A variable width laying method for trapezoidal grid tow

Abstract

The present invention discloses a variable width laying method of a trapezoidal grid tow, comprising the following steps: step 1, determining the basic parameters of the mold rib groove; step 2, determining the thickness t of the prepreg tow; step 3, determining the total number of layers N of the prepreg tow laid in the mold rib groove; step 4, determining the maximum number of layers n of the prepreg tow bent and laid in the mold rib groove; step 5, bending and laying the first layer of prepreg tow in a manner close to the inner wall of the mold rib groove, bending and laying n-1 layers of prepreg tow in sequence in a manner close to the adjacent prepreg tow in the lower layer, and horizontally laying N-n layers of prepreg tow in sequence on the nth layer of prepreg tow in a manner close to the adjacent prepreg tow in the lower layer. For prepreg tows of the same thickness in the same mold rib groove, the number of cavities generated by the method of the present invention is reduced compared with the prior art, thereby reducing the volume ratio of the cavity, and further reducing the influence of the cavity on the performance of the rib.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material wire placement and molding, and in particular relates to a variable-width placement method for a trapezoidal grid wire bundle. Background Art

[0002] Longitudinal ring grid ribs are a common form of composite material reinforcement structure. Compared with other components, under the same conditions, they do not increase the thickness of the product, and can ensure that the grid rib structure has higher strength and higher stiffness. At the same time, it can reduce the mass of the reinforced structure to the greatest extent. Therefore, it is widely used in aerospace, low-altitude economy, shipbuilding and other fields, especially in some rotating body structures, such as the interstage, fairing, fuel tank and load-bearing cylinder of the launch vehicle. The ring longitudinal grid rib structure made of carbon fiber composite materials greatly reduces the weight of the structural parts and saves costs.

[0003] In the early days, in order to better demould after curing, the mold groove was designed as an inverted trapezoidal structure. In order to facilitate laying, the prepreg tows were laid horizontally layer by layer in the mold groove, such as Figure 1 As shown, both ends of each layer of prepreg tow are in contact with the inner wall of the mold rib groove, but the widths of the upper and lower cross-sections of the trapezoidal structure are inconsistent, which will lead to cavities of varying degrees during the laying process. The existence of cavities will reduce the performance of the rib structure within a certain range.

[0004] Based on this, the present application proposes a variable-width laying method for trapezoidal grid wire bundles based on trapezoidal mold rib grooves. By combining bending laying with horizontal laying, the number of cavities is reduced and the mechanical properties of the ribs are improved. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a variable-width laying method for trapezoidal grid tows.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A variable width laying method of a trapezoidal grid tow comprises the following steps:

[0008] Step 1, determine the basic parameters of the mold rib groove;

[0009] The basic parameters include the lower bottom width b of the rib groove, the height h of the rib groove, the length a1 of the first hypotenuse of the rib groove, the length a2 of the second hypotenuse of the rib groove, the angle α between the first hypotenuse of the rib groove and the lower bottom of the rib groove, and the angle β between the second hypotenuse of the rib groove and the lower bottom of the rib groove;

[0010] Step 2, determining the thickness t of the prepreg tow;

[0011] Step 3, determine the total number of layers N of prepreg tows placed in the mold rib groove, N is calculated as follows:

[0012]

[0013] Step 4, determining the maximum number n of prepreg tows bent and laid in the mold rib groove;

[0014] Step 5, bend and lay the first layer of prepreg tows in a manner close to the inner wall surface of the mold rib groove, and bend and lay n-1 layers of prepreg tows in a manner close to the adjacent prepreg tows of the lower layer, so that the top ends of the outer peripheral surfaces of all the bent and laid prepreg tows are flush with the top ends of the corresponding side oblique edges of the mold rib groove;

[0015] On the nth layer of prepreg tows, Nn layers of prepreg tows are horizontally laid in sequence in a manner of being closely attached to the adjacent prepreg tows of the lower layer, and both ends of each layer of horizontally laid prepreg tows are in contact with the inner side surface of the nth layer of prepreg tows;

[0016] The top surface of the Nth layer of prepreg tow is flush with the top of the oblique edge of the mold rib groove.

[0017] Preferably, in step 4, the method for determining the maximum number of layers n of prepreg tows bent and laid in the rib groove of the mold is as follows:

[0018] make Let r = [m], [m] is the largest integer not exceeding m;

[0019] When r≥N, the calculation formula for the maximum number of layers n of bending and laying in the mold rib groove is:

[0020] n=N-1 (4-1)

[0021] When r<N, the calculation formula for the maximum number of layers n of bending and laying in the mold rib groove is:

[0022] n=r (4-2)

[0023] Preferably, in step 5, the calculation formula for the wire width li of the i-th layer of prepreg tow laid in a bent manner is as follows:

[0024]

[0025] Among them, i≤n.

[0026] Preferably, in step 5, the prepreg tows from the nth layer onwards are laid horizontally, and the calculation formula for the wire width lk of the kth layer of prepreg tows is as follows:

[0027]

[0028] Among them, n+1≤k≤N.

[0029] The beneficial effects of the present invention are:

[0030] For prepreg tows with the same mold rib groove and the same thickness, the number of cavities generated by the method of the present invention is reduced compared with the prior art, thereby reducing the volume ratio of the cavity and further reducing the impact of the cavity on the rib performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0032] Figure 1 It is a schematic diagram of the prepreg tows being laid horizontally layer by layer in the rib groove of the mold in the background art;

[0033] Figure 2 Schematic diagram of the variable width laying method of the trapezoidal grid tow of the present invention;

[0034] Figure 3 It is a schematic diagram of calculating the wire width in the variable-width laying method of the trapezoidal grid wire bundle of the present invention. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] In the present invention, the directions or positional relationships indicated by terms such as "upper", "lower", "bottom", "top", etc. are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention. They do not specifically refer to any part or element in the present invention and cannot be understood as limitations on the present invention.

[0038] In the present invention, terms such as "connected" and "connection" should be understood in a broad sense, indicating that the connection can be fixed, integral or detachable; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meaning of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0039] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0040] A variable width laying method of a trapezoidal grid tow comprises the following steps:

[0041] Step 1, determine the basic parameters of the mold rib groove;

[0042] The basic parameters include the lower bottom width b of the rib groove, the height h of the rib groove, the length a1 of the first hypotenuse of the rib groove, the length a2 of the second hypotenuse of the rib groove, the angle α between the first hypotenuse of the rib groove and the lower bottom of the rib groove, and the angle β between the second hypotenuse of the rib groove and the lower bottom of the rib groove;

[0043] Step 2, determining the thickness t of the prepreg tow;

[0044] Step 3, determine the total number of layers N of prepreg tows placed in the mold rib groove, N is calculated as follows:

[0045]

[0046] Step 4, determining the maximum number n of prepreg tows bent and laid in the mold rib groove;

[0047] Step 5, such as Figure 2 As shown, the first layer of prepreg tows is bent and laid in a manner close to the inner wall surface of the mold rib groove, and n-1 layers of prepreg tows are bent and laid in sequence in a manner close to the adjacent prepreg tows of the lower layer, and the top ends of the outer peripheral surfaces of all bent and laid prepreg tows are flush with the top ends of the corresponding side oblique edges of the mold rib groove;

[0048] On the nth layer of prepreg tows, Nn layers of prepreg tows are horizontally laid in sequence in a manner of being closely attached to the adjacent prepreg tows of the lower layer, and both ends of each layer of horizontally laid prepreg tows are in contact with the inner side surface of the nth layer of prepreg tows;

[0049] The top surface of the Nth layer of prepreg tow is flush with the top of the oblique edge of the mold rib groove.

[0050] Specifically, in step 4, the method for determining the maximum number of layers n of the prepreg tows bent and laid in the rib groove of the mold is as follows:

[0051] make m is a parameter;

[0052] Let r = [m], [m] is the largest integer not exceeding m;

[0053] When r≥N, the calculation formula for the maximum number of layers n of bending and laying in the mold rib groove is:

[0054] n=N-1 (4-1)

[0055] When r<N, the calculation formula for the maximum number of layers n of bending and laying in the mold rib groove is:

[0056] n=r (4-2)

[0057] The principle for determining the maximum number of layers n in the mold rib groove is as follows:

[0058] like Figure 3 As shown in the figure, after the first layer of prepreg tow is bent and laid, the horizontal wire width of its top surface is A2A3|. According to the trigonometric function relationship, we can get:

[0059]

[0060] By analogy, we can get that after bending and laying the i-th layer, the horizontal wire width of the top surface of the i-th layer is

[0061]

[0062] The condition for successfully achieving the bending and laying of layer i is Then get Thus, the maximum number of layers for bending and laying is obtained as r = [m];

[0063] In addition, since the maximum number of layers in the mold rib groove is N, therefore:

[0064] When r≥N, the top layer needs to be laid horizontally, and the remaining layers can be bent and laid, so the calculation formula for the number of layers n bent and laid in the mold rib groove is: n=N-1;

[0065] When r<N, the calculation formula for the number of layers n bent and laid in the mold rib groove is: n=r.

[0066] Specifically, in step 5, the calculation formula for the wire width li of the i-th layer of prepreg tow laid in a bent manner is as follows:

[0067]

[0068] Among them, i≤n.

[0069] Specifically, in step 5, the prepreg tows from the nth layer onwards are laid horizontally, and the calculation formula for the wire width lk of the kth layer of prepreg tows is as follows:

[0070]

[0071] Among them, n+1≤k≤N.

[0072] In this application, if Figure 3 As shown, when bent and laid, the wire width of the first layer of prepreg tow is the inner length of the inner wall of the mold rib groove, and the inner length of the inner wall of the mold rib groove is the total length of the lower bottom O2O3 of the rib groove, the first oblique side O3O4 of the rib groove, and the second oblique side O1O2 of the rib groove, that is, l1=a1+b+a2; the wire width of the second layer of prepreg tow is the inner length of the first layer of prepreg tow, and the inner length of the first layer of prepreg tow is A1A2|+|A2A3|+|A3A4|. According to the trigonometric function relationship, it can be obtained:

[0073]

[0074] By analogy, we can obtain formula (5-1).

[0075] In step 5, after bending and laying n layers, the wire is laid horizontally. After bending and laying n layers, the horizontal wire width of the top surface of the nth layer is When the n+1th layer is laid horizontally, its wire width is When the n+2th layer is laid horizontally, its wire width is the wire width of the n+1th layer + |E1E2| + |E3E4|. The trigonometric function relationship can be obtained as By analogy, we can obtain formula (5-2).

[0076] In the laying method of the present application, when the method of bending and laying n layers and laying Nn layers horizontally in step 5 is adopted, cavities appear only during horizontal laying, and the number of cavities on the left is Nn, and the number of cavities on the right is Nn.

[0077] For the all-horizontal laying method in the prior art, the number of cavities on the left is N, and the number of cavities on the right is N.

[0078] For prepreg tows with the same mold rib groove and the same thickness, the number of cavities produced by the method of the present application is reduced compared with the prior art, thereby reducing the volume ratio of the cavity and further reducing the impact of the cavity on the performance of the rib.

[0079] Example:

[0080] A variable width laying method of a trapezoidal grid tow comprises the following steps:

[0081] Step 1, determine the basic parameters of the mold rib groove;

[0082] The basic parameters include the lower bottom width b of the rib groove of 4mm, the height h of the rib groove of 4mm, the length a1 of the first hypotenuse of the rib groove of 5mm, the length a2 of the second hypotenuse of the rib groove of 5mm, the angle α between the first hypotenuse of the rib groove and the lower bottom of the rib groove of 53.13°, and the angle β between the second hypotenuse of the rib groove and the lower bottom of the rib groove of 53.13°;

[0083] Step 2, determining the thickness t of the prepreg tow to be 0.1 mm;

[0084] Step 3, determining that the total number of layers N of prepreg tows laid in the mold rib groove is 40;

[0085] Step 4, determining the maximum number n of prepreg tows bent and laid in the mold rib groove;

[0086] After calculation, r>N, then n=39;

[0087] Step 5, bend and lay the first layer of prepreg tows in a manner close to the inner wall surface of the mold rib groove, bend and lay 38 layers of prepreg tows in sequence in a manner close to the adjacent prepreg tows of the lower layer, lay the 40th layer of prepreg tows horizontally on the top surface of the 39th layer of prepreg tows, and the top surface of the 40th layer of prepreg tows is flush with the top end of the oblique side of the mold rib groove.

[0088] The wire width of each layer of prepreg tow is shown in Table 1.

[0089] Table 1 Width of prepreg tows in each layer

[0090]

[0091]

[0092] In the embodiment, a method of laying 39 layers in a folded manner and laying one layer horizontally is adopted, and cavities appear only when the last layer is laid, and the cross-sectional area of ​​the cavity units in each part is consistent, and the number of cavities is 2. For the method of laying all layers horizontally in the prior art, the number of cavities is 80, so the number of cavities generated by the method of the present application is less than that of the prior art, thereby reducing the volume ratio of the cavities, and further reducing the impact of the cavities on the performance of the ribs.

[0093] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not a limitation of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the protection scope of the present invention.

Claims

1. A variable width laying method of a trapezoidal grid tow, characterized in that: The following steps are involved: Step 1, determine the basic parameters of the mold rib groove; The basic parameters include the lower bottom width b of the rib groove, the height h of the rib groove, the length a1 of the first hypotenuse of the rib groove, the length a2 of the second hypotenuse of the rib groove, the angle α between the first hypotenuse of the rib groove and the lower bottom of the rib groove, and the angle β between the second hypotenuse of the rib groove and the lower bottom of the rib groove; Step 2, determining the thickness t of the prepreg tow; Step 3, determine the total number of layers N of prepreg tows placed in the mold rib groove, N is calculated as follows: Step 4, determining the maximum number n of prepreg tows bent and laid in the mold rib groove; Step 5, bend and lay the first layer of prepreg tows in a manner close to the inner wall surface of the mold rib groove, and bend and lay n-1 layers of prepreg tows in a manner close to the adjacent prepreg tows of the lower layer, so that the top ends of the outer peripheral surfaces of all the bent and laid prepreg tows are flush with the top ends of the corresponding side oblique edges of the mold rib groove; On the nth layer of prepreg tows, Nn layers of prepreg tows are horizontally laid in sequence in a manner of being closely attached to the adjacent prepreg tows of the lower layer, and both ends of each layer of horizontally laid prepreg tows are in contact with the inner side surface of the nth layer of prepreg tows; The top surface of the Nth layer of prepreg tow is flush with the top of the oblique edge of the mold rib groove.

2. The variable width laying method of trapezoidal grid tow according to claim 1, characterized in that: In step 4, the method for determining the maximum number of layers n of prepreg tows bent and laid in the rib groove of the mold is as follows: make Let r = [m], [m] is the largest integer not exceeding m; When r≥N, the calculation formula for the maximum number of layers n of bending and laying in the mold rib groove is: n=N-1 (4-1) When r<N, the calculation formula for the maximum number of layers n of bending and laying in the mold rib groove is: n＝r (4-2)。 3. The variable width laying method of trapezoidal grid tow according to claim 2, characterized in that: In step 5, the calculation formula for the wire width li of the i-th layer of prepreg tow laid in a bent manner is as follows: Among them, i≤n.

4. The variable width laying method of trapezoidal grid tow according to claim 3, characterized in that: In step 5, the prepreg tows from the nth layer onwards are laid horizontally, and the calculation formula for the wire width lk of the kth layer of prepreg tows is as follows: Among them, n+1≤k≤N.

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