An apparatus for testing the bond properties of fiber reinforced polymer to concrete
By designing a device with a fixture assembly and FRP support components, flexible testing of FRP-concrete bond performance was achieved, solving the problem of difficult peel angle adjustment in existing technologies, improving testing efficiency and reliability, and making it suitable for pure shear and mixed modes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- YUNNAN XUANHUI EXPRESSWAY CO LTD
- Filing Date
- 2025-05-30
- Publication Date
- 2026-06-02
AI Technical Summary
In the existing technology, the FRP-concrete bond performance testing device is complex in design and difficult to flexibly adjust different peel angles, resulting in low testing efficiency and poor repeatability, and making it impossible to make lateral comparisons.
A testing device comprising a fixture assembly, an FRP support, and a concrete fixing module was designed. By adjusting the spacing between the bushings on both sides of the FRP support, the peel angle can be continuously adjusted. It is suitable for pure shear and mixed mode testing and is combined with a servo-hydraulic load testing frame for bonding performance evaluation.
It enables flexible testing of FRP-concrete bond performance, is applicable to the evaluation of different peel angles, improves testing efficiency and repeatability, and provides reliable design data support.
Smart Images
Figure CN224317486U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of civil engineering technology, and in particular to a device for testing the bonding performance between fiber-reinforced polymers and concrete. Background Technology
[0002] FRP (Fiber-Reinforced Polymer)-concrete composite structures are a type of structure that combines fiber-reinforced composite materials with concrete. This composite structure makes full use of the high strength and corrosion resistance of FRP materials and the compressive strength of concrete, and is widely used in civil engineering fields, such as bridge reinforcement, building repair, and new structural design.
[0003] The bond performance between FRP and concrete is one of the key factors in FRP-concrete composite structures. FRP-concrete testing modules can be used to measure parameters such as bond strength and bond stiffness at the FRP-concrete interface. The obtained experimental data can provide a basis for the design of FRP-concrete composite structures and can be used to verify the accuracy of theoretical models, thereby establishing theoretical models to predict their mechanical behavior. Therefore, various testing devices and modules have been designed to measure the bond performance between FRP and concrete.
[0004] Dai et al. (2007) and Wu et al. (2005) used small-sized, custom-designed beam specimens with a special loading mechanism that applied a normal force to the glass fiber composite at mid-span of the beam. Pan and Leung (2007) used a metal clamp attached to a concrete beam with an adjustable bottom to replicate different peel angles; Ghorbani et al. (2017) and Yao et al. (2005) used single-shear specimens with adjustable loading angles; Giurgiutiu et al. (2001) used single-shear specimens with hinged blades to change the loading direction, while Wan et al. (2004) used a similar setup but with an adjustable base angle; Alam et al. (2012) and Zhang (2016) employed double-shear tests, with half of the specimens having different cross-sections. One challenge in experimentally evaluating hybrid adhesives is the reproducibility of the tests. All the single-shear and beam tests mentioned above were designed specifically for each study. The loading mechanism used in the single shear test by Giurgiutiu et al. was specially designed and not commonly used. Although Dai et al. (2007) and Wu et al. (2005) provided details of the unique beam specimens used in each study, both studies required custom molds to fabricate the specimens.
[0005] These conditions make FRP-concrete bond performance testing inconvenient. Different test devices and test modules need to be designed for different peel angles in pure shear mode and mixed mode testing, which reduces testing efficiency, has poor repeatability, and makes it impossible or difficult to make cross-comparisons of the obtained performance test results. Utility Model Content
[0006] To overcome the aforementioned shortcomings of existing technologies, this paper proposes an apparatus for testing the bond performance between fiber-reinforced polymers (FRP) and concrete. This apparatus can be used to evaluate the bond performance of FRP-concrete structures under pure shear and mixed-mode failure, and the specimens used can be deployed with any servo-hydraulic load testing frame (e.g., a universal testing machine). The apparatus can test the bond performance of FRP-concrete by varying the peel angle in either pure shear or mixed-mode failure, thereby characterizing the shear / peel properties of the bonded joint.
[0007] To achieve the above objectives, this solution proposes a device for testing the bonding performance between fiber-reinforced polymers and concrete, comprising: a clamp assembly (1), an FRP support (2), and a concrete fixing module (3), wherein,
[0008] The clamp assembly (1) includes a clamp body (11) with an opening (113) on one side, a fixing block (12) and a first clamping post (13) embedded and connected to the fixing block (12). The fixing block (12) is fixed inside the clamp body (11) by bolts, and the first clamping post (13) extends out of the clamp body (11) through the opening (113) of the clamp body (11).
[0009] The FRP support (2) includes an I-beam (21) and bushings (22) located in the grooves on both sides of the I-beam (21) and positioned by pins (23) and rotatable around pins (23); the I-beam (21) is fixed in the fixture body (11) by bolts and the spacing between the bushings (22) on both sides can be changed.
[0010] The concrete fixing module (3) includes a strip FRP (31), a concrete specimen (32) and a second clamping column (33) embedded and connected to the concrete specimen (32). The two ends of the strip FRP (31) are fixedly connected to the two opposite planes of the concrete specimen (32), and the middle part of the strip FRP (31) passes through the inside of the clamp body (11) and is located between the fixing block (12) and the FRP support (2).
[0011] Furthermore, the two sides of the I-beam (21) are provided with corresponding elongated through holes (24), and the distance between the two bushings (22) is adjusted by sliding the pin (23) in the elongated through holes (24); wherein the pin (23) is equipped with a locking device.
[0012] In one implementation, the locking device may be a mechanical locking device such as a buckle, a self-locking rod, or a screw; a pneumatic locking device such as a cylinder clamping device or a linear guide clamp; or an electric locking device such as a motor-driven locking device or an electromagnet-type locking device.
[0013] Furthermore, the two ends of the strip FRP (31) are fixedly connected to the two opposite planes of the concrete specimen (32) by an adhesive method, wherein the adhesive used in the adhesive method includes resin, cement or inorganic adhesive.
[0014] Furthermore, the two ends of the strip FRP (31) are fixedly connected to the two opposite planes of the concrete specimen (32) by embedding. That is, the two ends of the strip FRP (31) are embedded in the two opposite planes of the concrete specimen (32) and are formed together with the concrete specimen (32).
[0015] Furthermore, the first clamping column (13) and the second clamping column (33) are steel-reinforced structures with threads at their distal ends. The threaded steel-reinforced structure facilitates clamping by the jaws of the universal testing machine to transfer the loads applied by the universal testing machine to the device in two opposite directions.
[0016] Furthermore, a linear variable displacement sensor (LVDT) is provided on one side surface of the fixed block (12) relative to the strip FRP (31). This sensor can be used to record the amount of interface slippage during a test, for example, in pure shear mode.
[0017] An LVDT (Low Voltage Detector) is an electromagnetic sensor that determines displacement by measuring changes in the induced electromotive force (EMF) of a coil. It typically consists of a primary coil and a secondary coil. When the iron core moves in a magnetic field, the induced EMF in the secondary coil changes, and by measuring this change, the displacement can be accurately determined.
[0018] Furthermore, multiple strain gauges are provided on the surface of the strip FRP (31). These strain gauges can be used to measure the strain distribution on the surface of the FRP (31) during testing, for example, in a mixed mode. As an example, these strain gauges can be positioned at equal intervals on both sides of the loading end on the surface of the strip FRP (31), for example, the interval is 50 mm, but not limited thereto. For example, these strain gauges can be positioned at 10 mm, 60 mm, 110 mm, 160 mm, and 210 mm from both sides of the loading end on the surface of the strip FRP (31). The loading end refers to the position where the strip FRP (31) is tangent to the two bushings (22). Therefore, it is easy to understand that in the technical solution of the present invention, the two sides of the I-beam (21) have two loading ends due to the two bushings (22). For each part of the strip FRP (31) on both sides of the I-beam (21), its loading end refers to the position where it is tangent to the bushing (22) on the same side.
[0019] The strain gauge can be a resistance strain gauge (which measures strain through the resistance strain effect), a fiber optic strain gauge (which measures strain by utilizing the characteristic that the wavelength of the reflected light from the fiber optic grating changes with strain), or a capacitive strain gauge (which measures strain by measuring the change in capacitance value of the strain gauge as the strip FRP deforms), and the measured strain data can be transmitted via wired or wireless means.
[0020] Compared with the prior art, the device for testing the bonding performance between fiber-reinforced polymers and concrete provided by this utility model has the following advantages:
[0021] 1. This utility model provides a testing device that allows for different initial peel angles to be given to concrete blocks of a given fixed size by changing the spacing between the bushings (22) on both sides of the FRP support (2), thereby adapting to shear mode or mixed mode testing and realizing continuous adjustment of the peel angle. Since the concrete sample size can remain unchanged, this instrument is particularly suitable for bonding performance testing in mixed mode, and can provide reliable data support for the design of FRP reinforced structures.
[0022] 2. The negative peel angle test can also be performed by manufacturing concrete blocks with a width greater than the I-beam bushing spacing or by adjusting the bushing spacing to be less than the width of the concrete block.
[0023] 3. The FRP support is equipped with bushings on both sides. The bushings are integrated with the I-beam through the pin, so that the bushings can rotate around the pin and ensure that the load is transmitted along the FRP plane. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the overall structure of an apparatus for testing the bonding performance between fiber-reinforced polymer (FRP) and concrete in one embodiment of the present invention.
[0025] Figure 2 This is a schematic diagram of the clamp assembly in one embodiment of the present invention.
[0026] Figure 3 This is a structural schematic diagram of an FRP support member in one embodiment of the present invention.
[0027] Figure 4 This is a structural schematic diagram of the concrete fixing module in a hybrid mode according to one embodiment of the present invention.
[0028] Figure 5 This is a structural schematic diagram of the concrete fixing module in shear mode according to one embodiment of the present invention.
[0029] Figure 6This describes the installation process of the concrete fixing module in one embodiment of the present invention.
[0030] Figure 7 This is a schematic diagram showing the connection between the testing device and the upper and lower jaws of the universal testing machine in one embodiment of this utility model.
[0031] [Explanation of Labels in the Attached Image]
[0032] 1-Clamp assembly; 11-Clamp body; 111-Screw hole; 112-Bolt; 113-Opening; 12-Fixing block; 13-First clamping post;
[0033] 2-FRP support; 21-I-beam; 22-shoulder sleeve; 23-pin; 24-elongated through hole;
[0034] 3-Concrete fixing module; 31-Strip FRP; 32-Concrete specimen; 33-Second clamping column;
[0035] 41 - Upper jaw of the universal testing machine; 42 - Lower jaw of the universal testing machine. Detailed Implementation
[0036] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.
[0037] While exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.
[0038] In the description of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.
[0039] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.
[0040] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "beneath" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0041] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0042] Example 1
[0043] like Figure 1 — Figure 5 As shown, this solution discloses a testing device for the bonding performance of fiber-reinforced polymer with concrete, including: a clamp assembly 1, an FRP support 2, and a concrete fixing module 3.
[0044] The clamp assembly 1 includes a clamp body 11 with an opening 113 on one side, a fixing block 12, and a first clamping post 13 embedded and connected to the fixing block 12. The fixing block 12 is fixed in the screw hole 111 of the clamp body 11 by bolts 112, and the first clamping post 13 extends out of the clamp body 11 through the opening 113 of the clamp body 11.
[0045] Specifically, the fixture body 11 is a hollow, six-sided, thin-walled structure. The internal working space extends from the first side of the thin-walled structure to the corresponding second side, thus forming a first entrance / exit on the first and second sides. An opening 113 is formed on the third side and extends along its length and thickness, thus forming a second entrance / exit on the third side. The thin-walled structure also includes a fourth side opposite to the third side, and a fifth and sixth side arranged opposite to each other. The fifth and sixth sides are provided with several screw holes for bolts to pass through and be fixed.
[0046] The fixture assembly 1 also includes a fixing block 12 and a first clamping post 13 that is perpendicularly embedded and fixedly connected to the working surface of the fixing block 12. The fixing block 12 includes two sides perpendicular to the working surface, and a plurality of holes are formed on the two sides through the fixing block.
[0047] The fixing block 12 is fixed in the screw hole 111 of the clamp body 11 by bolts 112. In the working state, the working surface of the fixing block 12 is in contact with the third side surface of the clamp body 11. Figure 2 The first clamping post 13 extends out of the clamp body 11 through the opening 113 of the clamp body 11 (middle and upper sides) to match and fit.
[0048] The FRP support 2 includes an I-beam member 21 and bushings 22 located in the grooves on both sides of the I-beam member 21 and fixed by pins 23. The I-beam member 21 is fixed in the screw holes 111 of the fixture body 11 by bolts 112. See also Figure 3 The FRP support 2 can change the distance between the two bushings 22. Specifically, the two opposite flanges of the I-beam 21 have four corresponding elongated through holes 24. The distance between the two bushings 22 is adjusted by sliding the pin 23 within the corresponding elongated through holes 24. It is easy to understand that the pin 23 has a locking device to secure the bushings 22, whose position has been determined by sliding. This locking device can be a bolt, a clip, a self-locking rod, etc., fixed to the pin 23 or the opposite flanges of the I-beam 21; or it can be locked by an externally applied cylinder clamping device or an electromagnet-type locking device.
[0049] The FRP support member 2 includes an H-beam member 21, which has two parallel bottom surfaces with an H-shape, defining a thickness between the two bottom surfaces. This forms parallel and opposing flanges on both sides of the center portion of the H-beam member 21. A pin 23 is disposed between the two flanges on the same side, with the axes of the two pins 23 located at the same position in the thickness direction of the H-beam member and arranged parallel to each other. A rotatable bushing 22 is fitted onto each pin 23, the length of which matches the spacing between the flanges on the same side. The outer diameter of the bushing 22 is equal to or greater than the thickness of the H-beam member 21. The center portion of the H-beam member has several through holes parallel to the pins. The H-beam member is preferably made of steel.
[0050] In the working state, the I-beam member 21 enters the internal working space through the first inlet / outlet of the clamp body 11 and is fixed in the working space of the clamp body 11 by means of bolts 12 passing through the central hole, and is located between the fixing block 12 and the fourth side of the thin-walled structure. One of the bottom surfaces of the I-beam member matches and fits against the fourth side of the thin-walled structure.
[0051] The concrete fixing module 3 includes a strip FRP 31, a concrete specimen 32, and a second clamping post 33 embedded and connected to the concrete specimen 32. The two ends of the strip FRP 31 are fixedly connected to the two opposite planes of the concrete specimen 32, and the middle part of the strip FRP 31 passes through the interior of the clamp body 11 and is located between the fixing block 12 and the FRP support 2.
[0052] In the working state, the middle section of the strip FRP 31 enters the working space through the second inlet / outlet of the clamp body 11 and is attached to and supported on the FRP support 2. Based on the distance between the two bushings of the FRP support 2, the strip FRP 31 unfolds to both sides, thereby forming a peel angle with the working surface of the concrete specimen 32.
[0053] Example 2 (Installation and debugging method of the test device)
[0054] like Figure 6 — Figure 7 As shown, in one implementation scheme, the test apparatus installation process is as follows:
[0055] (1) The I-beam member 21 of the FRP support member 2 with the selected bushing spacing is placed into the working space through the first inlet and outlet, and is attached to the fourth side of the fixture body 11 and fixed with bolts 112.
[0056] (2) Pass the prepared FRP 31 of the concrete fixing module 3 through the second inlet and outlet of the clamp body 11 and stick it to the FRP support 2 so that the concrete fixing module 3 hangs down naturally and the angle between the strip FRP 31 and the working surface of the concrete fixing module 3 is determined to be the ideal angle.
[0057] (3) The fixing block 12 is placed into the working space through the first inlet and outlet, and is attached to the third side of the clamp body 11 and fixed with bolts 112.
[0058] (4) The assembled device is arranged in the order of bottom to top. First, the second clamping column 33 of the concrete fixing module 3 is clamped by the lower jaw 42 of the universal testing machine, and then the first clamping column 13 of the foundation component 13 is clamped by the upper jaw 41 of the universal testing machine.
[0059] Example 3 (Operation method for testing using a testing device)
[0060] In FRP (fiber-reinforced polymer)-concrete performance testing, pure shear mode and mixed mode are two different loading methods used to study the bond performance and interfacial behavior between FRP and concrete. Pure shear mode refers to the specimen being subjected only to shear force, without other forms of external force (such as tension or compression). In this mode, the FRP-concrete interface mainly bears shear stress. Mixed mode refers to the specimen being subjected to both shear force and other forms of external force (such as tension or compression), resulting in a more complex interfacial stress state. This mode more closely resembles the stress conditions in actual engineering projects.
[0061] In one embodiment, the apparatus for testing the bond performance between fiber-reinforced polymers and concrete is operated in hybrid mode as follows:
[0062] (1) Prepare a concrete specimen with dimensions of 100mm×100mm×250mm and pre-embed a steel bar with a diameter of 16mm in the specimen. After water curing for 28 days, the concrete specimen is surface treated to remove laitance and expose aggregate.
[0063] (2) A 50mm wide U-shaped CFRP (Carbon Fiber-Reinforced Polymer) strip was attached to two opposite surfaces of the concrete specimen. Using a wet layup process, one end of the CFRP strip was immersed in epoxy resin, and then a thin layer of epoxy resin was applied to the concrete surface. The CFRP strip was then attached to the concrete surface and allowed to cure. Multiple capacitive strain gauges were placed on the CFRP strip.
[0064] (3) Install the prepared FRP-concrete specimen into the fixture assembly, adjust the bushing spacing of the FRP support, and adjust the peel angle to 30°. Install the device onto the universal testing machine with a servo hydraulic loading frame (not shown), ensuring that the fixture and specimen are correctly positioned and the peel angle meets expectations.
[0065] (4) Start the servo-hydraulic loading frame and apply load at a rate of 0.1 mm / min until the specimen fails. During loading, the strain of CFRP is monitored in real time by strain gauges. Since the bond strength is much weaker under mixed-mode conditions, the resulting CFRP elongation and machine slippage are negligible. Therefore, the displacement readings of the servo-hydraulic loading frame are used instead of the readings of the linear variable displacement sensor.
[0066] (5) During the loading process, record the load, strain, and displacement data. This data can be used to calculate the bond stress between CFRP and concrete, and a bond-slip curve can be plotted based on the displacement data. It can also be used to evaluate the bond performance between CFRP and concrete at a 30° peel angle.
[0067] In this embodiment, the testing device can achieve continuous variation of the peeling angle θ (0° to 45°) by adjusting the length of the FRP support (sleeve spacing), and only a single concrete specimen is needed to complete the pure shear and mixed mode tests.
[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. An apparatus for testing the bond performance between fiber-reinforced polymers and concrete, characterized in that, include: The fixture assembly (1), the FRP support (2), and the concrete fixing module (3) are, among which, The clamp assembly (1) includes a clamp body (11) with an opening (113) on one side, a fixing block (12) and a first clamping post (13) embedded and connected to the fixing block (12). The fixing block (12) is fixed inside the clamp body (11) by bolts, and the first clamping post (13) extends out of the clamp body (11) through the opening (113) of the clamp body (11). The FRP support (2) includes an I-beam (21) and bushings (22) located in the grooves on both sides of the I-beam (21) and positioned by pins (23) and rotatable around pins (23); the I-beam (21) is fixed in the fixture body (11) by bolts and the spacing between the bushings (22) on both sides can be changed. The concrete fixing module (3) includes a strip FRP (31), a concrete specimen (32) and a second clamping column (33) embedded and connected to the concrete specimen (32). The two ends of the strip FRP (31) are fixedly connected to the two opposite planes of the concrete specimen (32), and the middle part of the strip FRP (31) passes through the inside of the clamp body (11) and is located between the fixing block (12) and the FRP support (2).
2. The apparatus according to claim 1, characterized in that, The I-beam (21) has corresponding elongated through holes (24) on its two opposite flanges. The spacing between the bushings (22) on both sides is adjusted by sliding the pin (23) in the elongated through holes (24). The pin (23) is equipped with a locking device.
3. The apparatus according to claim 2, characterized in that, The locking device is a mechanical locking device, a pneumatic locking device, or an electric locking device.
4. The apparatus according to claim 1, characterized in that, The two ends of the strip FRP (31) are fixedly connected to the two opposite planes of the concrete specimen (32) by an adhesive method, wherein the adhesive used in the adhesive method includes resin, cement or inorganic adhesive.
5. The apparatus according to claim 1, characterized in that, The two ends of the strip FRP (31) are fixedly connected to the two opposite planes of the concrete specimen (32) by embedding.
6. The apparatus according to claim 1, characterized in that, The first clamping column (13) and the second clamping column (33) are steel reinforcement structures with threads at the far end.
7. The apparatus according to claim 1, characterized in that, A linear variable displacement sensor is provided on the surface of the fixture assembly (1) relative to the strip FRP (31).
8. The apparatus according to claim 1, characterized in that, Multiple strain gauges are provided on the surface of the strip FRP (31).
9. The apparatus according to claim 8, characterized in that, The plurality of strain gauges are arranged at equal intervals on both sides of the loading end of the strip FRP (31) surface.
10. The apparatus according to claim 9, characterized in that, The spacing is 50mm.