Method for controlling deformation of composite material L-shaped section ring frame

Abstract

The invention provides a deformation control method for a composite material L-shaped section ring frame. The method comprises the following steps: defining a simplified ring frame section; then filling a cavity between the cambered surface plate, the column surface plate laying layer and the edge of the mold with resin, which is equivalent to a resin film laying layer in the center of the cambered surface plate laminated plate; calculating an R angle filler equivalent laying layer; the filter paper is added to the two sides of the column panel and the arc panel, the thickness of resin films of the column panel and the arc panel is controlled, and therefore the thermal expansion coefficients of the column panel and the arc panel are adjusted and corrected till the thermal expansion coefficients of the arc panel and the column panel are consistent; calculating an equivalent thermal expansion system; and finally, determining a filter paper paving scheme. According to the ring frame deformation control method provided by the invention, indirect deformation control without changing the mold and the original laying layer is realized, the high cost requirement of modifying the mold and the product design period limitation corresponding to modifying the original laying layer are avoided, the problem of overcorrection caused by modifying the laying layer is avoided, and the production efficiency is improved. And the development cost and period of the large-size composite material I-shaped ring frame are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material L-shaped ring frame production and manufacturing, and in particular relates to a composite material L-shaped cross-section ring frame deformation control method. Background Art

[0002] Thermosetting resin-based composite materials have the characteristics of light weight, high specific strength and specific modulus, good fatigue resistance, and strong corrosion resistance. Therefore, they are widely used in aerospace, shipbuilding and other fields. There are many assembly structures in aircraft, with a large number of parts, large parts size, high precision requirements, complex coordination process, and each part must have precise dimensional tolerances to ensure smooth assembly. Due to the anisotropy of composite materials, structural asymmetry, resin curing shrinkage, uneven temperature field, uneven pressure field, and mold factors during the curing process, the parts after curing and molding are deformed, which not only affects the surface contour and dimensional accuracy of the parts, but also causes assembly gaps or interference, resulting in large assembly stresses during the assembly process. In severe cases, it may also affect the overall structural strength and aerodynamic efficiency of the aircraft, causing parts to be scrapped. Therefore, how to reduce curing deformation has become a widely concerned issue in the industry.

[0003] In order to meet the lightweight requirements of commercial aerospace, large-size, high-precision composite structures are gradually applied to large rocket cabins. As the size of composite structures increases, the impact of curing deformation on composite structures is also gradually magnified. The control of the molding size of parts such as composite stringers and ring frames has become a difficult point in the development of large composite cabin structures. In composite structures, the curing deformation problem of ring frames is relatively serious. Due to the curing deformation problem, large-size composite ring frames will have serious closing, resulting in the product size failing to meet the design requirements and use requirements. In the prior art, numerical solution technology is generally used to solve the theoretical value, and the test database is used to correct it, and finally the trial mold is used to manufacture the parts. Dealing with the curing deformation problem includes two problems: prediction and correction of curing deformation. Among them, the prediction of curing deformation faces the problem that traditional calculation methods involve many input parameters, the calculation procedure is complicated, and it is not suitable for direct engineering application. The correction of curing deformation includes mold compensation and layer modification. Mold compensation has the problems of high cost and irreversible mold modification, and is not suitable for the application of non-mass production products. Layer modification is suitable for the correction of curing deformation of thick plate composite materials, and it is easy to overcorrect for thin plate composite materials. Therefore, it is necessary to improve the existing molding control method. Summary of the invention

[0004] In view of this, the present invention aims to overcome the defects in the prior art and proposes a deformation control method for an L-section ring frame of a composite material.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A composite material L-section ring frame deformation control method comprises the following steps:

[0007] S1: Assume that the equivalent thermal expansion coefficients of the L-section ring frame column panel and the arc panel are consistent, and the ring frame has no obvious curing deformation; define the direction of the L-section ring frame perpendicular to the L-section as 0°, define the direction perpendicular to 0° in the laminate as 90°, and simplify the ring frame section;

[0008] S2: Fill the cavity between the arc panel and column panel ply and the edge of the mold with resin, which is equivalent to the resin film ply in the center of the arc panel laminate;

[0009] S3: Flatten the cross-sectional area of ​​the R-angle filler to form a 0° unidirectional tape ply, place it in the arc panel laminate ply at the centroid of the R-angle filler, and calculate the equivalent ply of the R-angle filler;

[0010] S4; by adding filter paper on both sides of the column panel and the arc panel, the thickness of the resin film of the column panel and the arc panel is controlled, thereby adjusting the thermal expansion coefficient of the column panel and the arc panel, and correcting the thermal expansion coefficient of the arc panel and the column panel to be consistent;

[0011] S5: Calculate the equivalent thermal expansion coefficient;

[0012] S6: Determine the amount of filter paper to be laid.

[0013] Furthermore, the equivalent resin film thickness corresponding to the edge cavity is calculated as, t q1 =S q1 / L 1 ;t q2 =S q2 / L 2 Among them, L 1 is the mold arc panel width, L 2 is the height of the mold column panel, S q1 is the area of ​​the cavity 1 at the edge of the curved panel, S q2 is the area of ​​cavity 2 at the edge of column panel, t q1 is the equivalent ply thickness of the cavity at the edge of the curved panel, t q2 is the equivalent ply thickness of the cavity at the edge of the column panel.

[0014] Furthermore, the equivalent ply formula for calculating R-angle filler is: R =S R / L 1 ; where t R It is the equivalent ply thickness of the R corner filler of the curved panel.

[0015] Furthermore, the thermal expansion coefficient, elastic modulus, shear modulus, and Poisson's ratio of the equivalent ply of the R-angle filler are consistent with those of the 0° direction ply of the unidirectional tape.

[0016] Furthermore, the thermal expansion coefficient, elastic modulus, shear modulus, and Poisson's ratio of the edge cavity equivalent ply are consistent with those of the unidirectional tape ply at 90°.

[0017] Furthermore, the material parameters of the equivalent resin film layer filled with the cavity resin are consistent with the material parameters of the resin film between the L-shaped ring frame arc panel, the column panel and the mold surface.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The ring frame deformation control method provided by the present invention realizes indirect deformation control without changing the mold and the original layup, avoids the high cost requirement of modifying the mold and the product design cycle limitation corresponding to modifying the original layup, avoids the problem of overcorrection in modifying the layup, and greatly reduces the development cost and cycle of large-size composite material I-shaped ring frames. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0021] Figure 1 A schematic cross-sectional view of the composite material L-shaped ring frame created by the present invention;

[0022] Figure 2 A simplified schematic diagram of the cross section of the composite material L-shaped ring frame created by the present invention. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0025] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0026] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0027] For composite L-shaped ring frame structures made of the same material, due to the use of a female mold + male mold molding scheme, the temperature is evenly transferred, and the difference in curing reaction is ignored. This paper assumes that if the cooling shrinkage of the L-shaped column panel and the arc panel is consistent, then the curing shrinkage of the column panel and the arc panel is also consistent. The curing deformation problem is simplified to a cooling shrinkage problem. A deformation control method for a large-size thin-walled composite L-shaped ring frame Figure 1 and Figure 2 As shown, the following steps are included:

[0028] S1: Assume that the equivalent thermal expansion coefficients of the L-shaped ring frame column panel and the arc panel are consistent, and the ring frame has no obvious curing deformation; define the direction of the L-shaped ring frame perpendicular to the L-shaped section as 0°, and define the direction perpendicular to 0° in the laminate as 90°. The process state of the ring frame section before simplification is as follows: Figure 1 . The L 1 is the mold arc panel width, L 2 is the width of the mold column panel, S q1 is the area of ​​the cavity 1 at the edge of the curved panel, S q2 is the area of ​​the cavity 2 at the edge of the column panel, S R is the cross-sectional area of ​​R corner filler; t e1 is the thickness of the resin film at the edge of the column panel 1, t e2 is the thickness of the resin film at the edge of the column panel 2, t e3 is the thickness of the resin film on the edge of the curved panel 3, t e4 The thickness of the resin film at the edge of the curved panel is 4.

[0029] S2: Flatten the cross-sectional area of ​​the R-angle filler to form a 0° unidirectional tape ply, and place it in the arc panel laminate ply at the centroid of the R-angle filler. Calculate the equivalent ply of the R-angle filler as follows:

[0030] t R =S R / L 1

[0031] Where t R S is the equivalent ply thickness of the R corner filler of the curved panel, R is the cross-sectional area of ​​the R-angle filler. The thermal expansion coefficient, elastic modulus, shear modulus, and Poisson's ratio of the equivalent ply of the R-angle filler are consistent with those of the 0° direction ply of the unidirectional tape. The elastic modulus E of the equivalent ply of the R-angle filler along the ring frame L , R angle filler equivalent ply vertical hoop direction elastic modulus E r , Poisson's ratio of the equivalent pavement surface of R angle filler υ LT and TL , the shear modulus G of the equivalent pavement surface of the R corner filler LT .

[0032] Considering the resin film between the L-shaped ring frame arc panel, column panel and mold surface, the resin film thickness t is defined e1 ,t e2 ,t e3 ,t e4 The elastic modulus, shear modulus and Poisson's ratio of the resin film are consistent with those of the 90° unidirectional tape. The elastic modulus E of the resin film along the ring frame r , elastic modulus E of the resin film in the vertical hoop direction r , Poisson's ratio in the in-plane direction υ LT and TL , the shear modulus G of the resin film in the in-plane direction LT ;

[0033] S3: The resin filling of the cavity between the column panel and the arc panel and the corresponding mold edge is equivalent to the resin film layer; considering the difference between the blanking size of the L-shaped ring frame column panel and the arc panel and the mold width, the resin filling of the cavity between the arc panel and the mold edge is equivalent to the resin film layer, which is placed in the center of the arc panel and column panel laminate. The equivalent resin film thickness corresponding to the edge cavity is calculated as follows:

[0034] t q1 =S q1 / L 1 ;t q2 =S q2 / L 2 ;

[0035] The L 1 is the mold arc panel width, L 2 is the height of the mold column panel, S q1 is the area of ​​the cavity 1 at the edge of the curved panel, S q2 is the area of ​​cavity 2 at the edge of column panel, t q1 is the equivalent ply thickness of the cavity at the edge of the curved panel, t q2is the equivalent ply thickness of the cavity at the edge of the column panel. The material parameters of the equivalent resin film ply for cavity resin filling are consistent with the material parameters of the resin film between the L-shaped ring frame arc panel, column panel and mold surface.

[0036] S4: Calculate the equivalent thermal expansion coefficient;

[0037] Thickness of each layer t R ,t e1 ,t e2 ,t e3 ,t e4 ,t q1 ,t q2 , the axial elastic modulus, hoop elastic modulus, in-plane Poisson's ratio, in-plane shear modulus of each layer and the original ply combination of the composite L-shaped ring frame arc panel and column panel. Assuming that the arc panel has m layers of original ply, the original thickness of the arc panel is t1~tm, and the original ply of the column panel is n layers, and the original thickness of the column panel is u1~un, then the arc panel ply after fusion process parameters is [t e3 / t 1 / t 2 / ... / t m / 2 / t q1 / t R / t m / 2+1 / ... / t m / t e4 ], the column panel layer is [t e1 / u 1 / u 2 / ... / u n / 2 / t q2 / u n / 2+1 / ... / u n / t e2 ].

[0038] According to the above parameters, the equivalent thermal expansion coefficient of the column panel and the arc panel is calculated by the following formula 1-6 to obtain the equivalent thermal expansion coefficient α of the arc panel. 1 and column panel equivalent thermal expansion coefficient α 2 .

[0039] According to the classical laminate theory, the laminate stiffness is calculated as the following formula 1-6, where Aij is an element in the laminate stiffness matrix A, and i and j are the row and column indexes of the stiffness matrix, respectively, corresponding to the stiffness relationship of the composite laminate in different directions. For a laminate with symmetrical and balanced plies, i and j are 1, 2, and 6, respectively. is the eccentric stiffness coefficient matrix of each layer of the laminate The elements in , i and j are the row and column indices of the stiffness matrix, corresponding to the stiffness relationship in different directions of the composite laminate. For a laminate with symmetrical and balanced plies, i and j are 1, 2, and 6 respectively. The total number of laminates is n, and the index k is calculated from 1 to n. The t (k) is the thickness of each layer of the laminate, and the index k from 1 to n corresponds to the thickness of different layers.

[0040]

[0041] Calculate the eccentric stiffness coefficient matrix of each layer As shown in the following formula, the index k from 1 to n corresponds to different plies.

[0042]

[0043] The T (k) is the stress conversion matrix of the kth layer, which is calculated as follows, where θ is the ply direction of each layer.

[0044]

[0045] The Q (k) is the stiffness coefficient matrix of the kth layer, calculated as follows, where E L is the elastic modulus in the fiber direction of the unidirectional prepreg, where E r is the elastic modulus of the unidirectional prepreg in the direction perpendicular to the fiber, where υ LT and TL is the Poisson's ratio in the in-plane direction of the unidirectional tape prepreg, where G LT It is the shear modulus of the unidirectional tape prepreg in the in-plane direction.

[0046]

[0047] The Δ t The calculation is as follows

[0048] Δ t =1-υ LT υ TL (5)

[0049] The calculation formula of equivalent thermal expansion coefficient of composite material ply is as follows: -1 is the inverse matrix of the laminate stiffness matrix A.

[0050]

[0051] The direction of the L-shaped ring frame perpendicular to the L-shaped section is defined as 0°, and the direction perpendicular to 0° in the laminate is defined as 90°.

[0052] Substituting formula (3) and (4) into formula (2), the eccentric stiffness coefficient matrix of each layer is calculated: Substitute into formula (6).

[0053] Take the inverse matrix of the laminate stiffness matrix A in formula 1 and substitute it into formula (6).

[0054] The α in the formula (6) (k) is the thermal expansion coefficient of the vertical ring frame section of each layer. The total number of laminate layers is n, and the index k is obtained from 1 to n by experiments.

[0055] In the formula (6), t (k) is the thickness of each layer, the total number of laminate layers is n, and the index k from 1 to n corresponds to the specific product design. The product design and process solution details in this article only correspond to t (k) changes.

[0056] S5; by adding or not adding filter paper on both sides of the column panel and the arc panel, the thickness of the resin film of the column panel and the arc panel is controlled, thereby adjusting the thermal expansion coefficient of the column panel and the arc panel, and correcting the thermal expansion coefficient of the arc panel and the column panel to be consistent;

[0057] S6: Calculate the equivalent thermal expansion coefficient;

[0058] S7: Determine the filter paper laying plan. The specific method is: if the filter paper is pasted on the outer surface of the web, e1 =0, if filter paper is not pasted on the outer surface of the web t e1 =0.05; if filter paper is pasted on the inner surface of the web, t e2 =0, if filter paper is not pasted on the inner surface of the web t e2 =0.05; if filter paper is pasted on the outer surface of the edge plate, t e3 =0, if filter paper is not pasted on the outer surface of the edge plate t e3 =0.05; if filter paper is pasted on the inner surface of the edge plate, t e4 = 0, if the filter paper is not pasted on the inner surface of the edge plate t e4 =0.05. According to the principle that the thermal expansion coefficients of the flange and web are consistent, adjust t e1 ,t e2 ,t e3 ,t e4 The thickness is 0 or 0.05, thus determining the paving plan of the filter paper.

[0059] The formula for calculating the equivalent layer of R angle filler is: R =S R / L 1 Where, t R S is the equivalent ply thickness of the R corner filler of the curved panel, R is the cross-sectional area of ​​R corner filler.

[0060] The thermal expansion coefficient, elastic modulus, shear modulus and Poisson's ratio of the equivalent ply of the R-angle filler are consistent with those of the 0° direction ply of the unidirectional tape. It should be noted that in the present invention, the curved panel and column panel are fixed terms for the L-shaped structure in the art. In addition, the curved panel and column panel formed by curing of multi-layer composite materials can also be understood as laminated panels.

[0061] Filling the cavity between the arc panel, column panel and the edge of the mold with resin is equivalent to the resin film layer in the center of the arc panel laminate. The material parameters of the resin film layer equivalent to the cavity resin filling are consistent with the material parameters of the resin film between the L-shaped ring frame arc panel, column panel and the mold surface.

[0062] The equivalent resin film thickness corresponding to the edge cavity is calculated as, t q1 =S q1 / L 1 ;t q2 =S q2 / L 2 ;

[0063] Among them, L 1 is the mold arc panel width, L 2 is the height of the mold column panel, S q1 is the area of ​​the cavity 1 at the edge of the curved panel, S q2 is the area of ​​cavity 2 at the edge of column panel, t q1 is the equivalent ply thickness of the cavity at the edge of the curved panel, t q2 is the equivalent ply thickness of the cavity at the edge of the column panel. The material parameters of the equivalent resin film ply for cavity resin filling are consistent with the material parameters of the resin film between the L-shaped ring frame arc panel, column panel and mold surface.

[0064] The ring frame deformation control method provided by the present invention realizes indirect deformation control without changing the mold and the original layup, avoids the high cost requirement of modifying the mold and the product design cycle limitation corresponding to modifying the original layup, avoids the problem of overcorrection in modifying the layup, and greatly reduces the development cost and cycle of large-size composite material I-shaped ring frames.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite material L-section ring frame deformation control method, characterized in that: The steps include: S1: Assume that the equivalent thermal expansion coefficients of the L-section ring frame column panel and the arc panel are consistent, and the ring frame has no obvious curing deformation; define the direction of the L-section ring frame perpendicular to the L-section as 0°, define the direction perpendicular to 0° in the laminate as 90°, and simplify the ring frame section; S2: Fill the cavity between the arc panel and column panel ply and the edge of the mold with resin, which is equivalent to the resin film ply in the center of the arc panel laminate; S3: Flatten the cross-sectional area of ​​the R-angle filler to form a 0° unidirectional tape ply, place it in the arc panel laminate ply at the centroid of the R-angle filler, and calculate the equivalent ply of the R-angle filler; S4; by adding filter paper on both sides of the column panel and the arc panel, the thickness of the resin film of the column panel and the arc panel is controlled, thereby adjusting the thermal expansion coefficient of the column panel and the arc panel, and correcting the thermal expansion coefficient of the arc panel and the column panel to be consistent; S5: Calculate the equivalent thermal expansion coefficient; S6: Determine the filter paper laying plan.

2. A composite material L-section ring frame deformation control method according to claim 1, characterized in that: The equivalent resin film thickness corresponding to the edge cavity is calculated as, t q1 =S q1 / L1;t q2 =S q2 / L2; where L1 is the width of the mold arc panel, L2 is the height of the mold column panel, S q1 is the area of ​​the cavity 1 at the edge of the curved panel, S q2 is the area of ​​cavity 2 at the edge of column panel, t q1 is the equivalent ply thickness of the cavity at the edge of the curved panel, t q2 is the equivalent ply thickness of the cavity at the edge of the column panel.

3. A composite material L-section ring frame deformation control method according to claim 1, characterized in that: The formula for calculating the equivalent layer of R angle filler is: R =S R / L1; where t R It is the equivalent ply thickness of the R corner filler of the curved panel.

4. A composite material L-section ring frame deformation control method according to claim 1, characterized in that: The thermal expansion coefficient, elastic modulus, shear modulus and Poisson's ratio of the equivalent ply of R-angle filler are consistent with those of the 0° direction ply of unidirectional tape.

5. A composite material L-section ring frame deformation control method according to claim 1, characterized in that: The thermal expansion coefficient, elastic modulus, shear modulus and Poisson's ratio of the edge cavity equivalent ply are consistent with those of the 90° direction ply of the unidirectional tape.

6. A composite material L-section ring frame deformation control method according to claim 1, characterized in that: The material parameters of the equivalent resin film layer for cavity resin filling are consistent with the material parameters of the resin film between the L-shaped ring frame arc panel, the column panel and the mold surface.

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