CN115771610A - High-fatigue-strength transition section laying layer in bifurcation area and use method thereof - Google Patents

Abstract

The invention belongs to the technical field of helicopter rotor wing composite material design, and discloses a high fatigue strength transition section laying layer in a bifurcation area, which comprises V-shaped glass cloth and Y-shaped glass cloth, wherein the V-shaped glass cloth and the Y-shaped glass cloth are all prepreg of epoxy resin glass fiber fabric with the angle of +/-45 degrees; the sharp angle end of the Y-shaped glass cloth is wrapped outside the sharp angle of the V-shaped glass cloth, and the other end of the Y-shaped glass cloth extends into a forked groove of a girder belt of the helicopter blade. The layering of the high fatigue strength transition section in the bifurcation area can greatly enhance the fatigue strength and effectively prolong the service life of the root of the blade while ensuring that the structural rigidity is unchanged. Compared with the traditional laying layer, the laying layer has better manufacturability, and the glass fiber of the girder is not easy to wrinkle in the mould pressing process. The scheme has strong operability and extremely low additional cost.

Description

High-fatigue-strength transition section laying layer in bifurcation area and use method thereof

Technical Field

The invention belongs to the technical field of helicopter rotor composite material design, relates to a design technology of a high fatigue strength transition section in a bifurcation area of a helicopter rotor blade, and particularly relates to a high fatigue strength transition section layering in the bifurcation area and a use method thereof.

Background

In a helicopter rotor system, the root of a blade or the root of a flexible beam is mainly composed of a metal lining, a filling block and a girder strip. The girder belt is in the form of forking at the tip of the filling block and extending to wrap the filling block, so that the appearance of the root can be effectively maintained, and the load can be efficiently transferred. The blade or flexbeam use loads can be divided into flap, lag and twist, where flap loads cause the tip of the pad to press against the longerons at the bifurcation, creating stresses perpendicular to the fiber direction. At present, most of the blade girders are made of unidirectional belt materials, so that the blade girders have strong bearing capacity in the fiber direction but have weak bearing capacity perpendicular to the fiber direction. Therefore, the split part of the girder can be continuously expanded, and fatigue failure is caused.

At present, in a main rotor flexible beam of a certain type of helicopter, cracks appear in a bifurcation area for many times in a flapping fatigue test, so that the test is finished. During use, the crotch region of the tension torsion bar often develops cracks over the service life. And (4) counting fatigue failure characteristics of the paddle, wherein more than half of failure problems occur in a girder bifurcation area of a paddle root. Therefore, solving the stress concentration problem at the position can effectively prolong the service life of the rotor system.

The prior art designs often achieve the goal of reducing the extrusion stress by increasing the cross-sectional area of the tip of the filler block. However, as the cross-sectional area increases, the transition becomes severe, the angle of divergence of the girder becomes larger, the load transmission becomes more difficult, and the fatigue performance is also deteriorated, so that the method is not preferable. Some university groups of domestic subjects are studying to weave fibers perpendicular to the direction of the girder fibers in the crotch region by a three-dimensional weaving method to enhance the strength in that direction. However, the method is still in a searching stage, has no successful case, and has huge cost, and mass production cannot be carried out. At present and in the next few years, three-dimensional weaving cannot be applied to the research and manufacture of domestic rotor wing composite materials.

Disclosure of Invention

In order to solve the problems, the invention provides a high-fatigue-strength transition section laying layer of a bifurcation area and a using method thereof based on the structural characteristics of a rotor wing composite material.

The technical scheme of the invention is as follows:

a layer is spread on a high fatigue strength transition section of a bifurcation area, which comprises V-shaped glass cloth and Y-shaped glass cloth, wherein the V-shaped glass cloth and the Y-shaped glass cloth are both prepreg of plus or minus 45-degree epoxy resin glass fiber fabric; the sharp angle end of the Y-shaped glass cloth is wrapped outside the sharp angle of the V-shaped glass cloth, and the other end of the Y-shaped glass cloth extends into a forked groove of a girder belt of the helicopter blade.

Further, the width of the tip of the filling block is 0.3mm to 0.4mm, and the angle is not more than 20 degrees.

Further, the V-shaped glass cloth is a continuous and uncut glass fiber fabric.

Furthermore, the Y-shaped glass cloth is formed by bonding two glass cloths.

Furthermore, the joint of the tip of the forked section of the Y-shaped glass cloth and the V-shaped glass cloth is provided with two times of chamfers which are convex and concave.

Furthermore, the filling blocks, the V-shaped glass cloth and the tips of the Y-shaped glass cloth facing the girder strips are all provided with chamfers.

A method of using a high fatigue strength transition segment ply in a bifurcation region, comprising the steps of:

prefabricating a solidified helicopter blade filling block;

laying V-shaped glass cloth at the sharp corner of the helicopter blade filling block, and then laying Y-shaped glass cloth;

bonding the girder belt outside the sharp corner of the helicopter blade filling block wrapped with the V-shaped glass cloth and the Y-shaped glass cloth;

and step four, integrally molding by mould pressing and thermosetting.

Furthermore, the girder belt in the third step is an epoxy resin glass fiber prepreg belt.

The invention has the beneficial effects that:

1. the layering of the high fatigue strength transition section in the bifurcation area can greatly enhance the fatigue strength and effectively prolong the service life of the root of the blade while ensuring that the structural rigidity is unchanged.

2. Compared with the traditional laying layer, the laying layer has better manufacturability, and the glass fiber of the girder is not easy to wrinkle in the mould pressing process.

3. The scheme has strong operability and extremely low additional cost.

Drawings

FIG. 1 is a schematic view of a ply layout of a high fatigue strength transition at a bifurcation region;

the device comprises 1-V-shaped glass cloth, 2-Y-shaped glass cloth, 3-filling blocks and 4-girder belts.

Detailed Description

This section is an example of the present invention and is provided to explain and illustrate the technical solutions of the present invention. The embodiments of the invention and the features of the embodiments can be combined with each other without conflict.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate directions or positional relationships to give the drawings the orientation or positional relationships, and are used for convenience of description and simplicity of description, but do not indicate or imply that the device or case being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include more than one of the feature. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specified.

In the description of the present invention, it should be noted that unless otherwise explicitly stated or limited, the terms "mounted," "connected" and "connected" should be interpreted broadly, and may be, for example, a fixed connection, a detachable connection or an integrated connection; the connection can be mechanical connection or point connection; the connection may be direct or indirect via an intermediate medium, and may be a communication between the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

A layer is spread on a high fatigue strength transition section of a bifurcation area, which comprises a V-shaped glass cloth 1, a Y-shaped glass cloth 2,V and a Y-shaped glass cloth 2, wherein the V-shaped glass cloth 1 and the Y-shaped glass cloth 2 are both made of +/-45-degree epoxy resin glass fiber fabric prepreg; the sharp end of the V-shaped glass cloth 1 wraps the sharp part of the filling block 3 of the helicopter blade, the sharp end of the Y-shaped glass cloth 2 wraps the sharp corner of the V-shaped glass cloth 1, and the other end of the Y-shaped glass cloth 2 extends into a forked groove of a girder belt 4 of the helicopter blade.

The width of the tip of the filling block 3 is 0.3mm to 0.4mm, and the angle is not more than 20 degrees.

The V-shaped glass cloth 1 is a continuous, uncut glass fiber fabric.

The Y-shaped glass cloth 2 is formed by bonding two glass cloths.

The joint of the tip of the branch section of the Y-shaped glass cloth 2 and the V-shaped glass cloth 1 is provided with two times of chamfers which are convex and concave.

The filling block 3, the V-shaped glass cloth 1 and the tip of the Y-shaped glass cloth 2 facing the girder belt 4 are all provided with a chamfer.

A method of using a high fatigue strength transition segment ply in a bifurcation region, comprising the steps of:

prefabricating a solidified helicopter blade filling block;

laying V-shaped glass cloth at the sharp corner of the helicopter blade filling block, and then laying Y-shaped glass cloth;

bonding the girder belt outside the sharp corner of the helicopter blade filling block wrapped with the V-shaped glass cloth and the Y-shaped glass cloth;

and step four, integrally molding by mould pressing and thermosetting.

And step three, the girder belt is an epoxy resin glass fiber prepreg belt.

The high fatigue strength transition section layer structure of the bifurcation area consists of two glass cloths, a filling block 3 and a girder belt 4. The two glass cloth prepregs are respectively in a V shape and a Y shape, the tip parts of the filling blocks 3 are sequentially wrapped, the girder belts 4 on the two sides are bonded with the glass cloth and the filling blocks 3, the whole body is molded by mould pressing and thermosetting, and the structural layout is as shown in figure 1. The two pieces of glass cloth are prepreg of +/-45-degree epoxy resin glass fiber fabrics, the filling blocks 3 are epoxy resin chopped fiber pre-cured pieces, the girder belt 4 is an epoxy resin glass fiber pre-cured belt, and the whole body is molded through mould pressing and thermosetting.

The width of the tip of the filling block of the transition section stacking layer is very small and ranges from 0.3mm to 0.4mm, and the angle does not exceed 20 degrees.

The V-shaped glass cloth is continuous cloth and can not be cut.

The Y-shaped glass cloth is formed by bonding two glass cloths.

Chamfering is required to be carried out twice at the joint of the tip of the forked section of the Y-shaped glass cloth and the V-shaped cloth; the chamfer is not required, the sharp angle can generate girder fiber folds due to uneven transition, the girder fiber folds can be generated at the rear sharp angle after the chamfer is performed for one time, and the girder fiber folds can not be generated after the chamfer is performed for two times, namely, the chamfer is performed downwards firstly and then the chamfer is performed upwards.

The girder belt is branched at the tip of the Y-shaped glass cloth.

The tips of the filler blocks, the V-shaped cloth and the Y-shaped cloth need to be chamfered, the fiber folds of the crossbeam at the sharp corners due to uneven transition are prevented, and stress concentration is also prevented.

The foregoing is merely a detailed description of the embodiments of the present invention, and some of the conventional techniques are not detailed. The scope of the present invention is not limited thereto, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention will be covered by the scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (8)

1. The high-fatigue-strength transition section laying layer of the bifurcation area is characterized by comprising V-shaped glass cloth (1) and Y-shaped glass cloth (2), wherein the V-shaped glass cloth (1) and the Y-shaped glass cloth (2) are both prepreg of +/-45-degree epoxy resin glass fiber fabric; the sharp-angle end of the V-shaped glass cloth (1) wraps the sharp part of the filling block (3) of the helicopter blade, the sharp-angle end of the Y-shaped glass cloth (2) wraps the sharp angle of the V-shaped glass cloth (1), and the other end of the Y-shaped glass cloth (2) extends into a forked groove of a girder belt (4) of the helicopter blade.

2. A bifurcation area high fatigue strength transition ply according to claim 1, wherein the filler piece (3) has a tip width of 0.3mm to 0.4mm and an angle of not more than 20 °.

3. The bifurcation area high fatigue strength transition piece lay-up of claim 1, wherein the V-shaped glass cloth (1) is a continuous, uncut fiberglass fabric.

4. The bifurcation area high fatigue strength transition layer according to claim 1, wherein the Y-shaped glass cloth (2) is formed by bonding two glass cloths.

5. The bifurcation area high fatigue strength transition layer spreading according to claim 1, wherein the junction of the bifurcation tip of the Y-shaped glass cloth (2) and the V-shaped glass cloth (1) is provided with two chamfers which are convex and concave.

6. The bifurcation area high fatigue strength transition layer overlay according to claim 1, wherein the filler block (3), the V-shaped glass cloth (1) and the tip of the Y-shaped glass cloth (2) facing the girder strip (4) are chamfered.

7. A method of using a bifurcation area high fatigue strength transition ply, using the bifurcation area high fatigue strength transition ply of any one of claims 1 to 6, comprising the steps of:

prefabricating a solidified helicopter blade filling block;

laying V-shaped glass cloth at the sharp corner of the helicopter blade filling block, and then laying Y-shaped glass cloth;

bonding the girder belt outside the sharp corner of the helicopter blade filling block wrapped with the V-shaped glass cloth and the Y-shaped glass cloth;

and step four, integrally molding by mould pressing and thermosetting.

8. The method of using a bifurcation area high fatigue strength transition section lay-up as claimed in claim 7, wherein the girder belt of step three is an epoxy resin fiberglass prepreg belt.

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