Clamping tool suitable for I-II type fracture toughness test of composite material

Abstract

The utility model relates to the technical field of fracture toughness testing, in particular to a clamping tool suitable for I-II type fracture toughness testing of a composite material, which comprises a first clamping plate, the first clamping plate comprises a bottom plate, one side of the upper surface of the bottom plate is provided with a first placing step, and the other side of the upper surface of the bottom plate is movably provided with a second clamping plate; a guide column extending horizontally is arranged on one side of the first placing step, and the guide column and the second clamping plate are installed in a sliding and penetrating mode; the first clamping plate comprises a first placing step, a first baffle is arranged on the upper surface of the first placing step, the second clamping plate comprises a second placing step, a second baffle is arranged on the upper surface of the second placing step, and the first baffle and the second baffle are oppositely arranged; the side plate is detachably connected with the bottom plate; the side plate is connected with one side of the second clamping plate through a hydraulic cylinder; through the structural design of hydraulically controlling clamping force and spring ejection, the problems that in the prior art, the clamping force is difficult to control, and opening is difficult after a test is finished are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of fracture toughness testing, in particular to a clamping tool suitable for testing type I-II fracture toughness of composite materials. Background Art

[0002] Polymer-based composite materials have the advantages of high specific modulus, high specific strength, strong designability of mechanical properties, and excellent fatigue resistance. Compared with metal materials, they have obvious structural weight reduction benefits and have become one of the main structural materials used in the contemporary aerospace field. At present, composite laminate structures are very common in practical applications. They are made of unidirectional laminates with orthotropic properties. However, due to the lack of reinforcement in the thickness direction, the interlaminar performance of composite laminates is much lower than their in-plane performance, which leads to delamination as a major form of damage in composite laminate structures, which significantly reduces the strength and stiffness of composite materials.

[0003] Composite material damage can be categorized into four types: matrix cracking, fiber breakage, fiber-matrix debonding, and interlaminar delamination. Delamination is the most common and primary failure mode due to the low interlaminar strength of laminates. Delamination has numerous causes, occurring throughout the entire manufacturing and use process. Studying the patterns of delamination and the delamination characteristics of typical laminates, and improving their resistance to delamination, will help materials researchers develop tougher matrix resins, design laminates with increased delamination resistance, and fully utilize the material's performance.

[0004] According to different loading modes, composite material delamination can be divided into three basic forms: opening type (Type I), sliding type (Type II) and tearing type (Type III); Type I, that is, the phenomenon of crack tip opening under the action of external normal stress perpendicular to the crack surface, and the crack propagation direction is perpendicular to the external stress; Type II delamination, that is, the phenomenon of crack sliding and propagation under the action of shear stress parallel to the crack surface and pointing to the direction of crack propagation; Type III delamination, that is, the phenomenon of crack surface offset left and right under the action of shear stress parallel to the crack surface and perpendicular to the direction of crack propagation, and the crack propagates forward along the original direction, which is a tearing type; in most engineering practices, the proportion of Type III delamination extension component is small and can be ignored. Current research mainly focuses on Type I, Type II and Type I / II composite delamination; interlaminar fracture toughness is an indicator used to characterize the ability of composite materials to resist delamination extension and is an important input parameter for composite material delamination extension analysis. The critical strain energy release rate, as a characterization of interlaminar fracture toughness, is used to describe the material's ability to resist delamination damage.

[0005] At present, in the research of type I and type II fracture toughness in China, standards and testing technologies have been increasingly improved, including GB / T 28891-2012 "Determination of Type I Interlaminar Fracture Toughness of Unidirectionally Reinforced Materials of Fiber Reinforced Plastic Composites", HB7402-1996 "Test Method for Type I Interlaminar Fracture Toughness of Carbon Fiber Composite Laminates", HB 7403-1996 "Test Method for Type II Interlaminar Fracture Toughness of Carbon Fiber Composite Laminates", GB / T39484-2020 "Fiber Reinforced Plastic Composites - Determination of Type II Fracture Toughness of Unidirectionally Reinforced Materials by Calibrated End Load Split Test (CELS) and Effective Crack Length Method", etc.; the test method for type I-II mixed interlaminar fracture toughness of composite materials is mainly based on ASTM D6671, such as Figure 1 As shown in the figure, the MMB device is used to measure the mixed interlaminar fracture toughness. The device can obtain the interlaminar fracture toughness of different mixing ratios by changing the length of the lever; however, the original tooling connection method is to glue the hinge or piano block to the specimen. During this process, the hinge or piano block and the specimen are prone to slippage or torsion, and the specimen and the hinge or piano block may fall off during the test, affecting the accuracy of the test results; and for the tooling that also uses the clamping method to connect the composite materials for testing, its main fixing method is to manually tighten the bolts. The clamping force of the specimen is difficult to control. If the clamping force is too large, it is easy to cause unnecessary damage to the specimen. If the clamping force is too small, the specimen is easy to fall off, making it difficult to complete the test; and when there are multiple bolts, manual tightening will cause different locking forces of each bolt, resulting in bending in the test, etc., affecting the accuracy of the experimental results.

[0006] Therefore, in order to solve the above problems, the present invention urgently needs to provide a clamping tool suitable for testing the type I-II fracture toughness of composite materials. Utility Model Content

[0007] The purpose of the utility model is to provide a clamping tool suitable for type I-II fracture toughness testing of composite materials, which solves the problems of difficult control of clamping force and difficulty in opening after the test in the prior art through hydraulic control of clamping force and spring ejection structural design.

[0008] A clamping fixture suitable for testing the type II fracture toughness of composite materials, comprising a first clamping plate, the first clamping plate including a base plate, a first placement step being provided on one side of the upper surface of the base plate, and a second clamping plate being movably mounted on the other side, a horizontally extending guide post being provided on one side of the first placement step, the guide post being slidably mounted on the second clamping plate;

[0009] A first baffle is provided on the upper surface of the first placement step, the second clamping plate includes a second placement step, a second baffle is provided on the upper surface of the second placement step, and the first baffle is arranged opposite to the second baffle;

[0010] It also includes a side plate detachably connected to the bottom plate, and the side plate is connected to one side of the second clamping plate through a hydraulic cylinder;

[0011] The lower surface of the base plate is also provided with a connecting piece for connecting with the testing machine.

[0012] Furthermore, it also includes a spring installed between the first placement step and the second placement step, the spring is sleeved outside the guide column, and the two ends of the spring are respectively in contact with the first placement step and the second placement step.

[0013] Furthermore, the side panels and the bottom panel are detachably connected via bolts or buckles.

[0014] Furthermore, the plane where the upper surface of the first placement step is located coincides with the plane where the upper surface of the second placement step is located.

[0015] Furthermore, the height of the first baffle and the second baffle are both 25 mm.

[0016] Furthermore, the hydraulic cylinder includes a cylinder body and a telescopic rod fixed to one side of the side plate, and the telescopic rod extends outward and is in contact with one side of the second clamping plate.

[0017] Furthermore, the pressure of the hydraulic cylinder is 3 MPa.

[0018] Furthermore, the outer diameter of the spring is 6 mm, and the diameter of the steel wire is 0.5 mm.

[0019] Furthermore, the outer surface of the guide post is smoothly arranged.

[0020] Furthermore, the first clamping plate, the second clamping plate and the side plate are all made of steel, and the spring is made of steel wire.

[0021] The clamping fixture provided by the present invention for testing the type II fracture toughness of composite materials has the following improvements compared to the prior art:

[0022] The clamping fixture provided by the utility model is suitable for the II I type fracture toughness test of composite materials. Through the guide column, the first baffle and the second baffle for clamping the sample are kept parallel, thereby ensuring the stability of the sample clamping; the second clamping plate is pushed by the hydraulic cylinder installed on the side plate with a controllable force, thereby ensuring that the second clamping plate is evenly stressed, so that the stress on the sample is stable; through the spring installed between the first clamping plate and the second clamping plate, after the sample test is completed and the hydraulic pressure is withdrawn, the spring pushes the first clamping plate and the second clamping plate to separate from the sample, thereby facilitating the removal of the fixture; in summary, the utility model uses a jaw-type clamping connection method, thereby ensuring that the sample does not fall off, twist, or other problems caused by uneven force during the test, and the operation is simple, thereby improving the experimental efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the ASTM D6671 composite material type I-II mixed interlaminar fracture toughness test method;

[0025] Figure 2 Schematic diagram (stereoscopic view) of a clamping fixture suitable for testing the mode II I fracture toughness of composite materials described in the present invention;

[0026] Figure 3 This is a schematic diagram (stereoscopic view) of the installation of a clamping fixture suitable for the test of the mode II fracture toughness of composite materials described in the present invention.

[0027] Description of reference numerals:

[0028] 101. Bottom plate; 102. First placement step; 103. Guide column; 104. First baffle; 105. Connector; 201. Second placement step; 202. Second baffle; 3. Side plate; 4. Hydraulic cylinder; 5. Spring; 6. Specimen. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0031] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0032] like Figure 2 、 Figure 3 As shown, a clamping fixture suitable for testing the mode II fracture toughness of composite materials includes a first clamping plate, which includes a base plate 101. A first placement step 102 is provided on one side of the upper surface of the base plate 101, and a second clamping plate is movably mounted on the other side. A horizontally extending guide post 103 is provided on one side of the first placement step 102, and the guide post 103 is slidably mounted on the second clamping plate.

[0033] A first baffle 104 is provided on the upper surface of the first placement step 102, and the second clamping plate includes a second placement step 201. A second baffle 202 is provided on the upper surface of the second placement step 201. The first baffle 104 and the second baffle 202 are arranged opposite to each other.

[0034] It also includes a side plate 3 detachably connected to the bottom plate 101, and the side plate 3 is connected to one side of the second clamping plate through a hydraulic cylinder 4;

[0035] The lower surface of the base plate 101 is further provided with a connector 105 for connecting to a testing machine.

[0036] The clamping fixture provided by the present invention is suitable for the II I type fracture toughness test of composite materials. Through the guide column 103, the first baffle 104 and the second baffle 202 for clamping the sample are kept parallel to each other, thereby ensuring the stability of the sample clamping; the hydraulic cylinder 4 installed on the side plate pushes the second clamping plate with a controllable force, thereby ensuring that the second clamping plate is evenly stressed, so that the sample is stably stressed; through the spring 5 installed between the first clamping plate and the second clamping plate, after the sample test is completed and the hydraulic pressure is removed, the spring 5 pushes the first clamping plate and the second clamping plate to separate from the sample, thereby facilitating the removal of the fixture; in summary, the present invention uses a jaw-type clamping connection method to ensure that the sample does not fall off, twist, or other problems caused by uneven force during the test, and the operation is simple, thereby improving the experimental efficiency.

[0037] like Figure 2 、 Figure 3As shown, it also includes a spring 5 installed between the first placement step 102 and the second placement step 201. The spring 5 is sleeved outside the guide column 103, and the two ends of the spring 5 are respectively in contact with the first placement step 102 and the second placement step 201.

[0038] In the present invention, after the composite material II I fracture toughness test is completed, the hydraulic cylinder 4 is controlled to stop pushing the second clamping plate, and the spring 5 pushes the first clamping plate, the second clamping plate and the sample to facilitate the removal of the tooling.

[0039] In this embodiment, the side panels 3 and the bottom panel 101 are detachably connected via bolts or buckles.

[0040] like Figure 2 、 Figure 3 As shown, the plane where the upper surface of the first placement step 102 is located coincides with the plane where the upper surface of the second placement step 201 is located.

[0041] In this embodiment, the heights of the first baffle 104 and the second baffle 202 are both 25 mm.

[0042] like Figure 2 、 Figure 3 As shown, the hydraulic cylinder 4 includes a cylinder body and a telescopic rod fixed to one side of the side plate 3. The telescopic rod extends outward and contacts one side of the second clamping plate.

[0043] In this embodiment, the pressure of the hydraulic cylinder 4 is 3 MPa.

[0044] In this embodiment, the outer diameter of the spring 5 is 6 mm, and the diameter of the steel wire is 0.5 mm.

[0045] In this embodiment, the outer surface of the guide post 103 is smooth.

[0046] In this embodiment, the first clamping plate, the second clamping plate and the side plate 3 are all made of steel, and the spring 5 is made of steel wire.

[0047] The implementation method of the present utility model includes the following steps:

[0048] 1) Fit the spring 5 onto the outside of the guide column 103, place the second clamping plate on the bottom plate 101 and fit it onto the outside of the guide column 103, then install the side plate 3 and connect the telescopic rod of the hydraulic cylinder 4 to the side wall of the second clamping plate;

[0049] 2) Place the specimen 6 above the first placement step 102 and the second placement step 201, and align the side surface of the specimen with the first baffle 104. Control the hydraulic cylinders 4 to push the second clamping plate along the guide post 103 so that the second baffle 202 aligns with the side surface of the specimen.

[0050] 3) Control each hydraulic cylinder 4 to push the second clamping plate with the same force to clamp the sample at the set value;

[0051] 4) Using another clamping fixture suitable for composite material type II I fracture toughness testing according to the present invention, clamp the opposite sides of the same specimen 6 using steps 1) to 3); and connecting the two clamping fixtures holding the specimen 6 to the upper and lower fixtures of the testing machine via connectors 105, thereby completing the clamping work for the composite material type II I fracture toughness test.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A clamping fixture suitable for testing the mode I-II fracture toughness of composite materials, characterized by: The first clamping plate includes a bottom plate (101), a first placement step (102) is provided on one side of the upper surface of the bottom plate (101), and a second clamping plate is movably installed on the other side, a horizontally extending guide column (103) is provided on one side of the first placement step (102), and the guide column (103) and the second clamping plate are slidably installed; The upper surface of the first placement step (102) is provided with a first baffle (104), the second clamping plate includes a second placement step (201), the upper surface of the second placement step (201) is provided with a second baffle (202), and the first baffle (104) and the second baffle (202) are arranged opposite to each other; It also includes a side plate (3) detachably connected to the bottom plate (101), and the side plate (3) is connected to one side of the second clamping plate via a hydraulic cylinder (4); The lower surface of the bottom plate (101) is also provided with a connecting piece (105) for connecting to a testing machine.

2. The clamping fixture for composite material type I-II fracture toughness testing according to claim 1, characterized in that: It also includes a spring (5) installed between the first placement step (102) and the second placement step (201), the spring (5) is sleeved outside the guide column (103), and the two ends of the spring (5) are respectively in contact with the first placement step (102) and the second placement step (201).

3. The clamping fixture for composite material type I-II fracture toughness testing according to claim 2, characterized in that: The side panels (3) and the bottom panel (101) are detachably connected via bolts or buckles.

4. The clamping fixture for composite material type I-II fracture toughness testing according to claim 3, characterized in that: The plane where the upper surface of the first placement step (102) is located coincides with the plane where the upper surface of the second placement step (201) is located.

5. The clamping fixture for composite material type I-II fracture toughness testing according to claim 4, characterized in that: The heights of the first baffle (104) and the second baffle (202) are both 25 mm.

6. The clamping fixture for composite material type I-II fracture toughness testing according to claim 5, characterized in that: The hydraulic cylinder (4) comprises a cylinder body fixedly connected to one side of the side plate (3) and a telescopic rod, the telescopic rod extending outward and contactingly connected to one side of the second clamping plate.

7. The clamping fixture for composite material type I-II fracture toughness testing according to claim 6, characterized in that: The pressure of the hydraulic cylinder (4) is 3 MPa.

8. The clamping fixture for composite material type I-II fracture toughness testing according to claim 7, characterized in that: The outer diameter of the spring (5) is 6 mm, and the diameter of the steel wire is 0.5 mm.

9. The clamping fixture for composite material type I-II fracture toughness testing according to claim 8, characterized in that: The outer surface of the guide post (103) is smoothly arranged.

10. The clamping fixture for composite material type I-II fracture toughness testing according to claim 9, characterized in that: The first clamping plate, the second clamping plate and the side plate (3) are all made of steel, and the spring (5) is made of steel wire.

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