Carbon fiber thermoplastic composite box and preparation method thereof

Abstract

The invention provides a carbon fiber thermoplastic composite box and a preparation method, and relates to the technical field of box forming. Comprising the following steps: S1, arranging carbon fiber thermoplastic prepregs according to a set layer number to obtain a laminated green body, and preheating the laminated green body; s2, carrying out hot press molding on the laminated green body areas forming the box body flat plate parts, and keeping a softening state between the adjacent areas to obtain box body flat plates which are dispersedly arranged on the laminated green body; s3, carrying out hot stamping on the laminated blank body in the softened state to obtain a bulge in the same stamping direction; and S4, the protruding part of the laminated blank is heated and bent, and the box body structure is defined by the box body flat plates. Due to the fact that all the components of the box body are cured and formed step by step, that is, uncured hole channels are reserved in the laminated green body in the first hot press forming process, resin flowing and gas escaping in the laminated structure are facilitated, and therefore microdefects are eliminated, and the stability of the product performance is improved.

Description

Technical Field

[0001] The invention relates to the technical field of box forming, and in particular to a carbon fiber thermoplastic composite box and a preparation method thereof. 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 boxes are widely used in the fields of material transportation, equipment storage, construction operations, etc. in various industries. The comprehensive performance of the boxes, such as deformation resistance, impact resistance, weather resistance and durability, are the performances that are paid attention to during the use of the product. Traditional carbon fiber composite boxes use thermosetting resin as the matrix and high-performance fibers as reinforcing fabrics. The products have strong mechanical rigidity and good structural synergy. However, as the use time increases, its mechanical impact resistance, fatigue resistance, corrosion resistance and other unstable problems are gradually exposed, becoming a key factor affecting the service life of the box. In addition, when using thermosetting resins and fibers to make large box products, vacuum infusion molding is generally used. There are many supporting facilities for molding, the molding cycle is long, the processing cost is high, and the production efficiency of the product is also affected.

[0004] Thermoplastic resins can be repeatedly plasticized and molded, and they also have comprehensive mechanical advantages such as impact resistance and high durability. Their comprehensive performance advantages such as stable weather resistance are also gradually recognized by people. However, since fiber-reinforced thermoplastic composites are affected by the rheological properties of the resin matrix when forming special-shaped parts, there are often many micro-defects in the impregnation and composite molding process of fibers and resins, resulting in unstable product performance. 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 composite box and a preparation method, which performs array hot pressing on the laminated prepreg of the plane forming part, and then performs stamping and bending on the laminated prepreg of the bending part, so as to realize rapid molding from the carbon fiber thermoplastic prepreg laminated blank to the thermoplastic composite box, and can effectively reduce internal micro defects.

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

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

[0008] S1. Arranging carbon fiber thermoplastic prepreg according to a set number of layers to obtain a laminated blank, and preheating the laminated blank;

[0009] S2, hot pressing the laminated green body regions constituting the box flat plate portion, keeping the adjacent regions in a softened state, and obtaining the box flat plates dispersedly arranged on the laminated green body;

[0010] S3, hot stamping the laminated blank in a softened state to obtain a bulge in the same direction as the stamping;

[0011] S4. The raised portion of the laminated blank is heated and bent so that the box flat plates are surrounded to form a box structure.

[0012] Optionally, in S1, the preheating temperature is 60-70% of the hot pressing impregnation infiltration temperature.

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

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

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

[0016] Optionally, in S4, the raised portion is heated by local radiation heating.

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

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

[0019] Optionally, in S4, the connection method of adjacent box panels includes: one or more of mechanical connection and hot melt connection.

[0020] Optionally, the method further includes step S5 of cooling the box structure.

[0021] In a second aspect, a box body is prepared by the method for preparing the above-mentioned carbon fiber thermoplastic composite material box body.

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

[0023] Optionally, the two-dimensional planar fabric structure is selected from any one of plain weave, twill, and satin weave; the three-dimensional stereoscopic woven structure is selected from any one of three-dimensional four-directional, three-dimensional five-directional, three-dimensional six-directional, and three-dimensional seven-directional.

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

[0025] Optionally, the material of the thermoplastic resin matrix includes one or more of polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyether ketone, polyether ether ketone, polycarbonate and PETG (polyethylene terephthalate-1,4-cyclohexane dimethanol ester).

[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 the present invention are as follows:

[0028] 1. In the preparation method of the present invention, the flat plate part and the bent part of the box are processed separately. First, the flat plate part is heated and cured, and then the part to be bent is processed into a bulge by a hot stamping method to form a height difference with the flat plate part. Since the distances between the bulge and the flat plate part and the heat source are different during the heating process, it is possible to achieve the effect of only locally heating the bulge, and then bend the bulge to obtain a box structure. Compared with the preparation method of the thermosetting resin box, this method does not require a box-shaped mold, and the whole process has a short molding time and low processing difficulty. Compared with the traditional molding method of the thermoplastic composite box, since the various components of the box are cured and molded in steps, that is, the laminated blank has uncured channels inside during the first hot pressing molding, it is beneficial to the resin flow and gas escape inside the laminate structure, thereby eliminating micro-defects and improving the stability of product performance.

[0029] 2. The raw material processing of the entire molding process of the present invention is simple, and the plate hot pressing molding is adopted. The required processing equipment is simple, the production efficiency is high, it is conducive to automated or semi-automated production, can shorten the molding cycle, and reduce the processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] Figure 1 Schematic diagram of the structure of the laminated body in Example 1.

[0032] Among them, 1. Flat plate area; 2. Connecting grid area; 3. Cutting part. DETAILED DESCRIPTION

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

[0034] S1. Arranging carbon fiber thermoplastic prepreg according to a set number of layers to obtain a laminated blank, and preheating the laminated blank;

[0035] S2, hot pressing the laminated green body regions constituting the box flat plate portion, keeping the adjacent regions in a softened state, and obtaining the box flat plates dispersedly arranged on the laminated green body;

[0036] S3, hot stamping the laminated blank in a softened state to obtain a bulge in the same direction as the stamping;

[0037] S4. The raised portion of the laminated blank is heated and bent so that the box flat plates are surrounded to form a box structure.

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

[0039] Optionally, the two-dimensional planar fabric structure selects any one of plain weave, twill, and satin weave; the three-dimensional stereoscopic woven structure selects any one of three-dimensional four-way, three-dimensional five-way, three-dimensional six-way, and three-dimensional seven-way; and they can be matched with each other to obtain the required performance.

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

[0041] Optionally, the material of the thermoplastic resin matrix includes one or more of polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyether ketone, polyether ether ketone, polycarbonate and PETG (polyethylene terephthalate-1,4-cyclohexane dimethanol 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 set performance is obtained by matching with the resin matrix.

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

[0044] Optionally, in S2, the pressure of hot pressing is 0.5-10MPa. After the array hot pressing is completed, box plates are formed which are dispersed and arranged on the laminated blanks, and the laminated blanks between the box plates are kept in a softened state. Since the box plates generally have regular shapes, the box plates are arranged in an array on the laminated blanks, and the softened areas form a grid between the box plates, which avoids large-scale overall forming of the laminated blanks, is conducive to the resin flow and gas escape inside the laminate structure, thereby eliminating micro defects.

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

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

[0047] Optionally, in S4, the raised portion is heated to soften by local radiation heating. Since there is a height difference between the raised portion and the flat plate of the box, when the laminated body is heated as a whole on one side of the raised portion by a planar heat source, a local heating effect with a high temperature at the raised portion and a low temperature at the flat plate of the box can be obtained, which can be achieved using simple equipment.

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

[0049] Optionally, in S4, after the excess parts on the laminated blank are cut off, the adjacent box flat panels are connected, and the connection methods include: one or more of mechanical connection and hot melt connection: when hot melt connection, the seam positions of the box flat panels are heated until they are melted and then connected in a butt-jointed manner; when mechanical connection is performed, a mechanical structure is used to connect and fix the adjacent box flat panels after bending to form a box structure.

[0050] Optionally, the method further includes step S5, cooling the box structure; using compressed air cooling to quickly cool the temperature of the bending part to room temperature, thereby completing the basic forming process of the composite material box.

[0051] The hot press impregnation infiltration temperature refers to the temperature at which the resin matrix changes into a molten state under the stress state of hot pressing and can be melt-infiltrated into the fiber to prepare a prepreg.

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

[0053] Rapid pre-bending technology means that before formal bending, a convex-concave structure is obtained through rapid hot stamping, and then formal bending is performed on this convex-concave structure to improve the bending quality.

[0054] Example 1

[0055] A carbon fiber thermoplastic composite box is prepared by using a rapid pre-bending technology, the process including:

[0056] S1. 50 layers of single-layer carbon fiber prepreg of T300 carbon fiber with a polypropylene resin matrix having a volume content of 30% are overlapped in the thickness direction to form a laminated blank, which is placed in a blast oven at a temperature of 230° C. and preheated for 30 minutes, wherein the fibers adopt a unidirectional orthogonal arrangement structure.

[0057] S2. According to the positional relationship of each box plate in the three-dimensional structure of the box, the box plates are pressed by the upper and lower plate array molds under 1MPa conditions. The pressing time is 30 minutes, and the adjacent box plates are kept in a softened state. Figure 1 As shown, the flat plate areas 1 constituting the bottom plate and four side plates of the box body are spread out and distributed throughout the laminated blank, and the adjacent flat plate areas 1 are connected to each other by grid areas 2, which are kept in a softened state.

[0058] S3, using a specific hot stamping head to perform hot stamping on the softened connection grid area on the laminated blank at a pressure of 2MPa and a temperature of 275°C for 60s, and finally forming a connection grid groove with a width of 4mm and a depth of 4mm, such as Figure 1 As shown, at this time, the laminated blank becomes a hard plate, the connection grid area 2 distributed on the hard plate is a groove, the other side of the groove is convex, and the grid is the box flat plate obtained by the flat plate area 1 in S2.

[0059] S4. When preparing the box, Figure 1 The cut part 3 in the figure is redundant material. After removing the cut part 3, the laminated body is heated by radiation heating to heat the raised part to 250°C for 30 seconds. Then, it is bent 90° for 60 seconds, so that the four flat plate areas 1 outside the grid area 2 form a three-dimensional structure. Then, the seams of adjacent flat plate areas 1 are melted and connected to obtain a box structure including a bottom plate and four side plates.

[0060] S5. Use compressed air cooling to quickly cool the temperature of the bending part to room temperature to complete 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 itself is heated to 275°C before stamping the laminated blank.

[0062] Example 2

[0063] A carbon fiber thermoplastic composite material box body, prepared by using a rapid pre-bending technology, comprises:

[0064] S1. 48 layers of single-layer carbon fiber prepreg of T700 carbon fiber with a polyurethane resin matrix having a volume content of 40% are overlapped in the thickness direction to form a laminated blank, which is placed in a blast oven at a temperature of 220° C. and preheated for 20 minutes, wherein the fiber adopts a two-dimensional plain weave structure.

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

[0066] S3. Use a specific hot stamping head to perform hot stamping on the softened connection grid area on the laminated body at a pressure of 4 MPa and a temperature of 265°C for 30 seconds, and finally form a connection grid groove with a width of 4.5 mm and a depth of 4.5 mm. At this time, the laminated body becomes a hard plate with a grid formed by grooves distributed on the hard plate. The other side of the groove is convex, and the grid contains the box flat plate obtained in S2.

[0067] S4. After cutting off the excess parts on the laminated body, the laminated body is heated by radiation heating to heat the raised parts to 280°C for 10 seconds, and then it is bent 90° with the bending time controlled within 10 seconds to obtain the three-dimensional structure of the box. After that, the individual box panels are mechanically connected to form a box product.

[0068] S5. Use compressed air cooling to quickly cool the temperature of the bending part to room temperature to complete the basic forming process of the composite material box.

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

[0070] Example 3

[0071] A carbon fiber thermoplastic composite material box is prepared by adopting a rapid pre-bending technology.

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

[0073] In S1, a single layer of carbon fiber prepreg of T800 carbon fiber with a polyphenylene sulfide resin matrix with a volume content of 50% is overlapped in the thickness direction to form a laminated blank, wherein the fiber adopts a three-dimensional four-directional stereoscopic woven structure, the entire prepreg laminate thickness is 10 layers, the preheating temperature is 250°C, and the preheating time is 30 minutes.

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

[0075] In S3, the softened connection grid area on the laminated green body is hot stamped for 20 seconds at a pressure of 3 MPa and a hot pressing temperature of 265° C., and the obtained groove has a width of 3 mm and a depth of 3 mm.

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

[0077] Example 4

[0078] A carbon fiber thermoplastic composite material box is prepared by adopting a rapid pre-bending technology.

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

[0080] In S1, a single layer of carbon fiber prepreg of T1000 carbon fiber with a PETG resin matrix having a volume content of 60% is overlapped in the thickness direction to form a laminated blank, wherein the fibers adopt a unidirectional alternating ±45° bias structure, the entire prepreg laminate thickness is 60 layers, the preheating temperature is 240°C, and the preheating time is 50 minutes.

[0081] In S2, the box panel material is pressed under 5MPa conditions for 25min.

[0082] In S3, the softened connection grid area on the laminated green body was hot stamped for 20 seconds at a pressure of 6 MPa and a hot pressing temperature of 255° C., and the obtained groove had a width of 3.5 mm and a depth of 3.5 mm.

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

[0084] Comparative Example

[0085] The difference between this comparative example and the embodiment is that the hot stamping process in S3 is not used to form the grooves, and the softened connection grid area on the laminated blank is directly locally heated to 250°C and then bent; since the local heating occurs on the flat plate, the heating area is difficult to accurately control, and the bending position of the formed box produces defects such as delamination.

[0086] 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 method for preparing a carbon fiber thermoplastic composite material box, characterized in that: The following steps are involved: S1. Arranging carbon fiber thermoplastic prepreg according to a set number of layers to obtain a laminated blank, and preheating the laminated blank; S2, hot pressing the laminated green body regions constituting the box flat plate portion, keeping the adjacent regions in a softened state, and obtaining the box flat plates dispersedly arranged on the laminated green body; S3, performing rapid hot stamping on the laminated blank in a softened state to obtain a bulge in the same direction as the stamping; S4. The raised portion of the laminated blank is heated and bent so that the box flat plates are surrounded to form a box structure.

2. The method for preparing a carbon fiber thermoplastic composite material box according to claim 1, characterized in that: In S1, the preheating temperature is 60-70% of the hot press impregnation infiltration temperature; Optionally, in S2, the pressure of hot pressing is 0.5-10 MPa.

3. The method for preparing a carbon fiber thermoplastic composite material box according to claim 1, characterized in that: In S3, the pressure of the rapid hot stamping is 0.5-10 MPa, and the heating temperature of the stamping area is 120-150% of the thermal flow temperature value of the thermoplastic resin matrix.

4. The method for preparing a carbon fiber thermoplastic composite material box according to claim 1, characterized in that: 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.

5. The method for preparing a carbon fiber thermoplastic composite material box according to claim 1, characterized in that: In S4, the raised portion is heated by local radiation heating.

6. The method for preparing a carbon fiber thermoplastic composite material box according to claim 1, characterized in that: In S4, the bending direction is opposite to the convex direction.

7. The method for preparing a carbon fiber thermoplastic composite material box according to claim 1, characterized in that: The method further includes step S5 of cooling the box structure.

8. A box body prepared by the method for preparing a carbon fiber thermoplastic composite box body as described in any one of claims 1 to 7.

9. The box body according to claim 8, characterized in that: The carbon fiber thermoplastic prepreg is a two-dimensional planar fabric structure or a three-dimensional woven structure; Optionally, the two-dimensional planar fabric structure is selected from any one of plain weave, twill, and satin weave; the three-dimensional stereoscopic woven structure is selected from any one of three-dimensional four-directional, three-dimensional five-directional, three-dimensional six-directional, and three-dimensional seven-directional.

10. The box body according to claim 8, characterized in that: Optionally, the volume proportion of the thermoplastic resin matrix of the carbon fiber thermoplastic prepreg is 30 to 60%; Optionally, the material of the thermoplastic resin matrix includes one or more of polyethylene, polypropylene, polyurethane, polyphenylene sulfide, polyether ketone, polyether ether ketone, polycarbonate and PETG (polyethylene terephthalate-1,4-cyclohexane dimethanol ester); Optionally, the carbon fiber in the carbon fiber thermoplastic prepreg includes one or more of T300, T700, T800, T1000 and T1200.

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