Honeycomb core leading edge structure design method

Abstract

The invention provides a honeycomb core leading edge structure design method. The honeycomb core leading edge structure design method comprises the steps that the percentage of the maximum thickness and the percentage of the maximum curvature position of airfoils on the upper surface and the lower surface of a leading edge honeycomb core are obtained; obtaining upper and lower surface contour line expressions based on the obtained leading edge data; mounting a lower panel; obtaining the height of the honeycomb core in each area, arranging and placing the honeycomb core and the composite component, and inserting a cement between the honeycomb core and the composite component; obtaining an installation upper panel based on the obtained upper surface contour line expression; and packaging the whole body in a vacuum bag, feeding into hot-pressing equipment, and performing hot-pressing curing according to cementing process parameters. According to the invention, the geometrical shape and the surface profile of the leading edge honeycomb core are accurately designed, so that the radar cross section is effectively reduced, and the stealth performance is improved; an optimized honeycomb core structure and an advanced packaging and hot pressing process are combined, so that the balance between the strength and the low scattering characteristic is ensured.

Description

Technical Field

[0001] This invention belongs to the field of honeycomb core splicing technology, and particularly relates to a method for designing the leading edge structure of a honeycomb core. Background Technology

[0002] Existing design methods for low radar cross section (RCS) honeycomb core leading edge structures involve filling the honeycomb core with lightweight absorbing material. By adjusting the proportion and distribution of the absorbing agent, electromagnetic wave absorption efficiency is optimized, and the reflection coefficient is reduced. A hexagonal honeycomb configuration combined with curved surface weaving technology is used, and the shear resistance is improved by adjusting the weaving angle. The molding method involves serrifying the edges of the honeycomb core, filling the seams with epoxy film or expanding foam, and hot-pressing to form a continuous interface. Expanding foam is inserted between the honeycomb core and the panel, and simultaneously cured after high-temperature expansion to enhance the connection strength. However, existing technologies do not systematically link airfoil geometry parameters with RCS performance, resulting in insufficient aerodynamic-stealth synergy. The splicing process mainly relies on sawtooth seams and foam to fill physical gaps, but it does not quantitatively control the stress in the adhesive layer caused by thermal expansion differences, which can easily lead to microcracks or electromagnetic discontinuities due to uneven curing deformation. In terms of contour generation, there is a lack of a closed-loop feedback mechanism to dynamically optimize the contour curve through shape control factors to match the RCS target. The adhesive application does not establish a mathematical model for the difference in thermal expansion coefficients, resulting in interface stress concentration and weakening the integrity of the stealth structure. Summary of the Invention

[0003] To improve existing honeycomb core design and splicing methods, a honeycomb core leading edge structure design method is provided. This method ensures a high degree of fit between the structure and stealth effect through precise calculation and optimization of the contour line, while enhancing the strength and stability of the components, improving bonding quality and production efficiency, and has significant engineering application advantages.

[0004] The technical solution adopted in this invention is as follows: A method for designing a honeycomb core leading edge structure includes: Step 1: Obtain the percentage of maximum airfoil thickness and the percentage of maximum curvature location on the upper and lower surfaces of the leading edge honeycomb core; Step 2: Based on the leading edge data, calculate and obtain the contour lines of the upper and lower surfaces; Step 3: Obtain the mounting bottom panel based on the lower surface contour expression; Step 4: Based on the upper and lower surface contour lines, obtain the height of the honeycomb core in each area, arrange and place the honeycomb core and composite components, and insert adhesive between them; Step 5: Based on the obtained upper surface contour expression, obtain the mounting top panel; Step Six: Vacuum-seal the entire assembly and send it into a hot press to cure it according to the bonding process parameters.

[0005] The calculation of the upper and lower surface contour expressions based on the acquired leading edge data specifically includes: By taking a set of distinct values ​​for the shape control factor in the first formula, a set of upper surface contour expressions is obtained, wherein the first formula is:

[0006] Where x is the coordinate along the chord length, with the origin located at the leading edge, and y... up (x) represents the vertical height of the upper surface profile line at position x relative to the chord line, c is the chord length of the wing, m is the percentage of the maximum thickness of the airfoil, p1 is the percentage of the position of maximum curvature of the upper surface, and μ1 is the shape control factor of the upper surface profile line, which is an "adjustable degree of freedom" introduced in the parametric design of the airfoil. Its value and optimization logic need to be combined with the design objectives or solved iteratively through aerodynamic optimization algorithms. Its core lies in flexibly adjusting the shape of the upper surface to meet performance requirements.

[0007] Based on the low RCS prediction results, select one profile expression from a set of upper surface profile expressions as the specific upper surface profile expression and use it for the design of the upper surface curve. By taking a set of distinct values ​​for the shape control factor in the second formula, a set of expressions for the lower surface contour line is obtained, wherein the second formula is:

[0008] Where x is the coordinate along the chord length, with the origin located at the leading edge, and y... down (x) represents the vertical height of the lower surface profile line at position x relative to the chord line, c is the chord length of the wing, m is the percentage of the maximum thickness of the airfoil, p2 is the percentage of the position of maximum curvature of the lower surface, and μ2 is the shape control factor of the lower surface profile line, which is an "adjustable degree of freedom" introduced in the parametric design of the airfoil. Its value and optimization logic need to be combined with the design objectives or solved iteratively through aerodynamic optimization algorithms. Its core lies in flexibly adjusting the shape of the lower surface to meet performance requirements.

[0009] Based on the low RCS prediction results, select one profile expression from a set of lower surface profile expressions as the specific lower surface profile expression and use it for the design of the lower surface curve.

[0010] The process of obtaining the height of the honeycomb core in each region based on the upper and lower surface contour lines, arranging and placing the honeycomb cores and composite components, and inserting adhesive between them specifically includes: Based on the contour lines of the upper and lower surfaces, the height of the honeycomb core in each region is obtained. Cellular core height at the leading edge section , Based on the height of the honeycomb core in the leading edge section, multiple honeycomb cores are placed between the bottom plate and the top plate; The adhesive is fully laid on the side of the composite component with the high coefficient of thermal expansion, where the length of the composite component with the high coefficient of thermal expansion is ∆H. The adhesive length on the side of the composite component with the low coefficient of thermal expansion is:

[0011] Where T1 and T2 are the temperatures of the composite components with high and low thermal expansion coefficients respectively when the adhesive is cured, and τ1 and τ2 are the thermal expansion coefficients of the composite components with high and low thermal expansion coefficients respectively.

[0012] Optionally, the honeycomb core is a NOMEX aramid honeycomb.

[0013] Optionally, the adhesive is a mixture of epoxy resin and foaming agent.

[0014] The beneficial effects of this invention are at least as follows: By precisely calculating the upper and lower surface contours of the leading-edge honeycomb core and the height of the core in each region, the structure of the honeycomb core can be optimized to meet specific radar reflection requirements. The design process considers the percentage of locations with maximum thickness and maximum curvature, ensuring that the geometry of the honeycomb core helps reduce radar wave reflection and scattering. Secondly, by rationally arranging the contours of the upper and lower surfaces and inserting adhesive between the honeycomb core and the composite components, the strength and stability of the structure are improved while maintaining low scattering characteristics. The installed non-porous and porous isolation membranes effectively control the radar wave propagation path, thereby further reducing the scattered signal. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the upper and lower surface contours and the honeycomb core of the method of the present invention; Figure 2 This is a schematic diagram illustrating the effect of the method of the present invention after splicing between honeycomb cores.

[0016] Wherein: 1-top panel, 2-honeycomb core, 3-adhesive, 4-bottom panel. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0019] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] This invention provides a method for designing a honeycomb core leading-edge structure. By precisely calculating the maximum thickness and maximum curvature positions of the airfoils on the upper and lower surfaces of the leading-edge honeycomb core, the structural design is optimized to ensure a high degree of compatibility with stealth capabilities. Based on the obtained contour line expression, the matching and manufacturing of each component can be precisely guided, improving accuracy and adaptability. The rational arrangement of non-porous and porous isolation membranes controls the interlayer stress distribution and enhances structural stability. Precise arrangement of the honeycomb core and composite material, along with the addition of adhesive, ensures a tight bond between components, enhancing overall strength and rigidity. The combination of vacuum bag packaging and thermosetting curing processes ensures uniform adhesive penetration, reduces defects, and improves the molding quality of the composite material.

[0022] Example 1: Reference Figure 1 A method for designing and splicing low RCS leading edge honeycomb cores, comprising the following steps: Step 1: Based on the obtained lower surface contour expression, obtain the mounting lower panel; Step 2: Based on the upper and lower surface contour lines, obtain the height of the honeycomb core in each area, arrange and place the honeycomb core and composite components, and insert adhesive between them; Step 3: Based on the obtained upper surface contour expression, obtain the mounting top panel; Step 4: Vacuum-seal the entire assembly and send it into a hot press to cure it according to the bonding process parameters.

[0023] Determining the upper surface contour expression specifically includes taking a set of distinct values ​​for the shape control factor in the first formula to obtain a set of upper surface contour expressions, wherein the first formula is:

[0024] Where x is the coordinate along the chord length, with the origin located at the leading edge, and y... up (x) is the vertical height of the upper surface profile line at position x relative to the chord line, c is the chord length of the wing, m is the percentage of the maximum thickness of the airfoil, p1 is the percentage of the position of the maximum curvature of the upper surface, and μ1 is the shape control factor of the upper surface profile line, which is the "adjustable degree of freedom" introduced in the parametric design of the airfoil. Its value and optimization logic need to be combined with the design objectives or solved iteratively through aerodynamic optimization algorithms. Its core is to flexibly adjust the shape of the upper surface to meet performance requirements. Based on the low RCS prediction results, select one profile expression from a set of upper surface profile expressions as the specific upper surface profile expression and use it for the design of the upper surface curve. Determining the lower surface profile expression specifically involves taking a set of distinct values ​​for the shape control factor in the second formula to obtain a set of upper surface profile expressions. The second formula is:

[0025] Where x is the coordinate along the chord length, with the origin located at the leading edge, and y... down (x) represents the vertical height of the lower surface profile line at position x relative to the chord line, c is the chord length of the wing, m is the percentage of the maximum thickness of the airfoil, p2 is the percentage of the position of the maximum curvature of the lower surface, and μ2 is the shape control factor of the lower surface profile line, which is an "adjustable degree of freedom" introduced in the parametric design of the airfoil. Its value and optimization logic need to be combined with the design objectives or solved iteratively through aerodynamic optimization algorithms. Its core lies in flexibly adjusting the shape of the lower surface to meet performance requirements. Based on the low RCS prediction results, select one profile expression from a set of lower surface profile expressions as the specific lower surface profile expression and use it for the design of the lower surface curve.

[0026] Cellular core height at the leading edge section , Based on the height of the honeycomb core in the leading edge section, multiple honeycomb cores are placed between the bottom plate and the top plate; The adhesive is fully laid on the side of the composite component with the high coefficient of thermal expansion, where the length of the composite component with the high coefficient of thermal expansion is ∆H. The adhesive length on the side of the composite component with the low coefficient of thermal expansion is:

[0027] Where T1 and T2 are the temperatures of the composite components with high and low thermal expansion coefficients respectively when the adhesive is cured, and τ1 and τ2 are the thermal expansion coefficients of the composite components with high and low thermal expansion coefficients respectively.

[0028] Adhesive 3 that meets the specified strength requirements is inserted into each honeycomb core 2. The adhesive expands under the high temperature of the hot pressing plate and is simultaneously hot-pressed and cured with the adhesive in the board making process, thus bonding each honeycomb core 2 into one piece.

[0029] For example, the honeycomb core is a NOMEX aramid honeycomb.

[0030] For example, the adhesive is a mixture of epoxy resin and foaming agent.

[0031] The effect of the method described in this embodiment after implementation for inter-cell splicing is as follows: Figure 2 As shown, after the adhesive 3 foams, it fills the honeycomb core 2 and bonds and fixes it.

[0032] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A method for designing a honeycomb core leading edge structure, characterized in that, include: Obtain the percentage of maximum airfoil thickness and maximum curvature location on the upper surface of the leading edge honeycomb core, as well as the percentage of maximum airfoil thickness and maximum curvature location on the lower surface. Based on the percentage of the maximum airfoil thickness and the percentage of the maximum curvature location, the expressions for the upper and lower surface profiles are determined. Based on the lower surface contour expression, determine the shape of the lower panel to be installed; Based on the upper surface contour expression, determine the shape of the upper panel to be installed; The height of the honeycomb core in the leading edge section is obtained based on the lower surface contour expression and the upper surface contour expression. Multiple honeycomb cores are placed between the bottom plate and the top plate, and adhesive is applied between the multiple honeycomb cores to obtain a honeycomb core leading edge structure; The leading edge structure of the honeycomb core is vacuum-sealed, placed in a hot-pressing device, and cured by hot pressing according to the bonding process parameters.

2. The method according to claim 1, characterized in that, Determining the expression for the upper surface profile specifically includes: By taking a set of distinct values ​​for the shape control factor in the first formula, a set of upper surface contour expressions is obtained. The first formula is: Where x is the coordinate along the chord length, and the origin is located at the leading edge. Let be the vertical height of the upper surface profile line at position x relative to the chord line, c be the chord length of the wing, and m be the percentage of the maximum airfoil thickness. It is a percentage of the location of maximum curvature on the upper surface. The shape control factor of the upper surface profile is an "adjustable degree of freedom" introduced in the parametric design of airfoils. Its value and optimization logic are combined with the design objectives or solved iteratively through aerodynamic optimization algorithms.

3. The method according to claim 1, characterized in that, Determining the expression for the lower surface profile specifically includes: By taking a set of distinct values ​​for the shape control factor in the second formula, a set of expressions for the lower surface contour line is obtained. The second formula is: Where x is the coordinate along the chord length, and the origin is located at the leading edge. Let be the vertical height of the lower surface profile line at position x relative to the chord line, c be the chord length of the wing, and m be the percentage of the maximum airfoil thickness. It is a percentage of the location of maximum curvature on the lower surface. The shape control factor of the lower surface profile is an "adjustable degree of freedom" introduced in the parametric design of airfoils. Its value and optimization logic are combined with the design objectives or solved iteratively through aerodynamic optimization algorithms.

4. The method according to claim 1, characterized in that, Cellular core height at the leading edge section , Based on the height of the honeycomb core in the leading edge section, multiple honeycomb cores are placed between the bottom plate and the top plate; Adhesive is applied to the side of the composite component with a high coefficient of thermal expansion. The length of the composite component with a high coefficient of thermal expansion is... The adhesive length on the side of the composite component with a low coefficient of thermal expansion is: in, , These are the curing temperatures of the adhesive for composite components with high and low coefficients of thermal expansion, respectively. , The coefficient of thermal expansion is the coefficient of thermal expansion of the composite component with both high and low coefficients of thermal expansion.

5. The method according to claim 1, characterized in that, The honeycomb core is a NOMEX aramid honeycomb.

6. The method according to claim 1, characterized in that, The adhesive is a mixture of epoxy resin and foaming agent.

7. The method according to claim 1, characterized in that, Obtain the maximum thickness of the airfoil in the vertical direction and the total thickness of the airfoil. Calculate the ratio of the maximum thickness to the total thickness to obtain the percentage of the maximum thickness of the airfoil.

8. The method according to claim 1, characterized in that, The curvature of the upper and lower surfaces is calculated based on the airfoil data. The point where the maximum curvature value is located is obtained, and the ratio of the distance between this point and the front and rear of the airfoil is calculated to obtain the percentage of the location of the maximum curvature.

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