Determination method of fiber winding forming friction coefficient

Abstract

The invention discloses a method for measuring a fiber winding forming friction coefficient. The method comprises the following steps: step S1, establishing a winding core model geometric model in CADWIND software; s2, a pre-estimated friction coefficient and a winding angle matched with the pre-estimated friction coefficient are given to carry out winding line type design, so that the simulated winding line type just reaches a polar hole root cutting state; s3, generating a winding program which can be executed by the numerical control system; s4, processing the geometric model of the winding core model to a formal winding state, performing trial winding by using the winding program output in the step S3, and judging the relationship between the actual friction coefficient and the preset friction coefficient in the step S2; and S5, according to a judgment result obtained by trial winding in the step S4, adjusting the preset friction coefficient in the step S2 and the winding angle matched with the preset friction coefficient until the fiber is in a root cutting state during simulation, and taking the preset friction coefficient at the moment as an actual friction coefficient. According to the invention, the defects in conventional determination are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of fiber material molding, in particular to a method for determining a friction coefficient of fiber winding molding. Background Art

[0002] As an important composite material forming process, filament winding has the advantages of high automation, high production efficiency, good mechanical properties of products and low cost. It has been widely used in aerospace military industry, pressure vessels, municipal environment and other fields. There are two main ways to design the line of filament winding: geodesic and non-geodesic. The geodesic winding trajectory is the line with the shortest distance between any two points on the surface of the core mold. The position of the geodesic on the curved surface is the most stable. Geodesic winding is a stable winding without slippage. However, geodesic winding is greatly affected by the geometric shape of the product and has great process limitations. Theoretically, if the fiber bundle deviates from the geodesic trajectory, under the action of the winding tension, the fiber bundle has a tendency to automatically slide in the direction of the geodesic trajectory. In fact, due to the friction between the fiber bundle and the surface of the core mold or between the fiber layers, as long as the fiber deviates not far from the geodesic trajectory, it can still be stably wound, which provides a certain flexibility for the design of the wound product, so that the fiber winding meets both the process stability requirements and the design structural size requirements. Theoretical analysis shows that the condition for the stable winding of non-geodesic fibers is that the maximum slip coefficient of the designed line is not greater than the friction coefficient between the fiber and the core mold. It can be seen that the friction coefficient between the fiber and the core mold is an important parameter and basis in the design of winding line.

[0003] At present, when designing winding lines in the industry, the friction coefficient is mostly based on experience. For example, the maximum value of wet winding is generally 0.1~0.14, and the maximum value of dry winding is 0.3~0.37. Some scholars have also tried to test the friction coefficient of fiber winding under laboratory conditions using test methods such as the slider method and the pull-out method from the perspective of tribology. However, laboratory testing requires a dedicated test device, and because fiber winding molding is a complex dynamic process, the actual friction coefficient is affected by factors such as the surface state of the core mold (material, roughness, etc.), resin viscosity, fiber tension, glue content, and winding speed. In actual winding, there are often uneven tension, speed fluctuations, and fiber overhead phenomena, which will affect the fiber friction coefficient. The empirical value or the data obtained under laboratory conditions is difficult to fully match the actual winding production conditions, resulting in a large blindness in the design of the winding line. The winding line designed by the process has a greater risk of slipping in actual production. Summary of the invention

[0004] The present invention provides a method for measuring the friction coefficient of fiber winding molding to overcome the shortcomings and defects mentioned in the above background technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A method for determining a friction coefficient of a fiber winding process comprises the following steps: Step S1, establishing a winding core mold geometric model in CADWIND software; Step S2: Given an estimated friction coefficient f 1 And the matching winding angle α 1 , the non-geodesic winding function module in CADWIND software is used to design the winding line shape of the winding core mold geometric model, so that the simulated winding line shape just reaches the extreme hole cutting root state; Step S3, setting machine tool parameters in CADWIND software, performing post-processing, and generating a winding program executable by the CNC system;

[0006] Step S4: Process the winding core mold geometric model designed by the winding line in step S2 to the formal winding state, and use the winding program output in step S3 to perform trial winding, and judge the actual friction coefficient and the preset friction coefficient in step S2 according to the fiber root cutting state at the pole hole. f 1 relationship; Step S5: According to the judgment result obtained by the trial winding in step S4, the preset friction coefficient in step S2 is f 1 And the matching winding angle α 1 Adjust until the fiber is in the root cutting state during simulation and the fiber is in the root cutting state during the trial winding test. Record the preset friction coefficient at this time as the actual friction coefficient when the product is formally wound and formed. f n .

[0007] Furthermore, in step S1, the winding core mold has an isopolar hole structure or an unequal polar hole structure.

[0008] Furthermore, when designing the winding line in step S2, it is sufficient to ensure that the root cutting at either end of the front pole hole or the rear pole hole of the line can be simulated.

[0009] Furthermore, the process conditions during the trial winding in step S4 are consistent with the formal winding state.

[0010] Furthermore, the judgment process in step S4 is as follows: If the polar fiber is just cut at the root during the trial winding, it means that the actual friction coefficient is equal to the friction coefficient preset in step S2. f 1 If the polar fiber is in the expanded state during the winding test, it means that the actual friction coefficient is greater than the friction coefficient preset in step S2. f 1If the polar fiber is in a shrinkage state during the winding test, it means that the actual friction coefficient is less than the friction coefficient preset in step S2. f 1 .

[0011] Compared with the prior art, the present invention has the following advantages: (1) The present invention provides a method for measuring the friction coefficient between the fiber and the surface of the core mold during fiber winding, thereby avoiding the blindness of taking values ​​based on experience.

[0012] (2) When testing the fiber winding friction coefficient under conventional laboratory conditions, it is impossible to simulate the phenomena of uneven tension, speed fluctuation, and fiber overhead in the actual winding process, and the measurement results are biased. The measurement conditions of the fiber friction coefficient in the present invention are consistent with the actual product production status, and the measurement results are accurate and reliable.

[0013] (3) The method of the present invention does not require special test equipment and can be implemented by fiber winding production enterprises relying on existing production conditions. The operation is convenient, fast and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 These are the design parameters used when the non-geodesic line type design of the embodiment is first performed using CADWIND simulation software.

[0015] Figure 3 The line type simulation results of the non-geodesic line type design of the embodiment are performed for the first time using CADWIND simulation software.

[0016] Figure 4 To test the winding effect according to the embodiment, the non-geodesic line design parameters after optimization and adjustment are obtained.

[0017] Figure 5 To test the winding effect according to the embodiment, the simulation results of the non-geodesic line type after optimization and adjustment are shown. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0019] The present embodiment discloses a method for determining the friction coefficient of fiber winding, which is applicable to any fiber winding process of wet winding, dry winding or semi-dry winding, and the applicable winding core mold is an isopolar pore structure or an unequal pore structure. Specifically, a 38L IV type hydrogen storage gas cylinder is used as a winding core mold, the composite material layer adopts T700-12K grade carbon fiber, and the winding process is epoxy resin wet winding molding as an example for explanation. The outer diameter of the cylinder column section is φ285mm, the front and rear bottle mouth diameters are both φ80mm, and the total length is 660mm. This embodiment uses a method combining CADWIND simulation and actual product trial winding to determine the actual friction coefficient of fiber winding, such as Figure 1 As shown, the specific steps are as follows: Step S1, according to the size of the gas cylinder product, establish the winding core mold geometric model of the gas cylinder product in CADWIND software. When establishing the geometric model for longitudinal grid division, the number of frames of the front and rear heads are set to 20 frames, and the column section is set to 10 frames.

[0020] S2. Use the non-geodesic winding function module in CADWIND software to design the winding line type of the winding core mold geometric model of the gas cylinder product. Specifically, 6 bundles of T700-12K carbon fiber are used for winding, with a yarn width of 15mm and an estimated friction coefficient of f 1= 0.12 and the matching winding angle α 1= 11.5°, the turning area position is set by default, and the front and rear pole holes are not set with a dwell angle. The linear design parameters are shown in Figure 2 As shown, the simulated winding line just reaches the state of pole hole cutting root. Figure 3 shown.

[0021] S3. According to the actual winding equipment conditions, set the machine tool parameters in CADWIND software. The machine tool parameters include the speed and acceleration of each motion axis. Then perform post-processing, which includes calculation mode, control data optimization, safety distance, and motion step length. This generates a winding program that can be executed by the CNC system. The code format of the winding program is NC code.

[0022] S4, processing the winding core mold geometric model of the gas cylinder product that has been designed with winding lines in step S2 to a formal winding state, and evenly coating the surface of the winding core mold geometric model with winding resin.

[0023] Then, the winding program output in step S3 is used to test the winding core mold geometric model of the gas cylinder product. The test winding process parameters are consistent with the formal winding state, and the process parameters include the number of fiber bundles, tension, yarn width, glue content, and running speed. Among them, the tension of a single fiber bundle is set to 50N, and the maximum running speed of the yarn rack trolley is 30m / min.

[0024] Next, the actual friction coefficient and the preset friction coefficient in step S2 are determined according to the fiber cutting state at the pole hole. f 1 When the polar fiber is just cut at the root during the trial winding, the judgment result is that the actual friction coefficient is equal to the friction coefficient preset in step S2. f 1 When the polar hole fiber is in the expanded state (i.e. the yarn is away from the polar hole) during the trial winding, the judgment result is that the actual friction coefficient is greater than the friction coefficient preset in step S2 f 1 When the polar fiber is in a shrinkage state (i.e., yarn accumulation) during the trial winding, the judgment result is that the actual friction coefficient is less than the friction coefficient preset in step S2. f 1 .

[0025] In this embodiment, when the winding core mold geometric model of the gas cylinder product is tested, the result is that the polar fiber is in a shrinkage state (yarn accumulation), indicating that the actual friction coefficient is less than the preset friction coefficient in step S2. f 1= 0.12.

[0026] S5, according to the judgment result obtained by the trial winding in step S4, the preset friction coefficient in step S2 is f 1 And the matching winding angle α 1 Adjust the preset friction coefficient f 1 Adjust the setting to 0.1, the winding angle α 1 The adjustment setting was 13.5°. The fiber was in the root-cut state during the simulation, but it was still in the shrinkage state during the winding test, indicating that the actual friction coefficient was less than 0.1.

[0027] At this time Figure 4 As shown, the friction coefficient is preset when designing the non-geodesic line shape. f 1 Adjust the setting to 0.08, the wrap angle α 1 Adjust the setting to 15°, and CADWIND software simulates the root cutting state (such as Figure 5 As shown in the figure), the fiber is also in the root cutting state when it is put on the machine for trial winding.

[0028] When the fiber is in the root cutting state during simulation, record the preset friction coefficient at this time f 1= 0.08, as the actual friction coefficient of the Type IV hydrogen storage cylinder when it is formally wound under current production conditions f n,Right now f n = f 1= 0.08.

[0029] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction, and such combinations should also be regarded as the contents disclosed in the present disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0030] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by technical personnel in this field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A method for determining the friction coefficient of fiber winding, characterized in that: The following steps are involved: Step S1, establishing a winding core mold geometric model in CADWIND software; Step S2: Given an estimated friction coefficient f 1 And the matching winding angle α 1 , the non-geodesic winding function module in CADWIND software is used to design the winding line shape of the winding core mold geometric model, so that the simulated winding line shape just reaches the extreme hole cutting root state; Step S3, setting machine tool parameters in CADWIND software, performing post-processing, and generating a winding program executable by the CNC system; Step S4: Process the winding core mold geometric model designed by the winding line in step S2 to the formal winding state, and use the winding program output in step S3 to perform trial winding, and judge the actual friction coefficient and the preset friction coefficient in step S2 according to the fiber root cutting state at the pole hole. f 1 relationship; Step S5: According to the judgment result obtained by the trial winding in step S4, the preset friction coefficient in step S2 is f 1 And the matching winding angle α 1 Adjust until the fiber is in the root cutting state during simulation and the fiber is in the root cutting state during the trial winding test. Record the preset friction coefficient at this time as the actual friction coefficient when the product is formally wound and formed. f n .

2. The method for determining the friction coefficient of filament winding according to claim 1, characterized in that: In step S1, the winding core mold has an isopolar hole structure or an unequal polar hole structure.

3. The method for determining the friction coefficient of filament winding according to claim 1, characterized in that: When designing the winding line in step S2, it is sufficient to ensure that the root cutting at either end of the front pole hole or the rear pole hole of the line can be simulated.

4. The method for determining the friction coefficient of filament winding according to claim 1, characterized in that: The process conditions during the trial winding in step S4 are consistent with the formal winding state.

5. The method for determining the friction coefficient of filament winding according to claim 1, characterized in that: The judgment process in step S4 is as follows: If the polar fiber is just cut at the root during the trial winding, it means that the actual friction coefficient is equal to the friction coefficient preset in step S2. f 1 If the polar fiber is in the expanded state during the winding test, it means that the actual friction coefficient is greater than the friction coefficient preset in step S2. f 1 If the polar fiber is in a shrinkage state during the winding test, it means that the actual friction coefficient is less than the friction coefficient preset in step S2. f 1 .

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