A hybrid asymmetric layup structure for a bird strike delamination of a composite blade trailing edge

Abstract

The application belongs to the technical field of engine structure design, and particularly discloses a hybrid asymmetric layered structure of a composite blade tail edge for resisting bird strikes, which is used for forming a fan blade of a large-bypass-ratio turbofan engine, and comprises a bullet-facing surface, a central region and a bullet-facing back surface; a hybrid region is arranged in the central region, and high-toughness fibers different from those in other regions are arranged in the hybrid region to form a hybrid fiber layered structure; the hybrid region is not symmetric about the geometric median plane of the layered structure in the thickness direction, thereby forming an asymmetric layered structure. The application solves the contradiction between the stiffness and toughness of the single material system of the existing composite fan blade layered structure and the problem that the symmetric layered design limits the design freedom.

Description

Technical Field

[0001] This invention belongs to the field of engine structure design technology, specifically relating to a hybrid asymmetric layup structure for bird strike resistant layering of composite material blade trailing edge. Background Technology

[0002] Bird strikes are a significant safety hazard in the aviation industry that is difficult to completely avoid, especially when a bird is ingested into an aircraft engine. This can cause severe damage to fan blades and even lead to catastrophic aviation accidents, posing a serious threat to flight safety. Modern aircraft engine fan blades are widely made of composite materials to reduce weight and improve performance. However, composite blades are prone to delamination and fracture under bird strike conditions, significantly reducing structural integrity and safety.

[0003] Traditional composite blade layup designs utilize high-performance carbon fiber, which possesses excellent mechanical properties such as high modulus and high strength. However, its extremely low toughness makes it prone to delamination failure under soft impacts, resulting in weak anti-delamination performance. In contrast, high-ductility fibers, such as glass fiber, aramid, or polyethylene, offer higher toughness and excellent impact resistance. However, their lower modulus requires greater thickness or dimensions to achieve equivalent in-plane load-bearing capacity as carbon fiber, increasing weight and cost. Furthermore, while traditional symmetrical layup designs simplify the process, they significantly limit design freedom.

[0004] The carbon-glass hybrid asymmetric layup design can effectively overcome the above limitations: by mixing high-modulus, high-strength carbon fibers with high-toughness, high-ductility glass fibers, the complementary properties of the two are fully utilized, taking into account both the in-plane load-bearing capacity and impact toughness of the structure; further breaking the symmetry of the layup can greatly improve the degree of design freedom, maximize the structural advantages of the hybrid layup, and achieve precise control of mechanical properties.

[0005] To address the two major factors affecting the bird strike delamination resistance of existing composite fan blades—the contradiction between the stiffness and toughness of a single material system and the limitation of design freedom imposed by symmetrical layup designs—it is urgent to break through traditional design thinking and further broaden the design space of composite laminated blades through innovative layup designs or new material combinations, thereby meeting the increasingly stringent safety requirements of aero-engines for composite blades. Summary of the Invention

[0006] The purpose of this invention is to solve the contradiction between stiffness and toughness in existing composite fan blade layup single-material systems, as well as the problem of the limitation on design freedom in symmetrical layup design. A hybrid asymmetrical layup structure with bird strike resistant delamination on the trailing edge of composite blades is proposed.

[0007] The technical solution of the present invention is: a hybrid asymmetric ply structure for bird strike resistant layering on the trailing edge of a composite blade, comprising an attack surface, a central region, and a back surface;

[0008] The central region contains a hybrid region composed of high-toughness fiber prepreg layers; the hybrid region is not symmetrical about the geometric center plane of the layer structure in the thickness direction, forming an asymmetric layer structure.

[0009] Preferably, the impact-receiving surface is made of woven carbon fiber prepreg.

[0010] Preferably, the central region is laid with a mixture of unidirectional carbon fiber and woven glass fiber prepreg.

[0011] Preferably, the back elastic surface is made of woven carbon fiber prepreg.

[0012] Preferably, the high-toughness fiber prepreg layer is a woven glass fiber prepreg.

[0013] Preferably, the hybrid region is located on one side of the central region, biased towards the back surface.

[0014] As a preferred option, the composite blade trailing edge anti-bird strike layered hybrid asymmetric ply structure adopts a π / 4 ply scheme, with ply angles including 0°, 90°, 45° and -45°.

[0015] As a preferred option, a composite material blade trailing edge bird strike resistant layered hybrid asymmetric layup structure is used to construct aero-engine fan blades.

[0016] The beneficial effects of this invention are:

[0017] This invention can be implemented on the trailing edge region of composite blades for aero-engines. It applies the above-mentioned hybrid asymmetric structure to the original pure carbon layup, combining the advantages of the two fibers. By leveraging the advantages of hybrid asymmetry, it eliminates the limitations of symmetrical layup design, thereby achieving a more significant improvement in the blade's resistance to delamination damage under impact at the same hybridization ratio. Attached Figure Description

[0018] Figure 1 The diagram shows a hybrid asymmetric ply structure for bird strike resistant layering on the trailing edge of a composite blade.

[0019] Figure 2 The diagram shows a pure carbon symmetrical layup scheme, a symmetrical hybrid layup scheme, and a hybrid asymmetrical layup scheme.

[0020] Figure 3 The diagram shown is a simulation of the working conditions.

[0021] Figure 4The figure shows the distribution of interlayer secondary stress along the thickness for three layup schemes.

[0022] Figure 5 The diagram illustrates the hybrid region of a composite material fan blade.

[0023] Figure 6 The image shows a comparison of the peak interlaminar stress in the trailing edge region of a composite fan blade made of pure carbon and hybrid lay-ups during a bird strike.

[0024] Explanation of reference numerals in the attached diagram: 1-Aiming surface, 2-Central area, 3-Back surface, 4-Mixed area. Detailed Implementation

[0025] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0026] Example 1:

[0027] like Figure 1 As shown, a hybrid asymmetric ply structure for bird strike resistant layering of composite blade trailing edge is used to form a composite fan blade for a high bypass ratio turbofan engine, including a projectile-facing surface 1, a central region 2, and a projectile-backing surface 3.

[0028] The central region 2 contains a hybrid region 4, which is composed of a high-toughness fiber prepreg layup. The hybrid region 4 is not symmetrical about the geometric center plane of the layup structure in the thickness direction, forming an asymmetrical layup structure. The hybridity is manifested in that the hybrid region 4 contains fibers that are different from those in other regions and have high toughness, forming a hybrid fiber layup structure.

[0029] The anti-missile surface 1 is made of woven carbon fiber prepreg.

[0030] The central region 2 is laid with a mixture of unidirectional carbon fiber and woven glass fiber prepreg.

[0031] The back elastic surface 3 is made of woven carbon fiber prepreg.

[0032] The high-toughness fiber prepreg layer is a woven glass fiber prepreg.

[0033] The hybrid region 4 is located on one side of the central region 2, biased towards the back surface 3.

[0034] The composite blade trailing edge anti-bird strike layered hybrid asymmetric ply structure adopts a π / 4 ply scheme, with ply angles including 0°, 90°, 45° and -45°.

[0035] Example 2:

[0036] Based on Example 1, this embodiment of the invention provides a typical flat plate component using the carbon-glass hybrid asymmetric layup structure, and verifies the anti-delamination damage performance of the typical flat plate component using numerical simulation.

[0037] Figure 2 The diagram shows a typical flat panel component and three corresponding ply layup schemes: a conventional pure carbon symmetrical ply, a carbon-glass hybrid symmetrical ply, and a carbon-glass hybrid asymmetrical ply. The pure carbon ply layup scheme serves as the control group, and the hybrid ply layup scheme serves as the test group. All three schemes have the same in-plane dimensions and thickness.

[0038] This typical flat panel adopts the π / 4 layup scheme commonly used in the aerospace field, which consists of four layup angles: 0°, 90°, 45°, and -45°. It includes three types of layups: unidirectional and woven carbon fiber prepreg and woven glass fiber prepreg.

[0039] For pure carbon layups, woven carbon fiber layers are placed on the outermost side of the layup (layers 1 and 20) to fully utilize the excellent damage propagation resistance of the woven structure. Unidirectional carbon fiber layers are placed inside the flat plate at different layup angles (layers 1 to 19) to provide the main structural stiffness by utilizing the high modulus and high strength properties of carbon fiber.

[0040] For the hybrid symmetrical layup scheme, woven fiberglass layers are placed on both sides of the mid-thickness surface (layers 9-12 of the original pure carbon layup), replacing the original unidirectional carbon fiber layers, with each layer maintaining the same layup angle as the original carbon layers. The thickness of a single woven fiberglass layer is exactly half that of a single unidirectional carbon fiber layer; using two layers of fiberglass to replace one layer of carbon fiber ensures consistency in thickness before and after the replacement. This scheme utilizes the high toughness of fiberglass and its woven structure to buffer local interlayer stress concentration, thereby improving delamination resistance.

[0041] For the hybrid asymmetric layup scheme, the woven glass fiber layer is placed on the side of the thickness closest to the back elastic surface (layers 7-10 of the original pure carbon layup), replacing the original unidirectional carbon fiber layer, and each layer maintains the same layup angle as the original carbon layer. The thickness of a single woven glass fiber layer is exactly half that of a single unidirectional carbon fiber layer. Using two layers of glass fiber to replace one layer of carbon fiber ensures the consistency of thickness before and after the replacement. This utilizes the high toughness of glass fiber and its woven structure to buffer local interlayer stress concentration, thereby improving anti-delamination performance.

[0042] Figure 3 A simulation model was established to evaluate the trailing edge damage of composite fan blades in aero-engines. Finite element method (FEM) software was used for simulation analysis, and the Chang-Chang criterion was adopted as the material failure criterion. The constitutive model parameters, i.e., the material parameters of the composite laminate, are shown in Table 1. The interlaminar stress components, including shear stress and normal stress, were extracted from the right free edge of the composite laminate at each time point, and the interlaminar secondary stress criterion was used. The delamination damage resistance of the two layup schemes was evaluated, and the definitions are as follows:

[0043]

[0044] in, and For shear stress, For normal stress, Interlaminar shear strength, This represents the interlayer normal strength.

[0045] Table 1 Material parameters of composite laminates

[0046]

[0047] Figure 4 The peak values ​​of the interlaminar secondary stress criterion are shown along the thickness direction for the three ply configurations. The peak value for the pure carbon ply is 1.31, located in the 8th layer. The peak value for the hybrid symmetric ply is 1.05, located in the 15th layer. The peak value for the hybrid asymmetric ply is 0.96, also located in the 15th layer. The peak value of the secondary stress criterion for the hybrid symmetric ply is 19.85% lower than that for the pure carbon ply, and the peak value for the hybrid asymmetric ply is 26.72% lower than that for the pure carbon ply. At the same mixing ratio, the hybrid asymmetric ply significantly improves the anti-delamination performance of typical flat parts.

[0048] Example 3:

[0049] Based on the research in Example 1, this invention proposes a high-bypass turbofan engine composite fan blade using the above-mentioned carbon-glass hybrid asymmetric layup structure, and verifies and analyzes its anti-delamination performance through numerical simulation.

[0050] Figure 5 This is a schematic diagram of a composite fan blade using this carbon-glass hybrid asymmetric layup structure. The hybrid region is located at the trailing edge of the blade, and the asymmetric layup in the thickness direction is arranged on the side of the neutral plane closer to the suction surface. The specific hybridization method is as follows: the carbon fiber layup in the corresponding area of ​​the trailing edge is replaced with a glass fiber layup, and the layup angle before and after the replacement remains consistent.

[0051] Figure 6This study compares the peak interlaminar stress in the trailing edge region of a composite fan blade made of pure carbon and hybrid layups during a bird strike. The results show that the peak interlaminar stress in the pure carbon layup is 79.45 MPa in the spanwise direction and approximately 62.34 MPa in the tangential direction, with the spanwise stress significantly higher than the tangential stress. In contrast, the peak interlaminar stress in both the spanwise and tangential directions of the hybrid layup is approximately 36–38 MPa, essentially the same, and significantly lower than that of the pure carbon layup (a reduction of nearly 50%). In conclusion, hybrid asymmetric layups can significantly reduce the peak interlaminar stress and eliminate the stress difference between the spanwise and tangential directions, resulting in a more uniform stress distribution.

[0052] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A hybrid asymmetric layup structure for bird strike resistant delamination on the trailing edge of a composite blade, characterized in that, It includes the incoming surface (1), the central region (2), and the back surface (3); The central region (2) is provided with a hybrid region (4), which is composed of high-toughness fiber prepreg layup; the hybrid region (4) is not symmetrical about the geometric center plane of the layup structure in the thickness direction, forming an asymmetric layup structure; the hybrid region (4) is located on one side of the central region (2) biased towards the back elastic surface (3); the central region (2) is made of unidirectional carbon fiber and woven glass fiber prepreg mixed layup; the high-toughness fiber prepreg layup is woven glass fiber prepreg; A hybrid asymmetric layup structure with bird strike resistant delamination on the trailing edge of composite blades is used to construct composite fan blades for high bypass ratio turbofan engines.

2. The hybrid asymmetric layup structure for bird strike resistant delamination of composite blade trailing edge according to claim 1, characterized in that, The anti-ballistic surface (1) is made of woven carbon fiber prepreg.

3. The hybrid asymmetric layup structure for bird strike resistant delamination of composite blade trailing edge according to claim 1, characterized in that, The back elastic surface (3) is laid with woven carbon fiber prepreg.

4. The hybrid asymmetric layup structure for bird strike resistant delamination of composite blade trailing edge according to claim 1, characterized in that, The composite blade trailing edge anti-bird strike layered hybrid asymmetric ply structure adopts a π / 4 ply scheme, with ply angles including 0°, 90°, 45° and -45°.

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