An in-plane shear performance test specimen, fixture, and method

Abstract

The embodiment of the application discloses an in-plane shear performance test sample, a clamp and a method for testing the in-plane shear performance of a ceramic matrix composite material, comprising: a sample body; a first constraint, a second constraint and a stress receiving part are symmetrically arranged on the sample body; the first constraint and the second constraint are located on both sides of the sample body, and the stress receiving part is located in the middle of the sample body; a first necking zone is arranged between the first constraint and the stress receiving part, and a second necking zone is arranged between the second constraint and the stress receiving part. The in-plane shear performance test sample provided by the application avoids the torsion effect of the sample body by symmetrically loading the sample body, improves the uniformity of the in-plane shear strain distribution of the necking zone of the sample body, and can simultaneously measure the shear stress-strain of the first necking zone and the second necking zone, so that two groups of test data are obtained in one test, and the utilization rate of the in-plane shear performance test sample is improved.

Description

Technical Field

[0001] This invention relates to the field of material mechanical property testing technology, and more specifically, to an in-plane shear performance testing specimen, fixture, and method, applicable to the testing of in-plane shear performance of ceramic matrix composites. Background Technology

[0002] Ceramic matrix composites are a class of thermal structural materials, and due to their excellent properties such as high temperature resistance, oxidation resistance, corrosion resistance, and wear resistance, they have important applications in aerospace, nuclear energy, and other fields. In-plane shear properties are a fundamental mechanical property of ceramic matrix composites, an important performance parameter characterizing the overall mechanical behavior of the material, and a necessary material parameter for high-precision simulation of ceramic matrix composite structures.

[0003] In existing technologies, methods for testing the in-plane shear properties of ceramic matrix composites can generally be divided into two categories: the first is the Iosipescu shear method, which uses a specimen with only a pair of V-notches for asymmetric four-point bending loading; the second is the double-notch specimen compression-shear method. For the Iosipescu shear method, due to the use of a pair of V-notches for asymmetric four-point bending loading, torsional deformation easily occurs during loading. The impact of this torsional deformation becomes more severe as the specimen thickness decreases, directly affecting the measurement accuracy of the in-plane shear stress-strain curve. Applying this method to the testing of ceramic matrix composites easily leads to crushing at the specimen-fixture contact point, resulting in ineffective test results. For the double-notch specimen compression-shear method, only the shear strength of the specimen can be measured, and the shear stress-strain curve cannot be obtained.

[0004] Therefore, improving the measurement accuracy, test effectiveness, and specimen utilization rate of in-plane shear properties of ceramic matrix composite specimens has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an in-plane shear performance test specimen to improve the measurement accuracy, test effectiveness and specimen utilization of the in-plane shear performance of ceramic matrix composite specimens;

[0006] Another object of the present invention is to provide an in-plane shear performance testing fixture for the above-mentioned in-plane shear performance test specimen;

[0007] Another object of the present invention is to provide a method for testing the in-plane shear performance of the above-mentioned in-plane shear performance testing fixture.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] An in-plane shear performance test specimen includes:

[0010] Specimen body;

[0011] The specimen body is provided with a first constraint part, a second constraint part, and a force-bearing part at equal intervals; the first constraint part and the second constraint part are located on both sides of the specimen body and are distributed in a mirror symmetrical manner, and the force-bearing part is located in the middle of the specimen body;

[0012] A first constriction region is provided between the first constraint part and the force-receiving part, and a second constriction region is provided between the second constraint part and the force-receiving part; the first constriction region and the second constriction region are distributed in a mirror image symmetrically with respect to the force-receiving part.

[0013] Optionally, in the above-mentioned in-plane shear performance test specimen, the first necking region includes a first V-shaped notch and a second V-shaped notch arranged symmetrically, and the tips of the first V-shaped notch and the second V-shaped notch are arranged opposite to each other; the second necking region includes a third V-shaped notch and a fourth V-shaped notch arranged symmetrically, and the tips of the third V-shaped notch and the fourth V-shaped notch are arranged opposite to each other.

[0014] Optionally, in the above-mentioned in-plane shear performance test specimen, a first test area is formed between the first V-notch and the second V-notch; a second test area is formed between the third V-notch and the fourth V-notch; the first test area and the second test area are areas for measuring the strain of the specimen body.

[0015] Optionally, in the above-mentioned in-plane shear performance test specimen, the opening angles of the first V-notch, the second V-notch, the third V-notch, and the fourth V-notch are 80° to 90°, and the tips are transitioned by a rounded arc.

[0016] Optionally, in the above-mentioned in-plane shear performance test specimen, the thickness of the specimen body is 2 mm to 4 mm; and / or,

[0017] The distance between the first necking region and the second necking region is 0.25 to 0.3 times the length of the specimen body; and / or,

[0018] The distance between the first necking region and the first end of the specimen body is 0.25 to 0.3 times the length of the specimen body; the distance between the second necking region and the second end of the specimen body is 0.25 to 0.3 times the length of the specimen body; and / or,

[0019] The width of the specimen body is 0.16 to 0.18 times its length; and / or,

[0020] The width of the first test area formed between the first V-shaped notch and the second V-shaped notch is 0.5 to 0.6 times the width of the specimen body; and / or,

[0021] The width of the second test area formed between the third V-shaped notch and the fourth V-shaped notch is 0.5 to 0.6 times the width of the specimen body.

[0022] An in-plane shear performance testing fixture for an in-plane shear performance testing specimen as described in any of the preceding claims, comprising:

[0023] A loading device includes a connecting part and a loading part, the connecting part being clamped by a testing machine; the loading part is provided with a loading groove, the loading groove being used to clamp the force-bearing part of the specimen body;

[0024] The wedge clips are provided in at least two pairs, and each pair of wedge clips, when combined, forms a clamping groove for clamping the specimen body; the wedge clips are respectively disposed at the positions of the first constraint portion and the second constraint portion of the specimen body;

[0025] The fixture base is provided with a rectangular groove for providing deformation space for the specimen body; trapezoidal grooves for engaging with the wedge clamp are respectively provided at both ends of the fixture base.

[0026] Optionally, in the above-mentioned in-plane shear performance testing fixture, the wedge clamp includes clamping blocks symmetrically arranged on both sides of the specimen body; each clamping block includes a clamping block inclined surface and a clamping block groove, the clamping block inclined surface is disposed on a first side of the clamping block for engaging with a trapezoidal groove of the fixture base, and the clamping block groove is disposed on a second side opposite to the first side of the clamping block for clamping the specimen body; the depth of the clamping block groove is less than half the thickness of the specimen body.

[0027] Optionally, in the above-mentioned in-plane shear performance testing fixture, the distance between the bottom of the wedge clamp and the bottom of the trapezoidal groove is at least 1 mm; and / or,

[0028] The width of the loading groove is equal to the width of the specimen body; and / or,

[0029] The depth of the groove in the clamping block is 0.1 mm to 0.5 mm less than the thickness of 0.5 times the specimen body.

[0030] A method for testing in-plane shear properties, specifically for the testing method of the in-plane shear property testing fixture described above, includes the following steps:

[0031] The cross-sectional areas S1 and S2 of the shear surfaces of the first and second test areas of the in-plane shear performance test specimen were measured respectively.

[0032] A constant displacement loading rate was used to compress the middle loading part of the in-plane shear performance test specimen using a testing machine, and the load P of the testing machine was collected during the loading process.

[0033] Based on the collected test machine load P, the cross-sectional area S1 of the shear surface of the first test area and the cross-sectional area S2 of the shear surface of the second test area, the shear stress τ1 of the first test area and the shear stress τ2 of the second test area are obtained, where τ1 = P / S1 and τ2 = P / S2.

[0034] During the loading process, the shear strain γ1 of the first test area and the shear strain γ2 of the second test area are measured simultaneously using a strain measurement device.

[0035] Based on the shear stresses τ1 and τ2 obtained in the first test region and the second test region respectively during the loading process, and the shear strains γ1 and γ2 measured in the first test region and the second test region respectively, the shear stress-strain curves of the first test region and the second test region are plotted respectively.

[0036] Optionally, in the above-described in-plane shear performance testing method, the strain measuring device is a strain gauge.

[0037] Optionally, in the above-described in-plane shear performance testing method, the in-plane shear performance testing method is applicable to the testing of ceramic matrix composites reinforced with continuous fibers, chopped fibers, whiskers, and particles.

[0038] The in-plane shear performance test specimen provided by this invention achieves symmetrical loading of the specimen body by setting a first constraint part, a second constraint part, and a force-bearing part on the specimen body, with the first and second constraint parts located on opposite sides of the specimen body in a mirror-symmetrical distribution, and the force-bearing part located in the middle of the specimen body. A first necking region is provided between the first constraint part and the force-bearing part, and a second necking region is provided between the second constraint part and the force-bearing part, with the first and second necking regions being mirror-symmetrically distributed with respect to the force-bearing part.

[0039] Compared with the prior art, the in-plane shear performance test specimen provided by the present invention avoids the torsional effect of the specimen body by symmetrically loading the specimen body, and improves the uniformity of the in-plane shear strain distribution in the necking region of the specimen body. This can improve the accuracy of shear strain measurement and the effectiveness of the test. Furthermore, since the specimen body is provided with a first necking region and a second necking region, the shear stress-strain of the first necking region and the second necking region can be measured simultaneously, so as to obtain two sets of shear performance data in one test, thereby improving the utilization rate of the in-plane shear performance test specimen. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 A front view of the in-plane shear performance test specimen provided in an embodiment of the present invention;

[0042] Figure 2 The left view of the in-plane shear performance test specimen provided in an embodiment of the present invention;

[0043] Figure 3 This is an isometric view of the in-plane shear performance testing fixture and the specimen after assembly, as provided in an embodiment of the present invention.

[0044] Figure 4 This is a left view of the in-plane shear performance testing fixture and the specimen after assembly, as provided in an embodiment of the present invention.

[0045] Figure 5 This is an axonometric view of the fixture base provided in an embodiment of the present invention;

[0046] Figure 6 This is a front view of the clamp base provided in an embodiment of the present invention;

[0047] Figure 7 This is a left view of the clamp base provided in an embodiment of the present invention;

[0048] Figure 8 An axonometric view of the clamping block provided in an embodiment of the present invention;

[0049] Figure 9 This is an isometric view of the in-plane shear performance test specimen and clamping block after assembly, as provided in an embodiment of the present invention.

[0050] Figure 10 This is an isometric view of the clamp loading device provided in an embodiment of the present invention;

[0051] Figure 11 Shear stress-strain curves of the in-plane shear performance test specimen at two pairs of V-notches provided in an embodiment of the present invention;

[0052] Figure 12 The shear strain contour plot of the in-plane shear performance test specimen provided in the embodiment of the present invention.

[0053] Wherein, 100 is the specimen body, 101 is the first test area, 1011 is the first V-shaped notch, 1012 is the second V-shaped notch, 102 is the second test area, 1021 is the third V-shaped notch, 1022 is the fourth V-shaped notch, 200 is the fixture base, 201 is the bottom of the trapezoidal groove, 202 is the first trapezoidal groove, 203 is the second trapezoidal groove, 204 is the rectangular groove of the base, 300 is the first clamping block, 301 is the second clamping block, 302 is the third clamping block, 3021 is the inclined surface of the clamping block, 3022 is the groove of the clamping block, 3023 is the end face of the clamping block, 303 is the fourth clamping block, 304 is the first gap, 305 is the second gap, 306 is the bottom of the wedge clamp, 307 is the clamping groove, 400 is the loading device, 401 is the connecting part, 402 is the loading part, and 403 is the loading groove. Detailed Implementation

[0054] The core of this invention is to provide an in-plane shear performance test specimen to improve the measurement accuracy, test effectiveness and specimen utilization of the in-plane shear performance of ceramic matrix composite specimens;

[0055] Another core aspect of this invention is to provide an in-plane shear performance testing fixture for the aforementioned in-plane shear performance test specimen.

[0056] Another core aspect of this invention is to provide a method for testing the in-plane shear performance of the aforementioned in-plane shear performance testing fixture.

[0057] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0058] like Figure 1 and Figure 2 As shown, this embodiment of the invention discloses an in-plane shear performance test specimen, including a specimen body 100. It should be noted that the material of the in-plane shear performance test specimen disclosed in this embodiment of the invention is mainly a silicon carbide fiber-reinforced silicon carbide-based composite material (hereinafter referred to as SiC). f SiC (SiC) is a laminated material prepared using a unidirectional prepreg layup method. However, due to the limitations of the prepreg melt-infiltration process, the SiC material preparation process is subject to these limitations. fThe thickness of SiC is generally 2mm to 4mm, and the thickness of the in-plane shear performance test specimen prepared in this embodiment is 2.3mm. Of course, the material of the in-plane shear performance test specimen can also be other types of ceramic matrix composites, such as continuous fibers, chopped fibers, and whiskers. As long as the material type of the in-plane shear performance test specimen disclosed in this embodiment is used, it is within the protection scope of this application.

[0059] Specifically, the specimen body 100 is provided with a first constraint part, a second constraint part, and a force-bearing part at equal intervals, and the first constraint part and the second constraint part are mirror-symmetrically distributed. The first constraint part and the second constraint part are located on both sides of the specimen body 100, and the force-bearing part is located in the middle of the specimen body 100. In one specific embodiment, the first constraint part and the second constraint part are located on both sides of the specimen body 100, specifically on the right and left sides of the specimen body 100, respectively. Figure 1 (From a certain perspective), in order to form shear deformation under symmetrical loading, the stressed part is located in the middle of the first and second constraint parts, thereby eliminating the torsional effect induced by the specimen body 100 under asymmetrical loading. It should be noted that the first and second constraint parts are the force-bearing positions constrained by the clamp support and providing the support reaction force, while the stressed part is the direct force-bearing position under the applied load.

[0060] Furthermore, a first necking region is provided between the first constraint part and the force-bearing part, and a second necking region is provided between the second constraint part and the force-bearing part. The first and second necking regions are mirror-symmetrically distributed with respect to the force-bearing parts. It should be noted that the middle portions of the first and second necking regions are the test areas for two shear tests on the specimen body 100, and the widths of the first and second necking regions are smaller than the width of the specimen body 100, with the width of the two test areas being 0.5 to 0.6 times the width of the specimen body 100. In this embodiment of the invention, the in-plane shear performance test is conducted in the first and second necking regions. Since the first and second necking regions are mirror-symmetrically distributed with respect to the force-bearing parts, the stress states of the first and second necking regions are the same. Therefore, ideally, the in-plane shear performance test results of the first and second necking regions should be consistent.

[0061] The in-plane shear performance test specimen provided by this invention achieves symmetrical loading of the specimen body 100 by setting a first constraint part, a second constraint part, and a force-bearing part on the specimen body 100, with the first constraint part and the second constraint part located on both sides of the specimen body 100 in a mirror-symmetrical distribution, and the force-bearing part located in the middle of the specimen body 100. A first necking region is provided between the first constraint part and the force-bearing part, and a second necking region is provided between the second constraint part and the force-bearing part, with the first necking region and the second necking region being mirror-symmetrically distributed with respect to the force-bearing part.

[0062] Compared with the prior art, the in-plane shear performance test specimen provided by the present invention avoids the torsional effect of the specimen body 100 by symmetrically loading the specimen body 100, improves the uniformity of the in-plane shear strain distribution in the necking region of the specimen body 100, and improves the measurement accuracy and test effectiveness of shear performance. Moreover, since the specimen body 100 is provided with a first necking region and a second necking region, the shear stress-strain of the first necking region and the second necking region can be measured simultaneously, so as to obtain two sets of shear performance data in one test, thereby improving the utilization rate of the in-plane shear performance test specimen.

[0063] like Figure 1 As shown, in one specific embodiment, the specimen body 100 is a symmetrical rectangular plate structure, and the first necking region includes a symmetrically arranged first V-shaped notch 1011 and a second V-shaped notch 1012, with the tips of the first V-shaped notch 1011 and the second V-shaped notch 1012 facing each other. The second necking region includes a symmetrically arranged third V-shaped notch 1021 and a fourth V-shaped notch 1022, with the tips of the third V-shaped notch 1021 and the fourth V-shaped notch 1022 facing each other. The first V-shaped notch 1011 and the second V-shaped notch 1012 form a pair, and a first test area 101 is formed between the first V-shaped notch 1011 and the second V-shaped notch 1012. The third V-shaped notch 1021 and the fourth V-shaped notch 1022 form a pair, and a second test area 102 is formed between the third V-shaped notch 1021 and the fourth V-shaped notch 1022. The first test area 101 and the second test area 102 are areas for measuring the strain of the specimen body 100. It should be noted that the four V-shaped notches are symmetrically mirrored with respect to the two central axes in the length and width directions of the specimen body 100.

[0064] Specifically, in the above embodiments, the opening angles of the first V-shaped notch 1011, the second V-shaped notch 1012, the third V-shaped notch 1021, and the fourth V-shaped notch 1022 are 80° to 90°. The depth of the four V-shaped notches is at least 0.2 to 0.25 times the width of the specimen body 100, thereby creating two test areas with a width of 0.5 to 0.6 times the width of the specimen body 100. This ensures that the specimen body 100 can be sheared at the V-shaped notches, and the tip is transitioned by a rounded arc with a radius of 1 mm to 1.5 mm to avoid stress concentration and affect the accuracy of the in-plane shear performance test.

[0065] Further, the thickness of the specimen body 100 is 2mm to 4mm; in this embodiment, the thickness of the specimen body 100 is 2.2mm. And / or, the length of the specimen body 100 is 110mm to 120mm. And / or, the distance between the first necked region and the second necked region is 0.25 to 0.3 times the length of the specimen body 100. And / or, the distance between the first necked region and the first end of the specimen body 100 is 0.25 to 0.3 times the length of the specimen body 100, and the distance between the second necked region and the second end of the specimen body 100 is 0.25 to 0.3 times the length of the specimen body 100. And / or, the width of the specimen body 100 is 0.16 to 0.18 times its length. And / or, the width of the first test area 101 formed between the first V-shaped notch 1011 and the second V-shaped notch 1012 is 0.5 to 0.6 times the width of the specimen body 100. And / or, the width of the second test area 102 formed between the third V-notch 1021 and the fourth V-notch 1022 is 0.5 to 0.6 times the width of the specimen body 100.

[0066] In a specific embodiment, the specific dimensions of the specimen body 100 are shown in Table 1. In actual use, other specimen dimensions can also be used, as long as they meet the dimensional requirements of the specimen body 100 described above. It should be noted that the specimen body 100 is the specimen shown in the table; the distance between the roots of the two V-shaped notches is the distance between the tips of the two V-shaped notches; the length of the parallel sections on both sides of the specimen refers to the distances from the first and second necked areas to the two ends of the specimen body 100, respectively, that is, the distance between the first necked area and the first end of the specimen body 100 and the distance between the second necked area and the second end of the specimen body 100, and the two distances are equal; the length of the parallel section in the middle of the specimen refers to the distance between the first and second necked areas.

[0067] Table 1. Specific dimensions of the specimen in this embodiment.

[0068] Size Name Size value / mm Specimen width 20 V-shaped notch opening angle 90° V-shaped notch radius 1.3 Specimen length 110 The distance between the roots of the two V-shaped notches 11 Length of parallel sections on both sides of the specimen 30 Length of the parallel section in the middle of the specimen 30

[0069] This invention also discloses an in-plane shear performance testing fixture for the in-plane shear performance testing specimen disclosed in the above embodiments. Therefore, this specimen possesses all the technical effects of the aforementioned in-plane shear performance testing specimen, which will not be repeated here. Wherein, as... Figure 3 As shown, the in-plane shear performance testing fixture includes a loading device 400, a wedge clamp, and a fixture base 200. It should be noted that the in-plane shear performance testing fixture disclosed in this embodiment is only for cases where the specimen body 100 of the in-plane shear performance test specimen is a rectangular plate structure. Of course, it can also be used for in-plane shear performance test specimens of other shapes, which will not be listed here.

[0070] Specifically, such as Figure 10 As shown, the loading device 400 includes a connecting part 401 and a loading part 402. The connecting part 401 is clamped by the testing machine, and the loading part 402 has a loading groove 403 for clamping the force-bearing part of the specimen body 100. In a specific embodiment, the connecting part 401 is a cylinder, the loading part 402 is a rectangular block, and the loading groove 403 is a rectangular slot. The length of the rectangular slot is equal to the length of the rectangular block, meaning the rectangular slot extends through the length of the rectangular block. The depth of the rectangular slot is equal to the width of the specimen body 100. By clamping the connecting part 401 with the testing machine, the load of the testing machine is transmitted to the force-bearing part of the specimen body 100.

[0071] Furthermore, such as Figure 4 and Figure 9 As shown, there are at least two pairs of wedge clamps. For ease of understanding, the two pairs of wedge clamps are defined as the first wedge clamp and the second wedge clamp, respectively. Each pair of wedge clamps forms a clamping groove 307 for clamping the specimen body 100. The first wedge clamp is located at the position of the first constraint part of the specimen body 100, and the second wedge clamp is located at the position of the second constraint part of the specimen body 100. The first wedge clamp and the second wedge clamp are used to constrain the first constraint part and the second constraint part of the specimen body 100 and provide support reaction force when the testing machine is loaded at the force-bearing part position of the specimen body 100.

[0072] like Figures 5 to 7 As shown, the fixture base 200 has a rectangular groove 204 extending through the thickness of the fixture base 200, which provides movement space for the loading device 400 and deformation space for the specimen body 100. Trapezoidal grooves for engaging with wedge clamps are respectively formed at both ends of the fixture base 200. For ease of understanding, the trapezoidal groove engaging with the first wedge clamp is defined as the first trapezoidal groove 202, and the trapezoidal groove engaging with the second wedge clamp is defined as the second trapezoidal groove 203. The first trapezoidal groove 202 extends from the right end of the fixture base 200 (…). Figure 5 The second trapezoidal groove 203 extends from the left end of the clamp base 200 and connects to the rectangular groove 204 of the base. Figure 5 (View) Through and connected to the rectangular groove 204 of the base, so as to ensure that the specimen body 100 can be installed on the fixture base 200 under the clamping of the wedge clamp.

[0073] Furthermore, such as Figure 3 As shown, the first wedge clamp includes a first clamping block 300 and a second clamping block 301 symmetrically disposed on both sides of the specimen body 100, and the second wedge clamp includes a third clamping block 302 and a fourth clamping block 303 symmetrically disposed on both sides of the specimen body 100. Wherein, as... Figure 8As shown, each clamping block includes a clamping block inclined surface 3021, a clamping block groove 3022, and a clamping block end face 3023. The clamping block inclined surface 3021 is disposed on the first side of the clamping block for engaging with the trapezoidal groove of the clamping base 200. The clamping block groove 3022 is formed on the second side opposite to the first side of the clamping block for clamping the specimen body 100. Figure 9 As shown, the width of the clamping block groove 3022 is equal to the width of the specimen body 100. When the surfaces of the clamping block grooves 3022 of the two clamping blocks are combined face to face, a clamping groove 307 for clamping the specimen body 100 is formed. Further, the clamping block end face 3023 is a plane located on the second side of the clamping block and protruding from the clamping block groove 3022. It should be noted that the depth of the clamping block groove 3022 is less than half the thickness of the specimen body 100, so that when the first clamping block 300 and the second clamping block 301 are combined, a first gap 304 is formed at the position of the clamping block end face 3023, and when the third clamping block 302 and the fourth clamping block 303 are combined, a second gap 305 is formed at the position of the clamping block end face 3023.

[0074] The first gap 304 and the second gap 305 facilitate the centering of the specimen body 100. At the same time, as the load is applied, the trapezoidal groove sidewall of the fixture base 200 generates a clamping force that reacts to the wedge clamp. This clamping force can be transmitted to the two sides of the specimen body 100, providing stable lateral support, preventing out-of-plane deformation, and avoiding stress concentration at the contact point between the specimen body 100 and the in-plane shear performance testing fixture.

[0075] Furthermore, the distance between the bottom 306 of the wedge clamp and the bottom 201 of the trapezoidal groove is at least 1 mm. And / or, the width of the loading groove 403 is equal to the width of the specimen body 100 to ensure that the contact between the loading part 402 and the specimen body 100 is a surface-to-surface contact, avoiding stress concentration. And / or, the depth of the clamping block groove 3022 is 0.1 mm to 0.5 mm less than 0.5 times the thickness of the specimen body 100, thereby ensuring that after the specimen body 100 and the two pairs of wedge clamps are assembled, a first gap 304 and a second gap 305 of 0.2 mm to 1 mm are formed between the two pairs of wedge clamps, respectively.

[0076] The in-plane shear performance testing fixture disclosed in this invention can eliminate the gap between the specimen body 100 and the in-plane shear performance testing fixture under high temperature conditions. During the test, the assembly of the specimen body 100 and the in-plane shear performance testing fixture only needs to be completed at room temperature. During the loading stage after high-temperature heating and heat preservation, the gap between the specimen body 100 and the in-plane shear performance testing fixture can be eliminated through pre-loading and unloading.

[0077] It should be noted that the in-plane shear performance testing fixture can be made of ordinary low-carbon steel when operating at room temperature; it can be made of high-temperature alloy when operating at temperatures below 1000°C; and it can be made of high-temperature resistant ceramic material when operating at temperatures above 1000°C. In this embodiment of the invention, the in-plane shear performance test is conducted at room temperature; therefore, the in-plane shear performance testing fixture is made of ordinary low-carbon steel.

[0078] This invention also discloses an in-plane shear performance testing method. This method is for testing the in-plane shear performance test specimen and fixture disclosed in the above embodiments. The specimen and fixture possess all the technical effects of the aforementioned in-plane shear performance test specimen and fixture, which will not be elaborated upon here. The in-plane shear performance testing method includes the following steps:

[0079] The first step is to measure the thickness h1 and h2 of the in-plane shear performance test specimen at the first test area 101 and the second test area 102, respectively, and the distance L1 and L2 between the tips of the two V-shaped notches. According to S1 = h1 × L1 and S2 = h2 × L2, the cross-sectional areas S1 and S2 of the shear surface of the first test area 101 and the second test area 102 of the in-plane shear performance test specimen are obtained respectively.

[0080] The second step is to clamp the right side of the in-plane shear performance test specimen to the right side ( Figure 3 In the clamping groove 307 formed by the first wedge-shaped clamp (view angle), the left side of the in-plane shear performance test specimen is clamped in the left side in the same manner. Figure 3 The in-plane shear performance test specimen is inserted into the clamping groove 307 formed by the second wedge clamp (view) and then the assembly of the in-plane shear performance test specimen and the two pairs of wedge clamps is embedded into the fixture base 200, so that the two pairs of wedge clamps slide into the trapezoidal grooves at both ends of the fixture base 200 to ensure the centering of the in-plane shear performance test specimen in the fixture. Then, the fixture base 200 with the in-plane shear performance test specimen and wedge clamps assembled is placed at the center of the lower pressure plate of the testing machine, and the connecting part 401 of the loading device 400 is clamped in the upper chuck of the testing machine to complete the assembly of the in-plane shear performance test specimen and the fixture.

[0081] The third step involves controlling the chuck on the testing machine to move downwards, causing the loading device 400 to move downwards accordingly. This allows the loading device 400 to pass through the middle parallel section of the in-plane shear performance test specimen (the middle parallel section is the stress-bearing part). As the chuck on the testing machine continues to move downwards, the root of the loading groove 403 of the loading device 400 contacts the top of the middle parallel section of the in-plane shear performance test specimen. Then, the chuck on the testing machine continues to move downwards at a slow rate, while monitoring the load value of the testing machine. When the load value reaches approximately 50N, loading is stopped. Then, the chuck on the testing machine is slowly moved upwards until the load reading of the testing machine approaches zero. This operation eliminates the gap between the in-plane shear performance test specimen and the fixture. After eliminating the gap between the in-plane shear performance test specimen and the fixture, the in-plane shear performance test specimen is loaded using a testing machine at a constant displacement loading rate. In this specific embodiment, the loading rate is 2 mm / min. During the loading process, the testing machine load P is collected, and the shear strain of the first test area 101 and the second test area 102 is also collected. It should be noted that when testing in a high-temperature environment, the position of the heating device needs to be adjusted before starting the heating. After reaching the target temperature, it should be held for 20 minutes before starting the loading process.

[0082] Fourthly, based on the collected testing machine load P, the cross-sectional area S1 of the shear surface of the first test area 101, and the cross-sectional area S2 of the shear surface of the second test area 102, the shear stress τ1 of the first test area 101 and the shear stress τ2 of the second test area 102 are obtained, where τ1 = P / S1 and τ2 = P / S2. During the loading process, the shear strain γ1 of the first test area 101 and the shear strain γ2 of the second test area 102 are simultaneously measured using a strain measuring device.

[0083] In a specific embodiment, the strain measurement device can be a strain gauge. When using a strain gauge, it is attached to the front and rear surfaces of the in-plane shear performance test specimen. In this embodiment, a stacked biaxial strain gauge is preferred. Four biaxial strain gauges are attached to the front and rear surfaces of the first test area 101 and the second test area 102 of the in-plane shear performance test specimen, and the sensitive grids of the two stacked biaxial strain gauges are arranged at ±45° angles to the lines connecting the tips of the two V-shaped notches. Before measurement, the biaxial strain gauges are balanced and zeroed. Then, the displacement loading mode is set on the testing machine, the loading rate is set to 2 mm / min, the testing machine is started, and the data acquisition of the biaxial strain gauges begins. It should be noted that the shear strain γ1 of the first test area 101 and the shear strain γ2 of the second test area 102 are the average values ​​of the measured data of the front and rear biaxial strain gauges.

[0084] Fifth, based on the shear stresses τ1 and τ2 obtained in the first test region 101 and the second test region 102, and the shear strains γ1 and γ2 measured in the first test region 101 and the second test region 102, respectively, the shear stress-strain curves for the first test region 101 and the second test region 102 are plotted. The shear modulus G is obtained by linear fitting based on the data of the linear segment of the shear stress-strain curve. The maximum load P at failure of the in-plane shear performance test specimen is also determined. max The ratio of the in-plane shear strength to the cross-sectional area of ​​the sheared test region is the in-plane shear strength.

[0085] In a specific embodiment, the in-plane shear performance test method is used to test SiC. f / SiC was tested, and the shear stress-strain curves of the first test region 101 and the second test region 102 were obtained, as shown below. Figure 11 As shown ( Figure 11 Only the shear stress-strain curves of the first test region 101 and the second test region 102 before failure are shown; the failure stages of the first test region 101 and the second test region 102 are not shown. By fitting the linear segments of the two curves, the in-plane shear modulus G1 of the first test region 101 is obtained as 66.4 GPa, and the in-plane shear modulus G2 of the second test region 102 is obtained as 66.5 GPa. Since the first test region 101 was sheared, the corresponding stress in the first test region 101 is 244 MPa, and the in-plane shear strength is 244 MPa.

[0086] For the above embodiments, finite element models of the in-plane shear performance test specimen with two test regions (two pairs of V-notches) and symmetrical loading method disclosed in the embodiments of the present invention were established using the finite element software ABAQUS, as well as a traditional finite element model of the in-plane shear performance test specimen with only one test region (a pair of V-notches) and asymmetric loading method. The shear strain distribution of the in-plane shear performance test specimen with two test regions was analyzed and obtained, such as... Figure 12 As shown in (a) above, and the shear strain distribution of an in-plane shear performance test specimen containing only one test area, as shown below. Figure 12 As shown in (b) of the diagram, a comparative analysis reveals that, compared to the traditional specimen with only one test area, the in-plane shear performance test specimen with two test areas disclosed in this embodiment of the invention significantly expands the range of the uniform shear strain zone, resulting in more accurate strain measurements. It should be noted that, ideally, since the in-plane shear performance test specimen with two test areas (two pairs of V-notches) is symmetrically distributed and subjected to symmetrical loading, the shear strain near the first test area 101 and the second test area 102 has the same distribution. Figure 12(a) shows the shear strain distribution in only one of the test areas.

[0087] Furthermore, the in-plane shear performance testing method disclosed in this embodiment of the invention can not only test SiC f The test can be performed on SiC, and can also be applied to the testing of ceramic matrix composites reinforced with continuous fibers, chopped fibers, whiskers and particles. As long as it is the material type involved in this embodiment, it is within the protection scope of this application.

[0088] The terms "first" and "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units may include steps or units not listed, but rather steps or units not listed.

[0089] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A test specimen for in-plane shear properties, used for testing the in-plane shear properties of ceramic matrix composites, characterized in that, include: Specimen body (100); The specimen body (100) is provided with a first constraint part, a second constraint part and a force-bearing part; the first constraint part and the second constraint part are located on both sides of the specimen body (100) and are distributed in a mirror symmetrical manner; the force-bearing part is located in the middle of the specimen body (100), and the first constraint part, the second constraint part and the force-bearing part are arranged at equal intervals along the length direction of the specimen body; A first constriction region is provided between the first constraint part and the force-receiving part, and a second constriction region is provided between the second constraint part and the force-receiving part; the first constriction region and the second constriction region are distributed in a mirror image symmetrically with respect to the force-receiving part; The first necking region includes a first V-shaped notch (1011) and a second V-shaped notch (1012) symmetrically arranged, with the tips of the first V-shaped notch (1011) and the second V-shaped notch (1012) facing each other; the second necking region includes a third V-shaped notch (1021) and a fourth V-shaped notch (1022) symmetrically arranged, with the tips of the third V-shaped notch (1021) and the fourth V-shaped notch (1022) facing each other; The opening angles of the first V-shaped notch (1011), the second V-shaped notch (1012), the third V-shaped notch (1021), and the fourth V-shaped notch (1022) are 80° to 90°, and the tips are transitioned by a rounded arc with a radius of 1mm to 1.5mm.

2. The in-plane shear performance test specimen according to claim 1, characterized in that, A first test area (101) is formed between the first V-notch (1011) and the second V-notch (1012); a second test area (102) is formed between the third V-notch (1021) and the fourth V-notch (1022); the first test area (101) and the second test area (102) are areas for measuring the strain of the specimen body (100).

3. The in-plane shear performance test specimen according to claim 1, characterized in that, The thickness of the specimen body (100) is 2mm to 4mm; and / or, The distance between the first necking region and the second necking region of the specimen body (100) is 0.25 to 0.3 times the length of the specimen body (100); and / or, The distance between the first necked region and the first end of the specimen body (100) is 0.25 to 0.3 times the length of the specimen body (100); the distance between the second necked region and the second end of the specimen body (100) is 0.25 to 0.3 times the length of the specimen body (100); and / or, The width of the specimen body (100) is 0.16 to 0.18 times its length; and / or, The width of the first test area (101) formed between the first V-shaped notch (1011) and the second V-shaped notch (1012) is 0.5 to 0.6 times the width of the specimen body (100); and / or, The width of the second test area (102) formed between the third V-shaped notch (1021) and the fourth V-shaped notch (1022) is 0.5 to 0.6 times the width of the specimen body (100).

4. A fixture for testing in-plane shear properties, characterized in that, For use in the in-plane shear performance test specimen as described in any one of claims 1-3, comprising: The loading device (400) includes a connecting part (401) and a loading part (402). The connecting part (401) is used to be clamped by the testing machine. The loading part (402) is provided with a loading groove (403), which is used to clamp the force-bearing part of the specimen body (100). The wedge clips are at least two pairs, and each pair of the wedge clips, when combined, forms a clamping groove (307) for clamping the specimen body (100); the wedge clips are respectively disposed at the positions of the first constraint part and the second constraint part of the specimen body (100); The fixture base (200) is provided with a rectangular groove (204) for providing deformation space for the specimen body (100); the two ends of the fixture base (200) are respectively provided with trapezoidal grooves for cooperating with the wedge clamp; The wedge clamp includes clamping blocks symmetrically arranged on both sides of the specimen body (100); each clamping block includes a clamping block inclined surface (3021) and a clamping block groove (3022). The clamping block inclined surface (3021) is arranged on the first side of the clamping block for engaging with the trapezoidal groove of the fixture base (200). The clamping block groove (3022) is arranged on the second side opposite to the first side of the clamping block for clamping the specimen body (100). The depth of the clamping block groove (3022) is less than half the thickness of the specimen body (100). The two pairs of wedge clamps are a first wedge clamp and a second wedge clamp. The first wedge clamp includes a first clamping block (300) and a second clamping block (301) symmetrically arranged on both sides of the specimen body (100). The second wedge clamp includes a third clamping block (302) and a fourth clamping block (303) symmetrically arranged on both sides of the specimen body (100). Each clamping block also includes a clamping block end face (3023), which is a plane located on the second side of the clamping block and protruding from the clamping block groove (3022). When the first clamping block (300) and the second clamping block (301) are combined, a first gap (3) is formed at the clamping block end face (3023). 04), when the third clamping block (302) and the fourth clamping block (303) are combined, a second gap (305) is formed at the end face (3023) of the clamping block; the setting of the first gap (304) and the second gap (305) facilitates the centering of the specimen body (100). At the same time, as the load is applied, the trapezoidal groove sidewall of the fixture base (200) forms a reaction force on the wedge clamp and is transmitted to the two sides of the specimen body (100), providing stable side support and preventing out-of-plane deformation, so as to avoid stress concentration at the contact position between the specimen body (100) and the in-plane shear performance test fixture.

5. The in-plane shear performance testing fixture according to claim 4, characterized in that, The distance between the bottom of the wedge-shaped clamp and the bottom of the trapezoidal groove is at least 1 mm; and / or, The width of the loading groove (403) is equal to the width of the specimen body (100); and / or, The depth of the clamping block groove (3022) is 0.1 mm to 0.5 mm less than the thickness of the specimen body (100) which is 0.5 times.

6. A method for testing in-plane shear properties, characterized in that, The testing method for the in-plane shear performance testing fixture as described in claim 4 includes the following steps: The cross-sectional areas S1 and S2 of the shear plane of the first test area (101) and the second test area (102) of the in-plane shear performance test specimen are measured respectively. A constant displacement loading rate was used to compress the middle loading part of the in-plane shear performance test specimen using a testing machine, and the load P of the testing machine was collected during the loading process. Based on the collected test machine load P, the cross-sectional area S1 of the shear surface of the first test area (101) and the cross-sectional area S2 of the shear surface of the second test area (102), the shear stress τ1 of the first test area (101) and the shear stress τ2 of the second test area (102) are obtained, where τ1=P / S1 and τ2=P / S2. During the loading process, the shear strain γ1 of the first test area (101) and the shear strain γ2 of the second test area (102) are measured simultaneously using a strain measuring device. Based on the shear stresses τ1 and τ2 obtained in the first test region (101) and the second test region (102) respectively during the loading process, and the shear strains γ1 and γ2 measured in the first test region (101) and the second test region (102) respectively, the shear stress-strain curves of the first test region (101) and the second test region (102) are plotted respectively.

7. The in-plane shear performance testing method according to claim 6, characterized in that, The strain measuring device is a strain gauge.

8. The in-plane shear performance testing method according to claim 6, characterized in that, The in-plane shear performance test method is applicable to the testing of continuous fiber, chopped fiber, whisker, and particle-reinforced ceramic matrix composites.

Images