A forming method for loose wires at the end frame of grid ribs

Abstract

The present invention provides a method for forming loose wires at the end frame of a grid rib. The present invention relates to the design of a loose wire process for the end frame of a composite material grid rib, belonging to the technical field of forming composite material grid ribs. The loose wire process design is carried out at the end frame of the composite material with grid ribs, including the dispersion design of the end frame wire bundles, the analysis of the binding force of the wire bundles and the layout of the loose wires. The method of the present invention solves the problems of the force connection at the boundary of the end frame of the grid rib and the problem of excessive thickness in the prior art, and realizes high strength at the end frame of the grid rib.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material grid rib forming, and particularly relates to a method for forming loose filaments at the end frame of a grid rib. Background Art

[0002] The automatic fiber placement technology is to lay several pre-impregnated filaments on the surface of a mandrel in a ribbon shape after being pressed by a multi-axis placement head (robot arm) according to the laying direction determined by the design requirements, and then compact and shape them. The whole process is completed by a computer measurement and control and coordination system. Carbon fiber grid ribs are a new type of fiber composite structure, with good overall mechanical properties and anti-slip properties, and have been widely used in the field of structural reinforcement in recent years.

[0003] However, in the prior art, the opening structure of the rib, the defects of adhesive bonding and their failure propagation phenomena seriously affect the stability of the structure. There is no research on the forming of loose filaments of composite material grid ribs, and many process improvements or upgrades are necessary. Summary of the Invention

[0004] To solve the above problems, the present invention discloses a method for forming loose filaments at the end frame of a grid rib, including the following steps:

[0005] Step 1: End frame partition design; when laying the grid rib, the end frame is divided into a front end frame and a rear end frame; the grid rib structure is composed of hoop ribs and longitudinal ribs;

[0006] Step 2: Loose filament partition design; each longitudinal rib filament is divided into n pieces; the loose filament area is divided into area I and area II, and the number of loose filament pieces is selected according to the length of the end frame. The width of the end frame is d, and the loose filament range is c;

[0007] Step 3: Loose filament angle design; when loosening the filaments, with the positive direction of the end frame as the reference, the angle is 0°, and the maximum angle of deflection of the pre-impregnated filament relative to the end frame is 30°;

[0008] Step 4: End frame pre-preg cutting design; cuttings are designed at the front and rear end frame positions of the mold for the pre-preg; the cutting size is 70°;

[0009] Step 5: Sequential fiber placement design; at the end frame of the mold and the inner core ribs of the mold are placed simultaneously, and the automatic fiber placement forming method is used to place and compact at the front end frame. The width of the front and rear end frames is 40 - 60 mm. Starting from the front end frame to loosen the filaments, the starting angle is α. After each layer of fiber placement at the end frame is completed, change the loose filament angle to θ, and disperse left and right alternately from the middle to lay the next layer of loose filament ribs. The loose filament length is l mm. To meet the uniformity of loose filaments and reduce blank gaps, the loose filaments in area I and area II are laid alternately;

[0010] Step 6: Trim the edges to cut off the excess pre-preg to make the loose filament shape fan-shaped; the loose filament width is 30 - 50 mm;

[0011] Step 7: Repeat step (5) until all longitudinal bars are laid. In step 2, the number of paving layers is k layers, the thickness of each layer of prepreg is 0.125 mm, and the width is x, where x ranges from 4 to 10 mm, and commonly used prepreg wires are 5 mm, 6.35 mm, and 8 mm.

[0012] In step 3: According to the spreading wire angle, a trapezoidal cut is made at the spreading wire position of the end frame prepreg. The upper side of the trapezoid is a, the bottom side is b, and the height is h.

[0013] The spreading wire range c can be expressed as:

[0014]

[0015] The number of spreading wires m can be expressed as:

[0016]

[0017] The spreading wire angle θ can be expressed as:

[0018]

[0019] In step 4: A cut is made at the overlapping position of the spreading wire position and the end frame prepreg, and after curing is completed, machining treatment is carried out.

[0020] The mold end frame and the mold inner core rib are laid simultaneously. The automatic fiber placement forming method is used to lay and compact the front end frame. Spreading wire starts from the front end frame. After each layer of wire laying on the end frame is completed, the spreading wire angle is changed, and the next layer of spreading wire rib and end frame are laid.

[0021] Furthermore, this spreading wire process improves the bonding ability between the rib and the end frame, changes the stress distribution of the original structure, and improves the bonding quality between the end frame and the stiffened structure.

[0022] Furthermore, a cut is made at the connection between the end frame and the spreading wire to solve problems such as wrinkles and uneven thickness at the spreading wire position.

[0023] Beneficial effects

[0024] (1) Relying on the process solution provided by the present invention, the bonding ability between the rib and the end frame is improved, and the interface peeling problem caused by too thick ribs and uneven stress distribution at the end frame is solved.

[0025] (2) The process solution of the present invention adopts a cut design for the dispersed wire bundle port to avoid defects such as wrinkles and delamination caused by uneven spreading wire thickness. Description of the drawings

[0026] Figure 1 It is a partial schematic diagram of the longitudinal bar spreading wire in area I with a prepreg width of 6.35 mm, and the spreading wire angle is 20°;

[0027] Figure 2 It is a partial schematic diagram of the longitudinal wire dispersion in the II region with the width of the prepreg being 6.35 mm and the dispersion angle being 20°;

[0028] Figure 3 It is a schematic diagram of the superimposed laying of the I region and the II region with the end frame being 40 mm;

[0029] Figure 4 It is a partial schematic diagram of the longitudinal wire dispersion in the I region with the width of the prepreg being 5 mm and the dispersion angle being 10°;

[0030] Figure 5 It is a partial schematic diagram of the longitudinal wire dispersion in the II region with the width of the prepreg being 5 mm and the dispersion angle being 5°;

[0031] Figure 6 It is a schematic diagram of the superimposed laying of the I region and the II region with the end frame being 60 mm.

[0032] Figure 7 It is the front view and top view of the shear notch.

[0033] Figure 8 It is the overall diagram of the wire dispersion. Specific Embodiments

[0034] The following further clarifies the present invention in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the accompanying drawings, and the terms "inner" and "outer" respectively refer to the directions towards or away from the geometric center of a specific component.

[0035] Embodiment 1

[0036] For the end frame wire dispersion process of this embodiment, there are end frames at the ends of the housing, namely the front end frame and the rear end frame, as Figure 1 .

[0037] The grid rib structure is composed of hoop ribs and longitudinal ribs and can withstand a large axial pressure.

[0038] Step 1: Determine the width x of the prepreg wire and the maximum deflection angle;

[0039] Step 2: Measure the width d of the end frame;

[0040] Step 3: Determine the size of the shear notch, including the upper side a, height h and bottom side b, and calculate the maximum range c of the wire dispersion;

[0041] Step 4: Calculate the number m of the dispersed wires and the dispersion angle θ through the width x of the prepreg and the maximum range c of the wire dispersion;

[0042] Step 5: Plan the actual number of loose filaments and the actual loose filament angle by calculating the obtained number of loose filaments and the loose filament angle, and perform zoning and numbering;

[0043] Step 6: The length of the loose filament is less than the width of the end frame, and the length is l;

[0044] Step 7: Compact the longitudinal reinforcement prepreg at the front end of the filament laying head, and perform loose filament at the front and rear end frames, with the loose filament angle being θ;

[0045] Step 8: Specify that the positive direction of the end frame is 0°, and use the angle between the first longitudinal reinforcement prepreg and the positive direction of the end frame as the starting loose filament angle, with the starting angle being α;

[0046] Step 9: Perform loose filament of the second longitudinal reinforcement, with the loose filament angle being θ;

[0047] Step 10: Perform loose filament of the remaining longitudinal reinforcements, and lay the prepreg alternately on the left and right of the loose filament;

[0048] Embodiment 2

[0049] For the end frame loose filament process of this embodiment, there are end frames at the ends of the housing, namely the front end frame and the rear end frame, as Figure 1 .

[0050] The grid rib structure is composed of hoop ribs and longitudinal ribs and can withstand a large axial pressure.

[0051] Taking an end frame with a width of 40 mm as an example, the specific steps are as follows:

[0052] Step 1: Adopt the automatic fiber placement forming method to lay and compact at the front end frame. The fiber placement head starts to perform loose filament at the front end frame of the mold and lays the longitudinal reinforcement at the shear notch.

[0053] Step 2: Design a trapezoidal shear notch at the loose filament position of the end frame according to the maximum deflection angle of the prepreg, as Figure 7 , to solve the problems of loose filament wrinkles and uneven thickness.

[0054] Step 3: Perform loose filament laying in Area I. Use the angle between the first longitudinal reinforcement prepreg and the positive direction of the end frame as the starting loose filament angle, with the starting angle being 80°, as Figure 1 .

[0055] Step 4: Compact the longitudinal reinforcement prepreg at the front end of the fiber placement head, and perform loose filament at the front and rear end frames, with the loose filament angle being 20°, as Figure 1 .

[0056] Step 5: The length of the loose filament is less than the width of the end frame, and the length is 30 mm.

[0057] Step 6: Loosen the second longitudinal wire, with the loosening angle being 20°, and the included angle with the end frame being 100°.

[0058] Step 7: The second loosened prepreg wire is 20° different from the starting loosened prepreg wire.

[0059] Step 8: Loosen the third longitudinal wire, with the loosening angle being 20°, and the included angle with the end frame being 120°.

[0060] Step 9: Loosen the fourth longitudinal wire, with the loosening angle being 20°, and the included angle with the end frame being 60°. Do not perform the loosening operation on the fifth prepreg wire.

[0061] Step 10: Perform the loosening and laying in Area II, with the included angle between the first longitudinal prepreg wire and the positive direction of the end frame as the starting loosening angle, and the starting angle being 90°, as Figure 2 .

[0062] Step 11: Compact the longitudinal prepreg wire through the front end of the fiber placement head, and perform loosening at the front and rear end frames, with the loosening angle being 20°, as Figure 1 .

[0063] Step 12: The loosened length is less than the width of the end frame, and the length is 30 mm.

[0064] Step 13: Loosen the second longitudinal wire, with the loosening angle being 20°, and the included angle with the end frame being 70°.

[0065] Step 14: The second loosened prepreg wire is 20° different from the starting loosened prepreg wire.

[0066] Step 15: Loosen the third longitudinal wire, with the loosening angle being 20°, and the included angle with the end frame being 110°. Do not perform the loosening operation on the fourth prepreg wire.

[0067] Step 16: Lay in Area I and Area II alternately, as Figure 3 .

[0068] Step 17: The end frame layup and the rib layup are 100 layers, with each layer having a thickness of 0.125 mm and a width of 6.35 mm. Repeat the above laying and loosening steps to complete the layup.

[0069] Embodiment 3:

[0070] For the end frame loosening process of this embodiment, there are end frames at the ends of the housing, namely the front end frame and the rear end frame, as Figure 1 .

[0071] The grid rib structure is composed of hoop ribs and longitudinal ribs and can withstand a large axial pressure.

[0072] Taking the end frame with a width of 40 mm as an example, the specific steps are as follows:

[0073] Step 1: Lay and compact on the front frame by using the automatic fiber placement method. The fiber placement head starts to unwind the fiber at the front frame of the mold, and longitudinal fibers are laid at the cutting point after unwinding.

[0074] Step 2: Design a trapezoidal cutting point at the fiber unwinding position on the end frame according to the maximum deflection angle of the prepreg, as shown in Figure 7 , to solve the problems of fiber unwinding wrinkles and uneven thickness.

[0075] Step 3: Conduct fiber unwinding and laying in Area I. Take the angle between the first longitudinal prepreg and the positive direction of the end frame as the starting fiber unwinding angle, and the starting angle is 90°, as shown in Figure 1 .

[0076] Step 4: Compact the longitudinal prepreg through the front end of the fiber placement head, and conduct fiber unwinding at the front and rear end frames. The fiber unwinding angle is 10°, as shown in Figure 1 .

[0077] Step 5: The fiber unwinding length is less than the width of the end frame, and the length is 50 mm.

[0078] Step 6: Conduct fiber unwinding of the second longitudinal fiber, with the fiber unwinding angle of 10° and the angle with the end frame of 80°.

[0079] Step 7: The second unwound prepreg is 10° different from the starting unwound prepreg.

[0080] Step 8: Conduct fiber unwinding of the third longitudinal fiber, with the fiber unwinding angle of 10° and the angle with the end frame of 100°.

[0081] Step 9: Conduct fiber unwinding of the fourth longitudinal fiber, with the fiber unwinding angle of 10° and the angle with the end frame of 70°. The fifth to eighth fibers are alternately laid according to the above steps, and no fiber unwinding operation is performed on the eighth fiber.

[0082] Step 10: Conduct fiber unwinding and laying in Area II. Take the angle between the first longitudinal prepreg and the positive direction of the end frame as the starting fiber unwinding angle, and the starting angle is 90°, as shown in Figure 2 .

[0083] Step 11: Compact the longitudinal prepreg through the front end of the fiber placement head, and conduct fiber unwinding at the front and rear end frames. The fiber unwinding angle is 5°, as shown in Figure 1 .

[0084] Step 12: The fiber unwinding length is less than the width of the end frame, and the length is 50 mm.

[0085] Step 13: Conduct fiber unwinding of the second longitudinal fiber, with the fiber unwinding angle of 5° and the angle with the end frame of 85°.

[0086] Step 14: The second unwound prepreg is 5° different from the starting unwound prepreg.

[0087] Step 15: Loosen the third longitudinal wire, with a loosening angle of 5° and an included angle of 95° with the end frame. The fourth to eighth wires are alternately laid according to the above steps, and the eighth wire does not undergo the wire loosening operation.

[0088] Step 16: Lay in an alternating pattern in Zone I and Zone II, as Figure 3 .

[0089] Step 17: The end frame layup and the rib layup are 100 layers, with each layer having a thickness of 0.125 mm and a width of 5 mm. Repeat the above laying and wire loosening steps to complete the layup.

[0090] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A forming method for the loose wire of the grid rib end frame, characterized in that: It includes the following steps: Step 1: End frame partition design; when laying grid ribs, the end frame is divided into a front end frame and a rear end frame; the grid rib structure consists of circular ribs and longitudinal ribs; Step 2: Loose fiber partition design; each longitudinal rib bar is divided into n pieces of loose fiber; the loose fiber area is divided into areas Ⅰ and Ⅱ, and the number of loose fiber pieces is selected according to the length of the end frame; the width of the end frame is d, the loose fiber range is c; the number of loose fibers is m; Step 3: Loose fiber angle design; when loosening the fiber, with the positive direction of the end frame as the reference, the angle is 0°, and the starting loose fiber angle is the angle between the first longitudinal pre-impregnated fiber and the positive direction of the end frame, and the starting angle is α; the maximum angle between the pre-impregnated fiber and the perpendicular line of the positive direction of the end frame is 30°; Step 4: End frame pre-preg cutting design; cuttings are designed at the front and rear end frame positions of the mold for the pre-preg; Step 5: Sequential fiber placement design; at the end frame of the mold, it is placed simultaneously with the inner core ribs of the mold, and is placed and compacted at the front end frame by using the automatic fiber placement forming method; the width of the front and rear end frames is 40 - 60 mm; starting from the front end frame to loosen the fiber, the starting angle is α, after each layer of fiber placement at the end frame is completed, change the loose fiber angle to θ, disperse left and right alternately from the middle, lay the next layer of loose fiber ribs, the loose fiber length is l mm, in order to ensure uniform loose fiber and reduce gaps, the loose fiber in areas Ⅰ and Ⅱ is laid alternately; areas Ⅰ and Ⅱ have different starting angles or loose fiber angles; Step 6: Trim the edges to cut off the excess pre-impregnated fiber, so that the loose fiber shape is fan-shaped; the loose fiber width is 30 - 50 mm; Step 7: Repeat step (5) until all longitudinal ribs are laid.

2. The method for forming loose wires at the grid rib end frame according to claim 1, characterized in that: In step 2, the number of laying layers is 100, the thickness is 0.125 mm, and the width of each pre-impregnated fiber is x, where x is 4 - 10 mm.

3. A method for forming loose wires at the end frame of a grid rib according to claim 1, characterized in that: The loose fiber range c is expressed as: The width of the end frame is d, according to the loose fiber angle, a trapezoidal cut is made at the loose fiber position of the end frame pre-preg, the upper side of the trapezoid is a, the bottom side is b, and the height is h. The number of loose fibers m is expressed as: The width of each pre-impregnated fiber is x, where x is 4 - 10 mm; According to the size of the cut, calculate the loose fiber angle, the size of the cut is 70°, and the loose fiber angle θ is expressed as:

4. A method for forming loose filaments at the end frame of a grid rib according to claim 2, characterized in that: Pre-impregnated fibers with widths of 5 mm, 6.35 mm, and 8 mm are used.

5. A method for forming loose filaments at the end frame of a grid rib according to claim 1, characterized in that: In step 4, a cut is designed at the connection between the loose fiber position of the mold and the end frame, and after the curing of the loose fiber pre-preg is completed, machining treatment is carried out.

6. A method for forming loose filaments at the end frame of a grid rib according to claim 1, characterized in that: The size of the cut in step 4 is 70°.

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