Carbon fiber thermoplastic prepreg fabric laminated structure, bending method and box body

Abstract

The invention provides a carbon fiber thermoplastic prepreg fabric laminated structure, a bending method and a box body, and relates to the technical field of box body forming. The laminated structure comprises a bottom intercalation alternate overlapping region, a middle interface transition reinforcing region and a top step transition region; the bottom intercalation alternate lap joint area comprises a plurality of layers of carbon fiber thermoplastic prepreg fabrics of which the edges are mutually lapped, and the lap joint areas of all the layers coincide in the thickness direction; the middle interface transition reinforcing area covers the lap joint area; the top step transition area comprises a plurality of layers of carbon fiber thermoplastic prepreg fabrics, wherein the edges of the carbon fiber thermoplastic prepreg fabrics are arranged at set distances, and cavity areas formed between the edges of all the layers coincide with the lap joint areas in the thickness direction. During bending, the middle interface transition reinforcing area is a neutral surface, the bottom intercalation alternate lap joint area generates tensile deformation, the lap joint structure generates interlayer slippage in the bending process, and deformation and cracking are prevented; the top step transition area generates compression deformation, and the cavity area is arranged in advance to prevent redundant materials from being extruded to generate wrinkles and interlayer separation.

Description

Technical Field

[0001] The invention relates to the technical field of box forming, and in particular to a carbon fiber thermoplastic preimpregnated fabric laminate structure, a bending method and a box. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Carbon fiber composite cabinets are widely used in the fields of material transportation, equipment storage, construction operations, etc. in various industries. The comprehensive performance of the cabinet, such as deformation resistance, impact resistance, weather resistance and durability, is the performance that is concerned during the use of the product. Traditional carbon fiber composite cabinets are formed using thermosetting resin-based carbon fiber composite materials. The process stability and consistency directly determine the product quality. The thermosetting composite cabinet is generally formed using an open mold vacuum-assisted molding method. The molding process requires complex molds and processes for processing. The processing process places high demands on the raw material layup design, process consistency, and controllable stability of the molding process, especially for large cabinets, where the molding efficiency is low and the product quality stability is low.

[0004] At present, thermoplastic resin matrix has gradually become the core resin matrix type used in carbon fiber composite materials. Thermoplastic resin has comprehensive advantages such as impact resistance, high durability, and stable weather resistance. When making box products, carbon fiber prepreg fabric is generally used as the raw material, and it is processed by laminated composite hot pressing molding. However, due to the poor fluidity of the thermoplastic resin matrix, the general production steps are: a single panel is hot pressed, and then assembled and connected by secondary hot melt to form the box structure. Due to the use of secondary hot melt connection technology, this processing method cannot guarantee the overall stability of the joints of the box. Moreover, the production efficiency of this processing method in which multiple panels are processed separately and multiple seams are welded separately is low and cannot meet the requirements of continuous production. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a carbon fiber thermoplastic preimpregnated fabric laminate structure, a bending method and a box body, and an easy-to-bend stepped transition interlayer structure is adopted for the parts that need to be bent in the laminate structure, which can meet the requirements of subsequent hot stamping and plate bending box processing methods and improve the stability of the box body at the bending point.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, a carbon fiber thermoplastic prepreg fabric laminate structure includes a bottom intercalation alternating overlap zone, an intermediate interface transition reinforcement zone, and a top stepped transition zone continuously distributed in the thickness direction;

[0008] The bottom intercalation alternate overlap region comprises: multiple layers of carbon fiber thermoplastic prepreg fabrics whose edges overlap each other, and the overlap regions of each layer overlap in the thickness direction;

[0009] The intermediate interface transition reinforcement zone includes a carbon fiber thermoplastic prepreg fabric covering the overlap area;

[0010] The top stepped transition area includes multiple layers of carbon fiber thermoplastic prepreg fabrics whose edges are spaced at a set distance, and the cavity area formed between the edges of each layer overlaps with the overlap area in the thickness direction.

[0011] Optionally, an edge of the carbon fiber thermoplastic prepreg fabric in the overlap region is parallel to an edge of the carbon fiber thermoplastic prepreg fabric in the cavity region.

[0012] Optionally, the thickness of the carbon fiber thermoplastic prepreg fabric outside the overlapping area of ​​the bottom interlayer alternating overlapping area is 50-60% of the thickness of the entire laminate structure, and the thickness of the carbon fiber thermoplastic prepreg fabric outside the cavity area of ​​the top stepped transition zone is 40-50% of the thickness of the entire laminate structure.

[0013] Optionally, the number of carbon fiber thermoplastic prepreg fabric layers in the intermediate interface transition reinforcement zone is 1 to 3 layers.

[0014] Optionally, in the top stepped transition zone, the distance between the edges gradually increases in a direction away from the middle interface transition reinforcement zone.

[0015] Optionally, in the top stepped transition zone, the thermoplastic resin end surfaces of the edges of the carbon fiber thermoplastic prepreg fabrics adjacent to each other in the thickness direction form a smooth inclined surface.

[0016] In a second aspect, a bending method based on the above-mentioned carbon fiber thermoplastic prepreg fabric laminate structure comprises the steps of:

[0017] S1, preparing the above-mentioned carbon fiber thermoplastic prepreg fabric laminate structure;

[0018] S2. The carbon fiber thermoplastic prepreg fabric laminate structure is heated to a set temperature, and is punched from one side of the top step transition area along the thickness direction to bend the carbon fiber thermoplastic prepreg fabric laminate structure at a set angle, and the edges of the prepreg on both sides of the cavity area are thermally bonded together.

[0019] Optionally, in S1, the bottom interlayer alternating overlap zone and the middle interface transition reinforcement zone are laid in the thickness direction according to the set laying method, and the top step transition zone is laid with a complete carbon fiber thermoplastic prepreg fabric. The surface of the top step transition zone is cut downward at a set angle to form a smooth cutting surface, and then the carbon fiber thermoplastic prepreg fabric in the cavity area is removed, leaving the cavity area.

[0020] Optionally, the cutting method is single-layer cutting, so that the cutting surfaces of multiple cutting steps are combined into a flat inclined surface.

[0021] In a third aspect, a box body comprises a bent portion obtained by the above-mentioned bending method.

[0022] Optionally, the raw materials for preparing the box body include one or more of unidirectional preimpregnated fabrics and flat woven preimpregnated fabrics, the flat woven fabric includes one or more of plain, twill or satin structures; the unidirectional preimpregnated fabric includes one or more of orthogonal, bias and quasi-isotropic structures.

[0023] Optionally, the thermoplastic resin of the plastic prepreg fabric is polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyether ketone, polyetheretherketone, polycarbonate or PETG.

[0024] Optionally, the carbon fiber in the carbon fiber prepreg fabric includes one or more of T300, T700, T800, T1000 and T1200.

[0025] Optionally, the volume proportion of the resin matrix of the carbon fiber preimpregnated fabric is 30-60%.

[0026] The beneficial effects of the present invention are as follows:

[0027] When the carbon fiber thermoplastic prepreg fabric laminated structure of the present invention is bent, the intermediate interface transition reinforcement zone is a neutral surface, and no compression or stretching occurs; the bottom intercalation alternating overlap zone is the outer area of ​​the bend, which will produce tensile deformation, so a structure where the edges overlap each other is set so that it can produce interlayer slip during the bending process to prevent deformation and cracking; the top step transition zone is the inner area of ​​the bend, which will produce compression deformation, so a cavity area is set in advance to avoid excess material being squeezed out during the compression process to produce wrinkles and interlayer separation. And adopting the step transition intercalation structure design, the laminated structure forms a reinforced laminated area at the corner during the hot stamping and bending process, so that the box structure is locally strengthened at the corner, and the mechanical properties are stable. Through the hot stamping and bending process, a special-shaped box structure can be quickly formed, and there is no splicing interface at the bending position, which can realize the continuous processing of thermoplastic composite plate materials without secondary splicing, and the production efficiency of preparing the box is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 Schematic diagram of the laminated structure of the carbon fiber thermoplastic prepreg fabric before bending in Example 1.

[0030] Figure 2 Schematic diagram of the laminated structure of the carbon fiber thermoplastic prepreg fabric after bending in Example 1; Figure 3 Schematic diagram of the laminated structure of the carbon fiber thermoplastic prepreg fabric after bending in Example 2.

[0031] Among them, 1. Bottom interlayer alternating overlap zone; 2. Middle interface transition reinforcement zone; 3. Top step transition zone; 4. Carbon fiber fabric; 5. Resin matrix. DETAILED DESCRIPTION

[0032] A carbon fiber thermoplastic prepreg fabric laminate structure, comprising a bottom intercalation alternating overlap zone, a middle interface transition reinforcement zone and a top stepped transition zone continuously distributed in the thickness direction;

[0033] The bottom intercalation alternate overlap region comprises: multiple layers of carbon fiber thermoplastic prepreg fabrics whose edges overlap each other, and the overlap regions of each layer overlap in the thickness direction;

[0034] The intermediate interface transition reinforcement zone includes a carbon fiber thermoplastic prepreg fabric covering the overlap area;

[0035] The top stepped transition area includes multiple layers of carbon fiber thermoplastic prepreg fabrics whose edges are spaced at a set distance, and the cavity area formed between the edges of each layer overlaps with the overlap area in the thickness direction.

[0036] The above structure conforms to the continuity assumption of material mechanics: when the laminated structure is bent, the middle interface transition reinforcement zone is a neutral surface and does not produce compression or stretching; the bottom interlayer alternating overlapping zone is the external area of ​​the bend and will produce tensile deformation, so a structure in which the edges overlap each other is set so that interlayer slip can occur during the bending process to prevent deformation and cracking; the top stepped transition zone is the internal area of ​​the bend and will produce compression deformation, so a cavity area is set in advance to avoid excess material being squeezed out during the compression process to produce wrinkles and interlayer separation. During the compression process of the bending, the materials on both sides of the cavity area are squeezed into the cavity area until they are joined together, thereby eliminating the cavity area and forming a complete bending structure.

[0037] Optionally, the edge of the carbon fiber thermoplastic prepreg fabric in the overlap area is parallel to the edge of the carbon fiber thermoplastic prepreg fabric in the cavity area, so that the areas to be bent have the same structure in the straight direction to ensure the structural uniformity of the bending position.

[0038] Optionally, the thickness of the carbon fiber thermoplastic prepreg fabric outside the overlapping area of ​​the bottom interlayer alternating overlapping zone is 50-60% of the thickness of the entire laminated structure, and the thickness of the carbon fiber thermoplastic prepreg fabric outside the cavity area of ​​the top step transition zone is 40-50% of the thickness of the entire laminated structure, so that the overlapping area of ​​the bottom interlayer alternating overlapping zone plays a reinforcing role and improves the impact resistance of the outer side of the bending position.

[0039] Optionally, the number of carbon fiber thermoplastic prepreg fabric layers in the intermediate interface transition reinforcement zone is 1 to 3 layers. The number of layers should not be too many and needs to be determined based on the thickness of the prepreg fabric itself to prevent defects such as interlayer separation or wrinkles from occurring inside the intermediate interface transition reinforcement zone.

[0040] Optionally, in the top stepped transition zone, the distance between the edges gradually increases along the direction away from the intermediate interface transition reinforcement zone, that is, the cavity area is in the shape of a cone that is larger at the top and smaller at the bottom, and the top of the cone is in contact with the intermediate interface transition reinforcement zone. Then, during the bending process, the top of the cone is close to the neutral plane, and its compression degree is the smallest, and the corresponding distance between the edges of the prepregs on both sides is the smallest, and the compression degree at the surface position is the largest, and the corresponding distance between the edges of the prepregs on both sides is the largest.

[0041] Optionally, in the top stepped transition zone, the thermoplastic resin end faces of the edges of the adjacent carbon fiber thermoplastic prepreg fabrics in the thickness direction form a smooth inclined surface, which enables natural fit during the bending process to avoid the formation of internal bubbles.

[0042] In a second aspect, a bending method based on the above-mentioned carbon fiber thermoplastic prepreg fabric laminate structure comprises the steps of:

[0043] S1, preparing the above-mentioned carbon fiber thermoplastic prepreg fabric laminate structure;

[0044] S2. The carbon fiber thermoplastic prepreg fabric laminate structure is heated to a set temperature, and is punched from one side of the top step transition area along the thickness direction to bend the carbon fiber thermoplastic prepreg fabric laminate structure at a set angle, and the edges of the prepreg on both sides of the cavity area are thermally bonded together.

[0045] In the above process, the alternating overlap area of ​​the bottom intercalation layer is stretched, the overlap range of each layer is gradually reduced, and the cavity area of ​​the top step transition zone is squeezed to elimination by the edges of the prepreg on both sides, forming a complete bending structure without cracks or wrinkles on the inside and outside.

[0046] Optionally, in S1, the bottom interlayer alternating overlap zone and the middle interface transition reinforcement zone are laid in the thickness direction according to the set laying method, the top step transition zone is laid with a complete carbon fiber thermoplastic preimpregnated fabric, and a single layer is cut downward at a set angle from the surface of the top step transition zone, so that the cutting surfaces of multiple cutting steps are combined into a flat inclined surface, and the carbon fiber thermoplastic preimpregnated fabric in the cavity area is removed, leaving the cavity area; the flat inclined surface of the cavity area is obtained by oblique cutting, so that the inclined surfaces on both sides can be smoothly fitted during the bending process, avoiding internal defects caused by uneven edges of the resin matrix.

[0047] In a third aspect, a box body comprises a bent portion obtained by the above-mentioned bending method.

[0048] Since the box body is a three-dimensional structure composed of multiple flat plates, after the multiple flat plate planes are unfolded, the bent parts are distributed in a grid shape. Therefore, carbon fiber thermoplastic prepreg fabric can be set on the plane in advance, and the above-mentioned laminated structure is distributed in a grid shape on the plane. Then, the multiple laminated structures are bent in sequence by hot stamping equipment to form a three-dimensional box structure. The production efficiency is high and can meet the requirements of continuous production.

[0049] Optionally, the raw materials for preparing the box body include one or more of unidirectional preimpregnated fabrics and flat woven preimpregnated fabrics, the flat woven fabric includes one or more of plain, twill or satin structures; the unidirectional preimpregnated fabric includes one or more of orthogonal, bias and quasi-isotropic structures.

[0050] Optionally, the thermoplastic resin of the plastic prepreg fabric is polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyether ketone, polyether ether ketone, polycarbonate or PETG (polyethylene terephthalate-1,4-cyclohexane dimethanol ester), and the actual hot pressing temperature needs to be determined according to the hot pressing molding temperature of the thermoplastic resin.

[0051] Optionally, the carbon fiber in the carbon fiber prepreg fabric includes one or more of T300, T700, T800, T1000 and T1200, and the material is selected according to the mechanical properties of the designed box.

[0052] Optionally, the volume ratio of the resin matrix of the carbon fiber preimpregnated fabric is 30-60%, which can be flexibly adjusted according to design requirements. The number of basic stacking layers can be flexibly adjusted according to the design requirements of the box body plate thickness.

[0053] Example 1

[0054] A carbon fiber thermoplastic composite box body, comprising a box body flat plate and a bending position connecting the box body flat plate, wherein the plurality of bending positions connect adjacent box body flat plates into a three-dimensional box body, and the carbon fiber fabrics in the bending positions and the adjacent box body flat plates are continuous with each other, and the entire box body is made of 17 layers of prepreg, wherein the prepreg is a T300 carbon fiber single-layer prepreg with a polypropylene resin matrix having a volume content of 30%, wherein the box body flat plate position is laminated with unidirectional prepreg fabrics in an orthogonal ply manner. The preparation method comprises:

[0055] S1. Lay out 8 layers of bottom intercalated layers in alternating overlap zone 1 (in the overlap zone, 8 layers of prepreg are overlapped to form 16 layers), 1 layer of middle interface transition reinforcement zone 2, and 8 layers of top transition zone according to the orthogonal laying method in the thickness direction, and then cut the single layer downward at a set angle from the surface of the top transition zone, so that the cutting surfaces of multiple cutting steps are combined into a flat inclined surface; prepare the cavity area by subtractive processing, and the two inclined surfaces of the cavity area are at 90° to each other to obtain the top stepped transition zone 3; wherein the width of the overlap zone is 50 mm.

[0056] S2. The carbon fiber thermoplastic prepreg fabric laminate structure is heated to a set temperature, and is punched from one side of the top stepped transition area 3 along the thickness direction to bend the carbon fiber thermoplastic prepreg fabric laminate structure at an angle of 90°, and the resin matrix 5 at the edges of the prepreg on both sides of the cavity area is thermally bonded together.

[0057] The outer side of the bending position of the prepared box body is flat and there are no cracks on the inner side. The carbon fiber fabric inside the top step transition zone 3 of the bending position is distributed in a butt-jointed form, and the mutual overlapping state of the carbon fiber fabric 4 in the bottom interlayer alternating overlapping zone 1 is not completely eliminated, so that the outer side of the bending position is thickened to play a reinforcing role.

[0058] Example 2

[0059] A carbon fiber thermoplastic composite box body, which differs from Example 1 in that: the entire laminated structure adopts T700 carbon fiber single-layer prepreg with a polyurethane resin matrix having a volume content of 40%, and is laminated using a unidirectional prepreg fabric ±45° bias ply method, with a total of 21 layers.

[0060] In S1, 10 layers of bottom interlayer alternating overlap areas (in the overlap area, 8 layers of prepreg are overlapped with each other to form 20 layers), 1 layer of middle interface transition reinforcement area, and 10 layers of top transition area are stacked in sequence according to the set layering method. The width of the overlap area is 46 mm.

[0061] The bending position obtained is as follows Figure 3As shown, the carbon fiber fabric inside the top stepped transition zone 3 is distributed in a butt-jointed manner, and relative interlayer sliding occurs between the carbon fiber fabrics 4 in the bottom interlayer alternating overlapping zone 1 until they are distributed in a butt-jointed manner, and the overlapping state is completely eliminated, so that the outer side of the bending position does not increase in thickness and is basically consistent with the thickness at other positions.

[0062] Example 3

[0063] A carbon fiber thermoplastic composite box body, which differs from Example 1 in that: the entire laminated structure adopts T800 carbon fiber single-layer prepreg with a polyphenylene sulfide resin matrix with a volume content of 45%, and is laminated by a unidirectional ±60° oblique laying method, with a total of 14 layers.

[0064] In S1, 6 layers of bottom interlayer alternating overlap areas (in the overlap area, 6 layers of prepreg are overlapped with each other to form 12 layers), 2 layers of middle interface transition reinforcement areas, and 6 layers of top transition areas are stacked in sequence according to the set layering method. The width of the overlap area is 40 mm, and the two inclined surfaces of the cavity area are at an angle of 60° to each other.

[0065] Example 4

[0066] A carbon fiber thermoplastic composite box body is different from Example 1 in that: the entire laminated structure uses T1000 carbon fiber single-layer prepreg with a PETG resin matrix with a volume content of 50%, and the total number of layers is 25.

[0067] In S1, 12 layers of bottom interlayer alternating overlap areas (in the overlap area, 12 layers of prepreg are overlapped with each other to form 24 layers), 1 layer of middle interface transition reinforcement area, and 12 layers of top transition area are stacked in sequence according to the set layering method. The width of the overlap area is 40 mm, and the two inclined surfaces of the cavity area are at an angle of 30° to each other.

[0068] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A carbon fiber thermoplastic prepreg fabric laminate structure, characterized in that: It includes a bottom intercalation alternating overlap zone, a middle interface transition reinforcement zone and a top step transition zone which are continuously distributed in the thickness direction; The bottom intercalation alternate overlap region comprises: multiple layers of carbon fiber thermoplastic prepreg fabrics whose edges overlap each other, and the overlap regions of each layer overlap in the thickness direction; The intermediate interface transition reinforcement zone includes a carbon fiber thermoplastic prepreg fabric covering the overlap area; The top stepped transition area includes multiple layers of carbon fiber thermoplastic prepreg fabrics whose edges are spaced at a set distance, and the cavity area formed between the edges of each layer overlaps with the overlap area in the thickness direction.

2. The carbon fiber thermoplastic prepreg fabric laminate structure according to claim 1, characterized in that: The edge of the carbon fiber thermoplastic prepreg fabric in the overlap region is parallel to the edge of the carbon fiber thermoplastic prepreg fabric in the cavity region.

3. The carbon fiber thermoplastic prepreg fabric laminate structure according to claim 1, characterized in that: The thickness of the carbon fiber thermoplastic prepreg fabric outside the overlapping area of ​​the bottom intercalation alternate overlapping area is 50-60% of the thickness of the entire laminated structure, and the thickness of the carbon fiber thermoplastic prepreg fabric outside the cavity area of ​​the top stepped transition area is 40-50% of the thickness of the entire laminated structure; Optionally, the number of carbon fiber thermoplastic prepreg fabric layers in the intermediate interface transition reinforcement zone is 1 to 3 layers.

4. The carbon fiber thermoplastic prepreg fabric laminate structure according to claim 1, characterized in that: In the top stepped transition zone, the distance between the edges gradually increases in a direction away from the intermediate interface transition reinforcement zone.

5. The carbon fiber thermoplastic prepreg fabric laminate structure according to claim 1, characterized in that: In the top stepped transition zone, the thermoplastic resin end surfaces of the edges of the adjacent carbon fiber thermoplastic prepreg fabrics in the thickness direction form a smooth inclined surface.

6. A method for bending a carbon fiber thermoplastic prepreg fabric laminate structure, characterized in that: Includes steps: S1. preparing a carbon fiber thermoplastic prepreg fabric laminate structure as described in any one of claims 1 to 5; S2. The carbon fiber thermoplastic prepreg fabric laminate structure is heated to a set temperature, and is punched from one side of the top step transition area along the thickness direction to bend the carbon fiber thermoplastic prepreg fabric laminate structure at a set angle, and the edges of the prepreg on both sides of the cavity area are thermally bonded together.

7. The method for bending a carbon fiber thermoplastic prepreg fabric laminate structure according to claim 6, characterized in that In S1, the bottom interlayer alternating overlap zone and the middle interface transition reinforcement zone are laid in the thickness direction according to the set laying method, and the top step transition zone is laid with a complete carbon fiber thermoplastic prepreg fabric. The surface of the top step transition zone is cut downward at a set angle to form a smooth cutting surface, and then the carbon fiber thermoplastic prepreg fabric in the cavity area is removed, leaving the cavity area.

8. The method for bending the carbon fiber thermoplastic prepreg fabric laminate structure according to claim 7, characterized in that: The cutting method is single-layer cutting, so that the cutting surfaces of multiple cutting steps are combined into a flat inclined surface.

9. A box body, comprising a bent portion, characterized in that: The bending portion is prepared by the bending method of the carbon fiber thermoplastic preimpregnated fabric laminate structure according to any one of claims 6-8.

10. The box body according to claim 9, characterized in that: The raw materials for preparing the box body include one or more of unidirectional prepreg fabrics and flat woven prepreg fabrics, the flat woven fabrics include one or more of plain, twill or satin structures; the unidirectional prepreg fabrics include one or more of orthogonal, biased and quasi-isotropic structures; Optionally, the thermoplastic resin of the plastic prepreg fabric is polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyether ketone, polyether ether ketone, polycarbonate or PETG; Optionally, the carbon fiber in the carbon fiber prepreg fabric includes one or more of T300, T700, T800, T1000 and T1200; Optionally, the volume proportion of the resin matrix of the carbon fiber preimpregnated fabric is 30-60%.

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