Zero poisson's ratio large deformation woven / molded integral wing skin and method of making

Abstract

The application discloses a zero-Poisson-ratio large-deformation woven / molded integral wing skin and a preparation method, and belongs to the field of aerospace. The method for preparing the zero-Poisson-ratio large-deformation skin preform of the integrated woven sandwich structure comprises the following steps: a lower structure of the preform is obtained by using three-dimensional six-directional weaving, then new yarns are introduced in parallel to the length direction, three-dimensional four-directional weaving is performed on the six-directional yarns of the lower layer to form a sandwich structure, finally, the six-directional yarns of the lower layer are used to continue three-dimensional six-directional weaving to obtain an upper structure, and the three-layer structure forms the zero-Poisson-ratio large-deformation skin preform of the sandwich structure; wherein the thickness ratio of the upper structure, the sandwich structure and the lower structure is 1:0.5-1.5:1. Then, polyether ether ketone and the preform are compounded to obtain the wing skin. The wing skin can achieve a large deformation of more than 80%, and has the advantages of low preparation cost, simple operation and easy industrial design.

Description

TECHNICAL FIELD

[0001] The present application relates to a zero Poisson's ratio large deformation woven / molded integral wing skin and a preparation method, belonging to the field of aerospace. BACKGROUND

[0002] The research of traditional flexible skin mainly focuses on two aspects of material and structure. In terms of material: the application materials are mainly rubber materials and composite materials. The skin made of these materials often has large deformation capacity, but the out-of-plane bearing capacity is poor; the skin using smart materials such as shape memory alloy overcomes the disadvantage of poor out-of-plane bearing capacity, but the production cost is high and cannot be widely used in aircraft fuselages. In terms of structure: laminated and segmented structures have considerable deformation capacity, but there are gaps between the parts, which cannot provide a smooth aerodynamic shape, greatly reducing the aerodynamic performance.

[0003] In order to solve the shortcomings of segmented and laminated structures, periodic concave structures have many advantages such as large out-of-plane stiffness, large deformation capacity, continuous deformation, and light weight. The concave structure is divided into positive Poisson's ratio concave structure, negative Poisson's ratio concave structure and zero Poisson's ratio concave structure. Due to the existence of positive / negative Poisson's ratio, when the positive / negative Poisson's concave structure is subjected to tensile deformation in one direction, contraction / expansion will occur in the other direction. When this contraction / expansion deformation is limited, the equivalent stiffness of the concave structure increases due to the additional constraint, resulting in an increase in the requirement for driving force. The zero Poisson's ratio effect of the zero Poisson's ratio concave structure mainly manifests as one-way deformation, i.e. tensile deformation in the plane will not cause deformation in the other direction, reducing the requirement for driving force. Therefore, the zero Poisson's ratio concave structure is more suitable for application in wing skin.

[0004] At present, composite skin uses a sandwich weaving method, which can be divided into three layers of upper, middle and lower. They are woven separately to form the structure of each layer, and then glued together. The connection between the skin and the core of the composite skin is mainly by gluing, but this connection method has a prominent problem, i.e. the elastic skin and the honeycomb core are prone to debonding. SUMMARY

[0005] [TECHNICAL PROBLEM]

[0006] The outer layer and the inner honeycomb frame of the current skin are separated.

[0007] [TECHNICAL SCHEME]

[0008] In order to solve the above problems, the application realizes a zero-poisson ratio large deformation skin preform of the integrated woven sandwich structure by combining three-dimensional six-way weaving and three-dimensional four-way weaving; then polyether ether ketone and the preform are compounded to obtain the wing skin. The wing skin obtained by the application can achieve a large deformation of more than 80%, and has low preparation cost, simple operation and easy industrial design.

[0009] The first object of the application is to provide a method for preparing a zero-poisson ratio large deformation skin preform of an integrated woven sandwich structure, which comprises the following steps:

[0010] The lower structure of the preform is obtained by three-dimensional six-way weaving, then new yarns are introduced parallel to the length direction, three-dimensional four-way weaving is performed with the six-way yarns of the lower layer to form a sandwich structure, and finally the upper structure is obtained by continuing three-dimensional six-way weaving with the six-way yarns of the lower layer; the three-layer structure forms a zero-poisson ratio large deformation skin preform of the sandwich structure together.

[0011] The thickness ratio of the upper structure, the sandwich structure and the lower structure is 1:0.5-2:1.

[0012] In an embodiment of the application, the yarns used for weaving are carbon fiber yarns, wherein the specification of the carbon fibers is 3k-12k, and the fineness is 200-800tex; the carbon fiber yarns are obtained by combining and twisting 2-3 bundles of carbon fibers, and the twist is 40-80 twists per meter.

[0013] In an embodiment of the application, the carbon fiber yarns used for weaving need to be desized first and then sized; the desizing is a desizing treatment of the carbon fiber yarns under high temperature and inert gas, the high temperature is 200-300℃, the inert gas is nitrogen, and the treatment time is 20-40min; the sizing is sizing with a polyamide acid solution, specifically, the carbon fiber yarns after desizing are immersed in the polyamide acid solution at room temperature for 10-60min, and then heat treated at 280-200℃ for 10-20min; the polyamide acid solution is a polyamide acid aqueous solution with a concentration of 10-20wt%.

[0014] In an embodiment of the application, the stitch height of the upper structure and the lower structure is 6-10mm, the stitch width is 1-4mm, and the weaving angle is 16-20°.

[0015] In an embodiment of the application, the stitch height of the sandwich structure is 2-6mm, the stitch width is 1-3mm, and the weaving angle is 25-45°.

[0016] The second object of the application is a zero-poisson ratio large deformation skin preform of a sandwich structure prepared by the method.

[0017] A third object of the present application is to provide a method for preparing a sandwich structure zero Poisson's ratio large deformation skin, comprising the following steps:

[0018] (1) Desizing:

[0019] The sandwich structure zero Poisson's ratio large deformation skin preform is desized with acetone to obtain the desized sandwich structure zero Poisson's ratio large deformation skin preform.

[0020] (2) Compounding:

[0021] The desized sandwich structure zero Poisson's ratio large deformation skin preform is immersed in a polyether ether ketone solution, then taken out, hot-pressed, cooled, and the sandwich structure zero Poisson's ratio large deformation skin is obtained.

[0022] In an embodiment of the present application, the desizing in step (1) is specifically:

[0023] The sandwich structure zero Poisson's ratio large deformation skin preform is immersed in acetone, heated in water bath at 50-70℃ for 36-72h, desized, then taken out and dried to obtain the desized sandwich structure zero Poisson's ratio large deformation skin preform.

[0024] In an embodiment of the present application, the polyether ether ketone solution in step (2) is a polyether ether ketone aqueous solution with a mass fraction of 40-60%.

[0025] In an embodiment of the present application, the immersion in step (2) is immersion at room temperature for 20-40min.

[0026] In an embodiment of the present application, the hot-pressing in step (2) is hot-pressing at a temperature rising rate of 10-20℃ / min, heated to 380-415℃, and at the same time, the pressure is set to 4-10MPa, and hot-pressed for 20-40min.

[0027] A fourth object of the present application is the sandwich structure zero Poisson's ratio large deformation skin prepared by the method of the present application.

[0028] A fifth object of the present application is the application of the sandwich structure zero Poisson's ratio large deformation skin of the present application in the field of aerospace.

[0029] [Advantages]

[0030] (1) The method for preparing the zero-poisson ratio large deformation skin with sandwich structure of the present application does not limit the size of the prepared part, and can prepare large-size and high-width parts, and the friction on the fiber during weaving is small, which can maximize the performance of the yarn; the introduction of the vertical yarn (six-direction yarn) can well improve the mechanical properties of the part in the vertical direction; the arrangement mode and parameter setting of the six-direction yarn are controllable, different yarn arrangement paths can be designed according to needs to obtain the expected zero-poisson ratio superstructure, and the design flexibility is high; when the reinforcing body is subjected to load, the whole material presents the characteristics of zero-poisson ratio superstructure.

[0031] (2) The method of the present application solves the shortcomings of the segmented and laminated structure.

[0032] (3) The zero-poisson ratio large deformation skin prepared by the present application can realize 80% large deformation, the tensile strength is above 120 MPa, the compression strength is above 80 MPa, and the basic characteristics of zero-poisson ratio superstructure are maintained.

[0033] (4) The method of the present application has low cost, simple operation, no pollution and is easy to put into industrial production.

[0034] (5) The surface of carbon fiber generally has a layer of sizing agent to protect the fiber, but the sizing agent starts to decompose at 200 DEG C, which is not conducive to the interface bonding of the wire, so desizing treatment is needed at high temperature, but without protective gas, the fiber is easy to be damaged at a temperature above 200 DEG C, so the continuous carbon fiber needs to be desized under the protection of oxygen or inert atmosphere.

[0035] (6) The sizing treatment makes the surface of the carbon fiber adhere to a layer of polyamide acid solution, which on the one hand reduces the surface roughness and polarity of the carbon fiber, increases the wettability of the carbon fiber, and on the other hand plays a lubricating and isolating role, reduces the damage of the carbon fiber in the subsequent process. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The figure shows the schematic diagram of the zero-poisson ratio large deformation skin before (A) and after (B) deformation. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present application are described below, and it should be understood that the embodiments are used to better explain the present application and are not used to limit the present application.

[0038] Test method:

[0039] 1. Test of tensile properties:

[0040] The standard used for the test is ASTM D-3039 "Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials", the testing machine is INSTRON-3385H type universal strength machine, the tensile speed is 2mm / min, and the tensile strength, tensile modulus and Poisson's ratio of the test sample in the warp direction are tested.

[0041] 2. Compression performance test:

[0042] The standard used for the test is ASTM D6641-14 "Standard Test Method for Compressive Properties of Polymer Matrix Composite using a Combined Loading Compression (CLC) Test Fixture 1", the testing machine is INSTRON-3385H type universal strength machine, the compression speed is 1.3mm / min, and the compression strength and Poisson's ratio of the test sample in the warp direction are tested and calculated according to the relevant formula in the experimental standard.

[0043] Raw materials used in the examples:

[0044] The carbon fiber yarn used for weaving has a specification of T700 12k and a fineness of 800tex; the carbon fiber yarn is obtained by combining and twisting 3 bundles of carbon fibers, and the twist is 60 twists / meter.

[0045] The solvent used in the examples and comparative examples is water when not specifically indicated, and the % used refers to the mass percentage when not specifically indicated.

[0046] Example 1

[0047] A method for preparing a zero-Poisson-ratio large-deformation skin preform of an integrated woven sandwich structure, comprising the following steps:

[0048] (1) Desizing of carbon fiber yarn:

[0049] The carbon fiber yarn is desized at 200℃ under nitrogen atmosphere for 40min to obtain the desized carbon fiber yarn;

[0050] (2) Sizing of carbon fiber yarn:

[0051] The desized carbon fiber yarn is immersed in a 15wt% polyamide acid aqueous solution at room temperature for 10min for sizing, and then taken out after being kept in a high-temperature oven at 200℃ for 15min to obtain the sized carbon fiber yarn.

[0052] (3) Integrated weaving:

[0053] The carbon fiber yarn after sizing is used as the weaving yarn for weaving;

[0054] The lower layer structure weaving adopts a four-step 1x1 weaving three-dimensional six-way structure, the weaving tray used is 20x4 (20 is the number of rows, and 4 is the number of columns), the total number of weaving yarns and longitudinal axial yarns is 104, 80 (the number of weaving yarns = XxY+X+Y; the number of longitudinal axial yarns = XxY), the stitch height is 8 mm, the stitch width is 2.16 mm, the weaving angle is 18°, 6 stitches are woven, and the thickness is 10 mm;

[0055] Then, the sandwich structure is woven, specifically: the six-way yarn of the lower layer three-dimensional six-way is used as part of the weaving yarn, then a new yarn is introduced in parallel to the length direction, and three-dimensional four-way weaving is performed with the six-way yarn of the lower layer to form a sandwich structure; the weaving tray is 4x4 (4 is the number of rows, and 4 is the number of columns), the stitch height is 4 mm, the stitch width is 2 mm, the weaving angle is 28°, 10 stitches are woven, and the sandwich structure thickness is 10 mm;

[0056] More specifically: 4 clusters of six-way yarns are introduced in the weaving width direction, each cluster has 12 roots, and each cluster is spaced apart by one yarn carrier; after weaving another stitch, 4 clusters of six-way yarns are introduced again, each cluster has 12 roots, and the introduction position is parallel to the length direction of the six-way yarns of the previous stitch; the 24 yarns inserted in parallel to the length direction of different stitches are the weaving yarns of the sandwich structure, the weaving tray is 4x4 (4 is the number of rows, and 4 is the number of columns), the weaving tray is 4x4 (4 is the number of rows, and 4 is the number of columns), the total number of weaving yarns and longitudinal axial yarns is 24, 16, and the yarns are introduced into a three-dimensional four-way weaving machine for weaving, the stitch height is 4 mm, the stitch width is 2 mm, the weaving angle is 28°, and the sandwich structure thickness is 10 mm;

[0057] Finally, the six-way yarn of the lower layer structure used in the sandwich structure is used as the six-way yarn, and the yarn is continuously introduced for three-dimensional six-way weaving, the weaving tray used is 20x4 (20 is the number of rows, and 4 is the number of columns), the stitch height is 8 mm, the stitch width is 2.16 mm, the weaving angle is 18°, 6 stitches are woven, the thickness is 10 mm, and the sandwich structure of the zero Poisson's ratio large deformation skin preform is obtained.

[0058] Example 2

[0059] A method for preparing a sandwich structure of a zero Poisson's ratio large deformation skin, comprising the following steps:

[0060] (1) Desizing:

[0061] The sandwich structure zero Poisson's ratio large deformation skin preform of Example 1 was immersed in acetone, heated in a water bath at 60°C for 36h, desized, then taken out, air dried for 24h, and dried at 120°C for 12h to obtain the desized sandwich structure zero Poisson's ratio large deformation skin preform;

[0062] (2) Compound:

[0063] The desized sandwich structure zero Poisson's ratio large deformation skin preform was immersed in a 40wt% polyether ether ketone aqueous solution at room temperature for 25min, then taken out, heated to 400°C at a heating rate of 15°C / min, while adjusting the pressure to 8MPa, and hot-pressed for 30min to obtain the sandwich structure zero Poisson's ratio large deformation skin.

[0064] Example 3

[0065] The sandwich structure zero Poisson's ratio large deformation skin was obtained by adjusting the sandwich structure thickness to 20mm in step (3) of Example 1, and keeping the other steps the same as in Examples 1 and 2.

[0066] Comparative Example 1

[0067] The sandwich structure zero Poisson's ratio large deformation skin was obtained by omitting step (2) in Example 1 and step (1) in Example 2, and keeping the other steps the same as in Examples 1 and 2.

[0068] Comparative Example 2

[0069] The sandwich structure zero Poisson's ratio large deformation skin was obtained by omitting step (1) in Example 2, and keeping the other steps the same as in Examples 1 and 2.

[0070] Comparative Example 3

[0071] The skin was obtained by adjusting step (3) of Example 1 to an integrated woven three-dimensional six-way structure, without weaving a three-dimensional four-way structure, and keeping the other steps the same as in Examples 1 and 2.

[0072] Comparative Example 4

[0073] The skin was obtained by adjusting step (3) of Example 1 to an integrated woven suture structure, specifically weaving the upper layer, the sandwich layer, and the lower layer, and then sutured with yarn, and keeping the other steps the same as in Examples 1 and 2.

[0074] Comparative Example 5

[0075] The carbon fiber yarn after sizing prepared in Example 1 was used as a woven yarn for three-dimensional weaving, and a three-dimensional woven concave structure large skin was formed by combining a molding process;

[0076] Specifically as follows:

[0077] The three-dimensional woven preform is prepared by using three shuttles to weave a sandwich structure with a warp density and a weft density of 65x55 roots / 10 cm and a right-angle interlocking weave, and the thickness of each layer of the sandwich structure is 10 mm;

[0078] Then, the preform is immersed in a polyether ether ketone solution (solvent: water) with a concentration of 40 wt% at room temperature for 25 min, and then taken out, heated to 400°C at a heating rate of 15°C / min, and adjusted to a pressure of 8 MPa, and hot-pressed for 30 min to form a concave structure, and then cooled and solidified to obtain a large concave structure.

[0079] The results of Comparative Examples 2 and 5 show that the wing skin prepared in Comparative Example 5 has a weak overall structure during weaving, and after vacuum hot pressing, the overall structure of the three-dimensional weaving is not as good as that of Example 2, and thus the zero Poisson's ratio structure is damaged.

[0080] The zero Poisson's ratio large deformation skin of the sandwich structure obtained in the examples and comparative examples is tested for performance, and the test is as shown in Table 1:

[0081] As can be seen from Table 1:

[0082] (1) As can be seen from Examples 2 and 3, when the thickness ratio of the upper structure, the sandwich structure, and the lower structure is 1:0.5-2:1, the mechanical properties of the prepared skin are good, and can satisfy 80% large deformation;

[0083] (2) As can be seen from Examples 2 and Comparative Example 1, the mechanical properties of the prepared skin are poor when the sizing and desizing process of polyamide acid is omitted;

[0084] (3) As can be seen from Examples 2 and Comparative Example 2, the mechanical properties of the prepared skin are poor when the desizing process of polyamide acid is omitted;

[0085] (4) As can be seen from Examples 2 and Comparative Example 3, the mechanical properties are poor and it is difficult to achieve zero Poisson's ratio when full three-dimensional six-way weaving is used;

[0086] (5) As can be seen from Examples 2 and Comparative Example 4, the mechanical properties of the prepared skin are poor and it is difficult to achieve zero Poisson's ratio when sewing is used;

[0087] (6) As can be seen from Examples 2 and Comparative Example 5, the performance of the three-dimensional woven large skin with a concave structure is much lower than that of Example 2.

[0088] Table 1

[0089]

[0090] Comparative Example 6

[0091] Adjust the thickness of the sandwich structure in step (3) of Example 1 to 30 mm, and keep other conditions the same as in Examples 1 and 2 to obtain a zero-Poisson's ratio large deformation skin with sandwich structure.

[0092] It is found that the skin performance is reduced when the sandwich structure is too thick.

[0093] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, and the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing a zero Poisson's ratio large deformation skin for a sandwich structure, characterized in that, Includes the following steps: (1) Desizing: The zero Poisson's ratio large deformation skin preform of the sandwich structure is de-slurried with acetone to obtain the de-slurried zero Poisson's ratio large deformation skin preform of the sandwich structure. (2) Composite: The zero Poisson's ratio large deformation skin preform of the sandwich structure after desizing is immersed in polyetheretherketone solution, then taken out, hot-pressed and shaped, and cooled to obtain the zero Poisson's ratio large deformation skin of the sandwich structure. The zero Poisson's ratio large deformation skin preform of the sandwich structure is prepared by a method for an integrated woven sandwich structure zero Poisson's ratio large deformation skin preform, the method of which includes the following steps: First, a three-dimensional six-directional weaving is used to obtain the lower structure of the preform. Then, new yarns are introduced parallel to the length direction and woven in three-dimensional four-directional with the six-directional yarns of the lower layer to form a sandwich structure. Finally, the six-directional yarns of the lower layer are used to continue three-dimensional six-directional weaving to obtain the upper structure. The three-layer structure together form a sandwich structure with zero Poisson's ratio and large deformation skin preform. The thickness ratio of the upper structure, sandwich structure, and lower structure is 1:0.5 to 2:

1.

2. The method according to claim 1, characterized in that, The carbon fiber yarn used for weaving needs to be desized and then sized. Desizing involves treating the carbon fiber yarn at high temperature and under an inert gas atmosphere. The high temperature is 200-300℃, and the inert gas is nitrogen. The treatment time is 20-40 minutes. Sizing is done using a polyamic acid solution. Specifically, the desized carbon fiber yarn is immersed in the polyamic acid solution at room temperature for 10-60 minutes, and then kept at 280-200℃ for 10-20 minutes. The polyamic acid solution is an aqueous solution of polyamic acid with a concentration of 10-20 wt%.

3. The method according to claim 1, characterized in that, The yarn used for weaving is carbon fiber yarn, with the carbon fiber specifications being 3k to 12k and the fineness being 200 to 800 tex. The carbon fiber yarn is obtained by combining and twisting 2 to 3 bundles of carbon fibers, with a twist of 40 to 80 twists / meter.

4. The method according to claim 1, characterized in that, The height of the knots woven in the upper and lower structures is 6–10 mm, the width of the knots is 1–4 mm, and the weaving angle is 16–20°.

5. The method according to claim 1, characterized in that, The height of the flower knots in the sandwich structure weaving is 2-6mm, the width of the flower knots is 1-3mm, and the weaving angle is 25-45°.

6. The method according to claim 1, characterized in that, The desizing process described in step (1) specifically involves: The zero Poisson's ratio large deformation skin preform of the sandwich structure is immersed in acetone, heated and refluxed in a water bath at 50-70°C for 36-72 hours to remove the slurry, and then removed and dried to obtain the zero Poisson's ratio large deformation skin preform of the sandwich structure after slurry removal.

7. The zero Poisson's ratio large deformation skin of the sandwich structure prepared by the method of claim 1 or 6.

8. The application of the zero Poisson's ratio large deformation skin of the sandwich structure according to claim 7 in the aerospace field.

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