Device and method for testing slippage friction coefficient between prepreg layers

Abstract

The invention discloses a testing device and a testing method for a slippage friction coefficient between prepreg layers, and belongs to the technical field of mechanical testing of composite materials. The device comprises a clamping fixture connected with a mechanical testing machine, a cast aluminum heating plate for providing temperature and fixing a sliding prepreg, two fixing plates for fixing a static prepreg, two sliding table cylinders for providing normal pressure and a supporting bottom plate. The sliding table air cylinder can be controlled by the air compressor to drive the fixing plate to apply normal pressure to the cast aluminum heating plate, and the cast aluminum heating plate can be driven by the clamping fixture to move up and down along the Z axis, so that a friction force-displacement curve and a friction coefficient between prepregs in different fiber directions under different external processing conditions are obtained. The device for testing the interlayer sliding friction coefficient of the prepreg can flexibly test the interlayer friction coefficient of the prepreg in various fiber directions, and ensures the temperature uniformity and the pressure accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material mechanical testing, and particularly relates to a device and method for testing the sliding friction coefficient between prepreg layers. Background Art

[0002] Carbon fiber composites are widely used in high-end manufacturing fields such as aerospace due to their excellent mechanical properties and designability. However, during the preforming process of composite components, relative slip occurs between prepreg layers due to the influence of external processing conditions such as temperature and pressure. When interlayer slip behavior is hindered, defects such as in-plane buckling and out-of-plane wrinkling can easily occur, leading to a decrease in the mechanical properties of the composite component. Therefore, studying the interlayer slip behavior of prepreg materials and accurately determining the interlayer friction coefficient can provide model parameters for numerical simulations, which is of great significance for optimizing the molding process and improving molding quality.

[0003] The existing testing devices for the interlayer sliding friction coefficient of prepregs have the following main problems: first, due to the limitations of the prepreg fixing method, it is difficult to accurately measure the interlayer friction coefficient of prepregs with different fiber angles; second, the heating method cannot ensure temperature uniformity during dynamic measurement; third, the pressurization method cannot provide accurate and continuously adjustable pressure values.

[0004] Chinese invention patent publication number CN 118914067 A discloses a device and method for measuring the slippage behavior of prepregs. In this device, the prepreg is fixed using a U-shaped bend. This fixation method can easily cause fiber breakage or prepreg bending and wrinkling in the prepreg sample, resulting in cracks or bulges in the prepreg during slippage, thereby affecting the accuracy of the test process.

[0005] Chinese invention patent publication number CN 114062249 A discloses a prepreg clamping mechanism and a device and method for measuring interlayer friction behavior. This patent utilizes a heating plate installed in the support section for heating. However, during long-distance sliding, the prepreg is prone to losing contact with the heat source, making it impossible to guarantee uniform temperature throughout the entire prepreg test. Because the resin state in the prepreg is highly temperature-dependent, this method is prone to biased test results.

[0006] Chinese invention patent publication number CN 116026756 A discloses a device and modeling method for measuring slip characteristics in prepreg molding processes. This device applies pressure by controlling the compression distance of a spring. However, this method requires a pressure sensor to calibrate the spring pressure, resulting in a cumbersome experimental process and consistency issues. Furthermore, the testing process is limited by the spring compression distance, making it impossible to achieve wide-range pressure control. Furthermore, temperature fluctuations during actual testing can cause changes in the spring's elastic modulus or hysteresis during repeated loading and unloading, making stable pressure output impossible.

[0007] Therefore, in view of the above shortcomings, it is necessary to provide a testing device and a testing method that can accurately measure the sliding friction coefficient between prepreg layers with different fiber directions, while ensuring good temperature uniformity and pressure accuracy. Summary of the Invention

[0008] The purpose of the present invention is to overcome the defects in the prior art and provide a prepreg interlayer sliding friction coefficient testing device and testing method, which can accurately measure the interlayer friction coefficient at different temperatures, pressures, speeds and different fiber directions.

[0009] The specific technical solutions adopted in the present invention are as follows:

[0010] In a first aspect, the present invention provides a device for testing the sliding friction coefficient between prepreg layers, comprising a clamping fixture, a cast aluminum heating plate, a fixing plate, and a slide cylinder;

[0011] The top of the clamping fixture can be connected to the mechanical testing machine through a connecting pin, and the lower part can adjust the distance between the two clamping blocks through a clamping screw to clamp the top of the cast aluminum heating plate; on the cast aluminum heating plate, the lower parts of the two sides parallel to the XOZ plane are used to symmetrically stick and fix the sliding prepreg; the outer sides of the two sliding prepregs are respectively provided with fixed plates, and the fixed plates include a horizontal bottom plate and a vertical plate connected in an L-shape; the horizontal bottom plate is fixed to the working end of the slide cylinder, and can drive the vertical plate to move back and forth along the Y-axis direction, and the inner side of the vertical plate is used to stick and fix the stationary prepreg; the air compressor can control the slide cylinder to drive the fixed plate to apply normal pressure to the cast aluminum heating plate, and the clamping fixture can drive the cast aluminum heating plate to move up and down along the Z-axis, thereby obtaining the friction force-displacement curve and friction coefficient between prepregs with different fiber directions under different external processing conditions.

[0012] Preferably, the clamping fixture comprises a connecting pin, a guide post, a clamping block and a clamping screw;

[0013] The connecting pin is located at the top of the clamp bracket, and its length direction is parallel to the Y-axis direction; the two clamping screws are respectively threadedly connected to the two sides of the clamp bracket, and their length directions are parallel to the Y-axis direction. The inner sides of the two clamping screws are respectively rotatably connected to clamping blocks, and the two clamping blocks are both slidably connected to the guide column. Under the drive of the clamping screws, they can slide back and forth along the guide column to adjust the degree of clamping of the cast aluminum heating plate; the guide column is fixed on the clamp bracket, and its length direction is parallel to the Y-axis direction.

[0014] Furthermore, the inner side of the clamping block is a serrated structure to increase the contact friction with the cast aluminum heating plate.

[0015] Preferably, the cast aluminum heating plate is a square column structure with its length direction parallel to the Z axis.

[0016] Preferably, the sliding prepreg is adhered to the cast aluminum heating plate by 502 strong instant glue, and the pasting position is determined by marking lines on the cast aluminum heating plate with a vernier caliper; the stationary prepreg is adhered to the fixed plate by 502 strong instant glue, and the pasting position is determined by marking lines on the fixed plate with a vernier caliper.

[0017] Preferably, the area of the stationary prepreg is smaller than that of the sliding prepreg.

[0018] Preferably, the cast aluminum heating plate is connected to a temperature control box via a temperature probe hole and a power terminal to achieve temperature adjustment from room temperature to 350°C.

[0019] Preferably, the fixing plate is of L-shaped structure and is made of die steel. Reinforcing ribs are provided between the horizontal bottom plate and the vertical plate to ensure the verticality of the two.

[0020] Preferably, the bottom of the slide cylinder is fixed on the supporting base plate and air is taken in by an air compressor; a digital pressure gauge is connected between the air compressor and the slide cylinder to achieve normal pressure control of 0 to 2.5 MPa.

[0021] In a second aspect, the present invention provides a testing method using the prepreg interlayer sliding friction coefficient testing device according to any one of the first aspects, as follows:

[0022] S1: Fix the clamping fixture on the mechanical testing machine, adjust the centering and lock it;

[0023] S2: Cut the prepreg to the target size and fiber orientation, then attach the prepreg to the cast aluminum heating plate and the fixed plate along the scribed lines. The prepreg attached to both sides of the cast aluminum heating plate is the sliding prepreg, and the prepreg attached to the fixed plate is the stationary prepreg. The stationary prepreg has a smaller area than the sliding prepreg to ensure a constant contact area in the pull-through test principle. The stationary and sliding prepregs are in full contact with the cast aluminum heating plate during the dynamic test.

[0024] S3: By rotating the clamping screw, the two clamps clamp the top of the cast aluminum heating plate and adjust the centering of the cast aluminum heating plate at the same time;

[0025] S4: Heat the cast aluminum heating plate to a test temperature of 60-80°C using a temperature control box, and adjust the normal pressure applied by the two fixed plates to the cast aluminum heating plate to a range of 0.1-0.3 MPa using a digital pressure gauge;

[0026] S5: The cast aluminum heating plate is driven upward by a mechanical testing machine, with the direction of movement being consistent with the centerline of the cast aluminum heating plate. A test program is set up to adjust the heating temperature of the cast aluminum heating plate, the normal pressure applied by the two fixed plates to the cast aluminum heating plate, the sliding rate and sliding displacement of the cast aluminum heating plate along the Z axis driven by the mechanical testing machine, and obtain the friction force-displacement curves and friction coefficients between prepregs with different fiber orientations under different external processing conditions.

[0027] S6: In order to deal with the slippage between the prepreg or isolation film and the mold, prepreg or isolation film is only pasted on both sides of the cast aluminum heating plate and used as a sliding prepreg or sliding isolation film. There is no need to paste prepreg on the fixed plate, so that the fixed plate made of mold steel is in direct contact with the sliding prepreg or sliding isolation film. Then, by setting up a test program, adjusting the heating temperature of the cast aluminum heating plate, the normal pressure applied by the two fixed plates to the cast aluminum heating plate, the sliding rate of the cast aluminum heating plate driven by the mechanical testing machine along the Z axis, and the sliding displacement, the friction force-displacement curve and friction coefficient of the prepreg or isolation film and the mold under different external processing conditions are obtained.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] In the present invention, the prepregs with different fiber directions are pasted in the specified position by using instant glue to fix the sheet, which can flexibly test the interlayer friction coefficient of prepregs with fibers of different orientations; at the same time, the use of additional fixed pressing plates is reduced, the bending problem of the prepreg sheet is avoided, and the flatness and fit of the prepreg sheet during the test are guaranteed. A cast aluminum heating plate and a temperature control box are used to adjust the temperature. The heating area can completely cover the area of the sliding prepreg and the static prepreg, ensuring the uniformity of the temperature during the dynamic test, and the temperature can be adjusted in a large range, which is more efficient than the overall heating method such as the oven. A sliding cylinder is used to drive the fixed plate to achieve normal pressurization, and the pressure is adjusted by a digital pressure gauge to achieve high-precision control of the pressure. It can realize the test of the interlayer friction coefficient of prepregs with different temperatures, pressures, sliding rates, and fiber directions, as well as the test of the friction coefficient between the prepreg / isolating film-mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0031] Figure 2 for Figure 1 Schematic diagram of the structure of the middle clamping fixture;

[0032] Figure 3 for Figure 1 Schematic diagram of the cast aluminum heating plate, fixed plate, slide cylinder and prepreg position;

[0033] Figure 4 The sliding resistance-sliding displacement curves under different normal pressure conditions in the embodiment;

[0034] Figure 5 The friction curve between the isolation film and the mold in the embodiment;

[0035] In the figure: 1-clamping fixture, 2-cast aluminum heating plate, 3-fixing plate, 4-slide cylinder, 5-support base plate, 6-connecting pin, 7-guide column, 8-clamping block, 9-clamping screw, 10-temperature probe hole, 11-power terminal, 12-reinforcement rib, 13-temperature control box, 14-digital pressure gauge. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0037] In the description of the present invention, it should be understood that when an element is considered to be "connected" to another element, it can be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0038] In the present invention, for the convenience of description, Figure 1 The XYZ coordinate axes in the figure are used as the reference to illustrate the positional relationship of the components in the device of the present invention. Unless otherwise specified, the positional relationship of the present invention is described in this manner.

[0039] like Figure 1 The figure shows a device for testing the sliding friction coefficient between prepreg layers provided by the present invention. The device primarily comprises a clamping fixture 1, a cast aluminum heating plate 2, a fixed plate 3, and a slide cylinder 4, forming a vertical measuring device. The structure and connection methods of each component are described in detail below.

[0040] In the device of the present invention, the top of the clamping fixture 1 can be connected to a mechanical testing machine via a connecting pin 6. During actual use, the centering can be adjusted and locked, and then the sliding portion of the device (primarily including the cast aluminum heating plate 2) can be driven upward by the mechanical testing machine. The lower portion of the clamping fixture 1 can adjust the distance between the two clamping blocks 8 via a clamping screw 9 to clamp the top of the cast aluminum heating plate 2.

[0041] As a preferred embodiment of the present invention, Figure 2 As shown, the clamping fixture 1 mainly includes a connecting pin 6, a guide column 7, a clamping block 8 and a clamping screw 9. Specifically, the connecting pin 6 is located at the top of the clamp bracket, and the length direction is parallel to the Y-axis direction. The two clamping screws 9 are respectively threadedly connected to the two sides of the clamp bracket, and the length directions are parallel to the Y-axis direction. The inner sides of the two clamping screws 9 (i.e., the side close to the cast aluminum heating plate 2) are respectively rotatably connected with clamping blocks 8, and the two clamping blocks 8 are both slidably connected to the guide column 7. In actual use, the inner side of the clamping block 8 can be set to a serrated structure to increase the contact friction with the cast aluminum heating plate 2 and prevent the cast aluminum heating plate 2 from sliding or shifting during the test. Driven by the two clamping screws 9, the two clamping blocks 8 can slide back and forth along the guide column 7 respectively to adjust the degree of clamping of the cast aluminum heating plate 2. The guide column 7 is fixed on the clamp bracket, and the length direction is parallel to the Y-axis direction. Multiple guide columns 7 can be provided as needed, as in the present embodiment Figure 2 There are two guide columns 7 in the middle to keep the clamping block 8 stable in the horizontal direction. In actual use, the clamping screws 9 on both sides push the clamping block 8 along the guide columns 7 to clamp the cast aluminum heating plate 2. The horizontal movement of the clamping block 8 along the guide columns 7 ensures the verticality of the clamping of the cast aluminum heating plate 2.

[0042] In the device of the present invention, the lower parts of the two sides of the cast aluminum heating plate 2 that are parallel to the XOZ plane are used to symmetrically stick and fix the sliding prepregs. The outer sides of the two sliding prepregs are respectively provided with fixed plates 3, and the fixed plates 3 include a horizontal base plate and a vertical plate connected in an L-shape. The horizontal base plate is fixed to the active end of the slide cylinder 4, and can drive the vertical plate to move back and forth along the Y-axis direction. The inner side of the vertical plate is used to stick and fix the static prepreg. The air compressor can control the slide cylinder 4 to drive the fixed plate 3 to apply normal pressure to the cast aluminum heating plate 2, and the clamping fixture 1 can drive the cast aluminum heating plate 2 to move up and down along the Z-axis, thereby obtaining the friction force-displacement curve and friction coefficient between prepregs with different fiber directions under different external processing conditions (that is, between the sliding prepreg and the static prepreg on the same side of the cast aluminum heating plate).

[0043] As a preferred embodiment of the present invention, Figure 3 As shown, the cast aluminum heating plate 2 is a square column structure with its length direction parallel to the Z axis. The cast aluminum heating plate 2 serves as both a heating module of the device and a fixing module for the sliding prepreg. The cast aluminum heating plate 2 can be connected to the temperature control box 13 through the temperature probe hole 10 and the power terminal 11, thereby achieving precise temperature adjustment from room temperature to 350°C. In actual use, the prepreg sheets of target angle and size are pasted on both sides of the cast aluminum heating plate 2 by 502 strong instant glue. The prepregs pasted on both sides of the cast aluminum heating plate 2 are used as sliding prepregs. The pasting positions of the two sliding prepregs on the cast aluminum heating plate 2 can be determined by marking the cast aluminum heating plate 2 with a height vernier caliper.

[0044] As a preferred embodiment of the present invention, there are two fixed plates 3, both of which are L-shaped structures, including a horizontal base plate and a vertical plate. The fixed plates 3 are made of mold steel, and the friction coefficient test between the prepreg / isolating membrane and the mold can be achieved by directly contacting the fixed plates 3 with the sliding prepreg or the sliding isolating membrane. Reinforcing ribs 12 are provided between the horizontal base plate and the vertical plate, and the reinforcing ribs 12 are used to ensure the verticality of the two and avoid skewing during the test. The bottom of the fixed plate 3 contains four bolt holes, which are connected to the slide cylinder 4 by detachable bolts. In actual use, the prepreg sheets of the target angle and size are pasted on the inner side of the two fixed plates 3 by 502 strong instant glue. The prepregs pasted on the two fixed plates 3 are used as static prepregs. The pasting positions of the two static prepregs on the two fixed plates 3 can be determined by marking lines on the fixed plates 3 with a height vernier caliper.

[0045] It should be noted that the stationary prepreg and the sliding prepreg on the same side of the cast aluminum heating plate 2 are grouped together. In each group, the area of the stationary prepreg should be smaller than that of the sliding prepreg, so as to ensure that the contact area in the pull-through test principle is constant.

[0046] In a preferred embodiment of the present invention, the bottom of the slide cylinder 4 is bolted to the support base plate 5, and air is supplied by an air compressor. A digital pressure gauge 14 is connected between the air compressor and the slide cylinder 4 to control the normal pressure within a range of 0 to 2.5 MPa, driving the fixed plate 3 to apply normal pressure to the cast aluminum heating plate 2. The slide cylinder 4 and digital pressure gauge 14 can also be combined with a pressure sensor to provide even more precise normal pressure readings.

[0047] In a preferred embodiment of the present invention, the two sets of fixed plates 3 and the slide cylinder 4 are symmetrically mounted to simultaneously apply the same normal pressure to both sides of the cast aluminum heating plate 2. The two sets of sliding prepregs and the stationary prepreg are both symmetrically attached. This symmetrical attachment arrangement reduces the need for additional fixed platens, avoids bending of the prepregs, and ensures uniform pressure on both sets of prepregs.

[0048] Based on the above-mentioned prepreg interlayer sliding friction coefficient testing device, the present invention also provides a testing method, and the steps of the method are as follows:

[0049] S1: Fix the clamping fixture 1 on the mechanical testing machine, adjust the centering and lock it.

[0050] S2: Use a blanking machine to cut prepreg to the target size and fiber orientation. Then, the prepreg to be tested is attached to the cast aluminum heating plate 2 and fixed plate 3 along the scribed lines. The prepreg attached to both sides of the cast aluminum heating plate 2 is used as the sliding prepreg, and the prepreg attached to the fixed plate 3 is used as the stationary prepreg. The area of the stationary prepreg is smaller than that of the sliding prepreg to ensure a constant contact area in the pull-through test principle. During the dynamic test, the stationary and sliding prepregs are in full contact with the cast aluminum heating plate 2.

[0051] S3: Fix the slide cylinder 4 to the supporting base plate 5, and install the fixing plate 3 on the slide cylinder 4. By turning the clamping screw 9, the two clamping blocks 8 clamp the top of the cast aluminum heating plate 2; at the same time, by adjusting the clamping screws 9 on both sides, the centering of the cast aluminum heating plate 2 is adjusted.

[0052] S4: Heat the cast aluminum heating plate 2 to a test temperature of 60-80° C. through the temperature control box 13 , and adjust the normal pressure applied by the two fixing plates 3 to the cast aluminum heating plate 2 to a range of 0.1-0.3 MPa through the digital pressure gauge 14 .

[0053] S5: The cast aluminum heating plate 2 is driven upward by the mechanical testing machine, with the direction of movement being consistent with the centerline of the cast aluminum heating plate 2. A test program is set up to adjust the heating temperature of the cast aluminum heating plate 2, the normal pressure applied by the two fixed plates 3 to the cast aluminum heating plate 2, the sliding rate and sliding displacement of the cast aluminum heating plate 2 along the Z axis driven by the mechanical testing machine, and obtain the friction force-displacement curves and friction coefficients between prepregs with different fiber orientations (sliding prepregs and stationary prepregs) under different external processing conditions.

[0054] S6: In view of the slippage between the prepreg or isolation film and the mold, the prepreg or isolation film is only pasted on both sides of the cast aluminum heating plate 2 and used as a sliding prepreg or sliding isolation film. There is no need to paste the prepreg on the fixed plate 3, so that the fixed plate 3 made of mold steel is in direct contact with the sliding prepreg or sliding isolation film. Then, by setting up a test program, adjusting the heating temperature of the cast aluminum heating plate 2, the normal pressure applied by the two fixed plates 3 to the cast aluminum heating plate 2, the sliding rate and sliding displacement of the cast aluminum heating plate 2 along the Z axis driven by the mechanical testing machine, the friction force-displacement curve and friction coefficient of the prepreg or isolation film and the mold (i.e., the fixed plate) under different external processing conditions are obtained.

[0055] The testing method of the above device of the present invention will be specifically described below through examples.

[0056] Example 1

[0057] This embodiment uses the above-mentioned prepreg interlayer sliding friction coefficient testing device to implement a method for testing the friction coefficient between prepregs. The specific steps of the testing method are as follows:

[0058] S1. Fix the clamp 1 on the mechanical testing machine, adjust the centering and lock it.

[0059] S2, use a height vernier caliper to mark a line 100mm away from the bottom of the cast aluminum heating plate 2, and use instant glue to cut the size of 50×100mm 2 , the sliding prepreg with a fiber direction of 0° is pasted on the scale range on both sides of the cast aluminum heating plate 2; use a height vernier caliper to mark the 100mm and 50mm distance from the top of the fixed plate 3, and use instant glue to cut the size of 50×50mm 2 , the static prepreg with a fiber direction of 0° is pasted between the two engraved lines on both sides of the fixed plate 3;

[0060] Before pasting the prepreg, use a blade to scrape or wipe with acetone to remove dirt on the surface of the cast aluminum heating plate 2 and the fixed plate 3 to ensure the flatness of the prepreg sheet after pasting.

[0061] S3. Fix the slide cylinder 4 on the supporting base plate 5, install the fixed plate 3 on the slide cylinder 4, clamp the cast aluminum heating plate 2 in the clamping fixture 1, and adjust the centering of the device; after each set of sample tests, only the cast aluminum heating plate 2 and the fixed plate 3 need to be removed, and the slide cylinder 4 does not need to be repeatedly disassembled.

[0062] Adjust the initial position of the cast aluminum heating plate 2 to be above the slide cylinder 4 to avoid unnecessary friction between the cast aluminum heating plate 2 and the slide cylinder 4.

[0063] S4. Heat the device to 70° C. through the temperature control box 13, and adjust the normal pressure to 0.1 MPa, 0.2 MPa, and 0.3 MPa respectively through the digital pressure gauge 14, and maintain them for 2 minutes.

[0064] S5. Set the test speed to 4 mm / min and the sliding displacement to 20 mm. Use the mechanical testing machine to drive the cast aluminum heating plate 2 to move upward. The movement direction is consistent with the center line of the cast aluminum heating plate 2. Obtain the tension-displacement curve under the test conditions. The sliding resistance and friction coefficient can be calculated. Where f is the sliding resistance, μ is the friction coefficient, F is the tensile force measured by the mechanical testing machine, N is the applied normal pressure, and S is the contact area between the sliding prepreg and the stationary prepreg (i.e., the area of the stationary prepreg).

[0065] like Figure 4 The sliding resistance-sliding displacement curves under different normal pressure conditions are shown. The experimental results show that the sliding resistance gradually increases with the increase of normal pressure.

[0066] Example 2

[0067] This example utilizes the aforementioned prepreg interlayer sliding friction coefficient testing device to provide a method for testing the friction coefficient between the isolation diaphragm and the mold. The testing steps are largely the same as those in the previous example, differing only in that the prepreg is not attached to the fixed plate 3; instead, the mold steel fixed plate 3 directly contacts the sliding isolation diaphragm. At room temperature, the normal pressure is adjusted to 0.2 MPa using a digital pressure gauge 14 and maintained for 2 minutes. The test speed is set to 4 mm / min, and the sliding distance is 20 mm.

[0068] like Figure 5 As shown in FIG, the friction curve between the isolation film and the mold shows that the friction coefficient is stable at around 0.044 under the test conditions.

[0069] The prepreg interlayer sliding friction coefficient testing device of the present invention can flexibly test the interlayer friction coefficients between prepregs of various fiber directions and ensure temperature uniformity and pressure accuracy.

[0070] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A device for testing the sliding friction coefficient between prepreg layers, characterized in that: It comprises a clamping fixture (1), a cast aluminum heating plate (2), a fixing plate (3) and a slide cylinder (4); The top of the clamping fixture (1) can be connected to the mechanical testing machine through a connecting pin (6), and the lower part can adjust the distance between the two clamping blocks (8) through a clamping screw (9) to clamp the top of the cast aluminum heating plate (2); on the cast aluminum heating plate (2), the lower parts of the two sides parallel to the XOZ plane are used to symmetrically stick and fix the sliding prepreg; the outer sides of the two sliding prepregs are respectively provided with fixed plates (3), and the fixed plates (3) include a horizontal bottom plate and a vertical plate connected in an L shape; the horizontal bottom plate is fixed to the active end of the slide cylinder (4), and can drive the vertical plate to move back and forth along the Y-axis direction, and the inner side of the vertical plate is used to stick and fix the stationary prepreg; the slide cylinder (4) can be controlled by an air compressor to drive the fixed plate (3) to apply normal pressure to the cast aluminum heating plate (2), and the clamping fixture (1) can drive the cast aluminum heating plate (2) to move up and down along the Z-axis, thereby obtaining the friction force-displacement curve and friction coefficient between the prepregs with different fiber directions under different external processing conditions.

2. A prepreg interlayer sliding friction coefficient testing device according to claim 1, characterized in that: The clamping fixture (1) comprises a connecting pin (6), a guide column (7), a clamping block (8) and a clamping screw (9); The connecting pin (6) is located at the top of the clamp bracket, and its length direction is parallel to the Y-axis direction; the two clamping screws (9) are respectively threadedly connected to the two sides of the clamp bracket, and their length directions are parallel to the Y-axis direction. The inner sides of the two clamping screws (9) are respectively rotatably connected with clamping blocks (8), and the two clamping blocks (8) are both slidably connected to the guide column (7). Under the drive of the clamping screws (9), they can slide back and forth along the guide column (7) to adjust the degree of clamping of the cast aluminum heating plate (2); the guide column (7) is fixed on the clamp bracket, and its length direction is parallel to the Y-axis direction.

3. A prepreg interlayer sliding friction coefficient testing device according to claim 2, characterized in that: The inner side of the clamping block (8) is a sawtooth structure to increase the contact friction with the cast aluminum heating plate (2).

4. The device for testing the sliding friction coefficient between prepreg layers according to claim 1, wherein: The cast aluminum heating plate (2) is a square column structure with its length direction parallel to the Z axis.

5. The device for testing the sliding friction coefficient between prepreg layers according to claim 1, characterized in that: The sliding prepreg is adhered to the cast aluminum heating plate (2) by using 502 strong instant glue, and the adhering position is determined by marking lines on the cast aluminum heating plate (2) with a vernier caliper; the stationary prepreg is adhered to the fixed plate (3) by using 502 strong instant glue, and the adhering position is determined by marking lines on the fixed plate (3) with a vernier caliper.

6. The device for testing the sliding friction coefficient between prepreg layers according to claim 1, characterized in that: The area of the stationary prepreg is smaller than the area of the sliding prepreg.

7. The device for testing the sliding friction coefficient between prepreg layers according to claim 1, characterized in that: The cast aluminum heating plate (2) is connected to a temperature control box (13) via a temperature probe hole (10) and a power supply terminal (11) to achieve temperature regulation from room temperature to 350°C.

8. The device for testing the sliding friction coefficient between prepreg layers according to claim 1, characterized in that: The fixing plate (3) is an L-shaped structure, made of die steel, and a reinforcing rib (12) is provided between the horizontal bottom plate and the vertical plate to ensure the verticality of the two.

9. The device for testing the sliding friction coefficient between prepreg layers according to claim 1, characterized in that: The bottom of the slide cylinder (4) is fixed on the supporting base plate (5) and is supplied with air through an air compressor; a digital pressure gauge (14) is connected between the air compressor and the slide cylinder (4) to achieve normal pressure control of 0 to 2.5 MPa.

10. A testing method using the prepreg interlayer sliding friction coefficient testing device according to any one of claims 1 to 9, characterized in that: The details are as follows: S1: Fix the clamp (1) on the mechanical testing machine, adjust the centering and lock it; S2: Cut the prepreg to target size and fiber direction, and then paste the prepreg to be tested on the cast aluminum heating plate (2) and the fixed plate (3) along the scribed line positions; the prepregs pasted on both sides of the cast aluminum heating plate (2) are used as sliding prepregs, and the prepregs pasted on the fixed plate (3) are used as static prepregs; the area of the static prepreg is smaller than the area of the sliding prepreg, ensuring that the contact area in the pull-through test principle is constant, and the static prepreg and the sliding prepreg are in full contact with the cast aluminum heating plate (2) during the dynamic test; S3: by rotating the clamping screw (9), the two clamping blocks (8) clamp the top of the cast aluminum heating plate (2), and at the same time adjust the centering degree of the cast aluminum heating plate (2); S4: heating the cast aluminum heating plate (2) to a test temperature of 60 to 80° C. through a temperature control box (13), and adjusting the normal pressure applied by the two fixed plates (3) to the cast aluminum heating plate (2) to a range of 0.1 to 0.3 MPa through a digital pressure gauge (14); S5: The cast aluminum heating plate (2) is driven to move upward by a mechanical testing machine, and the direction of movement is consistent with the center line of the cast aluminum heating plate (2); a test program is set to adjust the heating temperature of the cast aluminum heating plate (2), the normal pressure applied by the two fixing plates (3) to the cast aluminum heating plate (2), the sliding rate and sliding displacement of the cast aluminum heating plate (2) along the Z axis driven by the mechanical testing machine, and obtain the friction force-displacement curve and friction coefficient between prepregs with different fiber directions under different external processing conditions; S6: In view of the slippage between the prepreg or isolation film and the mold, the prepreg or isolation film is only pasted on both sides of the cast aluminum heating plate (2) and used as a sliding prepreg or sliding isolation film, and there is no need to paste the prepreg on the fixed plate (3), so that the fixed plate (3) made of mold steel is directly in contact with the sliding prepreg or sliding isolation film, and then by setting a test program, adjusting the heating temperature of the cast aluminum heating plate (2), the normal pressure applied by the two fixed plates (3) to the cast aluminum heating plate (2), the sliding rate of the cast aluminum heating plate (2) driven by the mechanical testing machine along the Z axis and the sliding displacement, the friction force-displacement curve and friction coefficient of the prepreg or isolation film and the mold under different external processing conditions are obtained.

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