A method for determining structural parameters of large-scale composite wing spar

Abstract

The present application provides a method for determining the structural parameters of a large-scale composite wing spar, which belongs to the field of composite wing design. The method comprises: establishing a layup library, distributing layup directions of predetermined angles in the layup library according to a predetermined ratio, and using the same layup library for the spar's flanges and webs; obtaining initial parameters including the thickness of the upper and lower wall panel beam units and the initial cross-sectional area of ​​the upper and lower flange rod units of the spar according to a finite element model of the wing box section; performing initial parameter design on the span direction of the spar according to the cross-section at each rib position; determining the thickness of the upper and lower flanges of the spar; determining the diameter of the fasteners according to the thickness of the upper and lower wall panels and the thickness of the upper and lower flanges and the depth of the upper and lower wall panel countersinks; determining the cross-sectional area of ​​the upper and lower flanges according to the thickness of the upper and lower flanges and the width of the upper and lower flanges; determining the thickness of the middle web of the rib according to the thickness of the upper and lower flanges of the spar, the upper and lower web layer drop boundaries, and the layer drop ratio in the span direction and height direction of the spar; and performing strength iterative calculations until the wing box section meets the strength requirements.

Description

Technical Field

[0001] The present application relates to the field of composite wing design, and in particular to a method for determining the structural parameters of a large-scale composite wing spar. Background Art

[0002] Currently, high-aspect-ratio wings generally utilize a monolithic structure, with wing spars typically designed as shear beams. With the continuous improvement of composite material manufacturing capabilities, composite wing spars are also developing in the direction of being more integrated, larger, and thicker. A single spar can reach lengths of 20 to 30 meters, with local thicknesses exceeding 15 mm.

[0003] Compared to traditional small composite wing spars, large-scale composite wing spars have many structural design parameters and complex features, requiring simultaneous layer drop and thickness reduction along the span and height directions to reduce structural weight. The matching relationship between the various structures and parameters of these large-scale wing spar caps, webs, layer drop transition zones, wing rib corner boxes, and reinforcement struts is an important part of the wing spar structural design. Current composite wing spar design mainly relies on the experience of designers for parameter design. The wing spar structural parameters designed by different designers are not uniform and vary greatly. There is no relatively solidified design process and method, which affects design efficiency. In addition, due to the characteristics of the composite material molding process, its thickness tolerance is generally 5% to 8% of the local thickness. There are also assembly compensation issues between the wing spar and the wall panel and wing rib corner box. Summary of the Invention

[0004] The purpose of the present application is to provide a method for determining structural parameters of a large-scale composite wing spar to solve or alleviate at least one problem in the background technology.

[0005] The technical solution of the present application is: 1. A method for determining the structural parameters of a large-scale composite wing spar, comprising:

[0006] A layup combination is formed with layup directions at multiple predetermined angles as the main layup directions, and an orthotropic laminate layup library is established. The layup directions at predetermined angles in the layup library are distributed according to a predetermined ratio, and the cap and web in the wing spar use the same layup library;

[0007] According to the finite element model of the wing box, the initial parameters including the thickness of the upper and lower wall beam elements and the initial cross-sectional area of ​​the upper and lower cap bar elements of the wing spar are obtained;

[0008] Performing initial parameter design on the span direction of the spar according to the cross section at each rib position, and determining the cross-sectional structural parameters of each part of the spar, wherein the spar includes an upper rim, a lower rim, an upper web, an intermediate web, and a lower web, wherein the parameters of the upper rim are consistent with those of the upper web, and an upper rim sacrificial layer is formed at the connection corner between the upper rim and the upper web, the parameters of the lower rim are consistent with those of the lower web, and a lower rim sacrificial layer is formed at the connection corner between the lower rim and the lower web, the thickness of the intermediate web is not greater than the thickness of the upper web and / or the lower web, and the upper and lower webs are subjected to layer dropping and thickness reduction toward the intermediate web, thereby forming a spanwise layer dropping transition zone on both sides of the span direction of the intermediate web, and a heightwise layer dropping transition zone on both sides of the height direction;

[0009] Based on the thickness of the panel beam boss unit determined by the finite element model of the wing box section, the thickness of the upper and lower caps of the spar 3 is preliminarily determined, wherein the thickness of the upper and lower caps is 1.0 to 1.1 times the thickness of the upper and lower panel beam bosses;

[0010] Determine the diameter d of the fastener based on the thickness of the upper and lower panels and the upper and lower flanges and the depth of the countersinks of the upper and lower panels. The thickness of the panels and flanges should not be greater than 4 times the diameter of the fastener, and the depth of the countersinks of the upper and lower panel fasteners should not be greater than 2 / 3 of the thickness of the beam unit of the upper and lower panel thickness.

[0011] Determine the upper and lower cap cross-sectional areas based on their thickness and width. If the sum of the upper and lower cap cross-sectional areas is not less than the initial cross-sectional areas of the upper and lower cap rod elements of the wing spar in the finite element model of the wing box, the spar structural parameter design meets the requirements. Otherwise, adjust the upper and lower cap thickness and width.

[0012] The thickness of the middle web of the rib is determined based on the thickness of the upper and lower flanges of the spar, the upper and lower web layer loss boundaries, and the layer loss ratio in the span and height directions of the spar;

[0013] The overall strength of the wing box is iteratively calculated based on the finite element model and engineering algorithm until the wing box meets the strength requirements, and the final characteristic parameters of the composite wing spar are obtained.

[0014] Preferably, the predetermined angle ply directions include 0°, ±45° and 90° directions.

[0015] Preferably, the proportions of 0°, ±45° and 90° plies in the ply library are 30%, 60% and 10% respectively.

[0016] Preferably, the upper and lower sides of the wing spar are connected to the upper wall plate and the lower wall plate respectively, the front side of the wing spar is supported by the wing rib corner box, and the back side of the wing spar is connected to a reinforcing strut.

[0017] Preferably, the inner profile of the spar is a mold surface, which is paved and formed by a male mold to ensure the assembly accuracy of the wing rib corner box.

[0018] Preferably, the upper cap sacrificial layer and the lower cap sacrificial layer of the wing spar are machined with a cap thickness tolerance of 5% and a machining tolerance of 0.2 mm, and are processed using the same profile as the inner profile of the upper wall panel.

[0019] Preferably, the wing rib corner box is an aluminum alloy three-sided corner box structure, and the wing rib corner box is connected to the upper edge strip, lower edge strip, upper web, lower web and middle web of the wing spar. A gap of 1 mm is reserved between the outer side of the upper edge strip of the wing rib corner box and the inner side of the upper edge strip of the wing spar for compensation of the assembly gap of the wing rib corner box.

[0020] Preferably, the width of the upper and lower edge strips is determined according to the arrangement of fasteners and the thickness of the upper and lower webs. The width of the upper and lower edge strips is the distance between the outer boundary of the edge strip and the plane of the wing beam. The width of the upper and lower edge strips is 2.5d+4.5d+(d+2)+t1+t2, wherein the fasteners are arranged in parallel, the fastener margin is 2.5d, the row spacing is 4.5d, the distance between the inner nut of the edge strip and the corner of the wing beam is (d+2), the corner dimension is t1, the thickness of the upper and lower webs is t2, wherein t2 is the thickness of the upper edge strip or the thickness of the lower edge strip, and the positive mold forming t1=t2, wherein d is the diameter of the fastener.

[0021] Preferably, the upper and lower webs of the wing beam are simultaneously reduced in thickness by dropping layers in the spanwise and heightwise directions, the ratio of the layer loss in the spanwise layer-dropping transition zone is 1:100, and the ratio of the layer loss in the heightwise layer-dropping transition zone is 1:20.

[0022] Preferably, the upper and lower edge strips and the upper and lower webs have the same thickness in the rib corner box assembly area, and begin to lose layers and change thickness after passing the rib corner box connection area, with the layer loss boundary being 2 mm away from the rib boundary.

[0023] Preferably, in the strength verification of the wing box section, the verification items of the upper web, lower web and middle web of the wing spar include three-dimensional composite strain and shear stability of the web; the verification items of the upper edge strip and lower edge strip of the wing spar include axial strain control and axial compression stability analysis; the verification items of the reinforcing strut include minimum moment of inertia and minimum cross-sectional area.

[0024] Preferably, the connection strength of the wing spar includes the connection between the upper and lower wall panels and the upper and lower edge strips of the wing spar, the connection between the wing spar web and the wing rib corner box, and the connection between the wing spar web and the reinforcing strut, including the bolt shear strength and the nail hole extrusion strength.

[0025] The method for determining the structural parameters of large-size composite wing spars provided in this application can solidify the design process of large-size composite wing spars, improve the design efficiency of composite wing spars, and solve the assembly compensation problems between the wing spars and the wall panels and wing rib corner boxes caused by the composite molding process, thereby improving the assembly accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions provided by this application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0027] Figure 1 This is a schematic diagram of the front side connection structure of the wing spar in this application.

[0028] Figure 2 This is a schematic diagram of the rear side connection structure of the wing spar in this application.

[0029] Figure 3 This is a schematic diagram of the spar cross section in this application.

[0030] Figure 4 This is a partial enlarged view of the front side of the wing spar in this application.

[0031] Figure 5 Schematic diagram of the wing spar structural parameters in this application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0033] The present application provides a method for determining the structural parameters of a large-scale composite wing spar, which is used to solidify the design process of large-scale composite wing shear beams to improve design efficiency and solve the assembly compensation problems between beams, wall panels and wing rib corner boxes caused by the composite molding process.

[0034] The method for determining the structural parameters of a large-scale composite wing spar provided in this application comprises the following steps:

[0035] Step S10: forming a layup combination with layup directions of multiple predetermined angles as the main layup directions, establishing an orthotropic laminate layup library, wherein the layup directions of predetermined angles in the layup library are distributed according to a predetermined ratio, and the cap and web in the wing spar use the same layup library.

[0036] In the present application, the predetermined angle ply directions include 0°, +45°, -45° and 90° directions, and the proportions of 0°, ±45° and 90° plies in the ply library are 30%, 60% and 10% respectively.

[0037] Step S20: According to the finite element model of the wing box section, initial parameters including the thickness of the upper and lower wall panel beam units and the initial cross-sectional areas of the upper and lower cap bar units of the wing spar are obtained.

[0038] like Figure 1 and Figure 2The figure shows a schematic diagram of the connection structure between the wing spar and the wing box section. The upper and lower sides of the wing spar 3 are connected to the upper wall panel 1 and the lower wall panel 2 respectively. The front side of the wing spar 3 is supported by the wing rib corner box 4, and the back side of the wing spar 3 is connected to the reinforcing strut 5.

[0039] In the present application, the inner profile of the spar 3 is a mold surface, which is paved and formed by a male mold to ensure the assembly accuracy of the rib corner box 4.

[0040] Step S30: Initial parameter design is performed on the spanwise cross-section of the spar according to the rib positions.

[0041] like Figure 3 and Figure 4 As shown, the spar 3 includes an upper edge strip 31, a lower edge strip 32 (the upper edge strip 31 and the lower edge strip 32 can be collectively referred to as edge strips) and an upper web 33, an intermediate web 34 and a lower web 35 (the upper web 33, the intermediate web 34 and the lower web 35 can be collectively referred to as webs). The parameters of the upper edge strip 31 and the upper web 33 are consistent, and an upper edge strip sacrificial layer 38 is formed at the connecting corner (i.e., rounded corner) of the upper edge strip 31 and the upper web 33. The parameters of the lower edge strip 32 and the lower web 35 are consistent, and a lower edge strip sacrificial layer 39 is formed at the connecting corner (i.e., rounded corner) of the lower edge strip 32 and the lower web 35. The thickness of the middle web 34 is not greater than that of the upper web 33 and / or the lower web 35. The upper web 33 and the lower web 35 drop layers toward the middle web 34 to change thickness, thereby forming a spanwise layer-dropping transition zone 36 on both sides of the spanwise direction of the middle web 34, and a heightwise layer-dropping transition zone 37 on both sides of the height direction. Figure 5 Shown are the cross-sectional structural parameters of each structure or part of the wing spar.

[0042] In this application, the upper cap sacrificial layer 38 and the lower cap sacrificial layer 39 of the spar 3 are machined with a cap thickness tolerance of 5% and a tolerance of 0.2 mm, and are machined with the same profile as the upper wall panel inner profile to ensure the matching relationship with the upper and lower wall panels;

[0043] In this application, the rib corner box 4 is an aluminum alloy three-sided corner box structure with a support on the web of the rib corner box. The rib corner box 4 is connected to the upper edge strip 31, lower edge strip 32, upper web 33, lower web 34, middle web 35 and rib of the spar 3. A gap of 1 mm is reserved between the outer side of the upper edge strip of the rib corner box 4 and the inner side of the upper edge strip 31 of the spar for compensating the assembly gap of the rib corner box 4. Gaskets are added during assembly to eliminate the gap.

[0044] In this application, 1 / 5 to 1 / 4 of the airfoil height is used as the installation boundary of the leading and trailing edge partitions and the support arms; the airfoil height is defined as the upper web 33 and the lower web 35 at 1 / 5 to 1 / 4 of the airfoil height of the upper and lower wing surfaces, respectively, with the middle web 34 in the middle. The boundaries between the upper web 33, the lower web 35 and the middle web 34 are the layer-dropping boundaries of the wing spar web; the thickness of the upper web 33 and the lower web 35 is not less than the thickness of the middle web 34.

[0045] Step S40: Preliminarily determine the upper and lower edge strip thicknesses (tu and td) of the spar 3 based on the wall panel beam boss unit thickness determined by the finite element model of the wing box section, wherein the thickness of the upper and lower edge strips is 1.0 to 1.1 times the thickness of the upper and lower wall panel beam bosses.

[0046] Step S50: Determine the fastener diameter d based on the thickness of the upper and lower wall panels, the thickness of the upper and lower edge strips, and the countersink depth of the upper and lower wall panels. The thickness of the wall panels and edge strips shall not be greater than 4 times the fastener diameter, and the countersink depth of the upper and lower wall panel fasteners shall not be greater than 2 / 3 of the thickness of the upper and lower wall panel beam units.

[0047] The width of the upper and lower flanges is determined according to the arrangement of fasteners and the thickness of the upper and lower webs. The width of the upper and lower flanges is the distance between the outer boundary of the flange and the plane of the spar. The width of the upper and lower flanges (bu and bd) = 2.5d + 4.5d + (d + 2) + t1 + t2, where the fasteners are arranged in parallel, the fastener edge distance is 2.5d, the row spacing is 4.5d, the inner nut of the flange is (d + 2) away from the spar fillet, the inner fillet size is t1, the thickness of the upper and lower webs is t2, where t2 is tu or td, and t1 = t2 is generally taken for male mold forming, where d is the diameter of the fastener.

[0048] Step S60: Determine the upper and lower slat cross-sectional areas according to the upper and lower slat thicknesses (tu and td) and the upper and lower slat widths (bu and bd), the upper slat cross-sectional area Su = tu*bu, the lower slat cross-sectional area Sd = td*bd; if the actual lower slat cross-sectional areas Su and Sd calculated are not less than the initial cross-sectional areas of the upper and lower slat rod units of the wing spar in the finite element model of the wing box section, then it is determined that the structural parameter design of the wing spar meets the requirements, otherwise it is necessary to adjust the upper and lower slat thicknesses (tu and td) and the upper and lower slat widths (bu and bd).

[0049] Step S70: Determine the middle web thickness t of the rib based on the upper and lower edge strip thicknesses (tu and td), the upper and lower web layer loss boundaries (hu and hd), and the layer loss ratios in the span and height directions of the spar. The middle web thickness ensures that the layer loss boundaries and layer loss ratios of the upper and lower edge strips and the adjacent upper and lower webs meet the requirements.

[0050] In some embodiments of the present application, the upper and lower webs of the wing beam are simultaneously reduced in thickness by losing layers along the span direction and the height direction. The ratio of the layer loss in the span direction transition zone is 1:100, and the ratio of the layer loss in the height direction transition zone is 1:20.

[0051] In this application, the upper edge strip 31, the lower edge strip 32 and the upper and lower webs are of the same thickness in the assembly area of ​​the rib corner box 4. After passing the connection area of ​​the rib corner box 4, the thickness begins to drop layers and change. The layer dropping boundary is 2 mm away from the rib boundary.

[0052] Step S80: performing iterative calculations on the overall strength of the wing box segment based on the finite element model of the wing box segment and the engineering algorithm until the wing box segment meets the strength requirements, thereby obtaining the final characteristic parameters of the composite wing spar.

[0053] In the wing beam strength verification of the present application, the verification items of the upper web 33, the lower web 34, and the middle web 35 include three-dimensional composite strain and beam web shear stability; the verification items of the upper edge strip 31 and the lower edge strip 302 include axial strain control and axial compression stability analysis; the verification items of the reinforcing support 5 include minimum moment of inertia and minimum cross-sectional area.

[0054] In this application, the connection strength of the wing spar mainly includes the connection between the upper and lower wall panels and the upper and lower edge strips of the wing spar, the connection between the wing spar web and the wing rib corner box, and the connection between the wing spar web and the reinforcing strut, mainly including the bolt shear strength and the nail hole extrusion strength.

[0055] The method for determining the structural parameters of large-size composite wing spars provided in this application can solidify the design process of large-size composite wing spars, improve the design efficiency of composite wing spars, and solve the assembly compensation problems between the wing spars and the wall panels and wing rib corner boxes caused by the composite molding process, thereby improving the assembly accuracy.

[0056] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for determining structural parameters of a large-scale composite wing spar, characterized in that: include: A layup combination is formed with layup directions at multiple predetermined angles as the main layup directions, and an orthotropic laminate layup library is established. The layup directions at predetermined angles in the layup library are distributed according to a predetermined ratio, and the cap and web in the wing spar use the same layup library; According to the finite element model of the wing box, the initial parameters including the thickness of the upper and lower wall beam elements and the initial cross-sectional area of ​​the upper and lower cap bar elements of the wing spar are obtained; Performing initial parameter design on the span direction of the spar according to the cross section at each rib position, and determining the cross-sectional structural parameters of each part of the spar, wherein the spar includes an upper rim, a lower rim, an upper web, an intermediate web, and a lower web, wherein the parameters of the upper rim are consistent with those of the upper web, and an upper rim sacrificial layer is formed at the connection corner between the upper rim and the upper web, the parameters of the lower rim are consistent with those of the lower web, and a lower rim sacrificial layer is formed at the connection corner between the lower rim and the lower web, the thickness of the intermediate web is not greater than the thickness of the upper web and / or the lower web, and the upper and lower webs are subjected to layer dropping and thickness reduction toward the intermediate web, thereby forming a spanwise layer dropping transition zone on both sides of the span direction of the intermediate web, and a heightwise layer dropping transition zone on both sides of the height direction; Based on the thickness of the panel beam boss unit determined by the finite element model of the wing box section, the thickness of the upper and lower flanges of the wing spar is preliminarily determined. The thickness of the upper and lower flanges is 1.0 to 1.1 times the thickness of the upper and lower panel beam bosses. Determine the diameter d of the fastener based on the thickness of the upper and lower panels and the upper and lower flanges and the depth of the countersinks of the upper and lower panels. The thickness of the panels and flanges should not be greater than 4 times the diameter of the fastener, and the depth of the countersinks of the upper and lower panel fasteners should not be greater than 2 / 3 of the thickness of the beam unit of the upper and lower panel thickness. Determine the upper and lower cap cross-sectional areas based on their thickness and width. If the sum of the upper and lower cap cross-sectional areas is not less than the initial cross-sectional areas of the upper and lower cap rod elements of the wing spar in the finite element model of the wing box, the spar structural parameter design meets the requirements. Otherwise, adjust the upper and lower cap thickness and width. The thickness of the middle web of the rib is determined based on the thickness of the upper and lower flanges of the spar, the upper and lower web layer loss boundaries, and the layer loss ratio in the span and height directions of the spar; The overall strength of the wing box is iteratively calculated based on the finite element model and engineering algorithm until the wing box meets the strength requirements, and the final characteristic parameters of the composite wing spar are obtained.

2. The method for determining structural parameters of a large-scale composite material spar according to claim 1, wherein: The predetermined angle ply directions include 0°, ±45° and 90° directions.

3. The method for determining structural parameters of a large-scale composite material spar according to claim 2, wherein: The proportions of 0°, ±45° and 90° plies in the ply library are 30%, 60% and 10% respectively.

4. The method for determining structural parameters of a large-scale composite material wing spar according to claims 1 to 3, characterized in that: The upper and lower sides of the wing spar are respectively connected to the upper wall plate and the lower wall plate. The front side of the wing spar is supported by a wing rib corner box, and the back side of the wing spar is connected to a reinforcing support.

5. The method for determining structural parameters of a large-scale composite material spar according to claim 4, wherein: The inner profile of the wing spar is a mold surface, which is paved and formed by a male mold to ensure the assembly accuracy of the wing rib corner box.

6. The method for determining structural parameters of a large-scale composite material spar according to claim 4, wherein: The upper and lower edge sacrificial layers of the wing beam are machined with an edge thickness tolerance of 5% and a tolerance of 0.2 mm, and are processed using the same profile as the inner profile of the upper wall panel.

7. The method for determining structural parameters of a large-scale composite material spar according to claim 4, wherein: The wing rib corner box is an aluminum alloy three-sided corner box structure, which is connected to the upper edge strip, lower edge strip, upper web, lower web and middle web of the wing spar. A 1mm gap is reserved between the outer side of the upper edge strip of the wing rib corner box and the inner side of the upper edge strip of the wing spar for compensating the assembly gap of the wing rib corner box.

8. The method for determining structural parameters of a large-scale composite material spar according to claim 1, wherein: The width of the upper and lower flanges is determined according to the arrangement of fasteners and the thickness of the upper and lower webs. The width of the upper and lower flanges is the distance between the outer edge of the flange and the plane of the spar. The width of the upper and lower flanges is 2.5d+4.5d+(d+2)+t1+t2. The fasteners are arranged in parallel, the fastener edge distance is 2.5d, the row spacing is 4.5d, the distance between the inner nut of the flange and the corner of the spar is (d+2), the corner dimension is t1, the thickness of the upper and lower webs is t2, where t2 is the thickness of the upper flange or the lower flange, and the positive mold forming t1=t2, where d is the diameter of the fastener.

9. The method for determining structural parameters of a large-scale composite material spar according to claim 1, wherein: The upper and lower webs of the wing spar are simultaneously reduced in thickness by dropping layers along the span direction and the height direction. The ratio of the layer loss in the span direction transition zone is 1:100, and the ratio of the layer loss in the height direction transition zone is 1:

20.

10. The method for determining structural parameters of a large-scale composite material spar according to claim 9, wherein: The upper and lower edge strips and the upper and lower webs have the same thickness in the rib corner box assembly area. After passing the rib corner box connection area, they begin to lose layers and change thickness. The distance between the layer loss boundary and the rib boundary is 2mm.

11. The method for determining structural parameters of a large-scale composite material spar according to claim 1, wherein: In the strength check of the wing box section, the check items of the upper web, lower web and middle web of the wing spar include three-dimensional composite strain and shear stability of the web; the check items of the upper edge strip and lower edge strip of the wing spar include axial strain control and axial compression stability analysis; the check items of the reinforced support include minimum moment of inertia and minimum cross-sectional area.

12. The method for determining structural parameters of a large-scale composite material spar according to claim 4, wherein: The connection strength of the wing spar includes the connection between the upper and lower wall panels and the upper and lower edge strips of the wing spar, the connection between the wing spar web and the wing rib corner box, and the connection between the wing spar web and the reinforcing strut, including the bolt shear strength and nail hole extrusion strength.

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