Method for testing fracture toughness of heterogeneous materials, double-cantilever beam sample and manufacturing method of double-cantilever beam sample

Abstract

The invention relates to the technical field of material performance testing, in particular to a heterogeneous material fracture toughness testing method, a double-cantilever beam sample and a manufacturing method. The heterogeneous material fracture toughness testing method comprises the steps that a double-cantilever-beam sample is provided, the double-cantilever-beam sample comprises base body layers, a first base plate and isolation layers, the base body layers are arranged on the two sides of the first base plate in the first direction, the isolation layer is arranged between the first base plate and any base body layer, and the isolation layers are arranged on the two sides of the first base plate in the first direction; an isolation region and a to-be-tested region are formed between the first substrate and the matrix layer adjacent to the isolation layer in the second direction, and the isolation region has a prefabricated crack; a sample testing step: mounting the double-cantilever beam sample on a testing device, loading the double-cantilever beam sample through the testing device so as to layer the to-be-tested area, and obtaining target data; and a result calculation step: obtaining an I-type interlayer fracture toughness value according to the target data. The heterogeneous material fracture toughness testing method provided by the invention can improve the testing accuracy.

Description

Technical Field

[0001] This application relates to the technical field of material property testing, and particularly to a method for testing the fracture toughness of dissimilar materials, a double-cantilever beam specimen, and a manufacturing method thereof. Background Art

[0002] The delamination form between material layers can be divided into three basic forms: opening mode (Type I), sliding mode (Type II), and tearing mode (Type III) according to the crack surface and the load direction. As a mechanical test structure, the double-cantilever beam specimen has been widely used in testing the interlayer fracture toughness of materials.

[0003] Since the fracture behavior of the double-cantilever beam specimen depends on the material properties of the substrate, in related technologies, double-cantilever beam specimens are usually made based on the principle of equal bending stiffness using substrates made of two different materials to test the Mode-I interlayer fracture toughness of dissimilar materials.

[0004] However, there is still Type-II deformation in the above double-cantilever beam specimen during testing, which affects the test results and reduces the accuracy of the Mode-I interlayer fracture toughness test of dissimilar materials. Summary of the Invention

[0005] This application provides a method for testing the fracture toughness of dissimilar materials, a double-cantilever beam specimen, and a manufacturing method thereof, to solve the problem of low accuracy in the current Mode-I interlayer fracture toughness test of dissimilar materials.

[0006] To achieve the above object, the technical solution of this application is as follows: In the first aspect, this application provides a method for testing the fracture toughness of dissimilar materials, including the following steps: a step of providing a double-cantilever beam specimen, the double-cantilever beam specimen includes a matrix layer, a first substrate, and an isolation layer. The first substrate is provided with matrix layers on both sides in a first direction. An isolation layer is provided between the first substrate and any matrix layer. The matrix layer and the first substrate are fixedly connected. An isolation region and a region to be tested are formed in a second direction between the first substrate and the matrix layer adjacent to the isolation layer. The isolation region has a prefabricated crack; a specimen testing step of installing the double-cantilever beam specimen on a testing device and gradually loading the double-cantilever beam specimen through the testing device to cause delamination in the region to be tested and obtaining target data; and a result calculation step of obtaining the Mode-I interlayer fracture toughness value of the double-cantilever beam specimen according to the target data.

[0007] In a possible implementation manner, in the method for testing the fracture toughness of dissimilar materials provided by this application, in the step of providing the double-cantilever beam specimen, in the second direction, the elastic modulus of the matrix layer is greater than the elastic modulus of the first substrate.

[0008] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, the target data includes multiple load values applied by the testing device to the double-cantilever beam specimen and the displacement values corresponding to each load value one by one, and the displacement value is the opening displacement value of the double-cantilever beam specimen in the loading direction.

[0009] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, before the specimen testing step, it further includes a heat preservation step for the double-cantilever beam specimen, including: placing the double-cantilever beam specimen in a constant-temperature environment, determining the heat preservation temperature of the double-cantilever beam specimen according to the actual service environment temperature of the matrix layer and the first substrate; maintaining the double-cantilever beam specimen at a constant temperature for a predetermined duration according to the heat preservation temperature; respectively monitoring the temperatures of the matrix layer and the first substrate of the double-cantilever beam specimen to ensure that the temperature difference between the matrix layer and the first substrate is within the preset temperature difference range.

[0010] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, before the specimen testing step, it further includes: measuring the size of the double-cantilever beam specimen and making scale marks on the double-cantilever beam specimen.

[0011] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, the matrix layer includes a second substrate, and the two second substrates are respectively located on opposite sides of the first substrate in the first direction, and the isolation layer is arranged between the first substrate and any one of the second substrates.

[0012] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, the elastic modulus of the first substrate is E1, and the elastic modulus of the second substrate is E2, where E2≥1.4×E1; and / or, along the first direction, the thickness of the first substrate is h1, and the thickness of the second substrate is h2, where h2≥2.3×h1.

[0013] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, the matrix layer includes a second substrate and a reinforcing plate. Along the first direction, the second substrate is arranged closer to the first substrate than the reinforcing plate, and the isolation layer is arranged between the first substrate and any one of the second substrates.

[0014] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by the present application, the elastic modulus of the first substrate is E1, and the elastic modulus of the reinforcing plate is E3, where E3≥1.4×E1; and / or, along the first direction, the thickness of the first substrate is h1, and the thickness of the reinforcing plate is h3, where h3≥2.3×h1.

[0015] In a possible implementation, for the method for testing the fracture toughness of dissimilar materials provided by this application, along the first direction, the thickness of the first substrate is h1, and the thickness of the isolation layer is h4, where h4 ≤ 0.1×h1.

[0016] In a second aspect, this application provides a double-cantilever beam specimen, including: a matrix layer; a first substrate, with matrix layers provided on both sides of the first substrate in the first direction; an isolation layer, provided between the first substrate and any one of the matrix layers; where along the second direction, the extension length of the isolation layer is less than the extension length of the first substrate, and along the first direction, the isolation layer and the first substrate are stacked, so that an isolation region and a region to be tested are formed between the first substrate and the matrix layer adjacent to the isolation layer in the second direction, and the first direction and the second direction intersect.

[0017] In a third aspect, this application provides a method for manufacturing a double-cantilever beam specimen, which is applied to the above double-cantilever beam specimen, and includes: laying one of the two matrix layers in a specimen manufacturing mold; laying the first substrate and the isolation layer in the specimen manufacturing mold according to a predetermined laying sequence; laying the other of the two matrix layers in the specimen manufacturing mold, and the two matrix layers are symmetrically arranged along the first direction; connecting the matrix layer and the first substrate; where along the second direction, the isolation layer extends a predetermined length from one end of the first substrate towards the other end of the first substrate, so as to form an isolation region between the matrix layer adjacent to the isolation layer and the first substrate.

[0018] The method for testing the fracture toughness of dissimilar materials, the double-cantilever beam specimen and the manufacturing method provided by this application, the method for testing the fracture toughness of dissimilar materials includes the step of providing a double-cantilever beam specimen. The double-cantilever beam specimen includes a matrix layer, a first substrate and an isolation layer. Matrix layers are provided on both sides of the first substrate in the first direction, and an isolation layer is provided between the first substrate and any one of the matrix layers. The isolation layer is used to form an isolation region between the first substrate and the matrix layer adjacent to the isolation layer. The isolation region is a prefabricated crack, and the region without the isolation layer between the first substrate and the matrix layer adjacent to the isolation layer forms a region to be tested. With such a setting, the isolation region formed by the isolation layer is used as the starting point for delamination expansion, so as to guide the delamination phenomenon between the first substrate and the matrix layer adjacent to the isolation layer to start from the junction of the isolation region and the region to be tested and extend into the region to be tested along the second direction and towards the region to be tested. Thus, by providing matrix layers on both sides of the first substrate in the first direction, the geometric structure symmetry, material consistency and bending stiffness balance on both sides of the double-cantilever beam specimen in the first direction can be improved, thereby reducing the probability of type II deformation, and further improving the accuracy of the type I interlaminar fracture toughness test of dissimilar materials. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a schematic flowchart of a method for testing the fracture toughness of dissimilar materials provided by an embodiment of the present application; Figure 2 It is a schematic flowchart of the heat preservation step of a double-cantilever beam specimen provided by an embodiment of the present application; Figure 3 It is a schematic diagram of the structure of a double-cantilever beam specimen provided by an embodiment of the present application Figure 1 ; Figure 4 It is a schematic diagram of the structure of a double-cantilever beam specimen provided by an embodiment of the present application Figure 2 ; Figure 5 It is a schematic diagram of the structure of a double-cantilever beam specimen provided by an embodiment of the present application Figure 3 ; Figure 6 It is a schematic diagram for comparing the test results of the double-cantilever beam specimen provided by an embodiment of the present application with the double-cantilever beam specimen provided in the related art; Figure 7 It is a schematic flowchart of the manufacturing method of a double-cantilever beam specimen provided by an embodiment of the present application.

[0021] Explanation of reference numerals: 10 - Double-cantilever beam specimen; 100 - Substrate layer; 100a - First substrate layer; 100b - Second substrate layer; 110 - Second substrate; 120 - Reinforcing plate; 200 - First substrate; 300 - Isolation layer; X - First direction; Y - Second direction.

[0022] Through the above accompanying drawings, the clear embodiments of the present application have been shown, and there will be more detailed descriptions later. These accompanying drawings and the textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following will describe the technical solutions in the embodiments of this application in more detail with reference to the accompanying drawings in the preferred embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope protected by this application.

[0024] It should be noted that in the description of the embodiments of this application, terms such as "upper", "lower", "inner", "outer", etc., indicating the orientation or positional relationship are based on the directions or positional relationships shown in the drawings. These are only for convenience of description and do not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of this application.

[0025] In addition, it should also be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality" means two or more, unless otherwise specifically defined.

[0026] In this application, unless otherwise clearly specified and limited, terms such as "installation", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or capable of communicating with each other; it can be a direct connection, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] Since the fracture behavior of a double-cantilever beam specimen depends on the material properties of the substrate, in related technologies, when testing the mode-I interlaminar fracture toughness of dissimilar materials, double-cantilever beam specimens are usually made based on the principle of equal bending stiffness using two substrates made of different materials, that is, the two substrates have different materials and thicknesses but the same bending stiffness to test the mode-I interlaminar fracture toughness of dissimilar materials. However, due to the different materials and thicknesses, there is also a mode-II deformation in the above double-cantilever beam specimen during the test, which affects the test results and reduces the accuracy of the mode-I interlaminar fracture toughness test of dissimilar materials.

[0028] In view of this, the present application provides a method for testing the fracture toughness of dissimilar materials, a double cantilever beam specimen, and a manufacturing method thereof. The method for testing the fracture toughness of dissimilar materials includes the step of providing a double cantilever beam specimen. The double cantilever beam specimen includes a matrix layer, a first substrate, and an isolation layer. Matrix layers are provided on both sides of the first substrate in the first direction. An isolation layer is provided between the first substrate and any one of the matrix layers. The isolation layer is used to form an isolation region between the first substrate and the matrix layer adjacent to the isolation layer. The isolation region is a prefabricated crack. The region without the isolation layer between the first substrate and the matrix layer adjacent to the isolation layer forms a region to be tested. With such a setting, the isolation region formed by the isolation layer is used as the starting point for delamination expansion, so as to guide the delamination phenomenon between the first substrate and the matrix layer adjacent to the isolation layer to start from the junction of the isolation region and the region to be tested and expand into the region to be tested along the second direction and towards the region to be tested. Thus, by providing matrix layers on both sides of the first substrate in the first direction, the geometric structure symmetry, material consistency, and bending stiffness balance on both sides of the double cantilever beam specimen in the first direction can be improved, thereby reducing the probability of type II deformation, and further improving the accuracy of the type I interlaminar fracture toughness test of dissimilar materials.

[0029] The following will describe the present application in detail with reference to the accompanying drawings and specific embodiments.

[0030] The present application provides a method for testing the fracture toughness of dissimilar materials. Refer to Figure 1 , including the following steps: S1: The step of providing a double cantilever beam specimen 10. Refer to Figure 3 and Figure 5 , the double cantilever beam specimen 10 includes a matrix layer 100, a first substrate 200, and an isolation layer 300. Matrix layers 100 are provided on both sides of the first substrate 200 in the first direction X. An isolation layer 300 is provided between the first substrate 200 and any one of the matrix layers 100. The matrix layer 100 and the first substrate 200 are fixedly connected. An isolation region and a region to be tested are formed between the first substrate 200 and the matrix layer 100 adjacent to the isolation layer 300 in the second direction Y. The isolation region has a prefabricated crack.

[0031] Among them, the first direction X can be understood as the thickness direction of the double cantilever beam specimen 10, and the second direction Y can be understood as the length direction of the double cantilever beam specimen 10.

[0032] It should be noted that, in order to measure the type I interlaminar fracture toughness of heterogeneous materials, a double cantilever beam specimen 10 is first provided. The double cantilever beam specimen 10 may include two substrate layers 100, and the substrate layer 100 may include steel, unidirectional carbon fiber laminate, etc. One of the two substrate layers 100 may be a first substrate layer 100a, and the other may be a second substrate layer 100b, and the first substrate layer 100a and the second substrate layer 100b are made of the same material. The first substrate 200 may include glass fiber fabric, carbon-glass blended fabric, etc. The first substrate 200 is made of a different material from the substrate layer 100. Among them, the bending stiffness of the substrate layer 100 may be set to be greater than the bending stiffness of the first substrate 200. Thereby, it is helpful to improve the bending stiffness symmetry of the double cantilever beam specimen 10.

[0033] In a specific implementation, the first base layer 100a, the first substrate 200, and the second base layer 100b may be stacked in sequence along the first direction X. Figure 3 and Figure 4 , the isolation layer 300 can be arranged between the first base layer 100a and the first substrate 200, or between the first substrate 200 and the second base layer 100b. Take the isolation layer 300 arranged between the first base layer 100a and the first substrate 200 as an example for explanation. The isolation layer 300 partially isolates the first base layer 100a from the first substrate 200 to form an isolation area. The area between the first base layer 100a and the first substrate 200 where the isolation layer 300 is not arranged can be fixedly connected to form a test area, and the isolation area and the test area are arranged along the second direction Y. The second base layer 100b and the first substrate 200 can also be fixedly connected. The function of the isolation layer 300 is to form a prefabricated crack (i.e., an isolation area) between the first base layer 100a and the first substrate 200, so that during the test process, the delamination between the first base layer 100a and the first substrate 200 (which can also be understood as a crack between the first base layer 100a and the first substrate 200) initiates at the junction of the prefabricated crack and the area to be tested, and expands toward the area to be tested.

[0034] The isolation layer 300 may include a polytetrafluoroethylene film.

[0035] Take the two materials to be tested as co-cured steel and glass fiber fabric as an example, see Figure 6 According to the measurement, the strain energy release rate of the double cantilever beam specimen 10 provided by the present application at the crack tip is 0.1 J / m 2 , which is less than the mode II strain energy release rate of 7.8 J / m at the crack tip of the double cantilever beam specimen 10 in the related art. 2 Due to the influence of the type II shear load, the type I fracture toughness value of the double cantilever beam specimen in the related art is 164.9 J / m 2The mode I fracture toughness value of the double cantilever beam specimen provided in this application is 182.3 J / m 2 .

[0036] Therefore, by providing the base layer 100 on both sides of the first substrate 200 in the first direction X, the geometric structure symmetry, material consistency and bending stiffness balance of the double cantilever beam specimen 10 on both sides in the first direction X can be improved, thereby reducing the probability of type II deformation, and further improving the accuracy of type I interlaminar fracture toughness test of heterogeneous materials.

[0037] S2: Sample testing step, installing the double cantilever beam sample 10 on a testing device, gradually loading the double cantilever beam sample 10 through the testing device to cause stratification in the area to be tested, and obtaining target data.

[0038] The target data includes a plurality of load values ​​applied by the test device to the double cantilever beam specimen 10 and a displacement value corresponding to each load value, wherein the displacement value is an opening displacement value of the double cantilever beam specimen 10 in the loading direction.

[0039] In a specific implementation, the double cantilever beam sample 10 is first installed on the test device. Along the second direction Y, the double cantilever beam sample 10 may have a first end and a second end that are relatively arranged. The first end may be fixedly installed on the fixed end of the test device. The isolation area may be arranged to be arranged close to the first end relative to the area to be tested.

[0040] Illustratively, the testing apparatus may include a tensile testing machine.

[0041] It should be noted that the first end of the double cantilever beam specimen 10 is also connected to a loading block or a piano-style hinge on both sides along the first direction X, and the loading block or the piano-style hinge is also connected to the test device on the side away from the double cantilever beam specimen 10 to achieve loading on the double cantilever beam specimen 10. The test device may also be provided with a latch embedded in the loading block or a fixture clamping the piano-style hinge, so that the first end of the double cantilever beam specimen 10 can rotate relative to the test.

[0042] Specifically, the loading process of the test device can be performed in accordance with the test specification requirements (e.g., ASTM D5528). For example, the test device can load the double cantilever beam specimen 10 at a loading rate of 2 mm / min. The data acquisition system connected to the test device can collect target data at a frequency of 5 Hz, that is, collect the load value and the displacement value corresponding to the load value.

[0043] S3: result calculation step, obtaining the mode I interlaminar fracture toughness value of the double cantilever beam specimen 10 according to the target data.

[0044] It should be noted that after obtaining data such as the width, thickness, delamination length, load value, and displacement value of the double-cantilever beam specimen 10, the mode I interlaminar fracture toughness value of the double-cantilever beam specimen 10 can be calculated according to the calculation formula of the mode I interlaminar fracture toughness value: G Ic

[0045] = Pδ / (2b•a).

[0045]

[0046] Among them, the delamination length of the double-cantilever beam specimen 10 is a, the width of the double-cantilever beam specimen 10 is b, the applied load value is P, and the displacement value of the loading point is δ.

[0047]

[0048] In some embodiments, in the step of providing the double-cantilever beam specimen 10, in the second direction Y, the elastic modulus of the matrix layer 100 is greater than the elastic modulus of the first substrate 200.

[0049] Figure 2 It can be understood that the matrix layer 100 and the first substrate 200 are made of different materials. In order to improve the bending stiffness balance of the double-cantilever beam specimen 10 in the first direction X and reduce the difficulty of obtaining target data, the matrix layer 100 may include the one with a larger elastic modulus along the second direction Y among the two materials to be tested, and the first substrate 200 may include the one with a smaller elastic modulus along the second direction Y among the two materials to be tested. For example, when testing the fracture toughness between steel and fiberglass fabric, the matrix layer 100 includes steel and the first substrate 200 includes fiberglass fabric. Thus, during the loading process, it is convenient to observe the delamination length of the double-cantilever beam specimen 10, so as to collect the load value and displacement value. In other words, if the matrix layer 100 includes the one with a smaller elastic modulus along the second direction Y among the two materials to be tested, and the first substrate 200 includes the one with a larger elastic modulus along the second direction Y among the two materials to be tested, during the loading process, the delamination expansion trend of the double-cantilever beam specimen 10 is relatively fast, which is not conducive to the collection of target data, thus affecting the accuracy of the test results.

[0050] In some embodiments, before the step of specimen testing, referring to

[0050] S4: The heat preservation step of the double-cantilever beam specimen 10, including:

[0050] S41: Place the double-cantilever beam specimen 10 in a constant temperature environment, and determine the heat preservation temperature of the double-cantilever beam specimen 10 according to the actual use environment temperature of the matrix layer 100 and the first substrate 200.

[0050] It should be noted that the double-cantilever beam specimen 10 is thermally insulated according to the materials involved in the matrix layer 100 and the first substrate 200 at the actual operating ambient temperature. That is to say, the insulation temperature can be set to be the same as the actual operating ambient temperature, which can ensure that the double-cantilever beam specimen 10 reaches a stable temperature state before the specimen testing step, thereby reducing the influence of temperature on the test results.

[0051] In addition, by simulating the actual operating ambient temperature to thermally insulate the double-cantilever beam specimen 10, the test results of the mode-I interlaminar fracture toughness value can be made closer to the actual application situation, improving the accuracy and reliability of the test results.

[0052] S42: Keep the double-cantilever beam specimen 10 at a constant temperature for a predetermined duration according to the insulation temperature.

[0053] Among them, the double-cantilever beam specimen 10 can be placed in a thermal insulation structure capable of precisely controlling the temperature, and the temperature of the thermal insulation structure is set according to the insulation temperature to ensure that the double-cantilever beam specimen 10 is under constant temperature conditions during the thermal insulation process.

[0054] The predetermined duration can be determined according to the specific requirements of the test and the material properties of the double-cantilever beam specimen 10 to ensure that the internal temperature distribution of the double-cantilever beam specimen 10 is uniform and reaches a thermally stable state.

[0055] Optionally, the predetermined duration can be set between 2 hours and 10 hours.

[0056] S43: Respectively detect the temperatures of the matrix layer 100 and the first substrate 200 of the double-cantilever beam specimen 10 to ensure that the temperature difference between the matrix layer 100 and the first substrate 200 is within a preset temperature difference range.

[0057] It can be understood that temperature sensors can be used to respectively detect the temperatures of the matrix layer 100 and the first substrate 200. Thus, experimental errors caused by too large a temperature difference between the matrix layer 100 and the first substrate 200 can be avoided.

[0058] Optionally, the preset temperature difference range can be set below 2°C.

[0059] For example, when the materials involved in the matrix layer 100 of the double cantilever beam specimen 10 and the first substrate 200 are applied in the technical field of wind turbine blades, and the actual operating temperature of the wind turbine blades can be between -40°C and 60°C, then the mode I interlaminar fracture toughness values of the double cantilever beam specimen 10 can be tested under the two extreme temperature conditions of -40°C and 60°C. That is to say, the insulation temperature of the double cantilever beam specimen 10 can be set to -40°C for insulation and testing, and then the insulation temperature can be set to 60°C for insulation and testing. Thus, by simulating the actual operating temperature to insulate and test the double cantilever beam specimen 10, the test results of the mode I interlaminar fracture toughness value can be made closer to the actual application situation, improving the accuracy and reliability of the test results. Among them, the predetermined duration can be set between 2 hours and 5 hours.

[0060] In some embodiments, before the specimen testing step, it further includes: measuring the dimensions of the double cantilever beam specimen 10 and making scale markings on the double cantilever beam specimen 10.

[0061] It should be noted that measuring instruments can be used to measure the dimensions of the double cantilever beam specimen 10 to ensure the accuracy of the test results. Optionally, the measuring instruments can include micrometers, vernier calipers, etc. to ensure the precision of the obtained data. Among them, the measured dimensions can include the length, width, and thickness of the double cantilever beam specimen 10.

[0062] In addition, scale markings also need to be made on the double cantilever beam specimen 10. The purpose of the scale markings is to accurately measure the delamination length during the test.

[0063] See Figure 3 and Figure 4 , in some embodiments, the matrix layer 100 includes a second substrate 110. The two second substrates 110 are respectively located on opposite sides of the first substrate 200 in the first direction X, and the isolation layer 300 is disposed between the first substrate 200 and any one of the second substrates 110.

[0064] It can be understood that the first substrate 200 is made of one of the two materials to be tested, and the second substrate 110 is made of the other of the two materials to be tested. The two second substrates 110 are respectively located on opposite sides of the first substrate 200 in the first direction X. Thus, the geometric structure symmetry, material consistency, and bending stiffness balance on both sides of the double cantilever beam specimen 10 in the first direction X can be improved, thereby reducing the probability of type II deformation, and further improving the accuracy of the mode I interlaminar fracture toughness test of dissimilar materials.

[0065] In some embodiments, the elastic modulus of the first substrate 200 is E1, and the elastic modulus of the second substrate 110 is E2, where E2 ≥ 1.4 × E1.

[0066] It is understandable that E2 ≥ 1.4×E1, so that the second substrate 110 has a higher ability to resist deformation compared to the first substrate 200, or under the same deformation conditions, a greater external force is required for the second substrate 110 to produce the same deformation as the first substrate 200. With such a setting, the geometric structure symmetry and bending stiffness balance of the double cantilever beam specimen 10 can be improved.

[0067] Specifically, E2 can be set to 1.5×E1, 1.7×E1, etc., which helps to reduce the difficulty of obtaining target data. In other words, if E2 is set to 1.1×E1, 0.7×E1, the elastic modulus of the second substrate 110 is similar to or less than that of the first substrate 200. Thus, during the loading process, the delamination expansion trend of the double cantilever beam specimen 10 is relatively fast, which is not conducive to the acquisition of target data, thereby affecting the accuracy of the test results.

[0068] In some other embodiments, along the first direction X, the thickness of the first substrate 200 is h1, and the thickness of the second substrate 110 is h2, where h2 ≥ 2.3×h1.

[0069] It should be noted that h2 ≥ 2.3×h1 helps to improve the geometric structure symmetry of the double cantilever beam specimen 10. That is to say, if h2 is set to 1.2×h1, 1.4×h2, the thickness of the second substrate 110 is similar to that of the first substrate 200. Thus, the symmetry of the double cantilever beam specimen 10 will decrease, thereby affecting the accuracy of the test results.

[0070] See Figure 5 , in some embodiments, the matrix layer 100 includes a second substrate 110 and a reinforcing plate 120. Along the first direction X, the second substrate 110 is disposed closer to the first substrate 200 than the reinforcing plate 120, and the isolation layer 300 is disposed between the first substrate 200 and any second substrate 110.

[0071] It should be noted that the first substrate 200 can be made of one of the two materials to be tested, and the second substrate 110 can be made of the other of the two materials to be tested. When the elastic moduli of the two materials to be tested are similar and small, that is, when the elastic moduli of the first substrate 200 and the second substrate 110 are similar and small, a reinforcing plate 120 can be added to provide support for the first substrate 200 and the second substrate 110. While improving the geometric structure symmetry, material consistency, and bending stiffness balance on both sides of the double cantilever beam specimen 10 in the first direction X, it can avoid the delamination expansion trend of the double cantilever beam specimen 10 from being too fast. Thus, the difficulty of obtaining target data can be reduced, and the reliability and accuracy of the test results can be improved.

[0072] In some embodiments, the elastic modulus of the first substrate 200 is E1, and the elastic modulus of the reinforcing plate 120 is E3, where E3 ≥ 1.4 × E1.

[0073] Thereby, the reinforcing plate 120 has a higher ability to resist deformation compared to the first substrate 200. That is to say, under the action of the same external force, the deformation tendency of the reinforcing plate 120 relative to the first substrate 200 is smaller. With such a setting, the geometric structure symmetry and bending stiffness of the double-cantilever beam specimen 10 can be improved.

[0074] Exemplarily, E3 can be set to 1.6 × E1, 1.9 × E1, etc., which helps to improve the bending stiffness on both sides of the double-cantilever beam specimen 10 in the first direction X and reduces the difficulty of collecting target data. In other words, if E3 is set to 1.2 × E1, 0.8 × E1, the elastic modulus of the reinforcing plate 120 is similar to or less than the elastic modulus of the first substrate 200. Thereby, during the loading process, the delamination expansion trend of the double-cantilever beam specimen 10 is relatively fast, which is not conducive to the collection of target data.

[0075] In other embodiments, along the first direction X, the thickness of the first substrate 200 is h1, and the thickness of the reinforcing plate 120 is h3, where h3 ≥ 2.3 × h1.

[0076] Such a setting helps to improve the geometric structure symmetry of the double-cantilever beam specimen 10. That is to say, if h2 is set to 1.2 × h1, 1.4 × h2, the thickness of the second substrate 110 is relatively close to the thickness of the first substrate 200. Thereby, the symmetry of the double-cantilever beam specimen 10 will decrease.

[0077] In some embodiments, along the first direction X, the thickness of the first substrate 200 is h1, and the thickness of the isolation layer 300 is h4, where h4 ≤ 0.1 × h1.

[0078] In order to simulate the delamination cracks generated between two materials to be tested in actual applications and reduce the influence on the first substrate 200 and the second substrate 110 to ensure the accuracy of the test results, the thickness h4 of the isolation layer 300 can be set to be less than or equal to 0.1 × h1.

[0079] Based on the above embodiments, an embodiment of the present application provides a double-cantilever beam specimen 10, see Figures 3 to 5, comprising a base layer 100, a first substrate 200, and an isolation layer 300. Base layer 100. The base layer 100 is disposed on both sides of the first substrate 200 in the first direction X. The isolation layer 300 is disposed between the first substrate 200 and any base layer 100. In which, along the second direction Y, the extension length of the isolation layer 300 is less than the extension length of the first substrate 200, and along the first direction X, the isolation layer 300 and the first substrate 200 are stacked so that an isolation area and a test area are formed between the first substrate 200 and the base layer 100 adjacent to the isolation layer 300 in the second direction Y, and the first direction X and the second direction Y are intersecting.

[0080] By providing two base layers 100 in plate-like structures and symmetrically arranging them along the first direction X, the uniformity and symmetry of the double cantilever beam specimen 10 when subjected to force are ensured, which is beneficial to improving the accuracy and reliability of the test.

[0081] Secondly, the first substrate 200 is sandwiched between the two base layers 100, and the isolation layer 300 is provided to achieve effective isolation between one end of the first substrate 200 in the second direction Y and any base layer 100, so as to form an isolation area and a test area between the first substrate 200 and the base layer 100 adjacent to the isolation layer 300 in the second direction Y. The function of the isolation layer 300 is to form a prefabricated crack (i.e., the isolation area) between the first base layer 100a and the first substrate 200, so that the delamination between the first base layer 100a and the first substrate 200 (which can also be understood as the crack between the first base layer 100a and the first substrate 200) during the test process is initiated at the junction of the prefabricated crack and the test area, and expands to the test area.

[0082] Based on the above embodiment, the present application embodiment provides a method for manufacturing a double cantilever beam specimen, which is applied to the double cantilever beam specimen provided in the above embodiment, see Figure 7 ,include: S101: Lay one of the two base layers 100 in a sample preparation mold.

[0083] It should be noted that, when the base layer 100 includes a metal material, a surface treatment device may be used to perform surface treatment on the base layer 100 before laying the base layer 100. For example, when the base layer 100 includes steel, a dry vacuum sandblasting machine may be used to perform sandblasting on the base layer 100. In specific implementation, a spray pressure of 0.5 MPa may be used for 10 seconds to increase the roughness of the surface of the base layer 100. This arrangement is intended to improve the adhesion of the base layer 100.

[0084] Further, after sandblasting, the substrate layer 100 can be placed in an oven at 100 °C for drying. The drying time can be 30 to 40 minutes to ensure that the substrate layer 100 is completely dry. After being taken out of the oven, the substrate layer 100 is cooled to room temperature and left for 12 to 15 hours. Then, the substrate layer 100 is laid in a specimen production mold.

[0085] S102: Lay the first substrate 200 and the isolation layer 300 in the specimen production mold according to a predetermined laying order.

[0086] It can be understood that one of the two substrate layers 100 can be the first substrate layer 100a and the other can be the second substrate layer 100b. Taking the example of laying the second substrate layer 100b in the specimen production mold first, the predetermined laying order can be to lay the first substrate 200 first and then the isolation layer 300 so that the isolation layer 300 is located between the first substrate 200 and the first substrate layer 100a. Or it can be to lay the isolation layer 300 first and then the first substrate 200 so that the isolation layer 300 is located between the first substrate 200 and the second substrate layer 100b.

[0087] Wherein, when the first substrate 200 includes a fiberglass fabric, the fiber direction of the fiberglass fabric can be set parallel to the width direction or the length direction of the double cantilever beam specimen 10 itself, and specifically can be set according to the actual application scenario of the fiberglass fabric.

[0088] It should be noted that when the first substrate 200 includes a fiberglass fabric, the fiberglass fabric is usually arranged in multiple layers. Before laying the first substrate 200 and the isolation layer 300, the multiple layers of fiberglass fabric need to be impregnated and cured, and then the combination of the fiberglass fabric and the isolation layer 300 is cut, and a part of the isolation layer 300 is reserved. The isolation layer 300 can include a polytetrafluoroethylene film.

[0089] S103: Lay the other of the two substrate layers 100 in the specimen production mold, and the two substrate layers 100 are symmetrically arranged along the first direction X.

[0090] S104: Connect the substrate layer 100 and the first substrate 200.

[0091] After laying the other of the two substrate layers 100 in the specimen production mold to cover the first substrate 200 and the isolation layer 300, a vacuum-assisted resin infusion molding process can be used to infuse resin into the specimen production mold to bond and cure the substrate layer 100 and the first substrate 200 to form the double cantilever beam specimen 10. That is to say, by infusing resin, the two substrate layers 100 can be bonded and cured to the first substrate 200 except for the area where the isolation layer 300 is laid.

[0092] Among them, the resin may include epoxy resin. Specifically, the double cantilever beam specimen 10 can be cured at 70 °C for 3 hours.

[0093] Among them, along the second direction Y, the isolation layer 300 starts from one end of the first substrate 200 and extends a predetermined length toward the other end of the first substrate 200, so as to form an isolation area between the matrix layer 100 adjacent to the isolation layer 300 and the first substrate 200.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for testing the fracture toughness of dissimilar materials, characterized in that, Including the following steps: Step of providing a double cantilever beam specimen (10), the double cantilever beam specimen (10) includes a matrix layer (100), a first substrate (200) and an isolation layer (300), the matrix layer (100) is provided on both sides of the first substrate (200) in the first direction (X), an isolation layer (300) is provided between the first substrate (200) and any one of the matrix layers (100), the matrix layer (100) and the first substrate (200) are fixedly connected, an isolation area and a to-be-tested area are formed between the first substrate (200) and the matrix layer (100) adjacent to the isolation layer (300) in the second direction (Y), and the isolation area has a prefabricated crack; Step of specimen testing, installing the double cantilever beam specimen (10) on a testing device, gradually loading the double cantilever beam specimen (10) through the testing device to cause delamination in the to-be-tested area, and obtaining target data; Step of result calculation, obtaining the mode I interlaminar fracture toughness value of the double cantilever beam specimen (10) according to the target data.

2. The method for testing the fracture toughness of dissimilar materials according to claim 1, wherein In the step of providing the double cantilever beam specimen (10), in the second direction (Y), the elastic modulus of the matrix layer (100) is greater than the elastic modulus of the first substrate (200).

3. The method for testing the fracture toughness of dissimilar materials according to claim 1, characterized in that, The target data includes a plurality of load values applied by the testing device to the double cantilever beam specimen (10) and displacement values corresponding to each of the load values one by one, and the displacement value is the opening displacement value of the double cantilever beam specimen (10) in the loading direction.

4. The method for testing the fracture toughness of dissimilar materials according to claim 1, characterized in that Before the step of specimen testing, it further includes a heat preservation step of the double cantilever beam specimen (10), including: Placing the double cantilever beam specimen (10) in a constant temperature environment, and determining the heat preservation temperature of the double cantilever beam specimen (10) according to the actual use environment temperature of the matrix layer (100) and the first substrate (200); Keeping the double cantilever beam specimen (10) at a constant temperature for a predetermined time according to the heat preservation temperature; Respectively monitoring the temperatures of the matrix layer (100) and the first substrate (200) of the double cantilever beam specimen (10) to ensure that the temperature difference between the matrix layer (100) and the first substrate (200) is within a preset temperature difference range.

5. The method for testing the fracture toughness of dissimilar materials according to claim 1, characterized in that Before the step of specimen testing, it further includes: measuring the size of the double cantilever beam specimen (10) and making scale marks on the double cantilever beam specimen (10).

6. The method for testing the fracture toughness of dissimilar materials according to claim 1, wherein The matrix layer (100) includes a second substrate (110), and the two second substrates (110) are respectively located on opposite sides of the first substrate (200) in the first direction (X), and the isolation layer (300) is provided between the first substrate (200) and any one of the second substrates (110).

7. The method for testing the fracture toughness of dissimilar materials according to claim 6, characterized in that, The elastic modulus of the first substrate (200) is E1, and the elastic modulus of the second substrate (110) is E2, where E2≥1.4×E1; And / or, along the first direction (X), the thickness of the first substrate (200) is h1, and the thickness of the second substrate (110) is h2, where h2 ≥ 2.3×h1.

8. The method for testing the fracture toughness of dissimilar materials according to claim 1, characterized in that, The matrix layer (100) includes a second substrate (110) and a reinforcing plate (120). Along the first direction (X), the second substrate (110) is disposed closer to the first substrate (200) than the reinforcing plate (120). The isolation layer (300) is disposed between the first substrate (200) and any one of the second substrates (110).

9. The method for testing the fracture toughness of dissimilar materials according to claim 8, wherein The elastic modulus of the first substrate (200) is E1, and the elastic modulus of the reinforcing plate (120) is E3, where E3 ≥ 1.4×E1; And / or, along the first direction (X), the thickness of the first substrate (200) is h1, and the thickness of the reinforcing plate (120) is h3, where h3 ≥ 2.3×h1.

10. The method for testing the fracture toughness of dissimilar materials according to any one of claims 1 to 9, characterized in that, Along the first direction (X), the thickness of the first substrate (200) is h1, and the thickness of the isolation layer (300) is h4, where h4 ≤ 0.1×h1.

11. A double cantilever beam specimen, characterized in that, Comprising: A matrix layer (100); A first substrate (200), with the matrix layer (100) disposed on both sides of the first substrate (200) in the first direction (X); An isolation layer (300), disposed between the first substrate (200) and any one of the matrix layers (100); Wherein, along the second direction (Y), the extension length of the isolation layer (300) is less than the extension length of the first substrate (200), and along the first direction (X), the isolation layer (300) and the first substrate (200) are stacked, so that an isolation area and a test area are formed between the first substrate (200) and the matrix layer (100) adjacent to the isolation layer (300) in the second direction (Y). The first direction (X) and the second direction (Y) intersect.

12. A manufacturing method of a double cantilever beam specimen, applied to the double cantilever beam specimen as described in claim 11, characterized in that, Comprising: Laying one of the two matrix layers (100) in a specimen production mold; Laying the first substrate (200) and the isolation layer (300) in the specimen production mold according to a predetermined laying sequence; Laying the other of the two matrix layers (100) in the specimen production mold, and the two matrix layers (100) are symmetrically disposed along the first direction (X); Connecting the matrix layer (100) and the first substrate (200); Wherein, along the second direction (Y), the isolation layer (300) extends a predetermined length from one end of the first substrate (200) towards the other end of the first substrate (200), so as to form the isolation area between the matrix layer (100) adjacent to the isolation layer (300) and the first substrate (200).

Images