Method for determining fiber direction of composite material component with large slenderness ratio
By using the Frenet frame to define a local coordinate system in composite components with a large slenderness ratio, the problem of mismatch between fiber direction and main force transmission path was solved, achieving alignment between fiber direction and component, and improving the structural performance and manufacturing quality of the component.
Patent Information
- Application Number
- CN202511818767.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-03-31
AI Technical Summary
In the prior art, the fiber orientation definition method based on the global rectangular coordinate system leads to a mismatch between the fiber path and the main force transmission path in composite components with a large aspect ratio, resulting in resource waste, reduced axial efficiency and buckling stability, poor manufacturability, low material utilization, and geometric distortion and defects.
A local coordinate system was established using a Frenet frame, and the fiber direction was defined by the tangent vector to keep it tangent to the ridge line of the component. The layup sequence of the composite material was formed by combining ±45° and 90° layups, and the sheet unfolding and optimization were performed in the CAD/CAM system.
It significantly improves the axial stiffness and material utilization of high slenderness ratio composite components, enhances manufacturing quality and consistency, reduces internal defects, and strengthens the mechanical properties and durability of the components.
Smart Images
Figure CN121768539A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aircraft composite material manufacturing technology, and in particular, it is a method for determining the fiber orientation of composite material components with a large aspect ratio. Background Technology
[0002] Fiber-reinforced resin matrix composites possess a range of excellent properties, including high specific strength, high specific modulus, and corrosion resistance, making them a key material for modern aerospace structures. These structures contain numerous beams, stringers, and stringer-like components with high slenderness ratios, such as aircraft wing spars, wing panel stringers, fuselage stringers, and strips. These components mostly bear axial tensile and compressive loads, and their mechanical properties are strongly dependent on the alignment of the fiber direction with the main force transmission path.
[0003] Currently, in computer-aided design of composite materials, the fiber orientation of ply is generally defined using a global Cartesian coordinate system. This method fixes the 0° fiber orientation of the ply as parallel to a certain global coordinate system (such as the x-axis). While this traditional definition achieves design standardization, it exposes the following problems when dealing with components with significant three-dimensional curvature and large slenderness ratios: 1) Mismatch between fiber path and main force transmission path: In the overall layout, the large slenderness ratio component presents a spatial bending shape. The fixed 0° fiber direction in the global coordinate system cannot follow the actual bending force transmission path of the component, resulting in the fiber being in an off-axis state in most areas. This mismatch not only causes a huge waste of fiber strength and stiffness resources, but also significantly reduces the axial constant efficiency and buckling stability of the component, and forms stress concentration points, affecting fatigue life. 2) Poor manufacturability and low material utilization: In the process of unfolding from a 3D curved surface model to a 2D planar sheet, software such as CATIA needs to perform calculations based on a defined fiber orientation. When unfolding a curved component with a fixed 0° fiber orientation in the global coordinate system, the resulting 2D sheet may suffer from severe geometric distortion and twisting. Furthermore, irregular sheets will result in a large amount of unusable scrap material in subsequent layout drawings, and twisted sheets are more prone to defects such as wrinkles and bridging during the laying process.
[0004] Therefore, there is an urgent need in this field for an innovative definition method that can break through the constraints of the traditional global coordinate system and enable the fiber direction to adapt to the geometric characteristics of the component, especially the natural force transmission path of the component with a large slenderness ratio, so as to improve the structural performance, manufacturing quality and economy of composite components with a large slenderness ratio. Summary of the Invention
[0005] The purpose of this invention is to provide a method for determining the fiber orientation of composite material components with a high slenderness ratio, thereby solving the problems mentioned in the background art. Composite material components with a high slenderness ratio manufactured using this method can significantly improve their axial stiffness, load-bearing efficiency, and material utilization.
[0006] A method for determining the fiber orientation of composite components with a high slenderness ratio, comprising the following specific steps: 1. Data Measurement and Calculation: Obtain the geometric model of the component with a large slenderness ratio to be manufactured, measure and calculate the slenderness ratio (length to minimum cross-sectional width ratio) and average curvature of the component. When the slenderness ratio of the component is not less than 20, and the average curvature k is greater than the preset curvature threshold k... th When k is reached, proceed to the next step. th The value is 0.005mm. -1 ~0.02mm -1 ; 2. Ridge line extraction steps: Extract the ridge line from the geometric model of the composite component as the fiber guiding reference curve C(s), where s is the arc length parameter of the curve; 3. Steps for establishing a local coordinate system: At any point P on the fiber-guided reference curve C(s), establish a Frenet frame as a local coordinate system; 4. Fiber Orientation Definition Steps: Define the tangent vector of the Frenet frame. The direction is defined as the improved 0° fiber direction at point P.
[0007] Furthermore, high aspect ratio composite material components include, but are not limited to, aircraft stringers, stiffeners, and beams.
[0008] Furthermore, the method for extracting the ridge line in step 2 is as follows: for a component with a constant cross-section, the ridge line is the center line; for a component with a variable cross-section, the ridge line is a spatial curve generated by interpolation by connecting the centroid points of each cross-section.
[0009] Furthermore, the Frenet frame in step 2 includes: tangent vectors. From the formula Definition; Normal vector From the formula Definition; binormal vector From the formula definition.
[0010] Furthermore, the 0° fiber direction generated by the method is continuous along the entire length of the component and remains tangent to the component ridge line.
[0011] Furthermore, based on the definition of the 0° fiber direction in the layup, the composite component combines ±45° layups and 90° layups to form a layup sequence of the composite material.
[0012] Furthermore, the specific value of the curvature threshold k in step 1 is adjusted according to the strength zoning of the component: for the main load-bearing component, the curvature threshold k is used. th The range is 0.005mm. -1 ~0.01mm -1 For non-primary load-bearing components, a curvature threshold k is used. th The range is 0.01mm. -1 ~0.02mm -1 .
[0013] Furthermore, the method also includes a layup unfolding step: in a CAD / CAM system, based on the redefined 0° fiber orientation of the layup, sheet unfolding, cutting optimization, and manufacturing feasibility analysis are performed.
[0014] Compared with the prior art, the fiber orientation definition method for composite components with high aspect ratio described in this invention has the following advantages: 1) Improved structural performance: By defining the fiber 0° direction as consistent with the tangent direction of the girder ridge, the fiber direction is ensured to be highly consistent with the principal stress path of the component in actual service. This allows the fiber to maximize its axial high strength and high modulus characteristics, significantly improving the mechanical properties and durability of the component; 2) Manufacturing process optimization: This method, by dynamically defining fiber orientation, makes it possible to manufacture complex components with variable curvature and torsion, greatly expanding the design space and application range of composite materials. Through precise sheet unfolding, cutting, and arrangement, the overall material utilization rate is improved. 3) Improved quality consistency: By introducing mathematical models and objective criteria, the accuracy of sheet unfolding is improved, thereby avoiding deviations caused by inaccurate sheet unfolding and ensuring high consistency between different components and different batches of products. At the same time, precise control of fiber direction ensures uniform pressure transmission during resin curing, which helps to reduce internal defects such as porosity and delamination, resulting in denser and better-performing composite material components. Attached Figure Description
[0015] Figure 1a Comparison diagram of two methods for defining ply direction - based on the method of this invention; Figure 1b A comparison chart of two methods for defining ply direction - based on the traditional method; Figure 2 A schematic diagram for establishing the Frenet frame; Figure 3a Comparison of sheet unfolding effects - based on the method of this invention; Figure 3b Comparison of sheet unfolding effects - based on traditional methods; The numbers in the diagram are explained as follows: 1-T-type stringer, 2-ridge line, 3-improved 0° fiber direction of the layup, 4-conventional 0° fiber direction of the layup, 5-global rectangular coordinate system, 6-Frenet frame, 7-conventional 0° sheet, 8-improved 0° sheet. Detailed Implementation
[0016] 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, and 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 the present invention.
[0017] like Figure 1a and Figure 2 As shown, this invention takes the T-shaped stringer 1 of a large curvature wing panel as an example. The material of this component is T800 grade carbon fiber / epoxy prepreg. The transverse section of stringer 1 is T-shaped, and the spanwise section is V-shaped. The curvature threshold k of stringer 1 is... th =0.005mm -1 A method for determining the fiber orientation of a high aspect ratio composite component includes the following steps: 1. Data Measurement and Calculation: The geometric model of the T-shaped stringer 1 of the large curvature wing panel was obtained and run in the CAD system. The minimum envelope of stringer 1 was constructed in the digital model. The following basic geometric parameters were obtained through measurement and calculation: stringer 1 length L = 4000 mm, minimum cross-sectional width H = 100 mm, slenderness ratio L / H = 40, and average curvature k of stringer 1 = 0.006 mm. -1 Because its slenderness ratio L / H > 20 and its average curvature k > 0.005 mm -1 ; 2. Ridge line 2 extraction step: Extract ridge line 2 from the geometric model of T-shaped girder 1 as fiber guiding reference curve C(s), where s is the arc length parameter of the curve. Since the T-shaped girder 1 is a variable cross-section member, the fiber guiding reference curve C(s) is a spatial curve generated by interpolation by connecting the centroid points of each cross-section. 3. Steps for establishing the local coordinate system: At any point P on the fiber-guided reference curve C(s) of the T-shaped stringer 1 in the digital model, establish the Frenet frame 6 as the local coordinate system. The Frenet frame 6 includes: tangent vector From the formula Definition; Normal vector From the formula Definition; binormal vector From the formula definition; 4. Fiber orientation definition step: Define the tangent vector of the Frenet frame 6. The direction is defined as the improved 0° fiber direction 3 at point P; other ply directions are defined based on the local coordinate system, where the ±45° ply directions are relative to... Definition: 90° ply along Define the material orientation and assign it to all layers. After defining the fiber orientation of T-shaped stringer 1 using the above method, processability verification can be performed. For example... Figure 1b and Figure 3b As shown, the traditional 0° sheet 7 was unfolded using the traditional method of setting the fiber direction to 0° based on the global rectangular coordinate system 5. The V-shaped area of the sheet was severely distorted, and after completing the overall cutting diagram layout, the material utilization rate was only 71%. (As shown...) Figure 1a and Figure 3a As shown, the improved 0° sheet 8 generated using the method of the present invention has a flat V-shaped area and a material utilization rate of 83%.
[0018] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
Claims
1. A method of determining the fibre direction of a large aspect ratio composite component, characterised by, The method comprises the following steps: S1 data measurement and calculation: obtaining a geometric model of the large slenderness ratio composite component, measuring and calculating the slenderness ratio and average curvature of the composite component, the slenderness ratio being the ratio of length to minimum cross-sectional width; When the slenderness ratio of the composite member is not less than 20, and the average curvature k is greater than a preset curvature threshold k th , the next step is entered, in which k th is 0.005mm -1 ~0.02mm -1 ; S2 ridge line extraction: extracting a ridge line from the geometric model of the large slenderness ratio composite component as a fiber guide reference curve C(s), the fiber guide reference curve C(s) being a servo curve with arc length parameter s as the variable; S3 establishing a local coordinate system: at an arbitrary point P on the fiber guide reference curve C(s), a Frenet frame is established as a local coordinate system; S4 determining a fiber direction: the tangent vector of the Frenet frame at the point P direction as the ply 0° fiber direction at this point P.
2. The method of claim 1, wherein, The large slenderness ratio composite component is a long stringer, a rib or a beam of an airplane.
3. The method of claim 1, wherein, The method for extracting the ridge line in the step S2 is that, for an equal cross-section composite component, the ridge line is a center line; for a variable cross-section composite component, the ridge line is a spatial curve connecting the centers of each cross-section and generated by interpolation.
4. The method of claim 1, wherein, The Frenet frame in the step S2 includes a tangent vector defined by the formula ; a normal vector defined by the formula ; and a binormal vector defined by the formula .
5. The method of claim 1, wherein, The 0° fiber direction of the large slenderness ratio composite component is continuous over the entire component length and tangent to the component ridge line.
6. The method of claim 1, wherein, On the basis of defining the 0° fiber direction of the composite component, the ±45° ply and the 90° ply are combined to form a ply sequence of the composite material.
7. The method of claim 1, wherein, The specific value of the curvature threshold k in the step S1 is adjusted according to the strength partition of the component: for the main load-bearing component, the curvature threshold k is adopted th in the range of 0.005mm -1 ~ 0.01mm -1 ; for the non-main load-bearing component, the curvature threshold k th in the range of 0.01mm -1 ~ 0.02mm -1 is adopted.
8. The method of claim 1, wherein, The method further comprises a ply unfolding step: in a CAD / CAM system, based on the determined 0° fiber direction of the ply, sheet unfolding, blanking optimization and manufacturing feasibility analysis are performed.