A three-dimensional braided composite pull-twist strip structure

Abstract

The application belongs to the technical field of helicopter structure components, and discloses a three-dimensional woven composite material pull-torque strip structure, which comprises at least two layers of three-dimensionally woven pull-torque strips, a gauze and a bushing, the pull-torque strips are fixed by overlapping with the gauze in between, both ends of the pull-torque strips are provided with connecting holes, and the bushing is arranged in the connecting holes; wherein the pull-torque strips are made of composite material made by three-dimensional weaving process, and fiber yarns are distributed in a direction different from the surrounding direction of the pull-torque strips. The three-dimensional woven composite material pull-torque strip structure can effectively improve the tensile capacity, enhance the anti-delamination capacity under torsional deformation, and thus prolong the service life of the pull-torque strip. The typical section and the connecting section of the pull-torque strip are connected through a slow transition area with a size gradually decreasing from large to small, so that the warping normal stress of the connecting section of the pull-torque strip is reduced, and the warping normal stress is reduced by 20% to 30% under a unit torsional angle.

Description

Technical Field

[0001] The present invention belongs to the technical field of helicopter structural components, relates to a tension-twist strip design technology, and specifically relates to a three-dimensional braided composite material tension-twist strip structure. Background Art

[0002] The twist bar is a component in a helicopter rotor system that withstands centrifugal loads and torsional deformation. It connects the blades to the hub, bearing the vast majority of the centrifugal forces on the blades. By deforming itself, it replaces the rotor's pitch hinge to achieve pitch change. International companies like Bell, Lord, and Airwolf have decades of experience developing twist bars. Air Helicopters also has extensive experience developing twist bars for ducted tail rotors.

[0003] Over the past 50 years, Airbus Helicopters has refined the design of twist bars during the development of ducted tail rotors. The EC145 T2, the latest ducted tail rotor technology, certified in 2014, incorporates carbon fiber-reinforced blades and integrated twist bars. The twist bars used on the EC145 feature a two-dimensional braided structure, with a gradual transition from large to small at the ends, helping to alleviate stress at the base of the bars.

[0004] By importing production lines, China has considerable experience in manufacturing composite twist strips for certain ducted tail rotors, and also has experience developing metal tail rotor twist strips for certain aircraft. Unidirectional fiber-wound composite twist strips have also been developed in China, but there is no precedent for developing braided twist strips.

[0005] The enormous centrifugal force generated by high-speed rotating blades requires the twist bars to possess strong tensile strength. For helicopters that need to fly at high speeds, the wide range of control strokes increases the difficulty of developing the twist bars. Furthermore, high-frequency dynamic torsional deformation is also required, so the twist bars also need to possess high-frequency fatigue resistance. With the promotion of composite winding twist bar technology on domestic helicopters, the need for further strength improvement in twist bars for large-tonnage rotors has emerged. These twist bars need to withstand far greater tensile forces than existing twist bars.

[0006] Under centrifugal and torsional loads, the offset between the shear center and the torsional axis of the tension-twist strip cross section causes each strip of the tension-twist strip to be subjected to the combined effects of tension, twist, and bending. Composite tension-twist strips wrapped with unidirectional fibers (beams) experience large normal warping stresses at their ends, and the shear stress perpendicular to the fiber direction reaches its maximum value at the center of the strip's side. The presence of normal warping stresses adversely affects the strip's fiber-direction bearing capacity, and the shear stress can cause delamination damage. Because the tension-twist strips are subjected to complex multiaxial stresses, conventional unidirectionally and bidirectionally reinforced woven materials cannot meet the higher strength requirements of tension-twist strip designs. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a three-dimensional braided composite material tension and twist strip structure, which solves the problem of delamination damage that may occur in traditional composite material tension and twist strips and can withstand more complex multi-axial stress.

[0008] The technical solutions of the present invention are as follows:

[0009] A three-dimensional woven composite material twisted strip structure includes at least two layers of three-dimensional woven twisted strips, padding cloths and bushings. The twisted strips are overlapped and fixed with the padding cloths between them. Connecting holes are provided at both ends of the twisted strips, and bushings are provided in the connecting holes. The twisted strips are made of a composite material produced by a three-dimensional weaving process, and fiber yarns are distributed in a circumferential direction different from that of the twisted strips.

[0010] Furthermore, the torsion bar includes a connecting section, a transition section and a torsional typical section. The part of the torsion bar provided with a connecting hole is the connecting section, the middle of the two connecting sections of the torsion bar is the torsional typical section, and the transition area from the connecting section to the torsional typical section is the transition section; wherein, the vertical dimension of the connecting section is the largest, the vertical dimension of the torsional typical section is the smallest, and the vertical dimension of the transition section from the connecting section to the torsional typical section decreases gently from large to small.

[0011] Furthermore, at the transition section of the torsion strip, fiber yarns in a circumferential direction different from that of the torsion strip are added by puncture to achieve a gradual decrease in size from large to large along the direction from the connecting section to the torsion typical section.

[0012] Furthermore, the connecting section of the torsion strip is formed by weaving fibers in various directions into a wider and thicker structure.

[0013] Furthermore, the material of the torsion strip is a three-dimensional braided body, which is obtained by solidifying a fiber braided preform through an RTM injection molding process.

[0014] Furthermore, a three-dimensional braided body is first produced, and then the braided body, the bushing and the padding are combined, and finally the braided body structure is formed through secondary curing.

[0015] Furthermore, it comprises three pull-twist strips, two pads and two bushings. The three pull-twist strips are stacked with two pads between them, and the two bushings are respectively arranged in two overlapping holes at both ends of the three stacked pull-twist strips.

[0016] Furthermore, the three-dimensional weaving structure of the twist strip specifically includes: on the basis of using fiber yarns for weaving, periodically distributed fiber yarns inclined to the horizontal and vertical planes are added to be interspersed and wrapped around the fiber yarns in the original wrapping direction, and the inclination direction of the added fiber yarns also changes periodically and symmetrically.

[0017] Beneficial effects of the present invention:

[0018] 1. The three-dimensional braided composite material tension and twist strip structure provided by the present invention can effectively improve the tensile strength and enhance the ability to resist delamination under torsional deformation, thereby increasing the service life of the tension and twist strip.

[0019] 2. The typical section and the connecting section of the tension-twist strip are transitioned through a slow transition zone from large to small size, which can reduce the warping normal stress of the connecting section of the tension-twist strip. Under unit torsion angle, the warping normal stress is reduced by 20% to 30%.

[0020] 3. Compared with patent CN204937499, the difference is that the three-dimensional weaving of the present invention is not only longitudinal winding and transverse sewing, but also includes woven fibers that are not parallel to the direction of tension; the distribution of multi-directional fibers can better bear the warping stress and delamination stress caused by torsion, and its overall mechanical properties are stronger than those of fibers in two directions.

[0021] 4. Compared with Patent 200680022700, the difference is that the three-dimensional woven tension and twist strip of the present invention is an integral three-dimensional woven structure, and there is no distinction between the core and the skin, which has a higher degree of integration; and because the three-dimensional woven body of the present invention is used on the tension and twist strip, it bears the centrifugal force and torsional force under high speed conditions, as well as the swinging force of the blades, etc. For this reason, the present invention also designs different segmented designs, and the configuration of the segmented design and the three-dimensional woven configuration are combined to solve the difficulty of the tension and twist strip in bearing complex multi-axis complex stresses. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a structural layout diagram of the braided tension and twist strip assembly;

[0023] Figure 2 for Figure 1 Front view of

[0024] Figure 3 Schematic diagram of the twist strip segmentation

[0025] Figure 4 Schematic diagram of the bushing;

[0026] Figure 5 It is a schematic diagram of the transition section size;

[0027] Figure 6 This is a schematic diagram of the weaving direction of the twist strip;

[0028] Figure 7 Schematic diagram of three-dimensional braided fiber with twisted strips;

[0029] Among them, 1 is the tension and twist strip, 2 is the padding, 3 is the bushing, 11 is the connecting section, 12 is the transition section, and 13 is the typical torsional section. DETAILED DESCRIPTION

[0030] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0031] 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 directions or positional relationships for the purposes of the accompanying drawings, and are intended only to facilitate the description of the present invention and simplify the description, rather than to indicate or imply that the device or case 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. In addition, the terms "first", "second" and the like are used for descriptive purposes only, and should not be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second" and the like may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, detachable, or integrated connections; mechanical or point connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0033] A three-dimensional woven composite material twist strip structure includes at least two layers of three-dimensional woven twist strips 1, a padding cloth 2 and a bushing 3. The twist strips 1 are overlapped and fixed with the padding cloth 2 between them. Connection holes are provided at both ends of the twist strip 1, and bushings 3 are provided in the connection holes. The twist strip 1 is made of a composite material made using a three-dimensional weaving process, and fiber yarns are distributed in a circumferential direction different from that of the twist strip 1.

[0034] The tension and twist strip 1 includes a connecting section 11, a transition section 12 and a torsional typical section 13. The part of the tension and twist strip 1 provided with a connecting hole is the connecting section 11, the middle of the two connecting sections 11 of the tension and twist strip 1 is the torsional typical section 13, and the transition area from the connecting section 11 to the torsional typical section 13 is the transition section 12; among them, the vertical dimension of the connecting section 11 is the largest, the vertical dimension of the torsional typical section 13 is the smallest, and the vertical dimension of the transition section 12 from the connecting section 11 to the torsional typical section 13 decreases gently from large to small.

[0035] At the transition section 12 , the torsion strip 1 is provided with fiber yarns in a circumferential direction different from that of the torsion strip 1 by puncturing, so that the size thereof decreases gradually from large to small along the direction from the connecting section 11 to the torsion typical section 13 .

[0036] The connecting section 11 of the tension and twist strip 1 is a wider and thicker structure woven with fibers in various directions.

[0037] The material of the tension and twist strip 1 is a three-dimensional braided body, which is obtained by curing a fiber braided preform through an RTM injection molding process.

[0038] First, a three-dimensional braided torsion strip 1 is produced, and then the torsion strip 1, the bushing 3 and the padding 2 are assembled, and finally the torsion strip structure is formed through secondary curing.

[0039] The invention comprises three pull-twist strips 1, two pads 2 and two bushings 3. The three pull-twist strips 1 are stacked with two pads 2 between them. The two bushings 3 are respectively arranged in two overlapping holes at both ends of the three stacked pull-twist strips 1.

[0040] The three-dimensional weaving structure of the tension and twist strip 1 specifically includes: on the basis of using fiber yarns for weaving, periodically distributed fiber yarns inclined to the horizontal and vertical planes are added to be interspersed and wrapped around the fiber yarns in the original wrapping direction, and the inclination direction of the added fiber yarns also changes periodically and symmetrically.

[0041] The following is another embodiment of the present invention.

[0042] A three-dimensional braided composite material twist strip assembly, including one or more layers of three-dimensional braided twist strips, bushings, and padding. The twist strips are provided with holes at both ends that match the bushings. The twist strips, bushings, and paddings are solidified together to form the twist strip assembly structure. The structural layout diagram is attached. Figure 1 The twist strip is divided into three-dimensional braided connection section, three-dimensional braided transition section and three-dimensional braided twist typical section. The segmentation diagram is shown in the attached figure. Figure 2 shown.

[0043] Specific technical details: The material of the twist strip is a three-dimensional braided composite material. The three-dimensional braided body is obtained by curing the fiber braided preform through the RTM injection molding process. Then the three-dimensional braided twist strip, bushing and pad are secondary cured to form the twist strip component structure. The bushing is shown in the attached figure. Figure 3 At the transition section of the three-dimensional braiding, the twist strip is inserted with fiber yarns by puncture to achieve a gradual decrease in size from large to large along the direction from the connection section to the twisting typical section. The schematic diagram is shown in the attached figure. Figure 4 The schematic diagram of the winding direction of the twisted strip is shown in the attached Figure 5 As shown, the three-dimensional weaving process can ensure that the fiber yarns of the twist strip are distributed in directions different from the winding direction. The schematic diagram of the three-dimensional weaving fiber yarn is shown in Figure 6shown.

[0044] 1. The twist bar assembly uses a three-dimensional weaving process instead of unidirectional fiber winding;

[0045] 2. The pull-twist strip assembly as claimed in the above patent claim is characterized in that the twisted typical section of the pull-twist strip is three-dimensionally woven;

[0046] 3. The twist bar assembly as claimed in the above patent is characterized in that the twist bar is arranged in a direction from the typical section to the connecting section, and the three-dimensional woven transition section is formed by slowly increasing the size of the transition section by adding fibers in a different direction than the winding direction by puncturing;

[0047] 4. The twist strip as claimed in the above patent, characterized in that the connecting section of the twist strip is a wider and thicker structure woven with fibers having various directions;

[0048] 5. The twist strip as claimed in the above patent, characterized in that the three-dimensional weaving is such that the yarns (fiber bundles) are distributed in directions different from the winding direction of the twist strip;

[0049] 6. The twist bar assembly is symmetrical in vertical, horizontal and central directions;

[0050] 7. Schematic diagram of braided twist strips Figure 5 , there is a slow transition zone of size;

[0051] 8. Schematic diagram of twisted strip braided fiber yarn Figure 6 , there are fiber yarns distributed in all directions of space.

[0052] The above description is merely a detailed description of specific embodiments of the present invention. Any unspecified portions are conventional techniques. However, the scope of the present invention is not limited thereto. Any changes or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed in the present invention are intended to be encompassed within the scope of the present invention. The scope of the present invention shall be determined by the scope of the claims.

Claims

1. A three-dimensional braided composite material twist strip structure, characterized in that: The invention comprises at least two layers of three-dimensionally woven twist strips (1), a padding (2) and a bushing (3), wherein the twist strips (1) are overlapped and fixed with the padding (2) therebetween, and connecting holes are provided at both ends of the twist strips (1), and bushings (3) are provided in the connecting holes; wherein the twist strips (1) are made of a composite material made by a three-dimensional weaving process, and fiber yarns are distributed in a circumferential direction different from that of the twist strips (1); The pull-twist strip (1) comprises a connecting section (11), a transition section (12) and a torsional typical section (13); the portion of the pull-twist strip (1) provided with a connecting hole is the connecting section (11); the middle of the two connecting sections (11) of the pull-twist strip (1) is the torsional typical section (13); and the transition area from the connecting section (11) to the torsional typical section (13) is the transition section (12); wherein the vertical dimension of the connecting section (11) is the largest, the vertical dimension of the torsional typical section (13) is the smallest, and the vertical dimension of the transition section (12) from the connecting section (11) to the torsional typical section (13) decreases gradually from large to small. At the transition section (12) of the torsion strip (1), fiber yarns in a circumferential direction different from that of the torsion strip (1) are added by puncturing to achieve a gradual decrease in size from large to large along the direction from the connecting section (11) to the torsion typical section (13); The connecting section (11) of the tension-twist strip (1) is a structure woven from fibers in various directions and is wider and thicker than the torsion typical section (13) and the transition section (12); The material of the twist strip (1) is a three-dimensional braided body, which is obtained by solidifying a fiber braided preform through an RTM injection molding process. The three-dimensional braided structure of the twist strip (1) specifically includes: on the basis of using fiber yarns to surround the braid, periodically distributed fiber yarns inclined to the horizontal plane and the vertical plane are added to be interspersed and wrapped around the fiber yarns in the original wrapping direction, and the inclination direction of the added fiber yarns also changes periodically and symmetrically.

2. A three-dimensional braided composite material twist strip structure according to claim 1, characterized in that: First, a three-dimensional braided torsion strip (1) is produced, and then the torsion strip (1), the bushing (3) and the padding (2) are combined, and finally the torsion strip structure is formed through secondary curing.

3. The three-dimensional braided composite material twist strip structure according to claim 2, characterized in that: The invention comprises three pull-twist strips (1), two pads (2) and two bushings (3). The three pull-twist strips (1) are stacked with two pads (2) spaced therebetween, and the two bushings (3) are respectively arranged in two overlapping holes at both ends of the three stacked pull-twist strips (1).

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