CN104760300A - Thin wall cylindrical structure - Google Patents

Abstract

The invention discloses a thin wall cylindrical structure, which comprises multiple thin wall single layers with fibers; a spreading method of the fibers in each thin wall single layer is as follows: the track of the fibers is divided into multiple zones along the circumferential direction of a cylinder and the directional angle of the fibers at the boundary of each zone is different with others; meanwhile, the directional angle of each fiber in each zone changes in a linear or curve manner according to the angle of each boundary. According to the thin wall cylindrical structure, by controlling the drawing direction of a fiber bundle, the fiber direction changing continuously along the spatial position can be freely designed in each single layer; the purpose of adjusting the rigidity and the strength in each direction is realized; the entire mechanical performance is improved and the weight for desired structural performance can be minimized.

Description

Thin-walled cylindrical structure

technical field

The invention relates to the technical field of material and structure design, in particular to a thin-walled cylindrical structure of curved fiber composite material.

Background technique

Due to the characteristics of simple structure, reasonable force, low material consumption, and easy processing, thin-walled cylindrical structures are widely used in engineering and even in the field of life. However, the disadvantage is that the thin-walled cylindrical parts are prone to buckling. From a structural point of view, there are two ways to increase the critical buckling load of thin-walled cylindrical parts: one is to increase the wall thickness, but increasing the wall thickness will inevitably increase the weight, which is not allowed in the aerospace field; the other is to adopt a stringer structure, To a certain extent, its bending resistance can be improved, but to a certain extent, it causes a complex structure and increases the layout space of the thin-walled cylinder.

Traditional fiber composite parts are prepared by fiber fabrics formed by laying parallel and straight fibers. The fiber composite parts are prone to buckling failure when subjected to in-plane compression and shearing.

Contents of the invention

In view of this, the object of the present invention is to propose a thin-walled cylindrical structure to increase the critical buckling load of the thin-walled cylindrical structure.

Based on the above-mentioned purpose, the thin-walled cylindrical structure provided by the present invention includes several layers of thin-walled single layers laid with fibers, and the track laying mode of fibers in each thin-walled single layer is divided into multiple Different fiber direction angles are set at the boundary of each region, and the fiber direction angle in each region changes linearly or in a curve according to the angle at the boundary.

As an embodiment of the present invention, the linear or curved variation in each region is at least one of a first-order straight line, a second-order parabola, a third-order curve and a B-spline curve.

As another embodiment of the present invention, the fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

In the formula, θ is the changing angle of the circumference of the cylinder, T _i and T _i+1 are the fiber direction angles at the boundaries of each region of the thin-walled monolayer, respectively, and n is the number of regions divided along the circumference of the cylinder.

As a preferred embodiment of the present invention, the fiber direction angle in each region changes in a curve, and the trajectory equation of the fiber is:

or

In the formula, θ is the changing angle of the circumference of the cylinder, T _i and T _i+1 are the fiber direction angles at the boundaries of each region of the thin-walled monolayer, respectively, and n is the number of regions divided along the circumference of the cylinder.

As a preferred embodiment of the present invention, the cylinder is equally divided into multiple regions along the circumferential direction of the cylinder.

As an embodiment of the present invention, the track laying method of fibers in each thin-walled single layer is divided into 6 to 10 areas along the circumferential direction of the cylinder, and different fiber directions are set at the boundary of each area. For the angles T ₁ , T ₂ , T ₃ , T ₄ , . . . , the odd-numbered fiber direction angles are 0-45°, and the even-numbered fiber direction angles are 45-90°.

As a preferred embodiment of the present invention, among the odd-numbered fiber direction angles, the difference between fiber direction angles of adjacent numbers is 5° to 15°.

As a preferred embodiment of the present invention, among the even-numbered fiber direction angles, the difference between fiber direction angles of adjacent numbers is 0.5° to 25°.

As a preferred embodiment of the present invention, n is 8.

It can be seen from the above that the thin-walled cylindrical structure provided by the present invention can freely design the fiber orientation that changes continuously with the spatial position in each single layer by controlling the pulling direction of the fiber tow, so as to adjust the rigidity in all directions. In order to improve the overall mechanical properties and minimize the weight for the required structural properties, the thin-walled cylindrical structure optimizes the fiber angle arrangement through a reasonable layup design to maximize the buckling resistance Optimization, so as to achieve better lightweight design in the engineering field, can contribute to both improving structural performance and reducing energy consumption.

Description of drawings

Fig. 1 is a schematic diagram of the definition of a fiber path direction angle according to an embodiment of the present invention;

Fig. 2 is the fiber direction angle on the boundary of each layer of 8 regions of the embodiment of the present invention, and these 8 fiber direction angles are used as optimized design variables;

Fig. 3 is a schematic diagram of arranging curved fibers along the length direction according to an embodiment of the present invention;

Fig. 4 is a schematic diagram of arranging curved fibers along the circumferential direction according to an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Referring to FIG. 1 , it is a schematic diagram of the definition of the fiber path direction angle according to the embodiment of the present invention. The thin-walled tubular structure provided by the present invention comprises several layers of thin-walled monolayers laid with fibers, and the track laying mode of fibers in each thin-walled monolayer is divided into multiple regions along the circumferential direction of the cylinder, and each Different fiber direction angles T (T ₁ , T ₂ , T ₃ , T ₄ , .....) are set at the boundary of the region, and the fiber direction angle in each region changes linearly according to the angle at the boundary or curve change The thin-walled cylindrical structure is a composite material laid with curved fibers, and its whole is a cylindrical structure made of multi-layer composite materials formed by fibers with a certain track under the action of sutures or adhesives. The fibers may be carbon fibers, glass fibers, and the like. According to Fig. 1, in the present invention, the fiber direction angle T is defined as the fiber tangential angle tangent to the surface of the cylinder at the boundary of the region, and θ is defined as the circumferential direction between the fibers on the surface of the cylinder and the fibers at _T1. angle.

As an embodiment of the present invention, the linear or curved variation in each region is at least one of a first-order straight line, a second-order parabola, a third-order curve and a B-spline curve.

For example, the fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

In the formula, θ is the changing angle of the cylinder circumference, T _i and T _i+1 are the fiber direction angles at the boundary of each region of the thin-walled monolayer, respectively, and n is the number of regions divided along the direction of the cylinder circumference. Preferably, n is the number of regions equally divided along the circumferential direction of the cylinder.

Second-order parabolic trajectory equation:

The parameter description is the same as above.

The third-order curve trajectory equation:

The parameter description is the same as above.

In order to ensure the reliability of the design and ensure the feasibility of manufacturing, it is necessary to reasonably limit the number of fiber direction angles at the boundary of the area. The track laying method of fibers in each single layer can be divided into 8 according to the circumferential direction of the cylinder. Each region (region 1, region 2...region 8), the fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

It should be noted that since the fibers are laid in the circumferential direction of the cylinder, T ₉ is T ₁ , as shown in FIG. 2 .

As another embodiment of the present invention, the path laying method of fibers in each single layer can be divided into 10 areas in the circumferential direction of the cylinder, or can be divided into 7 areas, or 6 areas and so on.

Further, different fiber direction angles T ₁ , T ₂ , T ₃ , T ₄ , ....., fiber directions with odd numbers (T ₁ , T ₃ , T ₅ .....) are set at the boundary of each region The angle is 0-45°, and the fiber direction angle of even numbers (T ₂ , T ₄ , T ₆ . . . ) is 45-90°.

As a preferred embodiment of the present invention, among the odd-numbered fiber direction angles, the difference between fiber direction angles of adjacent numbers is 5° to 15°. More preferably, among the even-numbered fiber direction angles, the difference between fiber direction angles of adjacent numbers is 0.5° to 25°.

Example 1

The simulation modeling calculation is carried out in the Abaqus software, the size is φ610×810mm, and the wall thickness of the cylinder is t=3.2mm. It is formed by laying 16 layers of balanced and symmetrical curved fibers [±θ(x)] _4s , and the thickness of each layer is 0.2mm. The material parameters of the fibers are as follows:

project value Fiber direction Young's modulus E1 181Mpa Fiber transverse Young's modulus E2 10.27Mpa

In-plane shear modulus G12 7.17Mpa Poisson's ratio v12 0.28 density 1500kg/ ^m3

Loading method: The two free ends of the cylinder are fully fixed, and a pure bending moment of 1000Nm is applied on the outer surface of the cylinder at the middle end of the length. In the simulation modeling in Abaqus software, the model grid is divided into 231 grids in the length direction and 121 grids in the diameter direction. The track laying method of fibers in each single layer can be divided into 8 areas in the direction of the cylinder circumference, and the fiber direction angle at the boundary of each area of the single layer is:

direction angle T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ T ₇ T ₈ curve 27.2° 54.3° 17.7° 57.9° 26.6° 78.3° 36.4° 78.8°

The fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

According to the design guidelines for composite single layer layup sequence:

(1) To eliminate unnecessary (and difficult to analyze) membrane/bend couplings, the lay-up sequence of thin-walled cylinders should be symmetrical.

(2) To eliminate tension/shear coupling, the ply set should be balanced (in a thin-walled cylinder, each Laminates shall have a corresponding layer).

(3) In order to avoid bending/torsion coupling as much as possible, and The plies should be brought together.

As shown in Figures 3 and 4.

Comparing the thin-walled cylinder structure obtained by the above laying method with another group of composite thin-walled cylinders made of 16 layers of balanced and symmetrical linear fibers [±45,0 ₂ ,±45,90 ₂ ] _s direction angles, the results as follows:

Fiber layout straight line curve critical buckling load value 6624N 7242N

Accordingly, it can be seen that the buckling resistance of the thin-walled cylindrical structure provided by the present invention is significantly stronger than that of the ordinary linear fiber cylindrical structure.

Example 2

The track laying method of fibers in each single layer can be divided into 8 areas in the direction of the cylinder circumference, and the fiber direction angle at the boundary of each area of the single layer is:

direction angle T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ T ₇ T ₈ curve 25.8° 58.6° 37.9° 66.2° 22.4° 61.6° 26.3° 49.2°

The fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

Others are the same as embodiment 1.

Comparing the thin-walled cylinder structure obtained by the above laying method with another group of composite thin-walled cylinders made of 16 layers of balanced and symmetrical linear fibers [±45,0 ₂ ,±45,90 ₂ ] _s direction angles, the results as follows:

Fiber layout straight line curve critical buckling load value 6624N 7201N

Accordingly, it can be seen that the buckling resistance of the thin-walled cylindrical structure provided by the present invention is significantly stronger than that of the ordinary linear fiber cylindrical structure.

Example 3

The track laying method of fibers in each single layer can be divided into 6 regions in the direction of the cylinder circumference, and the fiber direction angle at the boundary of each region of the single layer is:

direction angle T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ curve 26.6° 59.6° 17.5° 59.9° 32.5° 77.9°

The fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

Others are the same as embodiment 1.

Comparing the thin-walled cylinder structure obtained by the above laying method with another group of composite thin-walled cylinders made of 16 layers of balanced and symmetrical linear fibers [±45,0 ₂ ,±45,90 ₂ ] _s direction angles, the results as follows:

Fiber layout straight line curve critical buckling load value 6624N 6855N

Accordingly, it can be seen that the buckling resistance of the thin-walled cylindrical structure provided by the present invention is significantly stronger than that of the ordinary linear fiber cylindrical structure.

Example 4

The track laying method of fibers in each single layer can be divided into 10 regions in the direction of the cylinder circumference, and the fiber direction angle at the boundary of each region of the single layer is:

direction angle T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ T ₇ T ₈ T ₉ T ₁₀ curve 28.1° 59.1° 16.0° 62.2° 30.6° 82.6° 23.5° 55.9° 38.0° 69.2°

The fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

Others are the same as embodiment 1.

Comparing the thin-walled cylinder structure obtained by the above laying method with another group of composite thin-walled cylinders made of 16 layers of balanced and symmetrical linear fibers [±45,0 ₂ ,±45,90 ₂ ] _s direction angles, the results as follows:

Fiber arrangement straight line curve critical buckling load value 6624N 6793N

Accordingly, it can be seen that the buckling resistance of the thin-walled cylindrical structure provided by the present invention is significantly stronger than that of the ordinary linear fiber cylindrical structure.

Example 5

The track laying method of fibers in each single layer can be divided into 8 areas in the direction of the cylinder circumference, and the fiber direction angle at the boundary of each area of the single layer is:

direction angle T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ T ₇ T ₈ curve 34.1° 51.4° 23.3° 65.1° 28.1° 76.9° 18.1° 48.0°

The fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

Others are the same as embodiment 1.

Comparing the thin-walled cylinder structure obtained by the above laying method with another group of composite thin-walled cylinders made of 16 layers of balanced and symmetrical linear fibers [±45,0 ₂ ,±45,90 ₂ ] _s direction angles, the results as follows:

Fiber layout straight line curve critical buckling load value 6624N 7222N

Accordingly, it can be seen that the buckling resistance of the thin-walled cylindrical structure provided by the present invention is significantly stronger than that of the ordinary linear fiber cylindrical structure.

Example 6

The track laying method of fibers in each single layer can be divided into 8 areas in the direction of the cylinder circumference, and the fiber direction angle at the boundary of each area of the single layer is:

direction angle T ₁ T ₂ T ₃ T ₄ T ₅ T ₆ T ₇ T ₈ curve 17.6° 71.9° 26.6° 83.8° 39.6° 70.2° 34.8° 86.5°

The fiber direction angle in each region changes linearly, and the trajectory equation of the fiber is:

Others are the same as embodiment 1.

Comparing the thin-walled cylinder structure obtained by the above laying method with another group of composite thin-walled cylinders made of 16 layers of balanced and symmetrical linear fibers [±45,0 ₂ ,±45,90 ₂ ] _s direction angles, the results as follows:

Fiber layout straight line curve critical buckling load value 6624N 7209N

Accordingly, it can be seen that the buckling resistance of the thin-walled cylindrical structure provided by the present invention is significantly stronger than that of the ordinary linear fiber cylindrical structure.

Advantage and effect of the present invention:

(1) Compared with ordinary composite material cylinders, the buckling resistance is significantly improved;

(2) Compared with the ordinary linear fiber composite material cylinder, the designability is stronger.

It can be seen that the thin-walled cylindrical structure provided by the present invention can freely design the fiber orientation that changes continuously with the spatial position in each single layer by controlling the pulling direction of the fiber tow, so as to achieve the purpose of adjusting rigidity and strength in various directions , so as to improve the overall mechanical properties and minimize the weight for the required structural properties. The thin-walled cylindrical structure optimizes its fiber angle arrangement through a reasonable layup design, which can maximize the buckling resistance. Better lightweight design in the engineering field can contribute to both improving structural performance and reducing energy consumption.

Those of ordinary skill in the art should understand that: the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention etc., should be included within the protection scope of the present invention.

Claims (9)

1. a thin-wall tube-shaped structure, it is characterized in that, comprise the thin-walled individual layer that some layers are equipped with fiber, in every layer of thin-walled individual layer, the track lay mode of fiber is divided into multiple region along the circumferencial direction of cylinder, arrange different machine direction angles at the boundary in each region, the machine direction angle simultaneously in each region carries out linear change or curvilinear motion according to the angle of described boundary.

2. thin-wall tube-shaped structure according to claim 1, is characterized in that, the linear or curvilinear motion mode in described each region is single order straight line, second order parabola, at least one in third degree curve and B-spline curves.

3. thin-wall tube-shaped structure according to claim 2, is characterized in that, the linear change of machine direction angle in described each region, and the equation of locus of its fiber is:

In formula, θ is cylindrical barrel angle changing, T _i, T _i+1be respectively the machine direction angle at each zone boundary place of thin-walled individual layer, n is the areal divided along the circumferencial direction of cylinder.

4. thin-wall tube-shaped structure according to claim 2, is characterized in that, the machine direction angle in described each region becomes curvilinear motion, and the equation of locus of its fiber is:

Or

In formula, θ is cylindrical barrel angle changing, T _i, T _i+1be respectively the machine direction angle at each zone boundary place of thin-walled individual layer, n is the areal divided along the circumferencial direction of cylinder.

5. the thin-wall tube-shaped structure according to claim 3 or 4, is characterized in that, the circumferencial direction equivalent along cylinder is divided into multiple region.

6. thin-wall tube-shaped structure according to claim 1, is characterized in that, in described every layer of thin-walled individual layer, the track lay mode of fiber is divided into 6 ~ 10 regions along cylindrical barrel direction, arranges different machine direction angle T at the boundary in each region ₁, T ₂, T ₃, T ₄... .., the machine direction angle of odd indexed is 0 ~ 45 °, and the machine direction angle of even number sequence number is 45 ~ 90 °.

7. thin-wall tube-shaped structure according to claim 6, is characterized in that, in the machine direction angle of described odd indexed, the difference of the machine direction angle of adjacent sequence number is 5 ~ 15 °.

8. thin-wall tube-shaped structure according to claim 6, is characterized in that, in the machine direction angle of described even number sequence number, the difference of the machine direction angle of adjacent sequence number is 0.5 ~ 25 °.

9. thin-wall tube-shaped structure according to claim 1, is characterized in that, n is 8.