Method for testing bonding strength of recombined bamboo test piece

Abstract

The invention discloses a method for testing the bonding strength of a reconstituted bamboo test piece, and relates to the technical field of bonding strength testing. According to the method, the first slotting and the second slotting are performed on the recombined bamboo test piece, so that the effective bonding area in the bonding strength testing process is effectively reduced, and the bonding strength of the recombined bamboo test piece is tested on the basis of not changing the existing standard testing equipment and testing method. Experimental results show that the testing method provided by the invention can be used for testing the bonding strength of the recombined bamboo test pieces with different densities.

Description

Technical Field

[0001] The invention relates to the technical field of bonding strength testing, and in particular to a testing method for the bonding strength of a reconstituted bamboo specimen. Background Art

[0002] Reconstructed bamboo refers to a material made by pressing bamboo bundles or bamboo bundles along the grain after being dipped in glue and dried. It has the characteristics of high density and high strength. Phenolic resin, isocyanate, etc. are usually used as adhesives, and it has excellent bonding properties. Bonding strength is a key indicator to measure the degree of bonding between materials. Through bonding strength testing, the performance of adhesives and the effectiveness of bonding processes can be accurately evaluated, which is crucial to ensuring the overall quality and reliability of products.

[0003] At present, there is still a lack of direct test methods for the bonding strength of reconstructed bamboo. The methods specified in "4.17 Bonding Strength Test" and "4.18 Glue Shear Strength Determination" in the national standard GB / T 17657-2022 are only applicable to the bonding strength test of linear bonding interfaces. The maximum test strength specified in "4.11 Internal Bonding Strength Determination" is limited by the bonding strength between the clamp and the specimen. The adhesive used in the standard will cause the clamp and the reconstructed bamboo bonding interface to be damaged during the test, but the specimen remains intact, which cannot meet the test requirements. Therefore, it is of great significance to complete the test of the bonding strength of reconstructed bamboo based on the existing standard regulations and equipment. Summary of the invention

[0004] In view of this, the present invention provides a method for testing the bonding strength of a reconstructed bamboo specimen. The present invention reduces the effective bonding area of ​​the bonding strength test by grooving the reconstructed bamboo specimen, keeps the maximum destructive load between the clamp and the specimen unchanged, and completes the test of the bonding strength of the reconstructed bamboo without changing the test instruments and equipment.

[0005] The present invention provides a method for testing the bonding strength of a reconstituted bamboo specimen, comprising: a) providing a reconstructed bamboo specimen, wherein the reconstructed bamboo specimen comprises a first surface, a second surface, a third surface and a fourth surface which are sequentially connected and have complete interlayer glue lines; The first surface and the third surface are opposite surfaces, and the second surface and the fourth surface are opposite surfaces; b) performing first grooves on the first surface and the third surface of the reconstructed bamboo specimen along the bamboo bundle arrangement direction to form symmetrical first grooves and second grooves; c) fixing the reconstructed bamboo specimen after the first groove obtained in step b) between clamps, wherein the fixing surfaces of the clamps are in contact with the second surface and the fourth surface of the reconstructed bamboo specimen respectively, and then applying a tensile force to the clamps in a direction perpendicular to the fixing surfaces until the reconstructed bamboo specimen is destroyed; d) recording the peak load when the reconstructed bamboo specimen is destroyed in step c), and calculating the bonding strength of the reconstructed bamboo specimen according to the peak load.

[0006] In some specific implementations, the first groove and the second groove are through grooves.

[0007] In some specific implementations, the first groove at least covers a complete interlayer glue line of the reconstructed bamboo specimen.

[0008] In some specific implementations, the difference between the height of the first surface or the third surface perpendicular to the arrangement direction of the bamboo bundles and the width of the first groove is ≥5 mm.

[0009] In some specific implementations, the cross-sections of the first groove and the second groove are rectangular.

[0010] In some specific implementations, the depths of the first groove and the second groove are positively correlated with the bonding strength of the reconstructed bamboo specimen.

[0011] In some specific implementations, the reconstructed bamboo specimen in step b) further comprises a second groove after the first groove; The second grooves are grooved on the second surface and the fourth surface of the reconstructed bamboo specimen along the bamboo bundle arrangement direction to form symmetrical third grooves and fourth grooves; The first groove, the second groove, the third groove and the fourth groove are coplanar.

[0012] In some specific implementations, the width of the second slot is the same as that of the first slot.

[0013] In some specific implementations, the interlayer bonding interface of the reconstructed bamboo specimen is a curve.

[0014] In some specific implementations, the density of the reconstructed bamboo specimen is 0.80 g / cm 3 ~1.35 g / cm 3 , length 50 mm, width 50 mm.

[0015] The present invention reduces the effective length and effective width of the reconstructed bamboo specimen for calculating the bonding strength by slotting, thereby reducing the effective bonding area of ​​the specimen test, maintaining the maximum destructive load between the clamp and the specimen unchanged, and realizing the test of the bonding strength of the reconstructed bamboo specimen through the current standard method without modifying the test instruments and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the first slotting of the reconstructed bamboo specimen; Figure 2The distribution diagram of interlayer glue lines of different reconstructed bamboo specimens; Figure 3 Schematic diagram of the simultaneous first and second notching of the reassembled bamboo specimen; Figure 4 Schematic diagram of the bonding strength test of reconstituted bamboo specimens; Figure 5 The bonding strength test and fracture photos of reconstituted bamboo specimens for the embodiment; Figure 6 The photos are the test results of bonding strength of reconstituted bamboo specimens of the embodiment and the comparative example; Figure 7 The load-displacement curves of the bonding strength test of the reconstituted bamboo specimens of the embodiment and the comparative example. DETAILED DESCRIPTION

[0017] It should be understood that the expression "one or more of..." includes each of the items recited after the expression individually and in various different combinations of two or more of the recited items, unless otherwise understood from the context and usage. The expression "and / or" in combination with three or more recited items should be understood to have the same meaning, unless otherwise understood from the context.

[0018] The use of the terms "comprising", "having" or "containing", including their grammatical synonyms, should generally be understood as open and non-restrictive, for example not excluding other unrecited elements or steps, unless otherwise specifically stated or otherwise understood from the context.

[0019] It should be understood that the order of steps or the order in which certain actions are performed is not important as long as the present invention remains operable. In addition, two or more steps or actions may be performed simultaneously.

[0020] The use of any and all examples or exemplary language, such as "for example" or "including", herein is intended only to better illustrate the invention and does not limit the scope of the invention unless otherwise claimed. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the invention.

[0021] In addition, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as accurately as possible. However, any numerical value inherently inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise expressly stated, it should be understood that all ranges, quantities, values ​​and percentages used in this disclosure are modified by "about". Here, "about" generally means that the actual value is within plus or minus 10%, 5%, 1% or 0.5% of a specific value or range.

[0022] The test method for the bonding strength of the reconstituted bamboo specimen provided by the present invention specifically includes: a) providing a reconstructed bamboo specimen, wherein the reconstructed bamboo specimen comprises a first surface, a second surface, a third surface and a fourth surface which are sequentially connected and have complete interlayer glue lines; The first surface and the third surface are opposite surfaces, and the second surface and the fourth surface are opposite surfaces; b) performing first grooves on the first surface and the third surface of the reconstructed bamboo specimen along the bamboo bundle arrangement direction to form symmetrical first grooves and second grooves; c) fixing the reconstructed bamboo specimen after the first groove obtained in step b) between clamps, wherein the fixing surfaces of the clamps are in contact with the second surface and the fourth surface of the reconstructed bamboo specimen respectively, and then applying a tensile force to the clamps in a direction perpendicular to the fixing surfaces until the reconstructed bamboo specimen is destroyed; d) recording the peak load when the reconstructed bamboo specimen is destroyed in step c), and calculating the bonding strength of the reconstructed bamboo specimen according to the peak load.

[0023] The present invention first provides a reconstructed bamboo specimen, the reconstructed bamboo specimen comprising a first surface, a second surface, a third surface and a fourth surface connected in sequence with complete interlayer glue lines, wherein the first surface and the third surface are opposite surfaces, and the second surface and the fourth surface are opposite surfaces. In some specific implementations, the interlayer bonding interface of the reconstructed bamboo specimen is a curve. In some specific implementations, the density of the reconstructed bamboo specimen is 0.80 g / cm 3 ~1.35g / cm 3 , length 50 mm, width 50 mm. The present invention has no special requirements on other properties of the reconstructed bamboo specimen, and those skilled in the art can select them according to their needs.

[0024] The present invention performs a first slotting on the recombinant bamboo specimen, see Figure 1 , Figure 1 The figure shows a schematic diagram of the first slotting of a reconstructed bamboo specimen provided by the present invention. Figure 1 A in the figure is the front view. Figure 1 B in the figure is the left view. Figure 1 C in the figure is the top view. Figure 1 D in the figure is an axonometric drawing, wherein 11 is the first groove, 12 is the second groove, b is the length of the reconstructed bamboo specimen, l is the width of the reconstructed bamboo specimen, b' is the effective bonding length of the reconstructed bamboo specimen, l' is the effective bonding width of the reconstructed bamboo specimen, d1 is the first groove depth of the reconstructed bamboo specimen, t is the thickness of the reconstructed bamboo specimen, and t' is the groove width of the reconstructed bamboo specimen.

[0025] like Figure 1As shown, the present invention selects two opposite surfaces of the reconstructed bamboo specimen with complete interlayer glue lines, and performs the first grooves symmetrically along the bamboo bundle arrangement direction to form symmetrical first grooves 11 and second grooves 12. The effective bonding area during the bonding strength test is reduced from the length b of the reconstructed bamboo specimen × the width l of the reconstructed bamboo specimen to the effective bonding length b' of the reconstructed bamboo specimen × the effective bonding width l' of the reconstructed bamboo specimen, thereby realizing the bonding strength test of the reconstructed bamboo specimen without changing the experimental equipment and experimental methods specified in the current standards.

[0026] Different reconstituted bamboo specimens have different raw material properties, preparation processes and density distribution. Figure 2 The figure shows the distribution of glue lines between different reconstructed bamboo specimens. Figure 2 A1 and Figure 2 A2 is made of green bamboo with a density of 1.2g / cm 3 Photos and schematic diagram of the distribution of glue lines between layers of reconstructed bamboo specimens; Figure 2 B1 and Figure 2 B2 in the figure is made of bamboo with a density of 1.2 g / cm 3 Photos and schematic diagram of the distribution of glue lines between layers of reconstructed bamboo specimens; Figure 2 C1 and Figure 2 C2 in the figure is made of bamboo with a density of 0.9 g / cm 3 Therefore, in some specific implementations of the present invention, the first slot at least covers a complete interlayer glue line of the reconstructed bamboo specimen to ensure the accuracy of the test results.

[0027] In the present invention, the thickness t of the reconstructed bamboo specimen used for testing is related to the thickness of the assembly unit and the compression ratio of the board. In some specific implementations, the difference between the height of the first surface or the third surface perpendicular to the bamboo bundle arrangement direction and the width of the first groove is ≥5 mm. Figure 1 For reference, the height of the first surface or the third surface perpendicular to the arrangement direction of the bamboo bundles is the thickness t of the reconstructed bamboo specimen, and the width of the first groove is the groove width t' of the reconstructed bamboo specimen. To ensure the accuracy of the test results, the difference between the thickness t of the reconstructed bamboo specimen and the groove width t' of the reconstructed bamboo specimen is ≥5 mm.

[0028] In order to simplify the test process and facilitate the calculation of the effective bonding area, in some specific implementations of the present invention, the first groove 11 and the second groove 12 are through grooves. The present invention has no special restrictions on the groove method. For example, a sliding table saw can be used for grooves. The width of the saw blade is the same as the groove width of the reconstructed bamboo specimen. The groove depth is the height of the saw blade exposed from the platform, ensuring that the groove width and groove depth of the same batch of specimens are consistent. In some specific implementations of the present invention, the cross-sections of the first groove 11 and the second groove 12 are rectangular.

[0029] The present invention flexibly controls the effective bonding area of ​​the test piece by changing the groove depth, and adjusts the test range of the internal bonding strength to meet the test requirements of the internal bonding strength of various types of reconstructed bamboo. In some specific implementations of the present invention, the depths of the first groove and the second groove are positively correlated with the bonding strength of the reconstructed bamboo test piece.

[0030] In order to adapt to reconstructed bamboo specimens with different bonding strengths, in some specific implementations of the present invention, a second groove is further provided after the first groove is provided on the reconstructed bamboo specimen; The second grooves are grooved on the second surface and the fourth surface of the reconstructed bamboo specimen along the bamboo bundle arrangement direction to form symmetrical third grooves and fourth grooves; The first groove, the second groove, the third groove and the fourth groove are coplanar.

[0031] See also Figure 3 , Figure 3 Schematic diagram of the reconstructed bamboo specimen with the first and second grooves being made simultaneously. Figure 3 A in the figure is the front view. Figure 3 B in the figure is the left view. Figure 3 C in the figure is the top view. Figure 3 D in the figure is an axonometric drawing, wherein 31 is the first groove, 32 is the second groove, 33 is the third groove, 34 is the fourth groove, b is the length of the reconstructed bamboo specimen, l is the width of the reconstructed bamboo specimen, b' is the effective bonding length of the reconstructed bamboo specimen, l' is the effective bonding width of the reconstructed bamboo specimen, d1 is the first groove depth of the reconstructed bamboo specimen, d2 is the second groove depth of the reconstructed bamboo specimen, t is the thickness of the reconstructed bamboo specimen, and t' is the groove width of the reconstructed bamboo specimen.

[0032] After the second slotting, the effective bonding area of ​​the reconstructed bamboo specimens was further reduced. Figure 3 In the embodiment, the effective bonding area of ​​the reconstructed bamboo specimen is the effective bonding length b'×the effective bonding width l'.

[0033] In some specific implementations, the width of the second slot is the same as that of the first slot.

[0034] After the grooves are cut, the bonding strength of the reconstructed bamboo specimen is tested according to the experimental method of "4.11 Internal bonding strength determination" in the national standard GB / T 17657-2022. Figure 4 As shown, the slotted reconstructed bamboo specimen is fixed between the fixtures. Figure 4 A in the figure is a schematic diagram of the bonding strength test of the reconstructed bamboo specimen after the first groove. Figure 4 B in the figure is a schematic diagram of the bonding strength test of the reconstructed bamboo specimens that are simultaneously subjected to the first and second grooves, wherein 1 is a clamp, 2 is a metal clamp, 3 is an adhesive, 4 is the reconstructed bamboo specimen after the first groove, and 5 is the reconstructed bamboo specimen that is simultaneously subjected to the first and second grooves; F is the tensile force applied to the clamp. The reconstructed bamboo specimen 4 or 5 is fixed to the metal clamp 2 by the adhesive 3. After the fixing is completed, a tensile force F is applied to the clamp until the reconstructed bamboo specimen is destroyed. The maximum load when the reconstructed bamboo specimen is destroyed is recorded, according to the formula: bonding strength ( ) = Maximum load (F max ) / effective bonding area (l'×b') to calculate the bonding strength of the reconstructed bamboo specimens.

[0035] The present invention reduces the effective length and effective width of the reconstructed bamboo specimen for calculating the bonding strength through the first groove and the second groove, thereby reducing the effective bonding area of ​​the specimen test, and maintaining the maximum destructive load between the clamp and the specimen unchanged without modifying the test instruments and equipment, thereby realizing the test of the bonding strength of the reconstructed bamboo specimen through the current standard method.

[0036] The present invention is further described below in conjunction with the following examples. The protection scope of the present invention is not limited by the following examples.

[0037] Example 1 See also Figure 1 , Figure 1 The figure shows the schematic diagram of slotting of the reconstructed bamboo specimen in this embodiment. Figure 1 A in the figure is the front view. Figure 1 B in the figure is the left view. Figure 1 C in the figure is the top view. Figure 1 D in the figure is an axonometric diagram, wherein 11 is the first groove, 12 is the second groove, b is the length of the reconstructed bamboo specimen, l is the width of the reconstructed bamboo specimen, b' is the effective bonding length of the reconstructed bamboo specimen, l' is the effective bonding width of the reconstructed bamboo specimen, d1 is the first groove depth of the reconstructed bamboo specimen, t is the thickness of the reconstructed bamboo specimen, and t' is the groove width of the reconstructed bamboo specimen. In this embodiment, the length b of the reconstructed bamboo specimen is 50±1 mm, the width l of the reconstructed bamboo specimen is 50±1 mm, the thickness t of the reconstructed bamboo specimen is 18.5±1 mm, the first groove is made along the bamboo bundle arrangement direction, the groove width t' is 6.0±1 mm, and the first groove depth d1 is 12.8±1 mm.

[0038] Comparative Example 1 The difference between the reconstructed bamboo specimen provided in this comparative example and Example 1 is that the reconstructed bamboo specimen is not grooved.

[0039] Test Example 1 The bonding strength of the reconstructed bamboo specimen provided in Example 1 was tested according to the specimen fixing and loading method of "4.11 Internal bonding strength test" in the national standard GB / T17657-2022. Figure 5 A in the figure is a schematic diagram of the loading device for the bonding strength test. As shown in the figure, the reconstructed bamboo specimen is glued to the metal clamp using hot melt adhesive, and a universal mechanical testing machine is used to apply a tensile force F for testing. 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 The reconstructed bamboo specimens were numbered 1 to 5 and tested respectively. According to the formula: bonding strength ( ) = Maximum load (F max ) / effective bonding area (l'×b'), the bonding strength of the reconstructed bamboo specimens was calculated, and the specimen with the same number was tested three times and the arithmetic mean value was taken. The results are listed in Table 1. Figure 5 B1 to B5 in the figure are photos of the fracture of the reconstructed bamboo specimens numbered 1 to 5 during the test process. It can be seen that the test method provided by the present invention can be applied to the test of reconstructed bamboo specimens with different densities.

[0040] Table 1 Gluing strength test results of reconstituted bamboo specimens in Example

[0041]

[0042] It can be seen from Table 1 that by slotting the reconstructed bamboo specimens and reducing the effective area of ​​the bonding strength test, the bonding strength test of reconstructed bamboo specimens with different densities can be completed without changing the original experimental device.

[0043] Test Example 2 The reconstructed bamboo specimens provided in Example 1 and Comparative Example 1 were respectively subjected to bonding strength tests, and the density of the reconstructed bamboo specimens was 1.20 g / cm 3 The test apparatus and method are the same as those in Test Example 1. The results are listed in Table 2. Figure 6 This is a photo of the bonding strength test results of the reconstructed bamboo specimens. Figure 6 A in the figure is a photo of the test results of comparative example 1. Figure 6 B in the figure is a photo of the test results of Example 1. Figure 6It can be seen that when the bonding strength of the reconstructed bamboo specimen of Comparative Example 1 is tested without grooving, the bonding interface between the specimen and the metal clamp will be destroyed first, while the bonding interface of the specimen itself is not destroyed, and effective testing cannot be performed; while in Example 1, since the effective bonding area is reduced by grooving, the bonding interface inside the specimen is effectively destroyed, and the bonding strength test can be performed.

[0044] Table 2 Gluing strength test results of the embodiments and comparative examples

[0045]

[0046] Figure 7 The load-displacement curves during the bonding strength test of the reconstructed bamboo specimens provided in Example 1 and Comparative Example 1 show that the maximum load value required for the bonding strength test of the reconstructed bamboo specimen provided in Example 1 is smaller.

[0047] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for testing the bonding strength of reconstituted bamboo specimens, characterized in that: include: a) providing a reconstructed bamboo specimen, wherein the reconstructed bamboo specimen comprises a first surface, a second surface, a third surface and a fourth surface which are sequentially connected and have complete interlayer glue lines; The first surface and the third surface are opposite surfaces, and the second surface and the fourth surface are opposite surfaces; b) performing first grooves on the first surface and the third surface of the reconstructed bamboo specimen along the bamboo bundle arrangement direction to form symmetrical first grooves and second grooves; c) fixing the reconstructed bamboo specimen after the first groove obtained in step b) between clamps, wherein the fixing surfaces of the clamps are in contact with the second surface and the fourth surface of the reconstructed bamboo specimen respectively, and then applying a tensile force to the clamps in a direction perpendicular to the fixing surfaces until the reconstructed bamboo specimen is destroyed; d) recording the peak load when the reconstructed bamboo specimen is destroyed in step c), and calculating the bonding strength of the reconstructed bamboo specimen according to the peak load.

2. The testing method according to claim 1, characterized in that: The first groove and the second groove are through grooves.

3. The testing method according to claim 1, characterized in that: The first slot at least covers a complete interlayer glue line of the reconstructed bamboo specimen.

4. The testing method according to claim 1, characterized in that: The difference between the height of the first surface or the third surface perpendicular to the arrangement direction of the bamboo bundles and the width of the first groove is ≥5 mm.

5. The testing method according to claim 1, characterized in that: The cross sections of the first groove and the second groove are rectangular.

6. The testing method according to claim 1, characterized in that: The depths of the first groove and the second groove are negatively correlated with the load peak value when the reconstructed bamboo specimen is destroyed.

7. The testing method according to claim 1, characterized in that: The step b) further includes a second groove after the first groove of the reconstructed bamboo specimen; The second grooves are grooved on the second surface and the fourth surface of the reconstructed bamboo specimen along the bamboo bundle arrangement direction to form symmetrical third grooves and fourth grooves; The first groove, the second groove, the third groove and the fourth groove are coplanar.

8. The testing method according to claim 7, characterized in that: The width of the second slot is the same as that of the first slot.

9. The testing method according to claim 7, characterized in that: The interlayer bonding interface of the reconstructed bamboo specimen is a curve.

10. The testing method according to claim 1, characterized in that: The density of the reconstituted bamboo specimen is 0.80 g / cm 3 ~1.35 g / cm 3 , length 50 mm, width 50 mm.

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