are respectively conformally matched with the bonding grooves 13a, 13b, 14a, and 14b provided on the first stretching plane 11 and the second stretching plane 12 of the test piece 1. A connecting hole 23 is provided at the other end of the metal loading block opposite to the bonding surface 21, which is used to fix and load the metal loading block 2. The cross-sectional structure of the metal loading block 2 along the AA section is shown as follows: Figure 2b As shown, the protruding height of the bonding edge 22a near the middle of the metal loading block 2 is relatively low, while the protruding height of the bonding edge 22b near the edge of the metal loading block 2 is relatively high, which is consistent with the bonding groove on the test piece 1. At the same time, the edge of the concave bonding surface 21 forms a bonding wall 22c, and the bonding wall 22c can be bonded to the circumferential edge of the test piece 1 to further improve the bonding strength. At the same time, since the width of the bonding wall 22c is not limited, the bonding wall 22c can be processed into a wider structure to make it have higher rigidity, thereby forming a better constraint on the edge of the test piece 1 during the tensile test to avoid the edge area from cracking first. It should be understood that the specific dimensions of the bonding edge and the bonding groove are set with reasonable tolerances. In other embodiments, the loading block can also be made of ceramic or other materials with sufficiently high strength.

[0036] In a preferred embodiment, if Figure 3 As shown, the tooling further includes a universal joint loading chain 24, and the metal loading block 2 is connected to the universal joint loading chain 24 via a connecting pin 25 inserted into a connecting hole 23. When performing a loading test, the tensile device applies a tensile load to the loading block 2 by clamping the end of the universal joint loading chain 24, thereby applying an out-of-plane tensile load to the test piece 1.

[0037] According to another embodiment of the present invention, a method for out-of-plane tensile testing of ceramic matrix composite materials is provided. First, a test piece 1 in any of the above embodiments is provided. In some embodiments, the test piece 1 can be prepared by grinding mutually perpendicular bonding grooves on both sides of a CMC sheet. Next, two metal loading blocks 2 are respectively bonded to the first tensile surface 11 and the second tensile surface 12 of the test piece 1, as shown in FIG. Figure 4a , Figure 4b As shown, the bonding edges 22a and 22b of the metal loading block 2 are respectively embedded in the bonding grooves 13a, 13b, 14a (not shown), and 14b (not shown). In some embodiments, the adhesive can be an organic adhesive such as an epoxy resin adhesive. In this way, in addition to the tensile strength provided by the adhesive in the out-of-plane direction, the adhesive in the bonding grooves 13a, 13b, 14a, and 14b and the adhesive between the side wall of the concave bonding surface 21 and the side of the test piece 1 can also provide shear strength, so that the bonding joint can provide a higher limit load. Subsequently, the bonding Figure 3 , the metal loading block 2 is connected to the universal joint loading chain 24 through the connecting pin 25, and then the end of the universal joint loading chain 24 is clamped and fixed on the tensile machine. Finally, the tensile load is applied by the tensile machine until the test piece 1 breaks and fails.

[0038] In a preferred embodiment, after a test, the adhesive can be removed by high-temperature heating. After cleaning the metal loading block 2, the test piece 1 is replaced for multiple tests. The sample data of the fracture surface of the test piece 1 that does not pass through the bonding groove is the effective test data, that is, the effective test result shows that the fracture occurs completely between the bonding grooves on the two tensile surfaces and the fracture process is not affected by the bonding grooves. The tensile strength of the CMC material in the out-of-plane direction can be calculated by the load when the fracture occurs and the area of ​​the test piece 1.

[0039] Through the above method, higher out-of-plane tensile loads can be effectively applied to CMC test pieces, the success rate of test experiments can be improved, the structural design of CMC parts can be more effectively guided, and more reliable predictions and estimates of the strength and life of parts can be made.

[0040] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the claims of the present invention, the optimization or equivalent replacement of the part structure or method steps involved, and the combination of implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A ceramic matrix composite material out-of-plane tensile test piece, characterized in that: It includes a first stretching plane and a second stretching plane, the first stretching plane and the second stretching plane are located on both sides of the thickness direction of the ceramic-based composite material out-of-plane tensile test piece, and a plurality of parallel bonding grooves are respectively arranged on the first stretching plane and the second stretching plane, and the bonding grooves in the first stretching plane and the second stretching plane are perpendicular to each other.

2. The ceramic matrix composite out-of-plane tensile test piece according to claim 1, characterized in that: The depth of each bonding groove is 1 / 3-2 / 5 of the thickness of the ceramic matrix composite material out-of-plane tensile test piece.

3. The ceramic matrix composite out-of-plane tensile test piece according to claim 1 or 2, characterized in that: 4 to 8 bonding grooves are arranged at equal intervals in the first stretching plane and the second stretching plane respectively.

4. The ceramic matrix composite out-of-plane tensile test piece according to claim 3, characterized in that: The width of the bonding groove is configured to be 0.5mm-1mm.

5. The ceramic matrix composite out-of-plane tensile test piece according to claim 3, characterized in that: The ceramic matrix composite material out-of-plane tensile test piece is configured as a rectangular piece with a side length of 15 mm to 20 mm and a thickness of 3 mm to 5 mm.

6. The ceramic matrix composite out-of-plane tensile test piece according to claim 1 or 2, characterized in that: The depth of the bonding groove close to the edge is greater than that of the bonding groove far from the edge.

7. The ceramic matrix composite out-of-plane tensile test piece according to claim 1 or 2, characterized in that: The ceramic matrix composite material out-of-plane tensile test piece is manufactured using a fiber preform, and the fiber preform is configured as a stack of multiple layers of two-dimensional fiber materials along the thickness direction, and the thickness of a single layer in the stack does not exceed 0.5 mm.

8. A ceramic matrix composite material out-of-plane tensile tool for testing the ceramic matrix composite material out-of-plane tensile test piece as claimed in any one of claims 1 to 7, characterized in that: The ceramic-based composite material out-of-plane stretching tooling includes two loading blocks, each of which includes a concave bonding surface on which a raised bonding edge is arranged, and the bonding edges on the bonding surfaces of the two loading blocks are respectively conformally matched with the bonding grooves of the first stretching plane and the second stretching plane of the ceramic-based composite material out-of-plane stretching test piece.

9. The out-of-plane stretching tool for ceramic matrix composite materials according to claim 8, characterized in that: It also includes a universal joint loading chain, and the two loading blocks are respectively connected to the universal joint loading chain, and the universal joint loading chain provides a loading fixed position for the tensile test.

10. A method for testing out-of-plane tensile strength of ceramic matrix composite materials, characterized in that: The following steps are involved: Providing an out-of-plane tensile test piece of a ceramic matrix composite material as claimed in any one of claims 1 to 7; Providing the ceramic matrix composite material out-of-plane stretching tool as claimed in claim 8 or 9, bonding the bonding surfaces of the two loading blocks to the first stretching plane and the second stretching plane respectively; An out-of-plane tensile load is applied to the ceramic matrix composite material out-of-plane tensile test piece by the loading block until the ceramic matrix composite material out-of-plane tensile test piece fractures and fails along the out-of-plane direction.

11. The out-of-plane tensile test method for ceramic matrix composite materials according to claim 10, characterized in that: The test was carried out for several times, and the sample data whose fracture surface did not pass through the bonding groove was regarded as the effective test data.

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