Method for calculating the interference range of polymer foam core layer in sandwich structure propeller blade

Abstract

The present invention discloses a method for calculating the interference range of a polymer foam core layer of a sandwich structure blade, step S1: determining the thickening direction on the cross-sectional airfoil of the blade foam core; step S2: determining the thickening range on the equally divided points according to the thickness and the thickening ratio range, step S3: determining the points after thickening in the thickening direction, connecting the thickening points of the same side with the same thickening ratio, and obtaining the interference design contour line and the upper and lower interference range of the foam core on the airfoil. The present invention designs the interference in different thickening directions according to the thickness that changes with the chord line in the variable cross-section of the foam core airfoil, and determines the thickening contour line range at the same time, and can selectively perform single-sided or double-sided thickening, which has stronger applicability, so that the foam core of the composite material / foam core sandwich structure blade can provide a more stable and uniform support reaction force during co-curing by molding, and at the same time, the damage and failure of the foam core at the trailing edge of the blade is controlled, the blade molding performance is good, and the yield rate is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter composite tail rotor blade and rotor forming, and in particular relates to a method for calculating the interference range of a sandwich structure blade polymer foam core layer. Background Art

[0002] The helicopter rotor system control includes two parts: the rotor and the tail rotor. The rotor is the symbol of the helicopter and is also a key component of the helicopter. It not only provides lift and forward force for the helicopter, but also provides the longitudinal and lateral control torque of the helicopter. The tail rotor is an important component for balancing the rotor anti-torque and improving directional stability on a single-rotor helicopter. The two work together to achieve the heading control of the helicopter. The quality of the rotor and tail rotor blades often directly affects the performance, flight quality, reliability, maintainability and supportability of the helicopter. Therefore, the blade structure control must meet the requirements of aerodynamic shape, dynamics, fatigue and strength, reliability and maintainability, processability and economy. Composite blades have strong controllability, which can optimize the structural control efficiency. They have better stiffness, quality and strength characteristics. They have been widely used and have a clear trend of continued growth.

[0003] Molding co-curing is one of the commonly used molding processes for composite blades. At this time, a hard foam core material is generally used as the sandwich inside the blade, so that the support reaction force required for molding is provided by controlling the interference of the foam core to ensure the molding surface quality of the composite skin / foam core sandwich structure blade, so that its key shape parameters meet the control requirements and reach the set dimensional accuracy requirements. However, the cross-section of these blades belongs to the airfoil, and its thickness varies with the relative position of the chord line, and the airfoil has a relative pre-twist along the span direction. Therefore, for the control of the interference of the foam core, that is, the part where the actual size of the foam core exceeds the design size, how to make it provide sufficient and stable internal pressure after the mold is closed has always been a difficulty in the development of composite blades. The existing single-sided equal thickening method, that is, adding a fixed value of interference to the upper mold surface, will cause the foam in the trailing edge area of ​​the blade to be thicker, and the trailing edge foam will collapse and the cracks will extend forward during the molding process, which will affect the surface quality of the molded blade. In view of the above problems, it is very necessary to provide a method for calculating the interference range of the polymer foam core layer of the sandwich structure blade to optimize the molding and manufacturing of the blade. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the interference range of the polymer foam core layer of a sandwich structure blade, which can design the interference in different thickening directions according to the thickness that changes with the chord line in the variable cross-section of the foam core airfoil, and at the same time determine the contour line range of the thickening, and can selectively perform single or double-sided thickening, thereby improving the foam core damage failure at the trailing edge of the blade, improving the blade molding performance, and improving the yield.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for calculating the interference range of a polymer foam core layer of a sandwich structure blade is used to calculate the interference of an airfoil of a blade foam core cross section; the method comprises the following steps:

[0007] Step S1: determining a thickening direction on a cross-sectional airfoil of a blade foam core;

[0008] Step S2: determining the thickening range at the equally divided points according to the thickness and the thickening ratio range;

[0009] Step S3: Determine the points after thickening in the thickening direction, connect the thickening points with the same thickening ratio on the same side, and obtain the interference design contour line and the upper and lower ranges of the interference of the foam core on the airfoil.

[0010] Preferably, in step S1, the cross-sectional airfoil of the blade foam core is defined to include an upper foam core profile and a lower foam core profile, and the same number of equally divided points are taken on the upper and lower contour lines of the upper foam core profile and the lower foam core profile, which are N1, N2, ..., N k ,…,N i and N 1' , N 2' ,…,N k' ,…,N i' ;

[0011] In step S2, the equally divided points N k and N k' Take this set of corresponding points as an example, the equally divided points N on the upper contour line k The thickness, thickening value and its upper and lower limits are respectively denoted as L(N k ), Δl(N k ), Δl u (N k ) and Δl d (N k ), the lower contour line is divided into two equal points N k' The thickness, thickening value and its upper and lower limits are respectively denoted as L(N k' ), Δl(N k' ), Δl u (N k' ) and Δl d (N k' ).

[0012] Preferably, the thickening direction in step S1 includes the normal direction of the equally divided point, the corresponding points N1 and N2 on the upper and lower contour lines, and the normal direction of the equally divided point. 1' , N2 and N 2' ,…,N k and N k',…,N i and N i' The connecting line direction and the closing direction of the mold during compression co-curing molding.

[0013] Preferably, the thickness L(N k ) and L(N k' ) are the equally divided points N k and N k' The thickness value along the thickening direction.

[0014] Preferably, in step S2, the relationship between the thickening value, the thickness and the thickening ratio is:

[0015] Δl(N k )=L(N k )·k' and Δl(N k' )=L(N k' )·k”(k=1,2,…,i)

[0016] Where k' and k" are N k and N k' Thickening ratio of the side;

[0017] Δl u (N k ) and Δl d (N k ) is k' and takes the maximum value k max and the minimum value k min When the equal division point N k The thickening value on the upper surface, that is, the upper and lower limits of the interference of the upper surface;

[0018] Δl u (N k' ) and Δl d (N k' ) is k” and takes the maximum value k max and the minimum value k min When the equal division point N k' The thickening value on the upper side is the upper and lower limits of the interference of the lower surface.

[0019] Preferably, the range of values ​​of the thickness ratios k' and k'' and their sum k'+k'' in the above relationship is calculated by foam test experiments and finite element simulation. min ~k max .

[0020] Preferably, the foam experimental test adopts a foam uniaxial compression test and obtains the foam stress-strain elastic stage result.

[0021] Preferably, the finite element simulation calculation steps are as follows: the test values ​​of the uniaxial compression test of the same foam are imported into the finite element simulation calculation software, the simulation calculation uses the thickened airfoil as the sandwich structure molding co-curing process of the foam core, and the simulation analysis obtains the value range of the thickening ratio. The result can provide sufficient support reaction force and ensure that the foam core does not yield.

[0022] Preferably, in step S3, selective single-sided or double-sided thickening is performed on the upper and lower molding surfaces of the foam core in the thickening direction.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention can design the interference in different thickening directions according to the thickness of the foam core airfoil variable section that changes with the chord line, and at the same time determine the thickening contour line range, and can selectively perform single-sided or double-sided thickening, which has stronger applicability.

[0025] (2) The present invention enables the foam core of the composite material / foam core sandwich structure blade to provide a more stable and uniform supporting reaction force during co-curing during molding, while at the same time, the failure of the foam core at the trailing edge of the blade is controlled, the blade molding performance is good, and the yield rate is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a method for calculating the interference range of a polymer foam core layer of a sandwich structure blade provided by an embodiment of the present invention;

[0027] The serial numbers in the figure are as follows:

[0028] 1-1, upper surface of foam core; 1-2, lower surface of foam core; 2-1, lower limit of interference of upper surface; 2-2, lower limit of interference of lower surface; 3-1, upper limit of interference of upper surface; 3-2, upper limit of interference of lower surface. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] Embodiment 1

[0031] like Figure 1 As shown, a method for calculating the interference range of the polymer foam core layer of a sandwich structure blade disclosed in this embodiment is used to calculate the interference of the cross-section airfoil of the blade foam core; the method comprises the following steps:

[0032] Step S1: Determine the thickening direction on the cross-sectional airfoil of the blade foam core, define the cross-sectional airfoil of the blade foam core to include the upper profile of the foam core and the lower profile of the foam core, and take the same number of equally divided points on the upper and lower contour lines of the upper profile of the foam core and the lower profile of the foam core, which are N1, N2, ..., N k ,…,N i and N 1' , N 2' ,…,N k' ,…,N i' .

[0033] Furthermore, the thickening direction in step S1 can be selected from: the normal direction of the equally divided point, the corresponding points N1 and N2 on the upper and lower contour lines, 1' , N2 and N 2' ,…,N k and N k' ,…,N i and N i' The connecting line direction, or the closing direction of the mold during compression co-curing molding.

[0034] Furthermore, in this embodiment, the thickness L (N k ) and L(N k' ) are the equally divided points N k and N k' The thickness value along the thickening direction.

[0035] Step S2: Determine the thickening range at the equally divided points according to the thickness and the thickening ratio range, and take the equally divided points N as k and N k' Take this set of corresponding points as an example, the equally divided points N on the upper contour line k The thickness, thickening value and its upper and lower limits are respectively denoted as L(N k ), Δl(N k ), Δl u (N k ) and Δl d (N k ), the lower contour line is divided into two equal points N k' The thickness, thickening value and its upper and lower limits are respectively denoted as L(N k' ), Δl(N k' ), Δl u (N k' ) and Δl d (N k' ).

[0036] The relationship between the thickening value, thickness and thickening ratio is:

[0037] Δl(N k )=L(N k )·k' and Δl(N k' )=L(Nk' )·k”(k=1,2,…,i)

[0038] Where k' and k" are N k and N k' Thickening ratio of the side;

[0039] Δl u (N k ) and Δl d (N k ) is k' and takes the maximum value k max and the minimum value k min When the equal division point N k The thickening value on the upper surface, that is, the upper limit of the interference of the upper surface is 3-1 and the lower limit of the interference of the upper surface is 2-1;

[0040] Δl u (N k' ) and Δl d (N k' ) is k” and takes the maximum value k max and the minimum value k min When the equal division point N k' The thickening value on the upper side, that is, the upper limit of the interference amount of the lower profile is 3-2 and the lower limit of the interference amount of the lower profile is 2-2.

[0041] Furthermore, in this embodiment, through the foam test experiment and the finite element simulation calculation relationship, the range of the thickness ratio k' and k'' and the sum of the two k'+k'' is k min ~k max .

[0042] The foam experimental test adopts the foam uniaxial compression test and obtains the foam stress-strain elastic stage results.

[0043] The finite element simulation calculation steps are as follows:

[0044] The test values ​​of the uniaxial compression test of the same foam are imported into the finite element simulation calculation software. The simulation calculation uses the thickened airfoil as the sandwich structure co-curing process of the foam core, and the simulation analysis obtains the value range of the thickening ratio. The result can provide sufficient support reaction force and ensure that the foam core does not yield.

[0045] Step S3: Determine the points after thickening in the thickening direction, connect the thickening points with the same thickening ratio on the same side, and obtain the interference design contour line of the foam core on the airfoil and its upper and lower ranges.

[0046] Furthermore, in this embodiment, the upper and lower profiles of the foam core are selectively thickened on one side or both sides in the thickening direction.

[0047] The following is a description based on specific implementation data:

[0048] The foam core model of a tail rotor blade uses domestic PMI foam material ZK52, and the k min ~k max The value range is 0.6%-2.0%. The normal thickness dimension at a certain equal point in a certain section of the foam core is 21.00mm. Substituting it into the formula, we can get Δld=21.00×0.6%=0.13mm, Δlu=21.00×2.0%=0.42mm, so the range of the process digital model interference of the foam at this point is: 0.13~0.42mm(±0.02mm).

[0049] Embodiment 2

[0050] In this embodiment, based on the first embodiment, the length of the line between the equally divided point and the corresponding point, that is, the thickness is 20.63 mm. Substituting it into the formula, it can be calculated that Δld = 20.63 × 0.6% =

[0051] 0.12mm, Δlu=20.63×2.0%=0.41mm, so the sum of the interference amounts on both sides of the foam here is in the range of: 0.12~0.41mm(±0.02mm).

[0052] The present invention can design the interference in different thickening directions according to the thickness of the foam core airfoil variable section that changes with the chord line, and at the same time determine the thickening contour line range, and can selectively perform single or double-sided thickening, which has stronger applicability. The present invention enables the foam core of the composite material / foam core sandwich structure blade to provide a more stable and uniform support reaction force during molding and co-curing, and at the same time, the damage and failure of the foam core at the trailing edge of the blade is controlled, the blade molding performance is good, and the yield rate is improved.

[0053] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0054] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0055] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for calculating the interference range of a polymer foam core layer of a sandwich structure blade, which is used to calculate the interference range of an airfoil of a blade foam core cross section; characterized in that: The steps include: Step S1: determining a thickening direction on a cross-sectional airfoil of a blade foam core; The cross-sectional airfoil of the blade foam core is defined as the upper profile of the foam core and the lower profile of the foam core. The same number of equally divided points are taken on the upper and lower contour lines of the upper and lower profiles of the foam core, which are N1, N2, ..., N k ,…,N i and N1', N2', ..., N k ', ..., N i '; The thickening direction can be selected from: the normal direction of the equally divided point, the corresponding points N1 and N1', N2 and N2' on the upper and lower contour lines, ..., N k and N k ', ..., N i and N i ', or the mold closing direction of the mold during co-curing molding; thickness L (N k ) and L(N k ') are the equally divided points N k and N k 'The thickness value along the thickening direction; Step S2: Determine the thickening range at the equally divided points according to the thickness and the thickening ratio range, and take the equally divided points N as k and N k 'Take this set of corresponding points as an example, the equally divided points N on the upper contour line k The thickness, thickening value and its upper and lower limits are respectively denoted as L(N k ), Δl(N k ), Δl u (N k ) and Δl d (N k ), the lower contour line is divided equally into points N k The thickness, thickness increase value and upper and lower limits of the k '), Δl(N k '), Δl u (N k ') and Δl d (N k '); The relationship between the thickening value, thickness and thickening ratio is: Δl(N k ) = L(N k )·k' and Δl(N k ') = L(N k ')·k” (k = 1, 2, …, i) Where k' and k'' are the thickness ratios of the Nk and Nk' sides, respectively; Δl u (N k ) and Δl d (N k ) is k' and takes the maximum value k max and the minimum value k min When the equal division point N k The thickening value on the upper surface, that is, the upper limit of the interference of the upper surface (3-1) and the lower limit of the interference of the upper surface (2-1); Δl u (N k ') and Δl d (N k ') is k" and takes the maximum value k max and the minimum value k min When the equal division point N k ', that is, the upper limit of the interference of the lower mold surface (3-2) and the lower limit of the interference of the lower mold surface (2-2); Through the foam test experiment and finite element simulation calculation formula, the range of thickness ratio k' and k'' and their sum k'+k'' is min ~k max ; Step S3: Determine the points after thickening in the thickening direction, connect the thickening points with the same thickening ratio on the same side, and obtain the interference design contour line and the upper and lower ranges of the interference of the foam core on the airfoil.

2. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 1, characterized in that: In step S1, the cross-sectional airfoil of the blade foam core is defined to include the foam core upper profile (1-1) and the foam core lower profile (1-2), and the same number of equally divided points are taken on the upper and lower contour lines of the foam core upper profile (1-1) and the foam core lower profile (1-2), which are N1, N2, ..., N k ,…,N i and N1', N2', ..., N k ', ..., N i '; In step S2, the equally divided points N k and N k 'Take this set of corresponding points as an example, the equally divided points N on the upper contour line k The thickness, thickening value and its upper and lower limits are respectively denoted as L(N k ), Δl(N k ), Δl u (N k ) and Δl d (N k ), the lower contour line is divided equally into points N k The thickness, thickness increase value and upper and lower limits of the k '), Δl(N k '), Δl u (N k ') and Δl d (N k ').

3. The method for calculating the interference range of the polymer foam core layer of the sandwich structure blade according to claim 2, characterized in that: The thickening direction in step S1 includes the normal direction of the equally divided point, the corresponding points N1 and N1', N2 and N2', ..., N k and N k ', ..., N i and N i 'The connecting line direction and the closing direction of the mold during compression co-curing molding.

4. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 2, characterized in that: The thickness L(N k ) and L(N k ') are the equally divided points N k and N k 'The thickness value along the thickening direction.

5. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 2, characterized in that: In the step S2, the relationship between the thickening value, the thickness and the thickening ratio is: Δl(N k ) = L(N k )·k' and Δl(N k ') = L(N k ')·k” (k = 1, 2, …, i) Where k' and k'' are the thickness ratios of the Nk and Nk' sides, respectively; Δl u (N k ) and Δl d (N k ) is k' and takes the maximum value k max and the minimum value k min When the equal division point N k The thickening value on the upper surface, that is, the upper limit of the interference of the upper surface (3-1) and the lower limit of the interference of the upper surface (2-1); Δl u (N k ') and Δl d (N k ') is k" and takes the maximum value k max and the minimum value k min When the equal division point N k ', that is, the upper limit of the interference of the lower mold surface (3-2) and the lower limit of the interference of the lower mold surface (2-2).

6. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 5, characterized in that: Through foam test experiments and finite element simulation calculations, the range of values ​​of the thickness ratios k' and k'' and their sum k'+k'' in the above relationship is min ~k max .

7. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 6, characterized in that: The foam testing experiment adopts a foam uniaxial compression test and obtains the foam stress-strain elastic stage results.

8. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 7, characterized in that: The finite element simulation calculation steps are as follows: the test values ​​of the uniaxial compression test of the same foam are imported into the finite element simulation calculation software, the simulation calculation uses the thickened airfoil as the sandwich structure co-curing process of the foam core, and the simulation analysis obtains the value range of the thickening ratio. The result can provide sufficient support reaction force and ensure that the foam core does not yield.

9. The method for calculating the interference range of the polymer foam core layer of a sandwich structure blade according to claim 1, characterized in that: In the step S3, selective single-side or double-side thickening is performed on the upper and lower molded surfaces of the foam core in the thickening direction.

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