Cutting method of T-shaped stringer preform

Abstract

This invention relates to the field of carbon fiber composite material processing technology, and discloses a cutting method for a T-shaped stringer preform, comprising the following steps: S1, vertically cutting according to the lower surface contour of the T-shaped stringer preform, with a cutting depth of the thickness h of the T-shaped stringer preform plus a first overcut; S2, chamfering the edge contour of the surface T-shaped stringer preform at a preset angle α along the fiber direction, with a cutting depth of the first depth along the thickness direction of the T-shaped stringer preform; S3, chamfering the edge of the T-shaped stringer preform at a preset angle α using multiple cuts along the thickness direction of the T-shaped stringer preform; S4, vertically cutting the contours of both ends of the T-shaped stringer preform, with a cutting depth of the thickness h of the T-shaped stringer preform plus a second overcut. The method of chamfering the edge contour of the surface T-shaped stringer preform at a preset angle α along the fiber direction, followed by chamfering the edge of the T-shaped stringer preform at a preset angle α using multiple cuts along the thickness direction of the T-shaped stringer preform, effectively avoids quality problems such as out-of-tolerance cutting dimensions and tearing in the T-shaped stringer preform.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite material processing technology, and in particular to a method for cutting a T-shaped stringer preform. Background Technology

[0002] Carbon fiber composites are a typical high-strength material, and due to their excellent properties, they are widely used in the main load-bearing structural components of civil aircraft, such as fuselages, wings, tail panels, and stringers. The manufacturing of fuselages, wings, tail panels, and stringers is mainly developing towards autoclave co-curing processes. This process significantly reduces manufacturing costs for stringer parts, which are numerous and have high individual curing costs. The key technology lies in the ultrasonic cutting technique for the net dimensions of the composite preform.

[0003] Composite preforms are composed of multiple layers of uncured carbon fibers and resin. The resin material is relatively soft, while the carbon fiber material is relatively hard. Cutting composite preforms requires solving the material property problem of cutting the harder carbon fibers while simultaneously cutting the softer resin between the carbon fibers. Currently, high-frequency vibration cutting of composite preforms using ultrasonic straight-blade cutters can effectively solve this material property problem. However, when multiple features are combined on the same part, the larger the chamfer angle, the longer the cutting length of the ultrasonic symmetrical straight-blade cutter in contact with the material, the greater the cutting resistance, the easier it is for the blade tip to deviate from its original position, and the more difficult it is to cut. During cutting, quality problems such as dimensional deviations and tearing are very likely to occur. Summary of the Invention

[0004] The purpose of this invention is to propose a cutting method for T-shaped stringer preforms, which solves the quality problems such as dimensional deviations and tearing that are easily caused during cutting in the prior art.

[0005] To achieve this objective, the present invention adopts the following technical solution: This invention provides a method for cutting a T-shaped stringer preform, comprising the following steps: S1. Cut vertically according to the lower surface contour of the T-shaped stringer preform, with a cutting depth of h of the T-shaped stringer preform plus the first overcut amount. S2. The edge profile of the surface T-shaped stringer preform is chamfered at a preset angle α and cut along the fiber, with the cutting depth along the thickness direction of the T-shaped stringer preform being the first depth. S3. Cut the edge strip with a pre-set angle α using multiple cuts according to the thickness direction of the T-shaped stringer preform; S4. Vertically cut the contours of both ends of the T-shaped stringer preform, with a cutting depth equal to the thickness h of the T-shaped stringer preform plus the second overcut amount.

[0006] The cutting method for this T-shaped stringer preform involves first vertically cutting along the lower surface contour of the T-shaped stringer preform to a depth equal to the thickness h of the T-shaped stringer preform plus a first overcut. Then, the edge contour of the surface T-shaped stringer preform is chamfered at a predetermined angle α, cut along the fiber direction to a depth equal to the first depth. The edge is then cut at a predetermined angle α using multiple cuts along the thickness direction of the T-shaped stringer preform. Finally, the two end contours of the T-shaped stringer preform are vertically cut to a depth equal to the thickness h of the T-shaped stringer preform plus a second overcut. This cutting method, with the edge contour of the surface T-shaped stringer preform being chamfered at a predetermined angle α along the fiber direction, avoids tearing of the surface layer. During further cutting, the edge is cut at a predetermined angle α using multiple cuts along the thickness direction of the T-shaped stringer preform, effectively preventing quality problems such as dimensional discrepancies and tearing in the T-shaped stringer preform.

[0007] As a preferred embodiment of the cutting method for the above-mentioned T-shaped stringer preform, in step S3, in the widening region of the T-shaped stringer preform, the cutting direction is from the allowance region to the net size region.

[0008] The above cutting method can effectively improve the cutting dimensional accuracy of the widened area.

[0009] As a preferred embodiment of the cutting method for the above-mentioned T-shaped stringer preform, in step S2, the first depth satisfies: 0.2mm ≤ first depth ≤ 1mm.

[0010] The first depth is taken within the above-mentioned range, which can cut the surface of the T-shaped stringer preform and avoid tearing during the cutting process.

[0011] As a preferred embodiment of the cutting method for the aforementioned T-shaped stringer preform, in step S3, the cutting depth of each cut is (h - first depth) / N, where N is a positive integer greater than 1.

[0012] The cutting depth of each cut is (h - first depth) / N, ensuring that the T-shaped stringer preform is cut by multiple cuts, reducing the cutting length and cutting resistance, and improving cutting accuracy.

[0013] As a preferred embodiment of the cutting method for the aforementioned T-shaped stringer preform, in step S3, the angle of each cut is the preset angle α, and the contact length L of the material cut by the blade is: cutting depth / sinα.

[0014] As a preferred embodiment of the cutting method for the aforementioned T-shaped stringer preform, the contact length L satisfies: L≤6mm.

[0015] The above settings prevent problems such as dimensional deviations and tearing caused by excessive contact length.

[0016] As a preferred embodiment of the cutting method for the above-mentioned T-shaped stringer preform, in step S3, the outer corner positions at both ends of the T-shaped stringer preform are overcut by a third overcut amount, and the third overcut amount satisfies: 2mm≤third overcut amount≤10mm.

[0017] The third overcut amount is made at the outer corner positions of both ends of the T-shaped stringer preform, so that the cut T-shaped stringer preform can be removed from the allowance area.

[0018] As a preferred embodiment of the above-mentioned cutting method for the T-shaped stringer preform, in step S3, when cutting at a preset angle α along the thickness direction of the T-shaped stringer preform, the overcut depth along the thickness direction of the T-shaped stringer preform is the second depth, and the second depth is ≤0.4mm.

[0019] The second depth satisfies the above conditions to avoid large steps in the preformed T-shaped stringer after cutting, thus ensuring cutting accuracy.

[0020] As a preferred embodiment of the cutting method for the above-mentioned T-shaped stringer preform, in step S3, when the T-shaped stringer preform has arc characteristics, the contact length L of the cutting blade is reduced.

[0021] When the T-shaped stringer preform has arc features, the contact length L of the cutting blade is reduced, thereby improving the cutting accuracy of the arc features.

[0022] As a preferred embodiment of the cutting method for the above-mentioned T-shaped stringer preform, the first overcut amount satisfies: 0.5mm ≤ first overcut amount < sacrificial layer thickness; And / or the second overcut amount satisfies: 0.5mm ≤ second overcut amount < sacrificial layer thickness.

[0023] The first and second overcut amounts are taken from the values ​​mentioned above, which can ensure the cutting accuracy of the T-shaped stringer preform, thereby facilitating the removal of the cut T-shaped stringer preform from the allowance area.

[0024] The beneficial effects of this invention are: The cutting method for the T-shaped stringer preform proposed in this invention first involves vertically cutting along the lower surface contour of the T-shaped stringer preform to a depth equal to the thickness h of the T-shaped stringer preform plus a first overcut. Then, the edge contour of the surface T-shaped stringer preform is chamfered at a predetermined angle α, cut along the fiber direction to a depth equal to a first depth. The edge is then cut at a predetermined angle α using multiple cuts along the thickness direction of the T-shaped stringer preform. Finally, the two end contours of the T-shaped stringer preform are vertically cut to a depth equal to the thickness h of the T-shaped stringer preform plus a second overcut. In this cutting method, the chamfered angle α cut along the fiber direction of the surface T-shaped stringer preform prevents tearing. Furthermore, the chamfered angle α cuts along the thickness direction of the T-shaped stringer preform during further cutting effectively prevent dimensional errors, tearing, and other quality problems in the T-shaped stringer preform. Attached Figure Description

[0025] Figure 1 This is a left view of the chamfering and cutting path of the edge strip of the T-shaped stringer preform provided by the present invention; Figure 2 This is a top view of the T-shaped stringer preform with the cutting direction and fiber direction provided by the present invention; Figure 3 This is a top view of the vertical cutting path of the edge strip of the T-shaped stringer preform provided by the present invention; Figure 4 This is a top view of the chamfering and cutting path of the edge strip of the T-shaped stringer preform provided by the present invention; Figure 5 This is a top view of the cutting path of the edge strip of the T-shaped stringer preform provided by the present invention; Figure 6 This is a top view of the cutting path of the T-shaped stringer preform provided by the present invention. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] In the current technology, composite preforms are composed of multiple layers of uncured carbon fibers and resin. The resin material is relatively soft, while the carbon fiber material is relatively hard. Cutting composite preforms requires cutting the harder carbon fibers while simultaneously cutting the softer resin between them. Currently, using ultrasonic straight-blade high-frequency vibration to cut composite preforms can effectively solve this material characteristic problem. However, when multiple features are combined on the same part, the larger the chamfer angle, the longer the cutting length of the ultrasonic symmetrical straight-blade tool in contact with the material, the greater the cutting resistance, the easier it is for the blade tip to deviate from its original position, and the more difficult it is to cut. During cutting, quality problems such as dimensional deviations and tearing are very likely to occur.

[0031] To solve the above problems, such as Figure 1 As shown, this embodiment provides a method for cutting a T-shaped stringer preform, used to cut a T-shaped stringer preform of carbon fiber composite material. The cutting method includes the following steps: S1. Make vertical cuts according to the lower surface contour of the T-shaped stringer preform, with a cut depth equal to the thickness h of the T-shaped stringer preform plus the first overcut (see...). Figure 1 and Figure 3 ).

[0032] The thickness of a typical T-shaped stringer preform is greater than 3mm.

[0033] The first overcut must satisfy the following condition: 0.5mm ≤ first overcut < sacrificial layer thickness; the sacrificial layer is a porous, permeable material fixed to the machine tool table or embedded in the tooling cutting groove, used to protect the machine tool table or part tooling. The sacrificial layer thickness is greater than 0.5mm, but the specific value is not specifically limited.

[0034] S2. The edge profile of the surface T-shaped stringer preform is chamfered at a predetermined angle α and cut along the fiber direction, with the cutting depth along the thickness direction of the T-shaped stringer preform being the first depth (see...). Figure 1 and Figure 4 ).

[0035] like Figure 2 As shown, the angle between the fiber direction and the cutting direction in the net size area is 90°≤є≤180° when cut along the fiber, and the angle between the fiber direction and the cutting direction in the net size area is 0°<є<90° when cut against the fiber. The edge strip of the surface T-shaped stringer preform is chamfered at a preset angle α when cut along the fiber.

[0036] Because the surface T-shaped stringer preform is cut along the fiber direction during cutting, it avoids fiber warping and tearing on the surface.

[0037] In step S2, the first depth satisfies: 0.2mm ≤ first depth ≤ 1mm. Taking the above-mentioned range for the first depth allows for cutting the surface of the T-shaped stringer preform without tearing during the cutting process. The first depth can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc.

[0038] S3. Cut the edge strips with a pre-set angle α using multiple cuts along the thickness direction of the T-shaped stringer preform (see...). Figure 2 and Figure 5 ).

[0039] Optionally, in the widening region of the T-shaped stringer preform, the cutting direction is from the allowance area towards the net dimension area. This cutting method can effectively improve the cutting dimensional accuracy of the widening region.

[0040] The T-shaped stringer preform is cut with multiple cuts along its thickness direction, with a pre-set angle α. This allows for layered cutting of the T-shaped stringer preform, avoiding quality issues such as dimensional deviations and tearing.

[0041] Optionally, in step S3, the cutting depth of each cut is (h - first depth) / N, where N is a positive integer greater than 1. The cutting depth of each cut (h - first depth) / N ensures that the T-shaped stringer preform is cut using multiple cuts, reducing contact length and cutting resistance, and improving cutting accuracy.

[0042] In step S3, the angle of each cut is a preset angle α, and the contact length L of the blade cutting the material is: cutting depth / sinα. The contact length L satisfies: L≤6mm. The above settings avoid problems such as dimensional deviations and tearing due to excessive contact length.

[0043] In step S3, the contact length L = cutting depth / sinα = (h - first depth) / (N × sinα) ≤ 6mm. Therefore, N ≥ (h - first depth) / (6sinα). h, first depth and α are known parameters during cutting. Thus, the number of cuts, i.e. the number of layers cut, can be obtained.

[0044] In step S3, the outer corner positions at both ends of the T-shaped stringer preform are overcut by a third overcut amount, which satisfies the following condition: 2mm ≤ third overcut amount ≤ 10mm. Overcutting the outer corner positions at both ends of the T-shaped stringer preform by the third overcut amount facilitates the removal of the cut T-shaped stringer preform from the allowance area.

[0045] The third overcut amount can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc. In this embodiment, the third overcut amount is preferably 5mm.

[0046] In step S3, when cutting at a pre-set angle α along the thickness direction of the T-shaped stringer preform, the cutting depth along the thickness direction of the T-shaped stringer preform is the second depth, which is ≤0.4mm. The second depth satisfies the above condition to avoid large steps forming in the cut T-shaped stringer preform, thus ensuring cutting accuracy.

[0047] The second depth can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, etc. For example... Figure 1 As shown, the second depth is 0.4mm, which, while meeting the accuracy requirements, facilitates subsequent measurement work through the formed steps.

[0048] In step S3, when the T-shaped stringer preform has arc features, the contact length L of the blade cutting the material is reduced, thereby improving the cutting accuracy of the arc features.

[0049] In step S3, the cutting direction of the blade can be either with or against the fiber direction, without limitation, and the cutting direction can be selected according to the requirements.

[0050] S4. Vertically cut the contours of both ends of the T-shaped stringer preform, with a cutting depth equal to the thickness h of the T-shaped stringer preform plus the second overcut (see...). Figure 1 and Figure 6 ).

[0051] The second overcut amount must satisfy the following condition: 0.5mm ≤ second overcut amount < sacrificial layer thickness. Using the above value for the second overcut amount ensures the cutting accuracy of the T-shaped stringer preform, thus facilitating the removal of the cut T-shaped stringer preform from the allowance zone. The sacrificial layer thickness is greater than 0.5mm, but the specific value is not limited.

[0052] The cutting method for the T-shaped stringer preform involves cutting the surface T-shaped stringer preform edge profile at a pre-set angle α along the fiber to avoid tearing. During further cutting, the edge is cut at a pre-set angle α in multiple cuts along the thickness direction of the T-shaped stringer preform, thereby effectively preventing quality problems such as out-of-tolerance cutting dimensions and tearing in the T-shaped stringer preform.

[0053] The following explanation uses a T-shaped stringer preform with a 30° chamfer and a cutting thickness of approximately 6mm as an example: 1. First, such as Figure 1 As shown, vertical cuts are made along the upper and lower edges of the bottom surface contour of the T-shaped stringer preform. Figure 1 In “Path 1”, the cutting depth is the thickness h of the T-shaped stringer preform plus an overcut of 0.5 mm.

[0054] 2. The edge profile of the surface T-shaped stringer preform is chamfered at 30° and cut along the fiber direction, with a cutting depth of 0.5mm according to the thickness direction of the T-shaped stringer preform. Figure 1 (Path 2 in the middle).

[0055] Among them, such as Figure 2 As shown, when cutting along the fiber direction, the angle between the fiber direction and the cutting direction in the net-size area is 90°≤є≤180°; when cutting against the fiber direction, the angle between the fiber direction and the cutting direction in the net-size area is 0°<є<90°. In this embodiment, when cutting the surface layer of the T-shaped stringer, cutting along the fiber direction is used to avoid fiber warping and tearing.

[0056] 3. The edge of the T-shaped stringer preform is ultrasonically cut with a chamfer of 30° to a depth of (h-0.5) / 3 along its thickness direction. Figure 1 Path 3, in the widening area, the cutting direction is from the allowance area to the net size area; the cutting path is shown below. Figure 5 The two ends were cut by 5mm.

[0057] like Figure 5 As shown, in the widening area of ​​the T-shaped stringer preform, the cutting proceeds from the allowance area to the net size area, cutting section 1 and section 2. Section 1 is overcut by 0.5mm at the end position, and section 2 is cut at the middle position of the T-shaped stringer preform.

[0058] Then, in the widening area of ​​the T-shaped stringer preform, the material is cut from the allowance area to the net size area, cutting sections 3 and 4. Section 4 is overcut by 0.5mm at the end position, and section 3 is cut at the middle position of the T-shaped stringer preform.

[0059] Then, in the widening area of ​​the T-shaped stringer preform, the material is cut from the allowance area to the net size area, cutting sections 5 and 6. Section 5 is overcut by 0.5mm at the end position, and section 6 is cut at the middle position of the T-shaped stringer preform.

[0060] Then, in the widening area of ​​the T-shaped stringer preform, the material is cut from the allowance area to the net size area, cutting sections 7 and 8. Section 8 is overcut by 0.5mm at the end position, and section 7 is cut at the middle position of the T-shaped stringer preform.

[0061] 4. Cutting depth as follows Figure 1 Cut along paths 4 and 5; see the cutting paths below. Figure 5 .

[0062] The cutting path follows the cutting path in step S3.

[0063] 5. Finally, vertically cut the contours of both ends, with a cutting depth of h equal to the thickness of the T-shaped stringer preform plus an overcut of 0.5 mm. See the cutting path below. Figure 6 Paths 9 and 10 are in the middle, with the two ends cut 5mm overcut.

[0064] Compared with existing technologies, the method of this invention has the following advantages: 1. The cutting method of this T-shaped stringer preform can effectively solve the quality problems such as dimensional deviation and tearing that occur during the cutting of T-shaped stringer preforms.

[0065] 2. Cutting in the variable width area from the allowance area to the net size area can effectively improve the cutting dimensional accuracy of the variable width area.

[0066] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for cutting a T-shaped stringer preform, characterized in that, Includes the following steps: S1. Cut vertically according to the lower surface contour of the T-shaped stringer preform, with a cutting depth of h of the T-shaped stringer preform plus the first overcut amount. S2. The edge profile of the surface T-shaped stringer preform is chamfered at a preset angle α and cut along the fiber, with the cutting depth along the thickness direction of the T-shaped stringer preform being the first depth. S3. Cut the edge strip with a pre-set angle α using multiple cuts according to the thickness direction of the T-shaped stringer preform; S4. Vertically cut the contours of both ends of the T-shaped stringer preform, with a cutting depth equal to the thickness h of the T-shaped stringer preform plus the second overcut amount.

2. The cutting method for the T-shaped stringer preform according to claim 1, characterized in that, In step S3, in the widening region of the T-shaped stringer preform, the cutting direction is from the allowance region to the net size region.

3. The cutting method for the T-shaped stringer preform according to claim 1, characterized in that, In step S2, the first depth satisfies: 0.2mm ≤ first depth ≤ 1mm.

4. The cutting method for the T-shaped stringer preform according to claim 1, characterized in that, In step S3, the cutting depth of each cut is (h - first depth) / N, where N is a positive integer greater than 1.

5. The cutting method for the T-shaped stringer preform according to claim 4, characterized in that, In step S3, the angle of each cut is the preset angle α, and the contact length L of the material cut by the blade is: cutting depth / sinα.

6. The cutting method for the T-shaped stringer preform according to claim 5, characterized in that, The contact length L satisfies: L≤6mm.

7. The cutting method for the T-shaped stringer preform according to claim 1, characterized in that, In step S3, the outer corner positions at both ends of the T-shaped stringer preform are overcut by a third overcut amount, and the third overcut amount satisfies: 2mm ≤ third overcut amount ≤ 10mm.

8. The cutting method for the T-shaped stringer preform according to claim 1, characterized in that, In step S3, when cutting at a preset angle α along the thickness direction of the T-shaped stringer preform, the overcut depth along the thickness direction of the T-shaped stringer preform is the second depth, and the second depth is ≤0.4mm.

9. The cutting method for the T-shaped stringer preform according to any one of claims 1-8, characterized in that, In step S3, when the T-shaped stringer preform has arc features, the contact length L of the blade cutting the material is reduced.

10. The method for cutting the T-shaped stringer preform according to any one of claims 1-8, characterized in that, The first overcut amount satisfies: 0.5mm ≤ first overcut amount < sacrificial layer thickness; And / or the second overcut amount satisfies: 0.5mm ≤ second overcut amount < sacrificial layer thickness.

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