Carbon fiber thermoplastic composite case and method of manufacture

Abstract

The application provides a carbon fiber thermoplastic composite box and a preparation method, and relates to the technical field of box forming. The method comprises the following steps: S1, arranging carbon fiber thermoplastic prepreg according to the set number of layers to obtain a laminated blank, and preheating; S2, hot-pressing forming the laminated blank area constituting the box flat plate part, keeping the adjacent areas in a softened state, and obtaining the box flat plate dispersedly arranged on the laminated blank; S3, hot-stamping the laminated blank in the softened state to obtain protrusions in the same direction as the stamping direction; and S4, heating and bending the protrusion part of the laminated blank to make the box flat plate surround the box structure. Since each component part of the box is cured and formed in steps, that is, the laminated blank has un-cured channels inside during the first hot-pressing forming, the resin flow and gas escape inside the layer structure are facilitated, micro-defects are eliminated, and the stability of product performance is improved.

Description

Technical Field

[0001] This invention relates to the field of box forming technology, and in particular to a carbon fiber thermoplastic composite box and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Carbon fiber composite material enclosures are widely used in various industries for material transportation, equipment storage, and construction operations. The comprehensive performance of these enclosures, such as resistance to deformation, impact resistance, weather resistance, and durability, are key performance indicators during use. Traditional carbon fiber composite enclosures use thermosetting resin as the matrix and high-performance fibers as reinforcing fabrics. While these products exhibit high mechanical rigidity and good structural integrity, their mechanical properties, such as impact resistance, fatigue resistance, and corrosion resistance, become unstable over time, becoming critical factors affecting their lifespan. Furthermore, the manufacture of large enclosures using thermosetting resin and fibers typically employs vacuum casting, which requires numerous supporting facilities, has a long molding cycle, and high processing costs, thus impacting production efficiency.

[0004] Thermoplastic resins offer advantages such as repeated plasticizing and molding, impact resistance, and high durability, while their stable weather resistance and other comprehensive performance advantages are increasingly recognized. However, due to the influence of the rheological properties of the resin matrix on the molding of irregularly shaped parts, the impregnation and composite molding process of fibers and resins often contains numerous micro-defects, leading to unstable product performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a carbon fiber thermoplastic composite box body and its preparation method. The method involves array-type hot pressing of the laminated prepreg in the planar forming part, followed by stamping and bending of the laminated prepreg in the bending part. This enables rapid forming from the carbon fiber thermoplastic prepreg laminate blank to the thermoplastic composite box body, and effectively reduces internal micro-defects.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, a method for preparing a carbon fiber thermoplastic composite box includes the following steps:

[0008] S1. Arrange the carbon fiber thermoplastic prepreg according to the set number of layers to obtain the laminated preform and preheat it;

[0009] S2. The stacked blank areas that make up the box plate are hot-pressed and formed, while the adjacent areas are kept in a softened state, to obtain a box plate that is dispersed on the stacked blank.

[0010] S3. The softened laminated blank is hot-stamped to obtain protrusions in the same direction as the stamping.

[0011] S4. Heat and bend the protruding parts of the laminated blank to form a box structure from the flat plate.

[0012] Optionally, in S1, the preheating temperature is 60 to 70% of the hot-press impregnation melting temperature.

[0013] Optionally, in S2, the pressure for hot pressing is 0.5 to 10 MPa.

[0014] Optionally, in S3, the pressure of hot stamping is 0.5 to 10 MPa, and the heating temperature of the stamping area is 120 to 150% of the heat flow temperature of the thermoplastic resin matrix.

[0015] Optionally, in S3, the depth of the protrusion is 20-50% of the thickness of the box plate, and the width of the protrusion is 20-50% of the thickness of the box plate.

[0016] Optionally, in S4, the protruding part is heated by localized radiation heating.

[0017] Optionally, in S4, the bending direction is opposite to the convex direction.

[0018] Optionally, in S4, adjacent box-shaped plates are connected to form a box structure.

[0019] Optionally, in S4, the connection method for adjacent box plates includes one or more of mechanical connection and thermofusion connection.

[0020] Optionally, step S5, cooling the enclosure structure, may also be included.

[0021] Secondly, a box obtained by a method for preparing the above-mentioned carbon fiber thermoplastic composite material box.

[0022] Optionally, the carbon fiber thermoplastic prepreg has a two-dimensional planar fabric structure or a three-dimensional woven structure.

[0023] Optionally, the two-dimensional planar fabric structure may be any one of plain weave, twill weave, or satin weave; the three-dimensional woven structure may be any one of three-dimensional four-way, three-dimensional five-way, three-dimensional six-way, or three-dimensional seven-way.

[0024] Optionally, the volume ratio of the thermoplastic resin matrix in the carbon fiber thermoplastic prepreg is 30-60%.

[0025] Optionally, the thermoplastic resin matrix may be made of one or more of polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyetherketone, polyetheretherketone, polycarbonate, and PETG (polyethylene terephthalate-1,4-cyclohexanediol).

[0026] Optionally, the carbon fiber in the carbon fiber thermoplastic prepreg includes one or more of T300, T700, T800, T1000 and T1200.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. In the preparation method of this invention, the flat plate portion and the bent portion of the box body are processed separately. First, the flat plate portion is heated and cured. Then, a protrusion is formed in the portion to be bent using a hot stamping method, creating a height difference with the flat plate portion. Because the distance between the protrusion and the heat source differs between the protrusion and the flat plate portion during heating, the effect of localized heating of only the protrusion portion can be achieved, thereby bending the protrusion portion to obtain the box structure. Compared to the preparation method of thermosetting resin boxes, this method does not require a mold for the box shape, and the entire process has a short molding time and low processing difficulty. Compared to the traditional molding method of thermoplastic composite box bodies, because the various components of the box body are cured and formed step by step, i.e., uncured channels are left inside the laminated preform during the first hot pressing, it is beneficial for resin flow and gas escape within the layup structure, thereby eliminating micro-defects and improving the stability of product performance.

[0029] 2. The raw material processing of the entire molding process of this invention is simple. It adopts hot pressing molding of sheet metal, requires simple processing equipment, has high production efficiency, is conducive to automated or semi-automated production, can shorten the molding cycle, and reduce processing costs. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 This is a schematic diagram of the structure of the laminated blank in Example 1.

[0032] Among them, 1. Flat area; 2. Connecting grid area; 3. Cut-out part. Detailed Implementation

[0033] A method for preparing a carbon fiber thermoplastic composite box includes the following steps:

[0034] S1. Arrange the carbon fiber thermoplastic prepreg according to the set number of layers to obtain the laminated preform and preheat it;

[0035] S2. The stacked blank areas that make up the box plate are hot-pressed and formed, while the adjacent areas are kept in a softened state, to obtain a box plate that is dispersed on the stacked blank.

[0036] S3. The softened laminated blank is hot-stamped to obtain protrusions in the same direction as the stamping.

[0037] S4. Heat and bend the protruding parts of the laminated blank to form a box structure from the flat plate.

[0038] Optionally, the carbon fiber thermoplastic prepreg is a two-dimensional planar fabric structure or a three-dimensional woven structure, and the appropriate thickness of prepreg can be selected to lay up the prepreg to obtain a laminated blank, and further obtain a box sidewall of a set thickness.

[0039] Optionally, the two-dimensional planar fabric structure can be any one of plain weave, twill weave, or satin weave; the three-dimensional woven structure can be any one of three-dimensional four-way, three-dimensional five-way, three-dimensional six-way, or three-dimensional seven-way; they can be combined to obtain the required performance.

[0040] Optionally, the thermoplastic resin matrix of the carbon fiber thermoplastic prepreg accounts for 30-60% of the volume to obtain the required flexibility during preheating.

[0041] Optionally, the thermoplastic resin matrix may be made of one or more of polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyetherketone, polyetheretherketone, polycarbonate, and PETG (polyethylene terephthalate-1,4-cyclohexanediol ester), and the temperature during the subsequent heating process needs to be determined according to the type of resin.

[0042] Optionally, the carbon fiber in the carbon fiber thermoplastic prepreg includes one or more of T300, T700, T800, T1000 and T1200, and the desired properties are obtained by combining it with the resin matrix.

[0043] Optionally, in S1, the preheating temperature is 60-70% of the hot-press impregnation melting temperature, and the preheating time is 10-60 minutes. The preheating temperature can be flexibly adjusted according to the type of resin matrix and the molding process design requirements.

[0044] Optionally, in S2, the pressure of hot pressing is 0.5–10 MPa. After array hot pressing is completed, box-shaped plates are formed dispersedly on the laminated preform, and the laminated preform between the box-shaped plates remains in a softened state. Since the box-shaped plates are generally regular in shape, the box-shaped plates are arranged in an array on the laminated preform, and the softened areas form a grid between the box-shaped plates. This avoids large-scale integral molding of the laminated preform, which is conducive to the flow of resin and the escape of gas inside the layup structure, thereby eliminating micro-defects.

[0045] Optionally, in S3, the pressure of rapid hot stamping is 0.5 to 10 MPa, the heating temperature of the stamping area is 120 to 150% of the thermal flow temperature of the thermoplastic resin matrix, the hot stamping time is 10 to 60 seconds, and the hot stamping temperature is flexibly adjusted according to the type of resin matrix. The heat source is the stamping head. Since the stamping area is arranged in a straight line on the laminated blank, it is possible to process the overall grid-shaped protrusion by step-by-step stamping.

[0046] Optionally, in S3, the depth of the protrusion is 20-50% of the thickness of the box plate, and the width of the protrusion is 20-50% of the thickness of the box plate, so as to form a height difference with the box plate. This not only achieves the subsequent local heating effect, but also serves as a pre-deformation process for formal bending, so as to reduce the material deformation range during bending and reduce possible defects.

[0047] Optionally, in S4, localized radiant heating is used to heat the raised portion until it softens. Since the raised portion and the box plate form a height difference, when the laminated blank is heated as a whole on one side of the raised portion with a planar heat source, a localized heating effect with a high temperature at the raised portion and a low temperature at the box plate portion can be achieved using simple equipment.

[0048] Optionally, in S4, the bending direction is opposite to the convex direction, the entire bending process is carried out at a heating and softening temperature, and the bending time is controlled within the range of 5-60 seconds, which is adjusted according to process requirements to form a three-dimensional box structure.

[0049] Optionally, in S4, after cutting off the excess portion on the stacked blank, the adjacent box-shaped plates are connected. The connection method includes one or more of mechanical connection and hot-melt connection. In hot-melt connection, the joint of the box-shaped plates is heated to melt and then connected by butt joint. In mechanical connection, a mechanical structure is used to connect and fix the bent adjacent box-shaped plates to form a box structure.

[0050] Optionally, step S5, cooling the box structure, is also included; compressed air is used for air cooling to quickly cool the temperature at the bending point to room temperature, thus completing the basic forming process of the composite material box.

[0051] Hot-press impregnation temperature refers to the temperature at which the resin matrix transforms into a molten state under hot-press stress, allowing it to melt into the fiber to prepare a prepreg.

[0052] Thermal flow temperature refers to the temperature at which the resin matrix transitions from a highly elastic state to a viscous flow state, and it is the main basis for determining the process parameters of polymer melt molding.

[0053] Rapid pre-bending technology refers to obtaining a raised-recessed structure through rapid hot stamping before the formal bending, and then performing the formal bending on this raised-recessed structure to improve the bending quality.

[0054] Example 1

[0055] A carbon fiber thermoplastic composite box body is manufactured using a rapid pre-bending technology, the process of which includes:

[0056] S1. 50 layers of T300 carbon fiber single-layer prepreg with a polypropylene resin matrix of 30% by volume are stacked in the thickness direction to form a laminated preform, and preheated in a forced-air oven at 230℃ for 30 minutes, wherein the fibers adopt a unidirectional orthogonal arrangement structure.

[0057] S2. Based on the positional relationship of the various box-shaped plates in the three-dimensional structure of the box, the box-shaped plates are pressed using an upper and lower plate array mold under a pressure of 1MPa for 30 minutes. Adjacent box-shaped plates remain in a softened state. Figure 1 As shown, the flat plate area 1 that constitutes the bottom plate and four side plates of the box body is distributed throughout the laminated blank, and the adjacent flat plate area 1 is connected by a grid area 2, which remains in a softened state.

[0058] S3. Using a specific hot stamping head, the softened connecting grid area on the laminated blank is hot stamped for 60 seconds at a pressure of 2MPa and a temperature of 275℃, ultimately forming a connecting grid groove with a width of 4mm and a depth of 4mm. Figure 1 As shown, at this time the stacked blank becomes a hard plate, the connecting grid area 2 distributed on the hard plate is a groove, the other side of the groove is raised, and the plate area 1 in the grid is the box plate obtained in S2.

[0059] S4. When preparing the box body Figure 1 The cut-out portion 3 is excess material. After removing the cut-out portion 3, the laminated blank is heated by radiation heating to heat the protruding part to 250°C for 30 seconds. Then, it is bent at 90° for 60 seconds to form a three-dimensional structure around the four flat plate areas 1 of the grid area 2. Then, the joints of the adjacent flat plate areas 1 are fused together to obtain a box structure including a bottom plate and four side plates.

[0060] S5. Compressed air cooling is used to quickly cool the temperature at the bending point to room temperature, completing the basic forming process of the composite material box.

[0061] The cross-sectional shape of the hot stamping head is the same as the shape of the groove formed by stamping. During operation, the hot stamping punch is heated to 275°C before stamping the laminated blank.

[0062] Example 2

[0063] A carbon fiber thermoplastic composite box body, manufactured using a rapid pre-bending technique, includes the following methods:

[0064] S1. 48 layers of T700 carbon fiber single-layer prepreg with a polyurethane resin matrix of 40% by volume are stacked in the thickness direction to form a laminated blank, and preheated in a forced-air oven at 220℃ for 20 minutes, wherein the fiber adopts a two-dimensional plain weave structure.

[0065] S2. Based on the positional relationship of each box plate in the three-dimensional structure of the box, the box plate is pressed by applying pressure at 3MPa using an upper and lower plate array mold. The pressing time is 15 minutes, and adjacent box plates are kept in a softened state.

[0066] S3. Using a specific hot stamping head, the softened connecting grid area on the laminated blank is hot stamped for 30 seconds at a pressure of 4MPa and a temperature of 265℃, finally forming a connecting grid groove with a width of 4.5mm and a depth of 4.5mm. At this time, the laminated blank becomes a hard plate with a grid formed by the groove distributed on the hard plate. The other side of the groove is raised, and the box plate obtained in S2 is in the grid.

[0067] S4. After cutting off the excess parts on the stacked blank, the stacked blank is heated by radiation heating to heat the protruding parts to 280°C for 10 seconds. Then, it is bent at 90° for 10 seconds to obtain the three-dimensional structure of the box. Then, the individual box plates are connected by mechanical connection to form the box product.

[0068] S5. Compressed air cooling is used to quickly cool the temperature at the bending point to room temperature, completing the basic forming process of the composite material box.

[0069] The hot-pressing punch used in this embodiment has the same structural features as that in Embodiment 1, except that its cross-sectional shape matches the groove shape in this embodiment.

[0070] Example 3

[0071] A carbon fiber thermoplastic composite box body is prepared using rapid pre-bending technology.

[0072] The difference between this embodiment and Embodiment 1 is that:

[0073] In S1, a single layer of T800 carbon fiber prepreg with a volume content of 50% polyphenylene sulfide resin matrix is ​​stacked in the thickness direction to form a laminated prepreg. The fibers adopt a three-dimensional four-way woven structure. The entire prepreg laminate has a thickness of 10 layers, a preheating temperature of 250℃, and a preheating time of 30 minutes.

[0074] In S2, the box panel is pressed under pressure at 2MPa for 20 minutes.

[0075] In S3, the softened connecting grid area on the laminated blank is hot-stamped for 20 seconds at a pressure of 3MPa and a hot-pressing temperature of 265℃, resulting in a groove with a width of 3mm and a depth of 3mm.

[0076] In S4, the protruding part is heated to 280°C for 15 seconds, and then bent at 90° for 10 seconds.

[0077] Example 4

[0078] A carbon fiber thermoplastic composite box body is prepared using rapid pre-bending technology.

[0079] The difference between this embodiment and Embodiment 1 is that:

[0080] In S1, a single layer of T1000 carbon fiber prepreg with a PETG resin matrix of 60% by volume is stacked in the thickness direction to form a laminated prepreg. The fibers adopt a unidirectional alternating ±45° oblique structure. The total thickness of the prepreg laminate is 60 layers. The preheating temperature is 240℃ and the preheating time is 50min.

[0081] In S2, the box panel is pressed under pressure at 5MPa for 25 minutes.

[0082] In S3, the softened connecting grid area on the laminated blank is hot-stamped for 20 seconds at a pressure of 6MPa and a hot-pressing temperature of 255℃, resulting in a groove width of 3.5mm and a depth of 3.5mm.

[0083] In S4, the protruding part is heated to 270°C for 25 seconds, and then bent at 90° for 20 seconds.

[0084] Comparative Example

[0085] The difference between this comparative example and the embodiment is that the hot stamping forming process in S3 is not used to form the groove. Instead, the softened connecting grid area on the laminated blank is locally heated to 250°C and then bent. Since the local heating occurs on the flat plate, the heating area is difficult to control precisely, resulting in defects such as delamination at the bending position of the box.

[0086] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a carbon fiber thermoplastic composite box, characterized in that, Includes the following steps: S1. Arrange the carbon fiber thermoplastic prepreg according to the set number of layers to obtain the laminated preform and preheat it; S2. The stacked blank areas that make up the box plate are hot-pressed and formed, while the adjacent areas are kept in a softened state, to obtain a box plate that is dispersed on the stacked blank. S3. The softened laminated blank is subjected to rapid hot stamping to obtain a protrusion in the same direction as the stamping. S4. Heat and bend the protruding part of the laminated blank to form a box structure from the flat plate. The bending time is 5-60 seconds. The depth of the protrusion is 20-50% of the thickness of the box plate, and the width of the protrusion is 20-50% of the thickness of the box plate. The raised part and the flat part are at different distances from the heat source. Only the raised part is heated locally, so the temperature of the raised part is high and the temperature of the flat part of the box is low, thus creating a temperature difference.

2. The method for preparing a carbon fiber thermoplastic composite box as described in claim 1, characterized in that, In S1, the preheating temperature is 60-70% of the hot-press impregnation melting temperature. In S2, the pressure for hot pressing is 0.5~10MPa.

3. The method for preparing a carbon fiber thermoplastic composite box as described in claim 1, characterized in that, In S3, the pressure of rapid hot stamping is 0.5~10MPa, and the heating temperature of the stamping area is 120~150% of the heat flow temperature of the thermoplastic resin matrix.

4. The method for preparing a carbon fiber thermoplastic composite box as described in claim 1, characterized in that, In S4, localized radiative heating is used to heat the protruding part.

5. The method for preparing a carbon fiber thermoplastic composite box as described in claim 1, characterized in that, In S4, the bending direction is opposite to the convex direction.

6. The method for preparing a carbon fiber thermoplastic composite box as described in claim 1, characterized in that, It also includes step S5, cooling down the box structure.

7. A box prepared by a method for preparing a carbon fiber thermoplastic composite box as described in any one of claims 1-6.

8. The housing as described in claim 7, characterized in that, The carbon fiber thermoplastic prepreg has a two-dimensional planar fabric structure or a three-dimensional woven structure; The two-dimensional planar fabric structure can be any one of plain weave, twill weave, or satin weave; the three-dimensional woven structure can be any one of three-dimensional four-way, three-dimensional five-way, three-dimensional six-way, or three-dimensional seven-way.

9. The housing as described in claim 7, characterized in that, The volume proportion of the thermoplastic resin matrix in the carbon fiber thermoplastic prepreg is 30-60%. The thermoplastic resin matrix is ​​made of one or more of polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyetherketone, polyetheretherketone, polycarbonate, and PETG (polyethylene terephthalate-1,4-cyclohexanediol ester). The carbon fiber in the carbon fiber thermoplastic prepreg includes one or more of T300, T700, T800, T1000 and T1200.

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