A method for preparing a test sample of a high-performance yarn for bending performance

Abstract

The application discloses a kind of high-performance yarn's bending performance sample preparation method, utilize sample preparation device to high-performance fiber yarn sample preparation, sample preparation device includes constant tension unwinding device, pressure roller mechanism, flat pressing mechanism and sample clamping device, constant tension unwinding device, pressure roller mechanism, flat pressing mechanism cooperate to high-performance fiber yarn constant tension unwinding, straightening, flattening, ensure that the obtained tow is in natural straightening no bending, and no damage state, then utilize sample clamping device to guarantee that tow is vertically centered when sample preparation, and sample is prepared.The application solves the problem that the bending performance of high-performance fiber yarn is measured by using KES-FB2 bending tester, the brittleness of high-performance fiber yarn itself is large, easy to fluff, poor flexibility, very small diameter, if not centering tow, the difference of inclined section is large, resulting in large difference in results, and the sample preparation efficiency is improved, the economic utility is high, and the operation is simple.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of textile measurement, and particularly relates to a sample preparation method for the bending performance of high-performance yarn. BACKGROUND

[0002] The bending performance of fibers determines the difficulty of weaving fabrics to a great extent. The existing test methods for the bending performance of yarn mainly include cantilever beam test method, slope method, KES-FB2 measurement method and single fiber measurement method. However, the yarns involved are traditional yarns, and the test and research on the bending performance of high-performance fiber yarn are less.

[0003] Currently, the KES-FB2 bending tester is mainly used to measure and characterize common high-performance yarns. However, there is a great difference between the data obtained by different laboratories, which is mainly caused by the lack of a unified sample preparation method. Through experimental experience, it is found that there are the following problems in sample preparation: first, the high-performance fiber has poor flexibility, which causes the yarn to have a certain bending when it is unwound; second, the high-performance fiber is brittle and prone to fuzzing, and the unwinding process of the high-performance fiber bundle from the yarn cylinder is prone to breakage and fuzzing; third, it is difficult to ensure the vertical centering of the yarn during manual sample preparation, and the efficiency is low, which seriously affects the test results. SUMMARY

[0004] The application provides a sample preparation method for the bending performance of high-performance yarn, which solves the problem of large difference in results caused by the large brittleness and fuzzing of high-performance fiber yarn, poor flexibility, small diameter and large difference in inclined section of the off-center fiber bundle when the KES-FB2 bending tester is used to measure the bending performance of high-performance fiber yarn, and improves the sample preparation efficiency, has high economic efficiency and is simple to operate.

[0005] The technical solution of the application is as follows: a sample preparation method for the bending performance of high-performance yarn, which uses a sample preparation device to prepare the high-performance fiber yarn. The sample preparation device comprises a constant-tension unwinding device, a roller pressing mechanism, a flat pressing mechanism and a sample clamping device. The constant-tension unwinding device, the roller pressing mechanism and the flat pressing mechanism cooperate to unwind, straighten and flatten the high-performance fiber yarn at a constant tension, so that the obtained fiber bundle is in a natural straightening and non-bending state without damage. Then, the sample clamping device is used to quickly vertically center the fiber bundle during sample preparation, and a sample is prepared. The method comprises the following steps:

[0006] Step 1: unwinding the high-performance fiber yarn wound on the yarn cylinder at a constant tension through the constant-tension unwinding device;

[0007] Step 2: the unwound high-performance fiber yarn enters the roller pressing mechanism along the horizontal direction, and the roller pressing mechanism is used to straighten the high-performance fiber yarn;

[0008] Step three, after the high-performance fiber yarn is straightened, the high-performance fiber yarn is pressed for 6 to 12 hours by a pressing mechanism according to the rigidity of the high-performance fiber yarn, and the remaining bending of the high-performance fiber yarn is eliminated again, at this time, the unwinding process is stopped, so that the high-performance fiber yarn can completely eliminate the bending deformation on the bobbin, and the fiber bundle is obtained;

[0009] Step four, the fiber bundle is fixed on the sample clamping device, and the sample clamping device is clamped to complete the sample preparation, and the sample is obtained.

[0010] Compared with the prior art, the present application has the following advantages:

[0011] (1) The present application solves the problem that the high-performance fiber yarn is fragile, easy to fluff, poor in flexibility, and small in diameter, and the difference between the inclined cross sections of the off-center fiber bundle is large when the KES-FB2 bending tester is used to measure the bending performance of the high-performance fiber yarn, and the sample preparation efficiency is improved, the economic effect is high, and the operation is simple.

[0012] (2) The high-performance fiber yarn is fragile and easy to fluff, and the high-performance fiber bundle is prone to breakage and fluffing during unwinding from the bobbin, and the high-performance fiber yarn is unwound by the constant tension unwinding device. The flexibility of the high-performance fiber is poor, and the bending of the high-performance fiber after unwinding is eliminated by straightening and flattening. The diameter of the yarn is very small, and the fiber yarn can be quickly centered by the sample clamping device, the cross-sectional shape of the yarn is maintained, and the large difference between the inclined cross sections of the off-center fiber bundle is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 It is a structure schematic view of the constant tension unwinding device, the pressing mechanism and the pressing mechanism of the present application.

[0014] Fig. 2 It is a structure schematic view of the sample clamping device of the present application.

[0015] Fig. 3 It is a schematic view of the sample clamping device of the present application clamped in the bending tester clamping jaw. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0017] It should be noted that all the directionality indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directionality indications will also change accordingly.

[0018] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixation" and the like should be understood in a broad sense, for example, "fixation" can be fixed connection, or detachable connection, or integral; "connection" can be mechanical connection, or electrical connection. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0019] In addition, the technical solutions of various embodiments of the present application can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor is it within the protection scope required by the present application.

[0020] The specific embodiments, technical difficulties and points of the present application will be further introduced below in combination with the design examples.

[0021] Since the high-performance fiber yarn is brittle and prone to fluffing, the high-performance fiber tows are prone to breakage and fluffing during unwinding from the yarn barrel, therefore, in order to avoid these phenomena, the high-performance fiber needs to be unwound at a constant tension, and thus a constant-tension unwinding device is designed to unwind the high-performance fiber yarn at a constant tension. Since the high-performance fiber yarn is less flexible, it is bent after being unwound from the yarn barrel, and thus the present application eliminates the existing bending of the high-performance fiber tows through straightening and flattening processes, and reduces experimental errors. The diameter of the fiber tows is very small, and if the tows are not centered, the cross-sectional difference will be large, which will greatly affect the experimental results, and the fiber tows need to be perpendicular to the jaws, and thus the present application can quickly center the fiber yarn through the sample clamping device, maintain the cross-sectional shape of the yarn, improve the test efficiency, and reduce experimental errors.

[0022] In combination Figs. 1-3 A sample preparation method for the bending performance of high-performance yarn, which utilizes a sample preparation device to prepare the high-performance fiber yarn, and the sample preparation device comprises a constant-tension unwinding device 1, a pressing roller mechanism 2, a flattening mechanism 3, and a sample clamping device 4, and comprises the following steps:

[0023] Step one, the high-performance fiber yarn wound on the yarn barrel is unwound at a constant tension by the constant-tension unwinding device 1.

[0024] The constant tension unwinding device 1 is arranged on a workbench and comprises a transmission mechanism 11, a rotating shaft 13, a brake 112, a support 121, a motor 111, a tension controller 14 and a tension detector. The motor 111, the brake 112 and the tension detector are fixed on a wire disc 12. The output end of the motor 111 is connected with the rotating shaft 13. The rotating shaft 13 and the brake 112 are connected through the transmission mechanism 11. The support 121 is located on the inner side of the wire disc 12. The rotating shaft 13 is vertically connected with the support 121 after penetrating through the wire disc 12. The tension detector measures the tension in real time. The transmission mechanism 11 controls the wire disc 12 to realize the unwinding of the high-performance fiber yarn with constant tension through the motor 111, the tension controller 14 and the brake 112.

[0025] In step two, the high-performance fiber yarn after unwinding enters the pressing mechanism 2. The pressing mechanism 2 is used to straighten the high-performance fiber yarn.

[0026] The high-performance fiber yarn is straightened and flattened to ensure that the high-performance fiber yarn can completely eliminate the bending deformation on the bobbin. The straightening process ensures that the high-performance fiber yarn is straightened without damage when different types of high-performance fiber yarns are changed. The bending phenomenon generated during the unwinding of the high-performance fiber yarn is improved, and the brittle fiber is not damaged.

[0027] The high-performance fiber yarn output by the constant tension unwinding device 1 enters the pressing mechanism 2 along the horizontal direction.

[0028] The pressing mechanism 2 comprises a pressing frame 21, a lower pressing roller 22, an upper pressing roller 23 and a driving cylinder 24 serving as a power source. The driving cylinder 24 is located on the top surface of the pressing frame 21. The upper pressing roller 23 and the lower pressing roller 22 are arranged in the pressing frame 21 from top to bottom. The gap between the lower pressing roller 22 and the upper pressing roller 23 changes by adjusting the pressure of the driving cylinder 24, so that the pressing force of the high-performance fiber yarn is adjusted to straighten the high-performance fiber yarn.

[0029] In step three, after the high-performance fiber yarn is straightened, the high-performance fiber yarn is pressed for 6 to 12 hours by the pressing mechanism 3 according to the stiffness of the high-performance fiber yarn to eliminate the remaining bending of the high-performance fiber yarn. At this time, the unwinding process is stopped to ensure that the high-performance fiber yarn can completely eliminate the bending deformation on the bobbin and obtain a fiber bundle.

[0030] The pressing mechanism 3 comprises an upper pressing block 31 and a bottom block 32. The upper pressing block 31 is located on the top surface of the bottom block 32 and is hinged to the bottom block 32. The bottom block 32 is fixed on an operating table. The upper pressing block 31 presses the straightened high-performance fiber yarn for 6 to 12 hours. The pressing time is adjusted according to the stiffness of the high-performance fiber yarn. The materials of the bottom block 32 and the upper pressing block 31 are both anti-static organic glass plates and acrylic plates. The top surface of the bottom block 32 is on the same horizontal line as the output end of the pressing mechanism 2.

[0031] Step 4: Fix the filament bundle onto the sample clamping device 4, and use the sample clamping device 4 to clamp the sample to complete the sample preparation and obtain the sample.

[0032] The sample clamping device 4 includes two fixing blocks 41, two fiber fixing plates 42, and two detachable positioning blocks 44. Each fixing block 41 has a fiber fixing plate 42 on its top surface. The fixing block 41 is elongated and has a fiber positioning groove 43 running through its width in the center. The two detachable positioning blocks 44 are arranged in parallel and symmetrical arrangement, and the two fixing blocks 41 are also arranged in parallel and symmetrical arrangement. The two ends of the fixing blocks 41 are in contact with the two detachable positioning blocks 44 respectively. The position of the fixing blocks 41 is determined by the detachable positioning blocks 44, and the position of the filament bundle is quickly determined by the fiber positioning grooves 43 on the two fixing blocks 41. The filament bundle is fixed by the cooperation of the fiber fixing plates 42 and the fiber positioning grooves 43 on the fixing blocks 41. The inside of the fiber positioning grooves 43 has textured patterns to increase roughness and increase the friction between the filament bundle and the groove. The bottom surface of the fiber fixing plates 42 also has textured patterns to increase roughness.

[0033] Before fixing the filament bundle, two detachable positioning blocks 44 are placed on both sides of the two fixing blocks 41. After fixing the position of the filament bundle, they are removed, ensuring that the two fixing blocks 41 are parallel. The fixing blocks 41 are elongated. The fiber positioning slot 43 allows the filament bundle to be quickly and vertically centered and fixed in the center of the fixing block 41. The fiber fixing plate 42 is used in conjunction with the fiber positioning slot 43 to fix the filament bundle. After sample preparation, the two fixing blocks 41 are used to clamp the sample in the jaws for testing.

[0034] Both the detachable positioning block 44 and the fixing block 41 are made of PVC sheet.

[0035] Place the sample clamping device 4 with the detachable positioning block 44 removed flat on the working platform of the KES-FB2 bending tester. Then, slowly push the fixing block 41 into the open clamping jaws of the KES-FB2 bending tester along the platform. Stop pushing when the test area of ​​the sample coincides with the test area of ​​the KES-FB2 bending tester. Turn on the KES-FB2 bending tester so that its clamping jaws clamp the fixing block 41 and start the test.

[0036] The high-performance fiber yarn sample first bends uniformly to the left along the clamping jaws of the KES-FB2 bending tester, then returns after reaching a certain position. It then bends to the right, reaching the same position before returning, and finally returns to its initial state. The KES-FB2 bending tester measures the bending moment M, obtaining a curve showing the relationship between bending moment M and curvature K. Based on the principle, the bending stiffness (cN·cm) is calculated. 2 The bending moment B per unit width is defined as the bending moment B exerted per unit curvature change.

[0037]

[0038] where M is the bending moment (cN-cm) experienced by the unit width sample and K is the curvature (cm -1 ) of the sample. The average stiffness is therefore represented by the slope of the bending moment M - curvature K curve. Due to the effect of friction between the yarn and the fiber, the stiffness changes significantly at the beginning of the bending, and then gradually changes to a constant. Therefore, the linear stage of the curve is intercepted and fitted to obtain the bending stiffness of the yarn.

[0039] The present application utilizes the cooperation of the constant tension unwinding device 1, the compression roller mechanism 2 and the flat pressing mechanism 3 to perform constant tension unwinding, straightening and flattening on the high-performance fiber yarn, so as to ensure that the unwound and pretreated sample is in a natural straightening and non-bending state without damage. The sample clamping device 4 ensures that the yarn is quickly vertically centered during sample preparation.

Claims

1. A method of preparing a test specimen for bending performance of a high performance yarn, characterized by, The high-performance fiber yarn is sampled by using a sampling device, the sampling device comprises a constant tension unwinding device (1), a roller pressing mechanism (2), a flat pressing mechanism (3) and a sample clamping device (4), the constant tension unwinding device (1), the roller pressing mechanism (2) and the flat pressing mechanism (3) cooperate to unwind, straighten and flatten the high-performance fiber yarn under constant tension, so that the obtained fiber bundle is in a natural straightening and bending-free state without damage, and the sample clamping device (4) is used to ensure that the fiber bundle is vertically centered during sampling, and the sample is prepared; The sample clamping device (4) comprises two fixed blocks (41), two fiber fixing plates (42) and two detachable positioning blocks (44), each fixed block (41) is provided with a fiber fixing plate (42) on the top surface, the fixed block (41) is in a strip shape, and a fiber positioning clamping groove (43) is formed in the center of the fixed block (41) in the width direction; the two detachable positioning blocks (44) are symmetrically arranged in parallel, the two fixed blocks (41) are symmetrically arranged in parallel, and the two ends of the fixed block (41) are in contact with the two detachable positioning blocks (44), respectively, the position of the fixed block (41) is determined by the detachable positioning block (44), the position of the fiber bundle is quickly determined by the fiber positioning clamping groove (43) on the two fixed blocks (41), and the fiber bundle is fixed by the fiber fixing plate (42) and the fiber positioning clamping groove (43) on the fixed block (41).

2. The method of preparing a test specimen of bending performance of a high- performance yarn according to claim 1, characterized in that, The method comprises the following steps: Step one, the high-performance fiber yarn wound on the yarn drum is unwound under constant tension by the constant tension unwinding device (1); Step two, the unwound high-performance fiber yarn enters the roller pressing mechanism (2) in the horizontal direction, and the high-performance fiber yarn is straightened by the roller pressing mechanism (2); Step three, after the high-performance fiber yarn is straightened, the high-performance fiber yarn is flat pressed for 6 to 12 hours according to the rigidity of the high-performance fiber yarn by the flat pressing mechanism (3), and the residual bending of the high-performance fiber yarn is eliminated again, at this time, the unwinding process is stopped, so that the high-performance fiber yarn can completely eliminate the bending deformation brought by the yarn drum, and the fiber bundle is obtained; Step four, the fiber bundle is fixed on the sample clamping device (4), and the sampling is completed after being clamped by the sample clamping device (4), and the sample is obtained.

3. The method for preparing a sample of the bending performance of the high-performance yarn according to claim 1, characterized in that: The constant tension unwinding device (1) arranged on the workbench comprises a transmission mechanism (11), a rotating shaft (13), a brake (112), a support (121), a motor (111), a tension controller (14) and a tension detector, the motor (111), the brake (112) and the tension detector are fixed on a wire reel (12), the output end of the motor (111) is connected with the rotating shaft (13), the rotating shaft (13) and the brake (112) are connected through the transmission mechanism (11), the support (121) is located on the inner side of the wire reel (12), the rotating shaft (13) is vertically through the wire reel (12) and is fixedly connected with the support (121), the tension detector measures the tension in real time, and the transmission mechanism (11) controls the wire reel (12) to realize the unwinding of the high-performance fiber yarn with constant tension through the motor (111), the tension controller (14) and the brake (112).

4. The method of preparing a test specimen of bending performance of a high- performance yarn according to claim 1, characterized in that: The pressing roller mechanism (2) comprises a pressing roller frame (21), a lower pressing roller (22), an upper pressing roller (23) and a driving cylinder (24) serving as a power source, the driving cylinder (24) is located on the top surface of the pressing roller frame (21), the upper pressing roller (23) and the lower pressing roller (22) are arranged in the pressing roller frame (21) from top to bottom, the gap between the lower pressing roller (22) and the upper pressing roller (23) is changed by adjusting the pressure of the driving cylinder (24), and then the pressing force of the high-performance fiber yarn is adjusted, so that the high-performance fiber yarn is straightened.

5. The method of preparing a test specimen of bending performance of a high- performance yarn according to claim 1, characterized in that: The flat pressing mechanism (3) comprises an upper pressing block (31) and a bottom block (32), the upper pressing block (31) is located on the top surface of the bottom block (32) and is rotationally connected with the bottom block (32); the bottom block (32) is fixed on the operation table, the upper pressing block (31) is controlled to flat press the straightened high-performance fiber yarn, the flat pressing time is adjusted according to the rigidity of the high-performance fiber yarn; the top surface of the bottom block (32) is on the same horizontal line as the output end of the pressing roller mechanism (2).

6. The method of preparing a test specimen of bending performance of a high- performance yarn according to claim 5, characterized in that: The materials of the bottom block (32) and the upper pressing block (31) are both anti-static organic glass plate acrylic plates.

7. The method of preparing a test specimen of bending performance of a high- performance yarn according to claim 1, characterized in that: The fiber positioning clamping groove (43) is internally provided with a roughness-increasing pattern to increase the friction between the fiber bundle and the clamping groove; the bottom surface of the fiber fixing pressing piece (42) is provided with a matching roughness-increasing pattern.

8. The method of preparing a test specimen of bending performance of a high- performance yarn according to claim 1, characterized in that: The detachable positioning block (44) and the fixing block (41) are both PVC thin plates.

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