Bending sandwich structure forming method based on overstretched honeycomb
By using CAD/CAE simulation and iterative optimization of tooling surfaces, combined with anti-slip strips and overstretched honeycomb splicing, the problem of surface springback in large-size bent sandwich structures was solved, achieving high-quality forming results.
Patent Information
- Application Number
- CN202411592883.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-01-28
AI Technical Summary
In the process of forming large-size bent sandwich structures, existing technologies make it difficult to accurately calculate the springback angle, which makes it difficult to control the springback deformation of the profile, affecting the structural strength and forming quality of the parts.
The initial springback angle was determined by simulation using CAD/CAE software, and anti-slip strips were placed on the forming fixture. Combined with the splicing and laying of overstretched honeycomb, the fixture surface was iteratively optimized to ensure the accurate forming of the honeycomb sandwich structure.
It enables accurate forming of large-size bent sandwich structures, avoids compression deformation, and ensures that the strength and shape of the parts meet the design requirements.
Smart Images
Figure CN119369759A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of bending sandwich structure forming methods, and in particular to a bending sandwich structure forming method based on an overstretched honeycomb. Background Art
[0002] Honeycomb sandwich structures are widely used in aerospace, transportation, construction and other fields due to their unique properties of light weight, high strength and high stiffness. The honeycomb structure inside the honeycomb core contains a large amount of air, making the overall density much lower than that of solid materials. While ensuring strength and stiffness, it can significantly reduce the weight of the structure, improve fuel efficiency and increase the effective load. At the same time, the geometric shape of the honeycomb structure gives it excellent compression, bending and shear resistance. When combined with the panel material, it forms a lightweight and high-strength sandwich structure that can withstand large loads.
[0003] The hexagonal aramid paper honeycomb, which is widely used at present, is prone to compression deformation at places where the surface changes greatly when forming complex sandwich structures such as large curvature and bends, which affects the structural strength of the parts. Therefore, when forming the above complex structures, butterfly-shaped over-stretched honeycombs can be used, which have good flexibility and can adapt to the shape changes of curved surfaces and bent structures. When complex sandwich structures such as large curvature and bends are cured and formed, rebound deformation occurs due to the influence of curing residual stress. Therefore, the rebound angle needs to be considered when designing the tooling. However, the calculation of the rebound angle is affected by factors such as the tooling structure, tooling materials, and curing system. It is difficult to obtain an accurate value through simulation calculation, and it needs to be explored. Summary of the invention
[0004] The purpose of the present invention is to provide a method for forming a bent sandwich structure based on an over-stretched honeycomb, aiming to solve the problems of large-size bent sandwich structure forming and surface springback, thereby manufacturing qualified large-size bent sandwich parts.
[0005] In order to solve the above technical problems, the present invention provides a method for forming a bent sandwich structure based on an overstretched honeycomb, comprising the following steps: Step A: Determine the springback angle of the tooling, simulate the initial springback angle θ1 of the forming tooling through CAD / CAE software, and arrange the anti-slip belt in the margin area of the forming tooling; Step B: Preparation of overstretched honeycomb, splicing of overstretched honeycomb on forming tooling; Step C: Laying out the sandwich structure, laying out the honeycomb sandwich parts on the forming tooling, the honeycomb sandwich parts are divided into three parts, namely the lower panel, the overstretched honeycomb and the upper panel; firstly, laying out and pre-pressing the prepreg of the lower panel, after which the overstretched honeycomb prepared in step B is laid out using projection positioning, and finally laying out, pre-pressing and packaging the prepreg of the upper panel; Step D: Curing and profile inspection: Curing is performed using the curing system of the prepreg, and after curing, the contour of the bent sandwich structure is inspected; Step E: Tool repair and iteration. At this time, according to the surface inspection results, the surface after setting the initial springback angle is obtained. After comparing with the theoretical surface of the part, the molding tool surface is repaired, that is, the springback angle θ2 after the tooling iterative optimization is corrected, and then steps C and D are repeated to form and inspect the test piece. Repeat the iteration to obtain the correct springback angle of the tooling and the iteratively optimized surface, and finally ensure that the surface of the formal part is qualified.
[0006] Preferably, in step A, the anti-slip tape is attached to the margin area of the forming tooling, 5 to 10 mm away from the net dimension line.
[0007] Preferably, in step B, the size of the overstretched honeycomb exceeds the width of the raw material by 1.2 m, and splicing in the L direction is required, and is carried out on a forming tool.
[0008] Preferably, in step B, the joint seams of the over-stretched honeycomb need to be staggered from the bending area of the parts, and after the over-stretched honeycomb contour size is formed by the chamfering machine, the honeycomb contour size needs to be projected and tested on the forming tooling to ensure that it is qualified.
[0009] Preferably, in step C, a layer of prepreg of the upper panel and the lower panel closest to the overstretched honeycomb needs to be fixed on an anti-slip tape.
[0010] Preferably, in step C, the pre-pressing pressure of the over-stretched honeycomb does not exceed -34 KPa, the pre-pressing pressure of the lower panel prepreg is at least -90 KPa, and the pre-pressing pressure of the upper panel prepreg is -60 KPa to -80 KPa.
[0011] Preferably, in step D, the curing temperature of the prepreg is 175-195° C., and the curing pressure is 0.2-0.4 MPa.
[0012] The present invention relates to a method for forming a bending sandwich structure based on an over-stretched honeycomb, and the forming of a large-size bending sandwich structure is achieved by applying spliced over-stretched honeycombs, anti-slip of material sheets and iterative optimization of tooling profiles in the large-size bending sandwich structure.
[0013] The main advantages of this technology are: (1) Overstretching the honeycomb can avoid compression deformation at the bend, which affects the strength of the sandwich structure after forming; (2) Anti-slip and pre-pressing pressure control can ensure that the over-stretched honeycomb does not slip during the laying and forming process, affecting the laminate assembly area; (3) Iterative optimization of the springback angle of the forming tooling to ensure that the surface springback deformation of the bent parts meets the requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 It is a schematic diagram of forming a large-size bent sandwich structure provided by the present invention; Figure 2 It is a schematic diagram of the iteration of the profile springback angle provided by the present invention.
[0015] In the figure: 1. Forming tooling; 2. Honeycomb sandwich parts; 3. Theoretical part profile; 4. Profile after initial springback angle; 5. Profile after iterative optimization; θ1, initial springback angle; θ2, springback angle after iterative optimization. DETAILED DESCRIPTION
[0016] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.
[0017] 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 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, 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 should not be understood as limiting the present invention.
[0018] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 present invention can be understood by specific circumstances.
[0019] In addition, the features, operations, and characteristics described in the specification can be combined in any appropriate manner to form various embodiments. Similarly, the steps or actions described in the method can also be adjusted in order in a manner that can be easily seen by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for the purpose of describing a certain embodiment, and are not necessarily such sequences, unless otherwise stated that a certain sequence must be followed.
[0020] Embodiment 1 The present invention provides a method for forming a bending sandwich structure based on an overstretched honeycomb, see Figure 1 and Figure 2 As shown, Step A: Determine the tooling springback angle. Use CAD / CAE software to simulate and obtain the initial springback angle θ1 of the forming tooling 1 , and arrange an anti-slip belt in the margin area of the forming tooling 1 , wherein the anti-slip belt is 5 to 10 mm away from the net dimension line.
[0021] Step B: Prepare the over-stretched honeycomb and perform splicing of the over-stretched honeycomb on the forming tool 1; specifically, the size of the over-stretched honeycomb exceeds the raw material width of 1.2m, so L-direction splicing is required, and this is performed on the forming tool 1; the splicing seams of the over-stretched honeycomb need to be staggered from the bending area of the parts, and after the over-stretched honeycomb outline size is formed by the chamfering machine, the honeycomb outline size needs to be projected on the forming tool 1 to ensure that it is qualified.
[0022] Step C: paving the sandwich structure, paving the honeycomb sandwich part 2 on the forming tool 1, the honeycomb sandwich part 2 is divided into three parts, namely the lower panel, the over-stretched honeycomb and the upper panel; firstly, the lower panel prepreg is paved and pre-pressed, and after completion, the over-stretched honeycomb prepared in step B is paved using projection positioning, and finally the upper panel prepreg is paved, pre-pressed and packaged; wherein, the layer of prepreg closest to the over-stretched honeycomb of the upper panel and the lower panel needs to be fixed on the anti-slip belt, and the pre-pressing pressure of the over-stretched honeycomb does not exceed -34KPa, the pre-pressing pressure of the lower panel prepreg is at least -90KPa, and the pre-pressing pressure of the upper panel prepreg is -60KPa to -80KPa.
[0023] Step D: curing and profile detection, curing is performed using the curing system of the prepreg, and after curing, the contour of the bent sandwich structure is detected; wherein the curing temperature of the prepreg is 175~195°C, and the curing pressure is 0.2~0.4MPa.
[0024] Step E: Tool repair and iteration. At this time, according to the surface inspection result, the small end is deflected 0.25° clockwise to obtain the surface 4 after setting the initial springback angle. After comparing with the theoretical surface 3 of the part, the surface of the forming tool 1 is repaired and lowered, that is, the springback angle θ2 (θ2=θ1-0.25°) after the tooling iterative optimization is corrected, and then steps C and D are repeated to form and inspect the test piece. Repeat the iteration to obtain the correct springback angle of the tooling and the iteratively optimized surface 5, and finally ensure that the surface of the formal part is qualified.
[0025] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.
Claims
1. A method for forming a bent sandwich structure based on an overstretched honeycomb, characterized in that: The steps include: Step A: Determine the springback angle of the tooling, obtain the initial springback angle θ1 of the forming tooling (1) by simulation using CAD / CAE software, and arrange an anti-slip belt in the margin area of the forming tooling (1); Step B: preparing the overstretched honeycomb and splicing the overstretched honeycomb on the forming tool (1); Step C: laying out the sandwich structure, laying out the honeycomb sandwich component (2) on the forming tool (1), the honeycomb sandwich component (2) being divided into three parts, namely a lower panel, an overstretched honeycomb and an upper panel; firstly laying out and pre-pressing the prepreg of the lower panel, after which the overstretched honeycomb prepared in step B is laid out using projection positioning, and finally laying out, pre-pressing and packaging the prepreg of the upper panel; Step D: Curing and profile inspection: Curing is performed using the curing system of the prepreg, and after curing, the contour of the bent sandwich structure is inspected; Step E: Tool repair and iteration. At this time, according to the surface inspection result, the surface after setting the initial springback angle (4) is obtained. After comparing with the theoretical surface of the part (3), the surface of the forming tool (1) is repaired, that is, the springback angle θ2 after the tooling is iteratively optimized is corrected, and then steps C and D are repeated to form and inspect the test piece. Repeat the iteration to obtain the correct springback angle of the tooling and the surface after iterative optimization (5), and finally ensure that the surface of the formal part is qualified.
2. A method for forming a bent sandwich structure based on an overstretched honeycomb according to claim 1, characterized in that: In step A, the anti-slip tape is attached to the margin area of the forming tool (1) at a distance of 5 to 10 mm from the net dimension line.
3. A method for forming a bent sandwich structure based on an overstretched honeycomb according to claim 1, characterized in that: In step B, the size of the overstretched honeycomb exceeds the width of the raw material by 1.2 m, and needs to be spliced in the L direction, which is carried out on a forming tool (1).
4. A method for forming a bent sandwich structure based on an overstretched honeycomb as claimed in claim 3, characterized in that: In step B, the joint seams of the overstretched honeycomb need to be staggered from the bending area of the parts, and after the overstretched honeycomb contour size is formed by the chamfering machine, a projection test is performed on the forming tool (1) to check whether the honeycomb contour size is qualified.
5. A method for forming a bent sandwich structure based on an overstretched honeycomb according to claim 1, characterized in that: In step C, a layer of prepreg closest to the overstretched honeycomb on the upper panel and the lower panel needs to be fixed on an anti-slip tape.
6. A method for forming a bent sandwich structure based on an overstretched honeycomb according to claim 1, characterized in that: In step C, the pre-pressing pressure of the over-stretched honeycomb does not exceed -34 KPa, the pre-pressing pressure of the lower panel prepreg is at least -90 KPa, and the pre-pressing pressure of the upper panel prepreg is -60 KPa to -80 KPa.
7. A method for forming a bent sandwich structure based on an overstretched honeycomb according to claim 1, characterized in that: In step D, the curing temperature of the prepreg is 175-195° C., and the curing pressure is 0.2-0.4 MPa.