Graphite bipolar plate adhesion performance testing device and testing method

Abstract

The application discloses a graphite bipolar plate bonding performance testing device and a testing method. The testing device comprises: an auxiliary slide group for fixing a to-be-tested sample cut from a graphite bipolar plate, having an upper auxiliary slide and a lower auxiliary slide, and bonding glue layers are arranged on opposite surfaces of the upper auxiliary slide and the lower auxiliary slide; a clamp tool comprising an upper pull claw and a lower pull claw, the upper pull claw being used for hooking the upper auxiliary slide, and the lower pull claw being used for hooking the lower auxiliary slide; and a testing machine for applying a pulling force; wherein the upper auxiliary slide is fixedly bonded with one side of the to-be-tested sample through the bonding glue layer, the lower auxiliary slide is fixedly bonded with the other side of the to-be-tested sample through the bonding glue layer, and the testing machine is connected to the upper auxiliary slide through the upper pull claw and connected to the lower auxiliary slide through the lower pull claw to apply a pulling force to the to-be-tested sample. The testing device and the testing method provided by the application can realize stable clamping of the bonded sample and obtain repeatable and quantifiable bonding strength data in cooperation with the testing machine.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a testing device and method for testing the bonding performance of graphite bipolar plates. Background Technology

[0002] Graphite bipolar plates are one of the core components of proton exchange membrane fuel cell stacks, offering advantages such as good conductivity, light weight, and low cost. In practical applications, graphite bipolar plates are typically made by bonding two graphite plates together with an adhesive layer. The bonding performance directly affects the sealing reliability of the bipolar plate, thus determining the safety and service life of the entire fuel cell stack.

[0003] Currently, the industry primarily relies on airtightness testing to evaluate the bonding performance of graphite bipolar plates. This method involves introducing pressurized gas into the bipolar plate to detect leaks. However, airtightness testing can only detect existing through-hole defects at the bonding interface; it cannot quantify the true bonding strength, nor can it assess the degradation trend of bonding performance under conditions such as long-term vehicle operation, temperature and humidity cycling, and vibration and shock. In other words, airtightness testing is a qualitative screening method for pass / fail, lacking the ability to quantitatively characterize bonding quality. On the other hand, while pull-out force testing, commonly used in material mechanical property testing, can provide quantitative strength data, it is difficult to directly apply to graphite bipolar plates. The fundamental reason is that graphite bipolar plates are thin, brittle, and have a narrow bonding area, making it impossible to hold them with conventional mechanical clamps without slippage or sample damage.

[0004] Therefore, it is necessary to propose a technical solution to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, this invention proposes a special testing device for the bonding performance of graphite bipolar plates, which can stably clamp the bonded sample and obtain repeatable and quantifiable bonding strength data in conjunction with a testing machine.

[0006] This invention is achieved through the following technical solution: a graphite bipolar plate bonding performance testing device, comprising: An auxiliary slide assembly is used to fix the sample to be tested cut from a graphite bipolar plate. The auxiliary slide assembly includes an upper auxiliary slide and a lower auxiliary slide, and an adhesive layer is respectively provided on the opposite surfaces of the upper auxiliary slide and the lower auxiliary slide. The fixture includes an upper pull jaw and a lower pull jaw, the upper pull jaw being used to hook the upper auxiliary carrier piece, and the lower pull jaw being used to hook the lower auxiliary carrier piece; and... Testing machine, used to apply tensile force; The upper auxiliary carrier is bonded to one side of the sample to be tested via an adhesive layer, and the lower auxiliary carrier is bonded to the other side of the sample to be tested via an adhesive layer. The testing machine is connected to the upper auxiliary carrier via an upper pull claw and to the lower auxiliary carrier via a lower pull claw to apply a pull-out force to the sample to be tested.

[0007] As a further improved technical solution, both the upper auxiliary piece and the lower auxiliary piece are metal plates.

[0008] As a further improved technical solution, adhesive grooves are respectively provided on the opposite surfaces of the upper auxiliary carrier and the lower auxiliary carrier, and the adhesive layer is disposed in the adhesive grooves. The area of ​​the adhesive grooves is smaller than the area of ​​the sample to be tested and is completely covered by the sample to be tested.

[0009] As a further improved technical solution, the two ends of the upper auxiliary carrier extend beyond the sample to be tested, the upper pull claw has an upper hook portion, the upper pull claw is installed from the two ends of the upper auxiliary carrier and hooked to the lower surface of the upper auxiliary carrier through the upper hook portion; the two ends of the lower auxiliary carrier extend beyond the sample to be tested, the lower pull claw has a lower hook portion, the lower pull claw is installed from the two ends of the lower auxiliary carrier and hooked to the upper surface of the upper auxiliary carrier through the lower hook portion.

[0010] As a further improved technical solution, the upper pull claw is provided with an upper clearance groove for the lower hook to be inserted, and the lower pull claw is correspondingly provided with a lower clearance groove for the upper hook to be inserted. The upper hook and the lower hook have a complementary tenon and mortise structure.

[0011] This invention is also achieved through the following technical solution: a method for testing the bonding performance of graphite bipolar plates, wherein the testing method uses the testing device described above, and the testing method includes the following steps: S1. Cut the sample to be tested, including the adhesive region, from the graphite bipolar plate; S2. Fix the sample to be tested between the auxiliary slides using the adhesive layer; S3. The adhesive layer is cured to form an integrated test unit with the sample to be tested, the upper auxiliary carrier, and the lower auxiliary carrier. S4. Connect the test unit to the testing machine through the fixture, so that the upper pull claw hooks onto the upper auxiliary carrier and locks it, and the lower pull claw hooks onto the lower auxiliary carrier and locks it. S5. Start the testing machine and apply a pull-out force to the test unit.

[0012] As a further improved technical solution, the sample to be tested cut in step S1 is a rectangular piece with a length of 30-50 mm and a width of 30-50 mm.

[0013] As a further improved technical solution, in step S2, the adhesive layer is applied to the adhesive groove provided on the upper auxiliary carrier and the lower auxiliary carrier. The adhesive groove has a length of 20-30 mm, a width of 20-30 mm, and a depth of 0.3-0.8 mm. The adhesive layer is epoxy resin adhesive, and the application amount is 0.3-0.6 g.

[0014] As a further improved technical solution, in step S3, the curing conditions are: curing in an oven at 95-110°C for more than 1.5 hours.

[0015] As a further improved technical solution, in step S3, during the curing process, a pressure of 2-5 kg ​​is also applied to the auxiliary carrier group and the sample to be tested.

[0016] The graphite bipolar plate bonding performance testing device provided by this invention, by setting upper and lower auxiliary carriers and forming adhesive layers on their opposite surfaces, can stably and centrally fix the brittle and thin graphite bipolar plate test sample, which is difficult to clamp directly, between the auxiliary carriers. Furthermore, with the help of dedicated upper and lower pull claws, the auxiliary carriers are reliably connected to the testing machine, thus successfully applying the traditional pull-out test method to the quantitative evaluation of the bonding performance of graphite bipolar plates. This device overcomes the technical bias that graphite sheets cannot be tensile tested, not only avoiding the problem of sample slippage or damage during conventional clamping, but also obtaining repeatable and comparable bonding strength data. It provides a scientific and quantitative testing method for bipolar plate process development, batch quality inspection, and durability assessment, overcoming the technical limitation of existing airtightness tests that can only qualitatively determine leakage defects and cannot characterize the true bonding strength. Attached Figure Description

[0017] Figure 1 This is a partial three-dimensional assembly diagram of an embodiment of the graphite bipolar plate bonding performance testing device of the present invention.

[0018] Figure 2 for Figure 1 Side view of the component shown.

[0019] Figure 3 for Figure 1 Exploded view of the component shown.

[0020] Figure 4 This is a diagram showing the combination of the auxiliary carrier group and the sample to be tested in one embodiment of the graphite bipolar plate bonding performance testing device of the present invention.

[0021] Figure 5 This is a flowchart of an embodiment of the graphite bipolar plate bonding performance testing method of the present invention.

[0022] Explanation of reference numerals: 11. Upper auxiliary carrier; 12. Lower auxiliary carrier; 121. Adhesive tank; 13. Upper adhesive layer; 14. Lower adhesive layer; 21. Upper pull claw; 211. Upper hook; 22. Lower pull claw; 221. Lower hook; 31. Upper connecting block; 32. Lower connecting block; 41. Upper locking element; 42. Lower locking element; 51. Upper fitting; 52. Lower fitting; 6. Sample to be tested; 61. Upper electrode plate; 62. Lower electrode plate; 63. Adhesive area. Detailed Implementation

[0023] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Please refer to Figures 1 to 4 This invention provides a graphite bipolar plate bonding performance testing device for quantitatively testing the bonding strength of graphite bipolar plates used in fuel cells. The device mainly includes an auxiliary substrate assembly, a fixture, and a testing machine (not shown in the figures). The auxiliary substrate assembly is used to fix the test sample 6 cut from the graphite bipolar plate. The fixture connects the auxiliary substrate assembly to the testing machine, which applies a pull-out force and provides force data. Through the coordinated operation of these components, this testing device can successfully apply traditional pull-out testing methods to brittle, thin, and difficult-to-grip graphite bipolar plate samples.

[0026] Specifically, the auxiliary slide assembly includes an upper auxiliary slide 11 and a lower auxiliary slide 12. The upper auxiliary slide 11 and lower auxiliary slide 12 are positioned opposite each other, above and below the sample 6 to be tested, respectively. Adhesive layers are provided on the opposing surfaces of the upper auxiliary slide 11 and lower auxiliary slide 12; specifically, the lower surface of the upper auxiliary slide 11 has an upper adhesive layer 13, and the upper surface of the lower auxiliary slide 12 has a lower adhesive layer 14. In actual operation, one side of the sample 6 to be tested, such as the upper surface, is bonded and fixed to the upper auxiliary slide 11 via the upper adhesive layer 13, and the other side of the sample 6 to be tested, such as the lower surface, is bonded and fixed to the lower auxiliary slide 12 via the lower adhesive layer 14. This arrangement provides the sample 6 to be tested with two rigid components that are easy to clamp or hook externally. Because graphite bipolar plates are thin, brittle, and have a narrow bonding area, conventional mechanical clamps cannot directly hold such samples without slippage or damage. By using the auxiliary carrier set described above, the sample 6 to be tested is fixed between two rigid carriers by bonding, avoiding the risks associated with directly applying clamping force to the graphite plate, making pull-out testing possible. Simultaneously, the presence of the auxiliary carriers ensures that the pull-out force is evenly distributed to the bonding interface of the sample 6, preventing stress concentration and thus guaranteeing the accuracy and repeatability of the test results.

[0027] In this embodiment, both the upper auxiliary carrier 11 and the lower auxiliary carrier 12 are metal plates. Metal materials possess high strength and rigidity, enabling them to maintain their shape without significant deformation during the pull-out test, thus ensuring that the pull-out force is efficiently and stably transmitted to the bonding interface of the sample 6 under test. If the auxiliary carrier is made of a material with lower strength, it may bend or warp under the pull-out force, causing some of the tensile force to be absorbed by the carrier deformation, resulting in a pull-out force value measured by the testing machine that is lower than the true strength of the bonding interface. Therefore, using metal plates as auxiliary carriers can maximize the reproduction of the true tensile force borne by the bonding interface and improve test accuracy. In this embodiment, both the upper auxiliary carrier 11 and the lower auxiliary carrier 12 are stainless steel. In one embodiment, their dimensions are defined as 100mm long, 52mm wide, and 2mm thick.

[0028] Furthermore, to prevent the adhesive from overflowing into the non-bonded areas of the sample 6 (e.g., the surface of the graphite plate) during the bonding process, and also to precisely control the application position and amount of adhesive, the present invention provides adhesive-containing grooves 121 on the opposing surfaces of the upper auxiliary carrier 11 and the lower auxiliary carrier 12. Specifically, the lower surface of the upper auxiliary carrier 11 has an upper adhesive-containing groove, and the upper surface of the lower auxiliary carrier 12 has a lower adhesive-containing groove. For simplicity, the adhesive-containing groove 121 on the lower auxiliary carrier 12 is shown as an example in the accompanying drawings; the structure of the upper adhesive-containing groove is similar. The adhesive layers are respectively disposed in the corresponding adhesive-containing grooves, specifically the upper adhesive layer 13 and the lower adhesive layer 14. The area of ​​the adhesive-containing groove 121 is designed to be smaller than the area of ​​the sample 6 to be tested, and after bonding, the sample 6 to be tested can completely cover the adhesive-containing groove 121. The adhesive reservoir 121 provides a space to hold the adhesive, preventing it from being squeezed out under pressure and overflowing onto the edge or surface of the sample 6 under test, contaminating the graphite plate surface, affecting subsequent tests, or causing deviations in test results. Furthermore, since the area of ​​the adhesive reservoir 121 is smaller than that of the sample 6 under test, the edge of the sample 6 extends beyond the boundary of the reservoir 121. This allows the peripheral area of ​​the sample 6 to directly contact the surface of the auxiliary carrier, forming a sealing ring effect and further preventing adhesive overflow. Additionally, the depth of the adhesive reservoir 121 limits the thickness of the adhesive layer, ensuring that the adhesive layer thickness is basically consistent for each test, thereby reducing fluctuations in test results caused by differences in adhesive layer thickness and improving the consistency and comparability of the tests. In this embodiment, the sample 6 under test is a rectangular piece with a length of 30–50 mm and a width of 30–50 mm. The adhesive reservoir 121 has a length of 20–30 mm, a width of 20–30 mm, and a depth of 0.3–0.8 mm, specifically, for example, a length and width of 25 mm and a depth of 0.5 mm. The adhesive layer is an epoxy resin adhesive, and the coating amount is 0.3 to 0.6g, specifically 0.4g, 0.5g, etc.

[0029] The fixture includes an upper pull claw 21 and a lower pull claw 22. The upper pull claw 21 is used to hook the upper auxiliary carrier 11, and the lower pull claw 22 is used to hook the lower auxiliary carrier 12. To achieve stable and centered hooking, the present invention optimizes the mating structure between the upper auxiliary carrier 11, the lower auxiliary carrier 12, and the upper pull claw 21 and the lower pull claw 22. Specifically, the two sides of the upper auxiliary carrier 11 extend beyond the corresponding edges of the sample 6 to be tested, that is, the lateral dimension of the upper auxiliary carrier 11 is larger than the lateral dimension of the sample 6 to be tested, so that the left and right sides of the upper auxiliary carrier 11 form a suspended portion beyond the sample 6 to be tested. Similarly, the two sides of the lower auxiliary carrier 12 also extend beyond the sample 6 to be tested. The upper pull claw 21 has an upper hooking portion 211, which is installed from the two sides of the upper auxiliary carrier 11 and hooked onto the lower surface of the upper auxiliary carrier 11 by the upper hooking portion 211. Meanwhile, the pull-down claw 22 has a lower hook portion 221. The pull-down claw 22 is installed from both ends of the lower auxiliary carrier 12 and hooks onto the upper surface of the lower auxiliary carrier 12 via the lower hook portion 221. It should be noted that since the upper auxiliary carrier 11 and the lower auxiliary carrier 12 are arranged opposite each other in the vertical direction, there is a certain gap between them. Therefore, the upper pull-down claw 21 hooks onto the lower surface of the upper auxiliary carrier 11, and the pull-down claw 22 hooks onto the upper surface of the lower auxiliary carrier 12. In this way, when the testing machine pulls the upper pull-down claw 21 upward and pulls the lower pull-down claw 22 downward, or fixes the lower pull-down claw 22 and pulls the upper pull-down claw 21 upward, a pure pull-out force state can be formed on the test sample 6 clamped in the middle, that is, the direction of the pull force is perpendicular to the bonding interface. Compared with the clamping method, this hooking method avoids the clamping force on the side or upper surface of the auxiliary carrier being transmitted to the test sample 6, generating additional shear or bending stress, and ensures that the test results only reflect the tensile strength of the bonding interface.

[0030] Furthermore, to ensure that the upper pull claw 21 and the lower pull claw 22 can simultaneously hook onto their respective auxiliary carriers within a limited space without interfering with each other, the present invention employs an ingenious avoidance design in the structure of the upper pull claw 21 and the lower pull claw 22. Specifically, the upper pull claw 21 has an upper avoidance groove for the lower hooking portion 221 of the lower pull claw 22 to be inserted, and correspondingly, the lower pull claw 22 has a lower avoidance groove for the upper hooking portion 211 of the upper pull claw 21 to be inserted. With this arrangement, the upper hooking portion 211 and the lower hooking portion 221 exhibit a complementary mortise and tenon structure after assembly, that is, they interlock in the vertical direction and embed into each other in the horizontal direction. This design allows for the simultaneous installation of the upper pull claw 21 and the lower pull claw 22 within a limited space, avoiding the need to increase the size of the device due to structural conflicts. Secondly, the mortise and tenon complementary structure enables the upper pull claw 21 and the lower pull claw 22 to automatically center during the pulling process. That is, when the testing machine applies a pulling force, the upper pull claw 21 and the lower pull claw 22 will automatically adjust to the position with the most balanced force along the direction of the pulling force, thereby ensuring that the line of action of the pulling force passes through the center of the sample 6 under test, avoiding the generation of eccentric torque that would cause the adhesive interface to tear first, affecting the accuracy of the test results. Finally, this structure also facilitates the quick installation and removal of samples by operators, improving testing efficiency.

[0031] In actual testing, the fixture needs to be connected to the testing machine. Therefore, this invention may also include an upper connecting block 31 and a lower connecting block 32. One end of the upper connecting block 31 is fixedly connected to the upper pull claw 21 via an upper locking member 41, and the other end of the upper connecting block 31 is connected to the upper chuck of the testing machine via an upper fitting 51. Similarly, one end of the lower connecting block 32 is fixedly connected to the lower pull claw 22 via a lower locking member 42, and the other end of the lower connecting block 32 is connected to the lower chuck of the testing machine via a lower fitting 52. In this embodiment, the upper locking member 41 and the lower locking member 42 are hand-tightening swivel nuts. The above connection structures are all conventional mechanical connection methods. Those skilled in the art can adapt the design according to the interface form of the actual testing machine, as long as the stability and coaxiality of the tensile force transmission can be guaranteed.

[0032] Please refer to Figure 5 and combined Figures 1 to 4 The present invention also provides a method for testing the bonding performance of graphite bipolar plates, which uses the testing device described in any of the above embodiments and includes the following steps S1 to S5.

[0033] Step S1: Cut the test sample 6 containing the adhesive region from the graphite bipolar plate. In practice, the graphite bipolar plate to be tested needs to be prepared first. The graphite bipolar plate is usually composed of an upper plate 61, a lower plate 62, and an adhesive region 63 located between them. The adhesive region 63 is the part whose adhesive performance needs to be tested. Using a cutting tool, such as a cutting machine or laser cutter, cut a sample containing the adhesive region 63 from the graphite bipolar plate as the test sample 6. To ensure the representativeness of the test results, the cutting location should be selected in an area of ​​the bipolar plate with a typical adhesive structure, avoiding the selection of edges or areas with obvious defects. The shape and size of the test sample 6 can be selected according to actual needs, but to ensure the consistency and comparability of the test, it is usually cut into a regular rectangular piece. For example, the length and width of the test sample 6 can be controlled between 30mm and 50mm. This size range is the preferred range proven in practice: if the sample size is too small, the bonding area is insufficient, resulting in poor representativeness of the test results, and small samples are more prone to edge defects during cutting and bonding; if the sample size is too large, the required auxiliary carrier size also increases, leading to increased testing costs. Furthermore, large samples are more susceptible to warping and deformation due to thermal stress during curing, affecting the accuracy of the test results. Therefore, controlling the sample size within the above range achieves a good balance between test representativeness, operational convenience, and cost control. Samples within this size range can fully encompass the adhesive area 63, facilitate subsequent bonding with the auxiliary carrier, and avoid the need for excessively large auxiliary carriers due to excessively large samples, thus preventing increased testing costs. During cutting, care should be taken to keep the sample edges smooth to avoid micro-cracks or burrs, which could affect the bonding effect or cause stress concentration.

[0034] Step S2: Fix the sample 6 to be tested between the auxiliary carriers using adhesive layers. Specifically, the operator first applies an appropriate amount of adhesive to the adhesive groove of the upper auxiliary carrier 11 to form an upper adhesive layer 13; and applies an appropriate amount of adhesive to the adhesive groove of the lower auxiliary carrier 12 to form a lower adhesive layer 14. Then, the sample 6 to be tested is placed on the upper surface of the lower auxiliary carrier 12, ensuring that the sample 6 completely covers the lower adhesive groove 121, i.e., the boundary of the lower adhesive groove 121 is within the boundary of the sample 6 and centered. Next, the upper auxiliary carrier 11 is placed over the sample 6 to be tested, so that the upper adhesive groove is also completely covered by the sample 6, and the upper auxiliary carrier 11 and the lower auxiliary carrier 12 are approximately aligned. To ensure bonding quality, the adhesive layer should be applied evenly to avoid air bubbles or voids. Epoxy resin adhesive can be selected as the bonding agent. This type of adhesive has advantages such as high bonding strength, low shrinkage after curing, and good temperature and moisture resistance, making it very suitable for bonding graphite materials. The coating amount can be controlled according to the volume of the adhesive container, for example, between 0.3g and 0.6g, to ensure that the adhesive layer is fully filled without overflowing. It should be noted that because the area of ​​the adhesive container is smaller than the area of ​​the test sample 6, even if the coating amount fluctuates slightly, excess adhesive will be confined within the container or blocked by the edges of the test sample 6, preventing it from overflowing onto the upper or lower surface of the test sample 6. This ensures the cleanliness of the test sample and the consistency of the test results.

[0035] Step S3: Curing the adhesive layer to form an integrated test unit with the test sample 6, upper auxiliary carrier 11, and lower auxiliary carrier 12. After assembling the test sample 6 and the auxiliary carriers, the adhesive layer needs to be cured to transform it from a liquid or paste state to a solid state, thereby generating sufficient bond strength. Curing is typically performed in an oven. The assembled test unit is placed inside the oven, and an appropriate temperature and time are set. For example, the oven temperature can be set to 95°C to 110°C, and the curing time to be at least 1.5 hours. This temperature range ensures sufficient curing of the epoxy resin adhesive without adversely affecting the material properties of the graphite bipolar plate due to excessive temperature. The curing time can be adjusted appropriately according to the technical parameters provided by the adhesive supplier to ensure complete curing. During the curing process, a certain pressure needs to be applied to the auxiliary carrier assembly and the test sample 6 to ensure tight contact at the bonding interface and to remove excess adhesive and air bubbles. Specifically, a weight, such as a counterweight, can be placed on the upper surface of the upper auxiliary carrier 11, or a clamp can be used to apply a pressure of 2 kg to 5 kg. This pressure range ensures sufficient contact at the bonding interface without causing the test sample 6 to bend or deform due to excessive pressure, or causing excessive extrusion of adhesive leading to insufficient adhesive. After the above curing treatment, the test sample 6 is firmly bonded to the upper auxiliary carrier 11 and the lower auxiliary carrier 12, forming an inseparable whole, namely the test unit. In this test unit, the upper and lower surfaces of the test sample 6 are connected to the rigid carrier through the cured adhesive layer, providing a stable force interface for subsequent pull-out tests.

[0036] Step S4: Connect the test unit to the testing machine using a fixture, ensuring that the upper pull claw 21 hooks and locks onto the upper auxiliary carrier 11, and the lower pull claw 22 hooks and locks onto the lower auxiliary carrier 12. After the test unit is removed from the oven and cooled to room temperature, the clamping operation can begin. First, install the upper pull claw 21 from both sides of the upper auxiliary carrier 11, so that the upper hook 211 hooks onto the lower surface of the upper auxiliary carrier 11; then install the lower pull claw 22 from both sides of the lower auxiliary carrier 12, so that the lower hook 221 hooks onto the upper surface of the lower auxiliary carrier 12. During installation, the upper pull claw 21 and the lower pull claw 22 interlock and align themselves using complementary tenons and mortises, then slide sideways to one end of the auxiliary carrier assembly. After assembly, use upper locking member 41 and lower locking member 42 to lock the upper pull claw 21 to the upper connecting block 31 and the lower pull claw 22 to the lower connecting block 32 respectively to prevent loosening or slippage during the pulling process. Then, use upper fitting 51 and lower fitting 52 to fix the upper connecting block 31 and lower connecting block 32 to the upper and lower clamps of the testing machine respectively. During clamping, pay attention to adjusting the position of the upper and lower clamps of the testing machine so that the test unit is in a natural vertical state, avoiding additional tensile or bending stress before testing.

[0037] Step S5: Start the testing machine and apply a pull-out force to the test unit. Start the universal testing machine, set a suitable tensile speed, such as 1 mm / min to 10 mm / min, and begin the test. The testing machine pulls the upper auxiliary carrier 11 upward through the upper pull claw 21, and simultaneously pulls the lower auxiliary carrier 12 downward through the lower pull claw 22, thereby applying a pull-out force perpendicular to the bonding interface to the test sample 6 bonded between the two. As the pull-out force gradually increases, stress concentration begins to appear at the bonding interface of the test sample 6, i.e., the adhesive area 63. When the pull-out force reaches the maximum limit that the bonding interface can withstand, the bonding interface will suddenly separate or fail. The maximum force value recorded by the testing machine at this time is the bonding strength value of the sample. The testing machine can usually automatically plot the force-displacement curve and record the peak force. This peak force can be directly used as a quantitative indicator to evaluate the bonding performance of graphite bipolar plates. By comparing the peak forces of bipolar plate samples prepared under different process conditions, the influence of process parameters on bonding performance can be evaluated; by testing the peak forces of multiple samples in the same batch, the average value and standard deviation of bonding strength can be calculated, thereby establishing quality control standards for mass production inspection.

[0038] As can be seen from the detailed description of the device structure and testing method above, the technical solution provided by this invention, by setting up an upper auxiliary carrier 11, a lower auxiliary carrier 12, and upper and lower pull claws 21 and 22 that cooperate with them, successfully applies the traditional pull-out test method to the evaluation of the bonding performance of graphite bipolar plates, a brittle and thin material. The design of this device overcomes the long-standing technical prejudice held by those skilled in the art that graphite sheets cannot be subjected to tensile testing, avoids the problem of sample slippage or damage during conventional clamping, and ensures the stability of the testing process and the repeatability of the test results. This method can obtain quantifiable and comparable bonding strength data, providing a scientific and quantitative testing method for bipolar plate process development, batch quality inspection, and durability assessment, overcoming the technical limitation of existing airtightness tests that can only qualitatively determine leakage defects and cannot characterize the true bonding strength.

[0039] This invention has been illustrated through several specific embodiments. Those skilled in the art will understand that various modifications and equivalent substitutions can be made to this invention without departing from its scope. Furthermore, various modifications can be made to this invention for specific situations or circumstances without departing from its scope. Therefore, this invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

Claims

1. A graphite bipolar plate adhesion performance testing device, characterized by, include: An auxiliary slide assembly is used to fix the sample to be tested cut from a graphite bipolar plate. The auxiliary slide assembly includes an upper auxiliary slide and a lower auxiliary slide, and an adhesive layer is respectively provided on the opposite surfaces of the upper auxiliary slide and the lower auxiliary slide. The fixture includes an upper pull jaw and a lower pull jaw, wherein the upper pull jaw is used to hook the upper auxiliary carrier piece, and the lower pull jaw is used to hook the lower auxiliary carrier piece; as well as, Testing machine, used to apply tensile force; The upper auxiliary carrier is bonded to one side of the sample to be tested via an adhesive layer, and the lower auxiliary carrier is bonded to the other side of the sample to be tested via an adhesive layer. The testing machine is connected to the upper auxiliary carrier via an upper pull claw and to the lower auxiliary carrier via a lower pull claw to apply a pull-out force to the sample to be tested.

2. The graphite bipolar plate adhesion test apparatus of claim 1, wherein Both the upper and lower auxiliary plates are metal plates.

3. The graphite bipolar plate adhesion test apparatus of claim 1, wherein The upper and lower auxiliary slides are respectively provided with adhesive grooves on their opposite surfaces, and the adhesive layer is disposed in the adhesive grooves. The area of ​​the adhesive grooves is smaller than the area of ​​the sample to be tested and is completely covered by the sample to be tested.

4. The graphite bipolar plate adhesion test apparatus of claim 3, wherein The two ends of the upper auxiliary carrier extend beyond the sample to be tested. The upper pull claw has an upper hook portion, which is installed from both ends of the upper auxiliary carrier and hooked to the lower surface of the upper auxiliary carrier through the upper hook portion. The two ends of the lower auxiliary carrier extend beyond the sample to be tested. The lower pull claw has a lower hook portion, which is installed from both ends of the lower auxiliary carrier and hooked to the upper surface of the upper auxiliary carrier through the lower hook portion.

5. The graphite bipolar plate adhesion test apparatus of claim 4, wherein The upper pull claw is provided with an upper clearance groove for the lower hook to be inserted, and the lower pull claw is provided with a corresponding lower clearance groove for the upper hook to be inserted. The upper hook and the lower hook have a complementary tenon and mortise structure.

6. A method of testing the adhesive properties of a graphite bipolar plate, characterized by, The testing method uses the testing apparatus as described in any one of claims 1 to 5, and the testing method includes the following steps: S1. Cut the sample to be tested, including the adhesive region, from the graphite bipolar plate; S2. Fix the sample to be tested between the auxiliary slides using the adhesive layer; S3. The adhesive layer is cured to form an integrated test unit with the sample to be tested, the upper auxiliary carrier, and the lower auxiliary carrier. S4. Connect the test unit to the testing machine through the fixture, so that the upper pull claw hooks onto the upper auxiliary carrier and locks it, and the lower pull claw hooks onto the lower auxiliary carrier and locks it. S5. Start the testing machine and apply a pull-out force to the test unit.

7. The method of testing the adhesion properties of graphite bipolar plates of claim 6 wherein, The sample to be tested cut in step S1 is a rectangular piece with a length of 30-50 mm and a width of 30-50 mm.

8. The method of testing the adhesion properties of graphite bipolar plates of claim 7 wherein, In step S2, the adhesive layer is applied to the adhesive grooves provided on the upper and lower auxiliary carriers. The adhesive grooves are 20-30 mm long, 20-30 mm wide, and 0.3-0.8 mm deep. The adhesive layer is epoxy resin adhesive, and the application amount is 0.3-0.6 g.

9. The method of claim 6, wherein the graphite bipolar plate adhesion test is performed by: In step S3, the curing conditions are: curing in an oven at 95-110°C for more than 1.5 hours.

10. The method of testing the adhesion properties of graphite bipolar plates of claim 6 wherein, In step S3, during the curing process, a pressure of 2-5 kg ​​is applied to the auxiliary carrier set and the sample to be tested.

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