Device and method for testing bonding strength of composite material rib plate structure

Abstract

The invention relates to a device and a method for testing the bonding strength of a composite material rib plate structure, and belongs to the technical field of connection mechanical property testing of the composite material rib plate structure. Comprising a tensile joint, a test piece clamp and a test piece base, the tensile joint is fixedly arranged on the upper side of the test piece clamp, the test piece clamp and the test piece base are installed on the two sides of a tensile test piece respectively, and the test piece clamp is perpendicular to the test piece base and used for fixing the tensile test piece in the tensile test process. The device is suitable for rib plate structures of various sizes, the bonding strength of the rib plate structures of different sizes can be tested, and meanwhile assembling is convenient.

Description

Technical Field

[0001] The invention relates to a device and a method for testing structural strength, belonging to the technical field of composite material rib plate structure joint mechanical performance testing. Background Art

[0002] Composite material rib plate structures are widely used in aviation, aerospace, and navigation. The use of reinforcement can further increase the stiffness of the structure while ensuring a certain quality, which is an effective way to achieve lightweight. For composite material structures, the integrated reinforcement setting can effectively solve the bonding problem of different interfaces, but the bond strength of the composite material's own resin base is still one of the forms of damage. In addition to overall buckling, local buckling, and local bulging, common forms of damage to reinforced structures include when the ribs are thick and high, and the rib plate has a stiffness greater than the board surface. Under load, it often fails due to insufficient bonding strength between the rib plate and the board surface. Due to the uncertainty of the carbon fiber preparation process, the instability of the preparation process is also one of the factors that lead to the peeling of ribs and board surfaces.

[0003] Therefore, the peeling of the ribs and the plate surface is one of the common forms of failure of the composite reinforced structure. Measuring the bonding strength between the ribs and the plate surface can avoid the failure caused by insufficient bonding strength to a certain extent. Measuring the bonding strength between the ribs and the plate surface can well avoid the unpredictable failure mode caused by process problems. The publication number is CN114689451A, and the invention is named as a test measurement device and method for the initiation of low-cycle fatigue cracks in a reinforced plate. Its technical scheme discloses that the clamping assembly includes a front cover body, a rear cover body, a first main screw, a second main screw, two auxiliary screws, two main clamps and two auxiliary clamps. The test measurement device and method for the initiation of low-cycle fatigue cracks in a reinforced plate are used to comprehensively consider the load conditions of the axial bottom plate and the rib plate of the reinforced plate under actual working conditions to test and measure the deformation and strain information of the reinforced plate pattern. The operation is simple, the measurement data is comprehensive and easy to process, and the error is small. It can provide a more accurate basis for the fatigue crack initiation life assessment of the reinforced plate under low-cycle load. However, it does not provide a test structure and method for measuring the bonding strength. The publication number is CN107700559A, and the name of the invention is a tension-compression integrated connection device for a power transmission line tower foundation strength test. The technical solution is to use a base connected to the tower foundation anchor bolts and a tension device and a pressure plate connected to the reaction device to form a connection device that can simultaneously meet the needs of transmitting external forces with completely opposite directions of tension and pressure in the tower foundation test. It has a reasonable structure and is easy to assemble, effectively avoiding the problem that the connection device cannot be disassembled after the tensile test affects the anchor bolts. However, the pressure plate it uses is used to test the pressure resistance rather than the tensile resistance. When testing the tensile resistance, it is directly fixed through the mounting holes on the bottom plate, which makes the force on the bottom plate uneven, thereby affecting the test results of the bonding strength between the bottom plate and the vertical plate. At the same time, its pressure plate is suitable for vertical plates arranged in a cross shape, but not for when there is only a single vertical plate. The publication number is CN108535110A, and the name of the invention is a self-balancing bolt tensile strength test device. Its technical solution discloses that a lower bolt hole is formed on the upper end plate of the base, and the bolt to be tested passes through the lower bolt hole and the upper bolt hole from bottom to top in sequence. The upper end of the bolt to be tested is fixedly connected to the bottom plate of the force converter through an upper gasket for clamping and a connecting nut, and the bolt cap of the bolt to be tested contacts the lower end surface of the upper end plate of the base through a lower gasket for clamping. This device is simple in structure and easy to install. However, if the piece to be tested is a non-cylindrical part, such as a T-type, it cannot be directly installed using its method, and the force converter with a plate structure on the top, bottom, left and right sides has a limit on the height of the part during installation, so it is not convenient to install it from top to bottom.

[0004] Therefore, it is urgent to propose a device and method for testing the bonding strength of composite material stiffener plate structures to solve the above technical problems. Summary of the invention

[0005] In order to solve the above problems, a device and method for testing the bonding strength of composite material stiffener plate structure are provided. A brief overview of the invention is given below to provide a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive overview of the invention. It is not intended to determine the key or important parts of the invention, nor is it intended to limit the scope of the invention.

[0006] The technical solution of the present invention:

[0007] A device for testing the bonding strength of a composite material stiffener plate structure comprises a tensile joint, a specimen fixture and a specimen base. The tensile joint is fixedly arranged on the upper side of the specimen fixture. The specimen fixture and the specimen base are respectively installed on both sides of the tensile specimen. The specimen fixture and the specimen base are vertically arranged to fix the tensile specimen during the tensile test.

[0008] Preferably, the tensile joint is cylindrical, the upper end of the tensile joint is connected to the universal testing machine through a pin, and the lower end of the tensile joint is welded to the upper end of the specimen fixture.

[0009] Preferably: a groove is processed at the lower end of the specimen fixture, two through holes with first threaded holes are processed at the side of the specimen fixture, the upper part of the tensile specimen is arranged in the groove, and the first bolt passes through the first threaded hole to tighten the tensile specimen, so that the tensile specimen is fixed to the groove.

[0010] Preferably: there is a mounting groove in the middle of the specimen base, a mounting hole is processed in the middle of the upper platform of the specimen base, and second threaded holes are processed on both sides of the specimen base. The upper part of the tensile specimen passes through the mounting hole, so that the lower part of the tensile specimen is fixed in the mounting groove. The length of the mounting hole is 120 mm, and the width of the mounting hole is 40 mm to ensure that the reinforced part of the rib plate specimen can pass through the platform plate, and the plate surface of the rib plate is limited below the platform plate. A through hole is opened in the lower bottom plate of the specimen base to form a connecting through hole.

[0011] Preferably: the left and right ends of the upper platform are respectively fixedly connected to the upper part of the longitudinal plate to form a mounting groove, the lower part of the longitudinal plate is fixedly connected to the bottom plate, and the middle part of the longitudinal plate of the specimen base is connected to the middle part of the bottom plate through a 45° inclined web.

[0012] Preferably: the tensile specimen is a ribbed plate, including a vertical plate (reinforced part or ribs) and a transverse plate (plate surface), the vertical plate is fixedly connected to the middle of the transverse plate, the upper vertical plate and the lower transverse plate are vertically arranged to form a T-shaped structure, the tensile specimen is made of a composite material, and the vertical plate and the transverse plate are bonded.

[0013] A method for testing the bonding strength of a composite material stiffener plate structure, using the device for testing the bonding strength of a composite material stiffener plate structure, comprises the following steps:

[0014] Step 1: Connect the tensile joint to the universal testing machine and fix it with a latch to ensure that the tensile joint and the universal testing machine are fixedly connected;

[0015] Step 2: Connect the specimen fixture to the vertical plate in the tensile specimen through the first bolt (M8 bolt) to ensure that the reinforcing ribs connected by the bolts do not shake;

[0016] Step 3: Pass the vertical plate of the tensile specimen through the mounting hole of the specimen base, extend the vertical plate of the tensile specimen from the mounting groove, and place the horizontal plate under the upper platform to ensure that the tensile specimen does not slip;

[0017] Step 4: Pass the bolts through the connecting holes of the specimen base and connect them with the threaded holes on the fixed platform to fix the specimen base, ensuring that the entire tooling of the specimen base will not move, and the tensile specimen will only have a strong effect in the test direction;

[0018] Step 5: Operate the universal testing machine to perform a tensile test to ensure that the damage that occurs is the bond strength damage at the rib-plate interface, so as to measure the bond strength.

[0019] The present invention has the following beneficial effects:

[0020] The present invention is suitable for rib plate structures of various sizes, can test the bonding strength of rib plate structures of different sizes, and is easy to assemble.

[0021] The testing method of the present invention solves the problem of testing the bonding strength of a rib plate structure, making the testing of the bonding strength convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A three-dimensional diagram of a device for testing the bonding strength of a composite material stiffener structure.

[0023] Figure 2 It is a front view of a device for testing the bonding strength of composite material stiffener plate structures.

[0024] Figure 3 It is a three-dimensional diagram of the specimen fixture.

[0025] Figure 4 is the front view of the specimen fixture.

[0026] Figure 5 It is a three-dimensional image of the specimen base.

[0027] Figure 6 It is a top view of the specimen base.

[0028] Figure 7 It is a three-dimensional image of the tensile specimen.

[0029] In the figure: 1- tensile joint, 2- specimen fixture, 21- groove, 22- first threaded hole, 3- specimen base, 31- mounting hole, 32- mounting groove, 4- tensile specimen. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0031] Specific implementation method 1: Combination Figure 1-7 The present embodiment is described. A device for testing the bonding strength of a composite material stiffener plate structure in the present embodiment comprises a tensile joint 1, a specimen fixture 2 and a specimen base 3. The tensile joint 1 is fixedly arranged on the upper side of the specimen fixture 2. The specimen fixture 2 and the specimen base 3 are respectively installed on both sides of a tensile specimen 4. The specimen fixture 2 and the specimen base 3 are vertically arranged to fix the tensile specimen 4 during the tensile test.

[0032] The tensile joint 1 is cylindrical, with a diameter of 40mm and a height of 50mm. The upper end of the tensile joint 1 is connected to the universal testing machine through a pin with a diameter of 18mm. The lower end of the tensile joint 1 is welded to the upper end of the specimen fixture 2. The tensile structure is designed to match the universal testing machine to ensure the consistency of the tooling and to ensure that the device of the testing machine is not affected when the specimen is replaced.

[0033] The specimen fixture 2 is U-shaped, with an upper width of 30 mm, and a left and right width of 11 mm at the bottom. The width of the groove 21 is 8 mm, and the height of the groove 21 is 50 mm. The height of the specimen fixture 2 is 70 mm, and the length is 80 mm. The lower end of the specimen fixture 2 is processed with a groove 21, and two through holes with first threaded holes 22 are processed on any side of the specimen fixture 2. The diameter of the first threaded hole 22 is 8 mm, and the center distance of the first threaded hole 22 is 20 mm from the two end boundaries. The upper part of the tensile specimen 4 is arranged in the groove 21, and the first bolt passes through the first threaded hole 22 to tighten the tensile specimen 4, so that the tensile specimen 4 is fixed to the groove 21; the diameter of the bolt (first bolt) of the specimen fixture is 8 mm, and the aperture ensures that the bolt has a certain strength, and at the same time has a certain distance from the edge of the rib plate to ensure that the edge of the rib plate will not be sheared.

[0034] The middle part of the specimen base 3 has a mounting groove 32, the middle part of the upper platform of the specimen base 3 is processed with a mounting hole 31, and the bottom plates on both sides of the specimen base 3 are processed with connecting through holes. The upper part of the tensile specimen 4 passes through the mounting hole 31, so that the lower part of the tensile specimen 4 is relatively fixedly arranged in the mounting groove 32. The length of the mounting hole 31 is 120mm, and the width of the mounting hole 31 is 40mm, so as to ensure that the reinforced part of the rib plate specimen can pass through the platform plate, and the plate surface of the rib plate is limited below the platform plate. During stretching, the upper platform plate acts evenly on the transverse plate, so that the transverse plate is evenly stressed, which is convenient for accurately testing the bonding strength. The lower bottom plate of the specimen base is opened with a through hole to form a connecting through hole, so as to ensure that the specimen base is not displaced by bolt connection. The diameter of the connecting through hole is 8mm, the hole distance between the bottom plates on both sides is 170mm, the hole distance in the same row is 50mm, and four connecting through holes are arranged in each row;

[0035] The left and right ends of the upper platform are respectively fixedly connected to the upper part of the longitudinal plate to form a mounting groove 32, and the lower part of the longitudinal plate is fixedly connected to the bottom plate. The thickness of the test piece base 3 is 10mm, the width of the mounting groove 32 of the test piece base 3 is 80mm, the bottom plate width at both ends of the bottom of the test piece base 3 is 55mm, the height of the longitudinal plates on both sides of the test piece base 3 is 40mm, and the middle part of the longitudinal plate of the test piece base 3 is connected to the middle part of the bottom plate through a 45° inclined web plate, the thickness and width of the inclined web plate is 10mm, and the length (depth) of the entire base is 200mm; the design of the mounting hole 31 and the mounting groove 32 can test panels of various widths and reinforcing ribs of various widths, which makes the range of the tested rib plate structure become wide; at the same time, the installation method of passing through the mounting hole 31 from the bottom is simple to operate and has no height limit;

[0036] The tensile specimen 4 is a ribbed plate, including a vertical plate (reinforced part or reinforcing rib) and a transverse plate (plate surface), the vertical plate is fixedly connected to the middle of the transverse plate, the upper vertical plate and the lower transverse plate are vertically arranged to form a T-shaped structure, the transverse plate of the tensile specimen 4 is 60-80 mm, the tensile specimen 4 is made of composite material, and the vertical plate and the transverse plate are bonded;

[0037] The present invention is suitable for rib plate structures of various sizes, can test the bonding strength of rib plate structures of different sizes, and is easy to assemble.

[0038] Specific implementation method 2: Combination Figure 1-7 The present embodiment is described. The present embodiment is a method for testing the bonding strength of a composite material stiffener plate structure. A device for testing the bonding strength of a composite material stiffener plate structure is used, including a tensile joint 1, a specimen fixture 2 and a specimen base 3. The tensile joint 1 is fixedly arranged on the upper side of the specimen fixture 2. The specimen fixture 2 and the specimen base 3 are respectively installed on both sides of a tensile specimen 4. The specimen fixture 2 and the specimen base 3 are vertically arranged to fix the tensile specimen 4 during the tensile test.

[0039] The tensile joint 1 is cylindrical, with a diameter of 40 mm and a height of 50 mm. The upper end of the tensile joint 1 is connected to the universal testing machine through a pin, the diameter of the pin is 18 mm, and the lower end of the tensile joint 1 is welded to the upper end of the specimen fixture 2;

[0040] The specimen fixture 2 is U-shaped, the upper end width of the specimen fixture 2 is 30mm, the left and right ends of the bottom are 11mm wide, the width of the groove 21 is 8mm, the height of the groove 21 is 50mm, the height of the specimen fixture 2 is 70mm, and the length is 80mm. The lower end of the specimen fixture 2 is processed with a groove 21, and two through holes with first threaded holes 22 are processed on any side of the specimen fixture 2. The diameter of the first threaded hole 22 is 8mm, and the center distance of the first threaded hole 22 is 20mm from the two end boundaries. The upper part of the tensile specimen 4 is set in the groove 21, and the first bolt passes through the first threaded hole 22 to tighten the tensile specimen 4, so that the tensile specimen 4 is fixed to the groove 21;

[0041] The middle part of the specimen base 3 has a mounting groove 32, the middle part of the upper platform of the specimen base 3 is processed with a mounting hole 31, and the bottom plates on both sides of the specimen base 3 are processed with second threaded holes. The upper part of the tensile specimen 4 passes through the mounting hole 31, so that the lower part of the tensile specimen 4 is relatively fixedly arranged in the mounting groove 32. The length of the mounting hole 31 is 120mm, and the width of the mounting hole 31 is 40mm, so as to ensure that the reinforced part of the rib plate specimen can pass through the platform plate, and the plate surface of the rib plate is limited below the platform plate. The bottom plate at the lower part of the specimen base is opened with a through hole to form a connecting through hole, so as to ensure that the specimen base is not displaced by bolt connection. The diameter of the connecting through hole is 8mm, the hole distance between the bottom plates on both sides is 170mm, the hole distance in the same row is 50mm, and four connecting through holes are arranged in each row;

[0042] The left and right ends of the upper platform are respectively fixedly connected to the upper part of the longitudinal plate to form a mounting groove 32, and the lower part of the longitudinal plate is fixedly connected to the bottom plate. The thickness of the specimen base 3 is 10 mm, the width of the mounting groove 32 of the specimen base 3 is 80 mm, the bottom plate width at both ends of the bottom of the specimen base 3 is 55 mm, the height of the longitudinal plates on both sides of the specimen base 3 is 40 mm, the middle part of the longitudinal plate of the specimen base 3 is connected to the middle part of the bottom plate through a 45° inclined web plate, the thickness and width of the inclined web plate is 10 mm, and the length (depth) of the entire base is 200 mm;

[0043] The tensile specimen 4 is a ribbed plate, including a vertical plate (reinforced part or reinforcing rib) and a transverse plate (plate surface), the vertical plate is fixedly connected to the middle of the transverse plate, the upper vertical plate and the lower transverse plate are vertically arranged to form a T-shaped structure, the transverse plate of the tensile specimen 4 is 60-80 mm, the tensile specimen 4 is made of composite material, and the vertical plate and the transverse plate are bonded;

[0044] The method comprises the following steps:

[0045] Step 1: Connect the tensile joint 1 to the universal testing machine and fix it with a latch to ensure that the tensile joint and the universal testing machine are fixedly connected;

[0046] Step 2: Connect the specimen fixture 2 to the vertical plate in the tensile specimen 4, and connect the two sides through the first bolt (M8 bolt) to ensure that the reinforcing ribs connected by the bolts will not shake. At the same time, there is a certain distance between the bolts and the upper part of the tensile specimen 4 to ensure that the reinforcing ribs will not be sheared.

[0047] Step 3: The vertical plate of the tensile specimen 4 is passed through the mounting hole 31 of the specimen base 3, and the vertical plate of the tensile specimen 4 extends out from the mounting groove 32. The area of ​​the transverse plate is larger than the area of ​​the mounting hole 31. The transverse plate is located at the lower side of the upper platform to ensure that the tensile specimen 4 will not slip. The width of the plate surface ensures that the plate surface will not be sheared.

[0048] Step 4: Pass the bolts through the connecting through holes of the specimen base 3 and connect them with the threaded holes on the fixed platform to fix the specimen base 3, ensuring that the entire tooling of the specimen base 3 will not be dislocated, and the tensile specimen 4 only has a strong effect in the test direction;

[0049] Step 5: Use a universal testing machine to perform a tensile test to ensure that the damage is caused by the bond strength at the rib-plate interface, thereby measuring the bond strength;

[0050] The testing method of the present invention solves the problem of testing the bonding strength of a rib plate structure, making the testing of the bonding strength convenient.

[0051] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for testing the bonding strength of composite material rib plate structure, characterized in that: It comprises a tensile joint (1), a specimen fixture (2) and a specimen base (3); the tensile joint (1) is arranged on the upper side of the specimen fixture (2); and the specimen fixture (2) and the specimen base (3) are respectively installed on both sides of a tensile specimen (4).

2. The device for testing the bonding strength of composite material stiffener structure according to claim 1, characterized in that: The tensile joint (1) is cylindrical, the upper end of the tensile joint (1) is detachably connected to the universal testing machine, and the lower end of the tensile joint (1) is welded to the upper end of the specimen fixture (2).

3. The device for testing the bonding strength of composite material stiffener structure according to claim 2, characterized in that: A groove (21) is processed at the lower end of the specimen fixture (2), a first threaded hole (22) is processed at the side of the specimen fixture (2), and the upper part of the tensile specimen (4) is arranged in the groove (21) and fixed.

4. The device for testing the bonding strength of composite material stiffener structure according to claim 3, characterized in that: The middle of the specimen base (3) is provided with a mounting groove (32), the upper portion of the specimen base (3) is processed with a mounting hole (31), and both sides of the specimen base (3) are processed with connecting through holes, and the upper portion of the tensile specimen (4) passes through the mounting hole (31), so that the lower portion of the tensile specimen (4) is arranged in the mounting groove (32).

5. The device for testing the bonding strength of composite material stiffener structure according to claim 4, characterized in that: The left and right ends of the upper platform are respectively fixedly connected to the upper part of the longitudinal plate to form a mounting groove (32), the lower part of the longitudinal plate is fixedly connected to the bottom plate, and the longitudinal plate of the specimen base (3) is connected to the bottom plate through an inclined web plate.

6. A device for testing the bonding strength of composite material stiffener structure according to claim 4 or 5, characterized in that: The tensile test piece (4) comprises a vertical plate and a transverse plate, wherein the vertical plate is fixedly connected to the middle of the transverse plate, the upper vertical plate and the lower transverse plate are vertically arranged, the tensile test piece (4) is made of a composite material, and the vertical plate and the transverse plate are bonded.

7. A method for testing the bonding strength of a composite material stiffener structure, characterized in that: The device for testing the bonding strength of a composite material stiffener structure according to claim 8 comprises the following steps: Step 1: Connect the tensile joint (1) to the universal testing machine and fix them with a latch to ensure that the tensile joint and the universal testing machine are fixedly connected; Step 2: Connect the specimen fixture (2) to the vertical plate in the tensile specimen (4) by means of a first bolt (M8 bolt), ensuring that the reinforcing ribs connected by the bolts do not shake; Step 3: The vertical plate of the tensile specimen (4) is passed through the mounting hole (31) of the specimen base (3), and the vertical plate of the tensile specimen (4) extends out from the mounting groove (32), and the transverse plate is located at the lower side of the upper platform to ensure that the tensile specimen (4) does not slip; Step 4: Pass the bolts through the connecting through holes of the specimen base (3) and connect them with the threaded holes on the fixing platform to fix the specimen base (3) and ensure that the specimen base (3) does not move. The tensile specimen (4) only exerts a strong force in the test direction. Step 5: Operate the universal testing machine to perform a tensile test.

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