Co-cured resistive test sample of a conductive fabric and method of making

Abstract

The present application relates to the technical field of functional composite material detection, and particularly relates to a co-cured resistance test sample of conductive fabric and a preparation method thereof. The co-cured resistance test sample comprises a test sample strip, an auxiliary sample strip, a prepreg layer and a release film. The test sample strip is a conductive fabric, and the auxiliary sample strip is a conductive fabric or a non-conductive fabric. A plurality of test sample strips are sequentially and spacedly arranged to form a test sample strip group. The auxiliary sample strip is arranged on opposite sides of the test sample strip group in the length direction. The upper and lower surfaces of the reserved electrode area of the test sample strip group are covered with folded release films. The upper and lower sides of the test sample strip group and the auxiliary sample strip are each laminated with at least one layer of prepreg layer. The co-cured area of the auxiliary sample strip and the test sample strip has the same length. The co-cured resistance test sample of conductive fabric and the preparation method thereof aim to solve the problems that the electrode in the resistance test sample is difficult to prepare and is easy to be damaged, and the co-cured resistance is difficult to be stably and accurately tested.

Description

Technical Field

[0001] This invention relates to the field of functional composite material testing technology, specifically to a co-cured resistance test sample of conductive fabric and its preparation method. Background Technology

[0002] Structural-functional integrated composite materials have received widespread attention in recent years, as their applications can lead to further weight reduction and integrated design. Conductive structural-functional integrated materials are an important category, and their functionality in aerospace structural components includes lightning protection, electric heating, antistatic properties, electromagnetic wave absorption, and modulation materials, attracting considerable interest.

[0003] Co-curing conductive thin film materials with composite materials can integrate conductive functions. However, co-curing conventional conductive films, such as conductive polymer films, with composite materials can lead to problems such as resin thickness affecting flow and interfacial bonding. Conductive fabrics, with their porous and loose structure, have less impact on resin flow and can exhibit better interfacial properties, making them ideal materials for co-curing. However, when conductive fabrics are co-cured with continuous fiber-reinforced resin prepregs, their resistance changes, especially for carbon nanomaterial-modified conductive fabrics. Resin penetration alters the gaps between carbon nanomaterials, resulting in a significant change in resistance. Therefore, determining the final post-cured resistance of conductive fabrics is crucial for application performance evaluation. In current applications, to test the true post-cured resistance of conductive fabrics, copper electrodes are typically sprayed onto the conductive fabric, copper wires are then welded onto the copper electrodes, and the copper wires are led out from the composite prefabricated plate. The composite prefabricated plate is then cured to obtain a test sample for fabric co-curing resistance testing. The preparation process is very complicated, and the costs of copper spraying and welding are high, resulting in high inspection costs. In addition, because the material properties of the metal and the carbon nanomaterial conductive layer are very different, the sprayed copper electrode and the carbon nanomaterial conductive layer on the fabric are prone to cracking, resulting in poor conductive contact and test errors. More seriously, the connection between the sprayed metal area and the carbon nanomaterial conductive layer may break under curing stress due to the large difference in thickness and material properties, causing the sample to fail and become untestable.

[0004] Therefore, the inventors provide a co-cured resistance test sample of conductive fabric and its preparation method. Summary of the Invention

[0005] (1) Technical problems to be solved This invention provides a co-cured resistance test sample of conductive fabric and its preparation method, which solves the technical problems of existing conductive fabrics, such as cumbersome and costly preparation of metal connecting electrodes and conductive fabrics, poor bonding of conductive layers, and easy damage at the connection points, which may lead to test sample failure.

[0006] (2) Technical solution This invention provides a co-cured resistance test sample of conductive fabric, comprising a test strip, an auxiliary strip, a prepreg layer, and a separator. The test strip is a conductive fiber fabric, and the auxiliary strip is a conductive or non-conductive fiber fabric. Multiple test strips arranged at intervals form a test strip group. The auxiliary strips are distributed on opposite sides of the test strip group along its length. The upper and lower surfaces of the reserved electrode area of ​​the test strip group are covered with the folded separator. At least one layer of prepreg is laid on the upper and lower sides of both the test strip group and the auxiliary strips. The co-cured area of ​​the auxiliary strips is the same length as that of the test strips.

[0007] Furthermore, the conductive fabric of the test strip and the auxiliary fabric of the auxiliary strip have the same fiber type and weaving method.

[0008] Furthermore, the lateral length of the reserved electrode area of ​​the test strip is ≥10mm.

[0009] Furthermore, the transverse length of the co-cured region of the test strip and the prepreg layup is b, and the longitudinal width of the test strip is c, where 5 ≤ b / c ≤ 15.

[0010] Furthermore, 100mm≤b≤450mm, 10mm≤c≤30mm.

[0011] Furthermore, the spacing between two adjacent test strips and between the test strip group and the auxiliary strip is 3 to 20 mm.

[0012] Furthermore, when the actual required number of prepreg layers on the upper / lower side of the test strip is ≤3 layers, the number of prepreg layers in the co-curing area is the same as the actual required number; when the actual required number of prepreg layers on the upper / lower side of the test strip is >3 layers, the number of prepreg layers in the co-curing area is 3 layers.

[0013] The present invention also provides a method for preparing a co-cured resistance test sample of the above-mentioned conductive fabric, comprising the following steps: The resin film is laid on the upper and / or lower surfaces of the conductive fabric and auxiliary fabric, and heated and vacuum pre-pressed until the resin completely wets the fabric to form the corresponding test strip and auxiliary strip. The unimpregnated area of ​​the test strip is the reserved electrode area. The actual required number of prepreg layers on the upper / lower sides of the test strip is selected, and the corresponding number of prepreg layers are laid in sequence with the prepreg layers, the test strip, and the auxiliary strip. An isolation film is then covered on the upper and lower surfaces of the reserved electrode area to obtain the test sample preform. The test sample preform is cured to obtain a co-cured resistance test sample.

[0014] Furthermore, the resin content in the impregnation area of ​​the conductive fabric is 40–70 wt.%.

[0015] Furthermore, an insulating film is used to cover the upper and lower surfaces of the reserved electrode area, and the upper and lower surfaces and ends of the reserved electrode area are wrapped by folding.

[0016] (3) Beneficial effects In summary, this invention uses a separator membrane to isolate the adhesive and embeds unimpregnated conductive fabric in the sample as a reserved electrode and auxiliary strip [1] to achieve stable testing of the co-curing resistance of the conductive fabric. It has the advantages of easy sample preparation and testing, and the reserved electrode and the test area are integrated conductive structures with good electrical continuity. In addition, the reserved electrode and the test area are both located in the same plane of the plate curing area, so the conductive fabric does not bend and the curing shrinkage stress of each area is consistent, so it has low internal stress and avoids problems such as deformation and tearing of the conductive layer and failure of the connection between the reserved electrode and the test area during the co-curing process. It has the advantages of reliable sample preparation and stable test values. At the same time, by using a single separator membrane to fold and cover the reserved electrode, a self-sealing effect is generated, making it difficult for the resin to penetrate into the reserved electrode area. The interface between the reserved electrode and the co-curing test area is clear, which further improves the test accuracy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a front view of the structure of a co-cured resistance test sample of conductive fabric provided in an embodiment of the present invention; Figure 2 This is a left view of the structure of a co-cured resistance test sample of conductive fabric provided in an embodiment of the present invention; Figure 3 This is a top view of the structure of a co-cured resistance test sample of conductive fabric provided in an embodiment of the present invention; Figure 4 This is a front view of the structure of the test strip laying layer in a co-cured resistance test sample of conductive fabric provided in an embodiment of the present invention; Figure 5 This is a schematic flowchart of a method for preparing a co-cured resistance test sample of conductive fabric provided in an embodiment of the present invention; Figure 6(a) is a physical image of the resistance test sample co-cured with conductive fabric and QW280 / AC319 prepreg; Figure 6(b) is a physical image of the resistance test sample co-cured with conductive fabric and QW120 / 1316 prepreg; Figure 6(c) is a physical image of the resistance test sample co-cured with conductive fabric and QW280 / 5429 prepreg; Figure 7(a) is a photograph of the resistance test sample after the prepreg covering the electrode area was removed, which is a photo of the conductive fabric and QW120 / 1316 prepreg co-cured resistance test sample. Figure 7(b) is a photograph of the reserved electrode area of ​​the resistance test sample co-cured with conductive fabric and QW120 / 1316 prepreg; Figure 8 This is a photograph of the reserved electrode area of ​​a resistance test sample co-cured with an ultrathin low-density conductive fabric and prepreg prepared in Example 9 of the present invention.

[0019] In the picture: 1-Test strip; 2-Auxiliary strip; 3-Prepreg layup; 4-Resting membrane; 5-Test fabric; 6-Auxiliary fabric; 7-Adhesive film; 100-Reserved electrode area; 200-Co-curing area. Detailed Implementation

[0020] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] A first aspect of this invention provides a co-cured resistance test sample of a conductive fabric, see [link to relevant documentation]. Figures 1-3 The co-cured resistance test sample includes a test strip 1, an auxiliary strip 2, a prepreg layer 3, and a release liner 4. The test strip 1 is a conductive fiber fabric, and the auxiliary strip 2 is a conductive or non-conductive fiber fabric. Multiple test strips 1 arranged in parallel and spaced intervals form a test strip group. The auxiliary strips 2 are distributed on opposite sides of the test strip group along its length. The upper and lower surfaces of the reserved electrode area 100 of the test strip group are covered with a folded release liner 4. At least one layer of prepreg layer 3 is applied to the upper and lower sides of both the test strip group and the auxiliary strip 2. The co-cured area 200 of the auxiliary strip 2 and the test strip 1 has the same length.

[0023] In the above embodiment, the conductive fabric of test strip 1 and the auxiliary fabric of auxiliary strip 2 have the same fiber type and weaving method. The lateral length a of the reserved electrode area 100 on both sides of test strip 1 is ≥10mm, and the reserved electrode area 100 serves as the electrode for the final resistance test; the lateral length b of the co-cured area 200 of test strip 1 and prepreg layer 3 is b, the longitudinal width c of test strip 1 is c, and 5≤b / c≤15. Furthermore, 100mm≤b≤450mm, 10mm≤c≤30mm; the spacing between two adjacent test strips 1 and between the test strip group and the auxiliary strip 2 is 3~20mm.

[0024] It should be noted that after the conductive fabric is impregnated and cured by resin during the co-curing process, its contact resistance increases rapidly, even leading to insulation. Existing methods to address this problem mainly involve spraying a metal material onto the fabric, creating physical contact and interlocking between the metal material and the conductive layer, thus preventing resin penetration and conductive connection loss during co-curing. However, metal spraying introduces a new conductive interface, and the two materials have completely different properties, making them prone to breakage under pressure and temperature changes during co-curing, resulting in a high risk of sample damage. Therefore, this application controls the sample preparation method to create electrodes in a portion of the test sample itself, making the test sample easily detectable. Simultaneously, the self-formed electrodes and the conductive layer of the conductive fabric in the test area exhibit low damage risk and high conductive continuity. Since the electrodes are pre-existing on the test sample, they have natural conductive continuity with the conductive layer of the co-cured area, minimizing contact / interface resistance between the electrode area and the test area. In specific implementation, firstly, the double-sided protection of the folded isolation film ensures that the conductive fabric reserved for the electrode area is almost not impregnated by resin, allowing direct connection of the testing instrument's electrodes to this area for testing. For testing conductive fabrics with extremely low resistance, it is also easy to apply highly conductive electrode adhesive to this area to reduce contact resistance. Secondly, by placing the reserved electrodes in the same interlayer region, the electrodes in this region and the test area have a consistent process environment, effectively preventing stress during curing from causing breakage of the conductive layers in the reserved electrode area and the test area. After the sample has cured, one side of the sample can be directly cut off, allowing the testing instrument's electrodes to be inserted for detection. Good conductive contact is formed under the pressure of the upper and lower cured composite material layers, and it is easy to apply conductive silver paste to the reserved electrodes (to further improve the testing accuracy for low resistances ≤1Ω). Thirdly, to ensure the accuracy of testing these samples, auxiliary test strips are set to ensure a consistent testing environment for all test strips, thus avoiding the test value deviation caused by the compression effect of uneven thickness at the edges of the test strips. By setting the size and spacing parameters of the test strips, the testing accuracy and applicability are improved.

[0025] Furthermore, using a single-sheet, double-sided folded separator provides better resin impregnation prevention in the conductive fabric connection area, clearly defining the boundary between the reserved electrode area (electrode) and the co-curing area, reducing testing errors. This is because the single-sheet separator, after folding and covering, creates a self-sealing effect after vacuum extraction, effectively preventing resin penetration. However, in cases where the reserved electrode area of ​​the conductive fabric is covered by two separators, pressurization can cause the resin to push the contained residual gas towards the open side, leading to the failure of the self-sealing effect and the possibility of resin entering the reserved electrode area. Resin penetration into the reserved electrode area of ​​the conductive fabric may increase the contact resistance between the reserved electrode and the copper sheet test electrode, thus affecting the test results of low-resistance samples. By placing electrodes within the test sample and controlling the separator thickness, the consistency of the environment in which the electrodes and co-curing area are located during the co-curing process is maintained, greatly minimizing the possibility of electrode breakage.

[0026] As an optional implementation, when the actual required number of prepreg layers on the upper / lower side of the test strip is ≤3 layers, the number of prepreg layers in the co-curing area is the same as the actual required number; when the actual required number of prepreg layers on the upper / lower side of the test strip is >3 layers, the number of prepreg layers in the co-curing area is 3 layers.

[0027] A second aspect of this invention provides a method for preparing a co-cured resistance test sample of a conductive fabric, see below. Figure 5 The method may include the following steps: S100. The resin film is laid on the upper and / or lower surfaces of the conductive fabric and auxiliary fabric, and heated and vacuum pre-pressed until the resin completely impregnates the fabric to form the corresponding test strip and auxiliary strip. The unimpregnated area of ​​the test strip is the reserved electrode area.

[0028] Specifically, the raw material preparation includes conductive fabric, auxiliary fabric, prepreg, resin film that can be co-cured with the prepreg, and release film for testing co-curing resistance; the auxiliary fabric and conductive fabric have the same fiber type and weaving method. Test strip preparation: See [link to documentation]. Figure 4 A resin film that can be co-cured with the prepreg is applied to one or both surfaces of the conductive fabric and auxiliary fabric used for testing co-curing resistance, either on one or both sides. The width of the film application area is b (100mm ≤ b ≤ 450mm). The fabric is then heated and vacuum-pressed until the resin completely impregnates it. The unimpregnated area is designated as the electrode area. The conductive fabric includes woven and nonwoven fabrics. Depending on the type, areal density, and apparent thickness of the conductive fabric, the total areal density of the two film layers is controlled. Specifically, the resin content in the impregnated area of ​​the woven fabric is controlled to be 30–70 wt.%, and the total areal density per unit area of ​​the resin layer in the impregnated area of ​​the nonwoven fabric is controlled to be ≤ the nonwoven fabric thickness (in μm) × 4 g / m². 2Cut the conductive fabric to a total length of (2a+2d+b), where d≥5mm and a≥5mm; the spacing between adjacent conductive fabrics and between conductive fabrics and auxiliary fabrics is 2~10mm; the width of the conductive fabric is c (10mm≤c≤30mm), and b / c is between 5.0 and 15.0; the width of the auxiliary fabric is not less than 10mm.

[0029] Among the parameters above, controlling the surface density of the adhesive film is to avoid insufficient resin in the conductive fabric layer of the sample, which would lead to insufficient resin and compression, and excessive resin, which would lead to excessive resin and squeezing effect, resulting in changes in resistance. Controlling parameters a, b, c, and d is to make the sample preparation more operable, reduce errors, and make the results more accurate.

[0030] S200. Based on the actual required number of prepreg layers on the upper / lower sides of the test specimen, select the corresponding number of prepreg layers, lay the prepreg layers, test specimen, and auxiliary specimen in sequence, and cover the upper and lower surfaces of the reserved electrode area with an isolation film to obtain the test specimen preform.

[0031] Specifically, based on the number of prepreg layers above or below the conductive fabric in the actual application, select an appropriate number of prepreg layers and lay them and the test strip in sequence. When the number of prepreg layers above or below the conductive fabric in the actual application is more than 3 layers, use 3 layers of prepreg in the corresponding position of the test strip; when it is no more than 3 layers, use the same number of prepreg layers as in the actual application. The electrode area of ​​the test strip is covered with a separator film on both sides of the reserved electrode, separating it from the prepreg. The separator film thickness is ≤50µm. Furthermore, cover the upper and lower surfaces of the reserved electrode area with a separator film, and wrap the upper and lower surfaces and ends of the reserved electrode area by folding it in half.

[0032] Based on statistical analysis of numerous sample results, among the parameters above, for unbonded carbon nanotube-modified conductive fabrics with a high rate of change in curing resistance, the resistance difference between the two fabrics is approximately 5-10% when the number of prepreg layers on the top or bottom is 0 or 1, respectively. Increasing the number of layers to 2 or 3 reduces the difference from 1 layer to no more than 5%, and beyond 3 layers, the difference is essentially the same as with 3 layers. For conductive fabrics with a low rate of change in curing resistance, such as montmorillonite quartz fabrics, the number of prepreg layers on the top or bottom results in a less significant difference in resistance. Therefore, the number of prepreg layers used in the test samples generally does not exceed 3, and can even be as low as 2, to reduce material waste. Using a separator membrane with a thickness ≤50µm is to avoid the risk of electrode breakage. Folding the separator membrane around the upper and lower surfaces and ends of the reserved electrode area is to more effectively prevent resin penetration into the reserved electrode area, which could increase the contact resistance between the reserved electrode and the resistance testing equipment.

[0033] S300. The test sample preform is cured to obtain the co-cured resistance test sample.

[0034] Specifically, the pre-laid test board is cured according to the curing process given by the prepreg. After curing, it is cooled, demolded, and removed. The two reserved electrode areas with a side length of d are cut off from the test laminate to obtain the co-cured resistance test sample.

[0035] The above processing method allows the pre-reserved electrodes to be exposed through simple cutting of the laminate. When the electrodes are inserted into the testing equipment, the pressing effect of the upper and lower prepreg plates makes testing convenient and effectively reduces the contact resistance.

[0036] This application has been validated through the preparation of hundreds of test samples (thousands of specimens) during material development. The prepared test samples maintained good conductive connectivity between the reserved electrodes and the co-cured region. Except for accidental pulling of the electrodes during operation, no spontaneous electrode breakage occurred after curing. Even for easily broken carbon nanotube films and carbon fiber films with very low areal density and a thickness of only a few micrometers, this method can still be used. The reserved electrodes and co-cured region of the co-cured carbon nanotube film showed good conductive continuity, and no breakage was observed. The method of this application has been used for co-curing resistance testing of several CNZK impedance film series products of the China Academy of Aeronautical Manufacturing Technology, replacing the traditional method of copper spraying and electrode welding. The sample preparation process is significantly shortened, the test stability and reliability are significantly improved, and the process cost is lower, generating good economic value.

[0037] Specific examples and comparative examples are listed below.

[0038] Example 1 The implementation process of this embodiment is as follows: (1-1) Raw material preparation: When testing the co-cured resistance, the test sample uses Q1-200 conductive fabric (resistance 200Ω, self-made, fabric fiber is quartz fiber, weave is plain weave, conductive fabric is multi-walled carbon nanotube modified quartz fiber fabric, total areal density 54g / m³). 2 [2], with a thickness of approximately 55 μm and a multi-walled carbon nanotube diameter of 5–11 nm), and auxiliary fabric for auxiliary samples (quartz fiber fabric Q1, plain weave, code, 50 g / m). 2 ), prepreg (QW280 / 1316), and resin film that can be co-cured with the prepreg (1316 film, 30g / m³). 2 ), and the isolation membrane (PTFE material, 25µm).

[0039] (1-2) Test strip preparation: Cut 6 strips of Q1-200, each 300mm×20mm in size, and cut 2 strips of Q1, each 300mm×20mm in size. Lay the Q1-200 and Q1 strips in the following order: 1 strip of Q1, 6 strips of Q1-200, 1 strip of Q1 on a 200mm×280mm 1316 adhesive film. The spacing between Q1-200 and Q1 is 10mm. The adhesive film is applied to the middle 200mm area of ​​Q1-200 and Q1, leaving 50mm areas at each end unattached. Finally, overlap and cover the other side of the test strip with another 200mm×280mm 1316 adhesive film, and use a vacuum bag pre-compression method to ensure that the resin adhesive film completely impregnates the fabric, thus obtaining the test strip.

[0040] (1-3) Test plate installation: The test is to test the resistance of the conductive fabric after curing when applied to the subsurface, i.e., 1 layer of prepreg on top and 15 layers of prepreg on the bottom. Take two 300×105mm isolation films, fold them in half and wrap them around the reserved electrode areas on both sides of the test strip. At the same time, take 4 sheets of QW280 / 1316 prepreg (300mm×300mm). Lay the prepreg and test strip in the order of [3 layers of prepreg + 1 layer of test strip + 1 layer of prepreg]. The orientation of the prepreg is 0° / 90°.

[0041] (1-4) Curing and Sample Preparation: The laid-up test board is cured according to the curing process given for QW280 / 1316 prepreg. After curing, it is cooled, demolded, and removed. 10mm is cut off from the sides of each of the two reserved electrode areas to obtain a test sample with a reserved electrode area length of 40mm.

[0042] (1-5) Test: Connect the two clips of the micro ohmmeter to a 22mm wide copper sheet, insert it into the gap between the two reserved electrode areas and the isolation membrane, and test the resistance values ​​of different strips respectively. The co-cured sheet resistance of the conductive fabric is obtained according to the resistivity calculation method.

[0043] Examples 2-8 The implementation process of technical solutions 2 to 8 of the present invention is similar to that of embodiment 1, except that the corresponding parameters are different. For details of the parameters, please refer to Table 1 below.

[0044] Table 1. Parameter values ​​for Examples 1-8 Table 2. Co-cured resistivity test values ​​(unit: Ω / sq.) Example 9 (9-1) Raw material preparation: When testing the co-cured resistance, the test strips used are carbon fiber nonwoven fabric CF05 (nonwoven fabric with a surface resistivity of 28Ω, a thickness of 13μm, and an areal density of 4g / m³).2 The auxiliary fabric used for the auxiliary samples is also CF05, prepreg (QW280 / 1316), and resin film that can be co-cured with the prepreg (1316 film, 25g / m). 2 ), and the isolation membrane (PTFE material, 25µm).

[0045] (9-2) Test strip preparation: Cut 8 CF05 strips, each 300mm×20mm in size, and lay all CF05 strips on a 200mm×280mm 1316 adhesive film, with a spacing of 15mm between each CF05 strip; the adhesive film is applied to the middle 200mm area of ​​the CF05 strips, leaving 50mm areas at each end unattached; use a vacuum bag pre-compression method to completely impregnate the fabric with the resin adhesive film to obtain the test strips.

[0046] (9-3) Test Plate Laying: The test involves measuring the cured resistance of the conductive fabric CF05 applied to the subsurface layer of the skin. In actual application, there is one layer of prepreg on top and seven layers of prepreg on the bottom. Take two 300×105mm release films, fold them in half, and wrap them around the reserved electrode areas on both sides of the test strip. Simultaneously, take four sheets of QW280 / 1316 prepreg (300mm×300mm). Lay the prepreg and test strip in the order of [3 layers of prepreg + 1 layer of test strip + 1 layer of prepreg]. The orientation of the prepreg is 0° / 90°. For example... Figure 8 As shown, even though the conductive fabric has a very low surface density and is easily broken, the conductive fabric in the reserved electrode and co-curing area still has clear boundaries, natural and flat connections, and no stress caused by bending deformation. Therefore, the conductivity continuity and integrity of the sample are good during the sample preparation process.

[0047] (9-4) Curing and Sample Preparation: Cure the laid test board according to the curing process given for QW280 / 1316 prepreg. After curing, cool, demold, and remove the test board. Cut off 10mm from the sides of each of the two reserved electrode areas to obtain a test sample with a reserved electrode area length of 40mm.

[0048] (9-5) Testing: During testing, conductive silver paste was applied to the side of the reserved electrodes of the six test samples near the co-curing area, with a coating width of 5 mm. After air drying, it was placed in a 60℃ oven for 30 min. A 22 mm wide copper sheet was connected to the two clips of the micro-ohmmeter and inserted into the gap between the two reserved electrode areas and the isolation film, contacting the conductive silver paste coating area. The resistance values ​​of different samples were measured. According to the resistivity calculation method, the co-curing sheet resistance of CF05 was obtained as 19.32 Ω / sq., 20.05 Ω / sq., 19.82 Ω / sq., 19.55 Ω / sq., and 20.20 Ω / sq., respectively. Two auxiliary samples were also tested, with resistances of 19.24 Ω / sq. and 18.84 Ω / sq., respectively.

[0049] Example 10 (10-1) Raw material preparation: When testing the co-cured resistance, the test sample uses graphene quartz fiber fabric (a conductive quartz fabric (woven fabric) with graphene grown on the fiber surface, with a surface resistance of 580Ω, a product of Beijing Graphene Research Institute, with a thickness of 160μm and an areal density of 171g / m³). 2 The auxiliary fabric used for the auxiliary samples is the same type of conductive fabric, prepreg (QW120 / 1316), and resin film that can be co-cured with the prepreg (1316 film, 60g / m). 2 ), and the isolation membrane (PTFE material, 25µm).

[0050] (10-2) Test strip preparation: Cut 8 strips of montmorillonite quartz fiber fabric, each 300mm×20mm in size. Lay all the montmorillonite quartz fiber fabric onto a 200mm×280mm 1316 adhesive film, with a spacing of 10mm between the montmorillonite quartz fiber fabrics. The adhesive film is applied to the middle 200mm area of ​​the montmorillonite quartz fiber fabric, leaving 50mm areas at each end unattached. Cover the same 1316 adhesive film on the other side of the fabric at the same position, and then use a vacuum bag pre-pressing method to completely impregnate the fabric with the resin adhesive film to obtain the test strip.

[0051] (10-3) Test plate installation: The curing resistance of the montmorillonite quartz fiber fabric applied to the third layer of the skin is to be tested. In actual application, two layers of QW120 / 1316 prepreg are laid on the top of the fabric and 14 layers of prepreg are laid on the bottom. Take two 300×105mm isolation films, fold them in half and wrap them around the reserved electrode areas on both sides of the test strip. At the same time, take four sheets of QW120 / 1316 prepreg (300mm×300mm). Lay the prepreg and test strip in the order of [3 layers of prepreg + 1 layer of test strip + 2 layers of prepreg]. The orientation of the prepreg is 0° / 90°.

[0052] (10-4) Curing and Sample Preparation: Cure the laid test board according to the curing process given for QW120 / 1316 prepreg. After curing, cool, demold, and remove the test board. Cut off 10mm from the sides of each of the two reserved electrode areas to obtain a test sample with a reserved electrode area length of 40mm.

[0053] (10-5) Testing: During testing, a 25mm wide copper sheet was connected to the two clips of the micro-ohmmeter and inserted into the gap between the two reserved electrode areas and the isolation membrane, contacting the reserved electrode area of ​​the conductive fabric. The resistance values ​​of different samples were tested respectively. According to the resistivity calculation method, the co-cured sheet resistance of the montmorillonite quartz fiber fabric was obtained as 558Ω / sq., 572Ω / sq., 574Ω / sq., 563Ω / sq., and 565Ω / sq. respectively. At the same time, two auxiliary samples were also tested, with resistances of 566Ω / sq. and 561Ω / sq. respectively.

[0054] Comparative Example 1 (Electrode lead-out using copper spraying-soldering method) In Comparative Example 1, a conventional resistance sample plate was prepared, and the process is as follows: (D1-1) Raw material preparation: Conductive fabric Q1-200 (resistance 200Ω, self-made, quartz fiber, plain weave, surface density 54g / m²) for testing co-cured resistance. 2 ), prepreg (QW280 / 1316), and resin film that can be co-cured with the prepreg (1316 film, 30g / m³). 2 ).

[0055] (D1-2) Test strip preparation: Cut 6 strips of Q1-200 fabric, each 300mm × 20mm in size. Using a copper spraying method, spray a copper electrode perpendicular to the length direction at positions 45-50mm and 250-255mm on each strip, with a width of 5mm. Then, solder a bundle of 100mm long copper wires to the copper electrodes. Lay the 6 Q1-200 strips with the soldered copper wires sequentially onto a 300mm × 300mm 1316 adhesive film, with a spacing of 10mm between each Q1-200 strip. Then, overlap and cover the other side of the strip with another 300mm × 300mm 1316 adhesive film. Use a vacuum bag pre-compression method to ensure that the resin film completely impregnates the fabric, thus obtaining the test strip.

[0056] (D1-3) Test plate laying: Take 4 sheets of QW280 / 1316 prepreg (300mm×300mm), lay the prepreg and test strip in the order of [3 layers of prepreg + 1 layer of test strip + 1 layer of prepreg]. The orientation of the prepreg is 0° / 90°. The copper wire is pulled out as an electrode and exposed outside the laminate prefabrication body.

[0057] (D1-4) Curing and Sample Preparation: Curing the laid test board according to the curing process given for QW280 / 1316 prepreg. After curing, cooling, demolding, and removal.

[0058] (D1-5) Test: Connect the two clips of the micro-ohmmeter to the two copper wire electrodes outside the plate for each sample, and test the resistance. The co-cured sheet resistance of the conductive fabric is obtained according to the resistivity calculation method.

[0059] Test results showed that resistance could not be measured on two samples, while resistance could be measured on four samples. Analysis indicated that the samples without measurable resistance were due to pressure on the conductive fabric during the curing process at some copper-sprayed locations, disrupting the continuity of the conductive layer and causing cracks in the copper electrodes of some samples. The resistivity values ​​obtained for the four samples were 822 Ω / sq., 792 Ω / sq., 801 Ω / sq., and 810 Ω / sq., similar to the values ​​in the previous example. However, this method suffers from problems such as complex copper electrode fabrication, high cost, long cycle time, and susceptibility to damage during the curing process.

[0060] Comparative Example 2 (copper foil electrodes are laid out and led out in the electrode area) The implementation process of Comparative Example 2 is as follows: (D2-1) Raw material preparation: Conductive fabric Q1-200 (resistance 200Ω, self-made, quartz fiber, plain weave, surface density 54g / m²) for testing co-cured resistance. 2 ), prepreg (QW280 / 1316), and resin film that can be co-cured with the prepreg (1316 film, 30g / m³). 2 ), copper foil (50μm thick).

[0061] (D2-2) Test strip preparation: Cut 6 strips of Q1-200, each 300mm × 20mm in size; sequentially lay the 6 strips of Q1-200 onto a 300mm × 300mm 1316 adhesive film, with a spacing of 10mm between each strip; then, lay a 70mm × 20mm copper foil above the electrode area (50mm long) of each conductive fabric (the 20mm portion of the copper foil longer than the electrode is located outside the conductive fabric, serving as an external electrode); then overlap and cover the other side of the strip with another 300mm × 300mm 1316 adhesive film. Use a vacuum bag pre-compression method to completely impregnate the fabric with the resin film, obtaining the test strip.

[0062] (D2-3) Test plate laying: Take 4 sheets of QW280 / 1316 prepreg (300mm×300mm), lay the prepreg and test strip in the order of [3 layers of prepreg + 1 layer of test strip + 1 layer of prepreg]. The orientation of the prepreg is 0° / 90°. The copper foil is used as the electrode and leaves 20mm outside the laminate preform.

[0063] (D2-4) Curing and Sample Preparation: Curing the laid test board according to the curing process given for QW280 / 1316 prepreg. After curing, cooling, demolding, and removal.

[0064] (D2-5) Test: Connect the two clips of the micro-ohmmeter to each sample strip and lead it to the two copper foil electrodes outside the plate. Test the resistance and obtain the co-cured sheet resistance of the conductive fabric according to the resistivity calculation method.

[0065] Test results showed that no resistance could be measured on four samples, and the resistivity of two samples was 21 kΩ / sq. and 59 kΩ / sq., respectively, which could not yield valid results. Analysis indicated that one of the samples with unmeasurable resistance had its conductive structure damaged by the copper foil during the curing process, and the other three samples did not form effective conductive contact with the conductive fabric.

[0066] Comparative Example 3 (using an isolation membrane but with reserved electrodes not placed in the same interlayer area within the plate) The implementation process of Comparative Example 3 is similar to that of Example 1, except that, compared with the test plate preparation step (1-3), the size of the cut QW280 / 1316 prepreg is (300mm × 200mm), and the prepreg is only laid in the co-curing area. After preparation, the reserved electrodes are distributed outside the test plate.

[0067] Test results showed that resistance could not be measured for any of the test samples. The reason for this was the resin shrinkage effect during the curing process. However, the samples were squeezed by the vacuum bag and could not shrink back effectively, causing the reserved electrode to break at the position where resin overflowed at the edge of the board.

[0068] Comparative Example 4 (Separator thickness is too large) The implementation process of Comparative Example 4 is similar to that of Example 1, except that the separator is replaced with a PTFE sheet with a thickness of 80 μm.

[0069] Test results showed that the resistance of the two test strips could not be measured. The reason for this was that the thicker PTFE sheet bent the conductive film during the molding process, making it impossible to measure the resistance.

[0070] Comparative Example 5 (The release liner is not folded in half) The implementation process of Comparative Example 5 is similar to that of Example 1, except that two isolation films are used to cover the upper and lower surfaces of the electrode area, instead of one isolation film folded in half.

[0071] Test results showed that resin wetting of 1-4 mm occurred in the electrode areas of three test strips, while no resin wetting was observed in the electrode area of ​​Example 1 (1316 film), and the boundaries were clear. Using a two-point electrode of a multimeter, the resin-wetted and unwetted areas of the reserved electrode in Comparative Example 5 were tested separately (10 mm apart). The results showed that after resin wetting, the resistance increased by approximately 5-30 Ω (varying at different locations), indicating that resin wetting of the reserved electrode may introduce certain test errors and should be avoided as much as possible. However, the surface resistivity obtained by testing and calculation was still close to that of Example 1, possibly because the increased contact resistance was significantly less than the resistance of the sample itself. This application also observed the wetting of AC319 film and 2305 film (refer to Examples 3 and 5). Two cut release films and a folded release film were used. The former was wetted by 2-5 mm and 2-7 mm respectively, while the latter was less than 1-3 mm or did not show electrode wetting, indicating that the resin wetting of the electrodes was improved. When the electrode wetting length is long, the ends are obviously uneven and the glue content varies, which may lead to testing errors.

[0072] Comparative Example 6 (without auxiliary splines) The implementation process of Comparative Example 6 is similar to that of Example 1, except that auxiliary splines are not used.

[0073] The test results show that the resistivity of the six test strips is 735 Ω / sq., 822 Ω / sq., 802 Ω / sq., 814 Ω / sq., 799 Ω / sq., and 747 Ω / sq., respectively. The resistivity of the two test strips at the edges shows a significant decrease. This phenomenon of increased resistance at the edges is particularly common in the co-curing resistance test of carbon nanotube-modified quartz fabrics, especially when the fabric resistance is ≥100 Ω.

[0074] It is evident that using auxiliary samples reduces edge influences, achieving higher stability in co-curing resistance testing. Conductive fabrics with significant co-curing resistance variation rates are affected by a combination of external environmental factors such as resin content and pressure, which can influence the rate of change in co-curing resistance. To approximate the environment of conductive fabrics in real-world applications, we used auxiliary samples to reduce edge influences. Comparative experiments showed that this effectively improved the resistance stability and consistency of edge samples, achieving higher stability in co-curing resistance testing. Preferably, auxiliary samples made of the same type of fabric are used to ensure that all test samples are subjected to the same resin flow and interlayer thickness environment, maintaining test consistency.

[0075] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0076] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A co-cured resistance test sample of conductive fabric, characterized in that, The test strip (1), auxiliary strip (2), prepreg layup (3), and separator (4) are included. The test strip (1) is a conductive fiber fabric, and the auxiliary strip (2) is a conductive or non-conductive fiber fabric. Multiple test strips (1) are arranged in sequence at intervals to form a test strip group. The auxiliary strips (2) are distributed on opposite sides of the length direction of the test strip group. The upper and lower surfaces of the reserved electrode area (100) of the test strip group are covered with the folded separator (4). At least one layer of prepreg layup (3) is laid on the upper and lower sides of the test strip group and the auxiliary strip (2). The co-cured area (200) of the auxiliary strip (2) and the test strip (1) has the same length.

2. The co-cured resistance test sample of the conductive fabric according to claim 1, characterized in that, The conductive fabric of the test strip (1) and the auxiliary fabric of the auxiliary strip (2) have the same fiber type and weaving method.

3. The co-cured resistance test sample of the conductive fabric according to claim 1, characterized in that, The lateral length of the reserved electrode area (100) of the test specimen (1) is ≥10mm.

4. The co-cured resistance test sample of the conductive fabric according to claim 1, characterized in that, The transverse length of the co-cured region (200) of the test strip (1) and the prepreg layer (3) is b, and the longitudinal width of the test strip (1) is c, where 5 ≤ b / c ≤ 15.

5. The co-cured resistance test sample of the conductive fabric according to claim 4, characterized in that, 100mm≤b≤450mm, 10mm≤c≤30mm.

6. The co-cured resistance test sample of the conductive fabric according to claim 1, characterized in that, The spacing between two adjacent test strips (1) and between the test strip group and the auxiliary strip (2) is 3 to 20 mm.

7. The co-cured resistance test sample of the conductive fabric according to claim 1, characterized in that, When the actual required number of prepreg layers on the upper / lower side of the test strip is ≤3 layers, the number of prepreg layers in the co-curing area is the same as the actual required number. When the actual required number of prepreg layers on the upper / lower side of the test strip is greater than 3 layers, the number of prepreg layers in the co-curing area is 3 layers.

8. A method for preparing a co-cured resistance test sample of a conductive fabric as described in any one of claims 1-7, characterized in that, The method includes the following steps: The resin film is applied to the upper and / or lower surfaces of the conductive fabric and auxiliary fabric, and then heated and vacuum-pressed until the resin completely impregnates the fabric to form corresponding test strips and auxiliary strips. The unimpregnated areas of the test strips are reserved electrode areas. Based on the actual required number of prepreg layers on the upper / lower sides of the test strip, select the corresponding number of prepreg layers, lay the prepreg layers, the test strip, and the auxiliary strip in sequence, and cover the upper and lower surfaces of the reserved electrode area with an isolation film to obtain the test sample preform. The test sample preform is cured to obtain a co-cured resistance test sample.

9. The method for preparing a co-cured resistance test sample of conductive fabric according to claim 8, characterized in that, The conductive fabric includes woven fabric and nonwoven fabric, and the resin content of the impregnation area of ​​the woven fabric is 30-70 wt.%.

10. The method for preparing a co-cured resistance test sample of conductive fabric according to claim 8, characterized in that, The upper and lower surfaces of the reserved electrode area are covered with an insulating film, which is then folded in half to wrap the upper and lower surfaces and ends of the reserved electrode area.

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