CN116728818A

CN116728818A - Ultrasonic welding method for fiber reinforced thermosetting composite material

Info

Publication number: CN116728818A
Application number: CN202310697695.2A
Authority: CN
Inventors: 赵天; 陈晓萱; 赵全月; 吴振波; 吴晗泰; 陈薪宇; 徐帅衡
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2023-06-13
Filing date: 2023-06-13
Publication date: 2023-09-12

Abstract

The invention discloses an ultrasonic welding method of a fiber reinforced thermosetting composite material, and belongs to the field of ultrasonic welding. The joint welded by the ultrasonic welding method of the fiber reinforced thermosetting composite material has excellent mechanical properties, and the defects of drilling damage, structural weight increase, surface pretreatment required by cementing, long-time solidification and the like are avoided. In the surface plasticizing process of the fiber reinforced thermosetting composite material, net-shaped pure glass fiber cloth is adopted to ensure that one surface of the pure glass fiber cloth is tightly attached to the prepreg in the hot pressing process, the pure glass fiber cloth is gradually pricked into fibers in the softened resin to form a pinning effect, and a large amount of gaps are reserved on one surface of the pure glass fiber cloth, so that the thermoplastic resin flows among the gaps during co-curing and is tightly connected with the thermoplastic resin film, and the compatibility among different resins is improved. The invention does not need to additionally carry out surface treatment on the thermosetting composite material, has short welding period, and provides a high-efficiency manufacturing mode for welding the fiber reinforced thermosetting composite material.

Description

Ultrasonic welding method for fiber reinforced thermosetting composite material

Technical Field

The invention relates to an ultrasonic welding method of a fiber reinforced thermosetting composite material, belonging to the field of ultrasonic welding.

Background

The fiber reinforced thermosetting composite material has the characteristics of high specific strength, high specific rigidity, excellent fatigue resistance and the like, so that the fiber reinforced thermosetting composite material is widely applied to the fields of aerospace and the like. With the great application of fiber reinforced thermosetting composite materials in structural materials of aerospace industry and the increasing enlargement and complicacy of components, challenges are brought to the preparation of the composite materials and the formation of the structures. The joining assembly process of the composite material is therefore an important factor in determining the service strength of the structure.

The connection between components is particularly important in the production and assembly of large or complex aeronautical structures. Conventional composite joining techniques have some significant drawbacks. Aiming at fiber reinforced thermosetting composite materials, attention is focused on a fusion welding technology with great potential while deep exploration is being made on novel and efficient mechanical connection and cementing methods. Ultrasonic welding is a welding technique commonly used in the industry, and is advantageous in that it is rapid and short-lived. Meanwhile, the ultrasonic welding has the characteristics of high efficiency, easiness in realizing automation and suitability for mass production. Unlike induction welding, resistance welding, and other welding modes requiring implantation of different materials or fibers, a layer of raised or flat resin material called ultrasonic waveguide energy ribs (ED) is paved on a welding interface, so that possible influence is reduced.

However, ultrasonic welding has limitations, one of which is that it requires the matrix of the composite material to have a secondary melting characteristic, and the application of this joining technique to joining of thermosetting composite materials will lead to decomposition of the resin matrix. The highly crosslinked molecular structure of the thermoset polymer matrix composite after curing does not achieve secondary melting after heating. In order to solve the problem, the welding surface of the composite material needs to be pretreated, the thermosetting composite material can be converted into a mixed laminated board with the surface layer having the thermoplastic resin characteristic, the method is that a thermoplastic polymer layer is introduced on the surface of a thermosetting composite material welding piece, and then the thermoplastic polymer layer and the thermosetting composite material are subjected to co-curing treatment, so that the welding strength can reach or even exceed the bonding strength of the adhesive. Although the method can realize ultrasonic welding of the thermosetting composite material laminated plate, the thermoplastic film used and the thermosetting polymer matrix are required to have better compatibility, and the method has higher limitation on the application range, complex operation and difficult industrialization, and is not suitable for mass production.

Disclosure of Invention

Aiming at the technical problems, the invention mainly aims to provide an ultrasonic welding method of a fiber reinforced thermosetting composite material, which is characterized in that an autoclave process is adopted to directly co-cure a thermoplastic resin film on the surface layer of the thermosetting composite material, and the welding of the thermosetting composite material is realized by adopting a higher welding pressure and ultrasonic amplitude and limiting the range of an interface heat affected zone through an ultrasonic welding technology.

The aim of the invention is achieved by the following technical scheme.

The invention discloses an ultrasonic welding method of a fiber reinforced thermosetting composite material, which comprises the following steps:

step (1), paving the prepreg lamination on the surface of a die by referring to a paving scheme, and curing and forming the prepreg lamination under the influence of curing and forming factors to prepare a thermosetting laminated plate; the curing profile factors include temperature, time and pressure.

Step (2), paving net-shaped pure glass fiber cloth of pre-impregnated thermoplastic resin between a thermosetting laminated plate and a thermoplastic resin film, and then co-curing the plasticized film and the thermosetting laminated plate by using an autoclave to prepare a fiber reinforced thermosetting composite laminated plate with a plasticized surface;

step (3), carrying out hot press molding on the energy guide ribs by adopting a wet compression molding technology;

step (4), placing the fiber reinforced thermosetting composite material plate prepared in the step (2) and the energy guide rib prepared in the step (3) in a to-be-welded area in a single lap joint mode, and fixing the to-be-welded area on an anvil block;

and (5) applying welding pressure and sinusoidal vibration displacement load perpendicular to the surface of the composite material to be welded on the area, which is overlapped in the step (4), of the second fiber reinforced thermosetting composite material plate by using an ultrasonic welding head, setting ultrasonic welding parameters in different control modes to realize welding of the composite material plate under different working conditions, and carrying out pressure maintaining on the welding area by using the welding head after welding, and unloading after cooling the energy guiding ribs to finish ultrasonic welding of the thermosetting composite material.

And (6) performing single lap tensile shear test on the welded sample of the thermosetting composite material welded in the step (5) by using a universal tester, and checking the welding strength of the welded joint.

As a further improvement of the invention, the resin matrix of the fiber reinforced thermosetting composite material is one of epoxy resin (EP), polyimide (PI) and Bismaleimide (BMI), and the invention is applicable to various thermosetting composite materials.

As a further improvement of the invention, the thermoplastic film and the pure glass fiber cloth in the step (2) are required to be cleaned and dried before being laid, so that the influence of impurity doping on the welding performance is avoided. The cleaning steps are as follows: respectively ultrasonically cleaning with absolute ethyl alcohol and acetone for 5-10min, removing surface impurities, and then putting into an oven for drying.

As a further improvement of the invention, the thermoplastic resin film in the step (2) is one of Polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyetherimide (PEI) and Polyaryl Ether Nitrile (PEN) polyether ether ketone (PEEK).

As a further improvement of the invention, the material of the energy guide rib in the step (3) is one of Polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyetherimide (PEI) and polyether nitrile (PEN) polyether ether ketone (PEEK).

As a further improvement of the invention, the thickness of the energy guiding ribs in the step (3) is controlled to be 0.1-0.4mm.

As a further improvement of the invention, the welding pressure in the step (5) is 500N and 1500N respectively.

As a further improvement of the invention, the welding amplitude of the step (5) is 25 μm and 40 μm respectively.

As a further improvement of the present invention, the stroke control parameter in the step (5) is set to 0.35mm.

As a further improvement of the present invention, the energy control parameters in the step (5) are respectively set to 930J, 1100J and 1550J.

As a further improvement of the invention, the time control parameters of the step (5) are respectively set to 0.5s and 1.6s.

The beneficial effects are that:

1. the ultrasonic welding method for the fiber reinforced thermosetting composite material has the advantages that the joint welded by the ultrasonic welding method for the fiber reinforced thermosetting composite material has excellent mechanical properties (high specific stiffness/specific strength, high fatigue life, high damage tolerance and the like), and the defects of drilling damage and structure weight increase caused by mechanical connection, surface pretreatment required by cementing, long-time solidification and the like are effectively avoided.

2. In order to enable a co-cured interface to have a good bonding effect, the ultrasonic welding method of the fiber reinforced thermosetting composite material disclosed by the invention adopts net-shaped pure glass fiber cloth in the surface plasticizing process of the fiber reinforced thermosetting composite material, so that one surface of the pure glass fiber cloth is tightly attached to a prepreg in the hot pressing process, the pure glass fiber cloth is gradually pricked into fibers in softening resin to form a pinning effect, and a large number of gaps are reserved on one surface, so that thermoplastic resin flows among gaps in the co-curing process and is tightly connected with a thermoplastic resin film, and the compatibility among different resins is improved.

3. The ultrasonic welding method of the fiber reinforced thermosetting composite material disclosed by the invention does not need to additionally carry out surface treatment on the thermosetting composite material, and meanwhile, the welding period is short, so that a high-efficiency manufacturing mode is provided for welding the fiber reinforced thermosetting composite material.

Drawings

FIG. 1 is a process flow diagram of a method of ultrasonic welding of a fiber reinforced thermoset composite material of the present invention;

FIG. 2 is a schematic illustration of the preparation of a fiber reinforced thermoset composite; wherein figure a is a schematic drawing of unreeling a fibrous prepreg; FIG. b is a schematic illustration of prepreg lay-up; figure c is a schematic view of autoclave placement; FIG. d is a schematic diagram of thermal press curing; FIG. e is a schematic diagram of autoclave cooling and pressure relief;

FIG. 3 is a schematic illustration of a surface plasticizing process for a fiber reinforced thermoset composite; wherein figure a is a schematic drawing of unreeling of pure glass fiber cloth; FIG. b is a schematic illustration of cleaning a pure glass cloth; figure c is a schematic illustration of a pure glass fiber cloth lay-up; FIG. d is a schematic drawing of surface plasticization of glass fiber cloth; FIG. e is a schematic illustration of placement within an autoclave; FIG. f is a schematic illustration of the thermal press curing of a thermoset composite; FIG. g is a schematic illustration of surface plasticization of a thermoset composite; FIG. h is a schematic diagram of autoclave cooling and pressure relief;

FIG. 4 is a schematic diagram of the compression molding process of the energy guiding rib; wherein figure a is a schematic illustration of a thermoplastic polymer mass injection process; figure b is a schematic diagram of hot press molding of the energy guiding ribs;

FIG. 5 is a schematic illustration of an ultrasonic welding process for a fiber reinforced thermoset composite of the present invention; wherein figure a is a schematic diagram of single lap joint of a welding sample; figure b is a schematic illustration of an ultrasonic welding process.

In the figure: 1-fiber prepreg, 2-mold, 3-thermosetting composite material, 4-pure glass fiber cloth roll, 5-spray gun, 6-thermoplastic film, 7-fiber reinforced thermosetting composite material, 8-nozzle, 9-thermoplastic polymer material, 10-polymer forming mold, 11-energy guiding rib, 12-lower welding composite material plate, 13-upper welding composite material plate, 14-aluminum gasket, 15-anvil and 16-ultrasonic welding head.

Detailed Description

It should be understood that the terms "comprises" and "comprising" when used in this specification and the appended claims;

the presence of a described feature, integer, step, operation, element, and/or component does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

It is also to be understood that the terminology used in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.

Various structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. The figures are not drawn to scale, wherein certain details may be exaggerated and some details may be omitted for clarity of presentation. The shapes of the various regions, layers and their relative sizes, positional relationships shown in the drawings are merely exemplary, may in practice deviate due to manufacturing tolerances or technical limitations, and one skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions as actually required.

The following is a further description of embodiments of the present invention, taken in conjunction with the accompanying drawings and technical solutions:

the invention provides an ultrasonic welding method of a fiber reinforced thermosetting composite material, which is characterized in that an autoclave process is adopted to directly co-cure a thermoplastic resin film on the surface layer of the thermosetting composite material, and an ultrasonic welding technology is adopted to limit the range of an interface heat affected zone by adopting higher welding pressure and ultrasonic amplitude, so that the welding of the thermosetting composite material is finally realized.

As an embodiment of the invention, the specific implementation process is as follows:

step one, unreeling and cutting the fiber prepreg 1 as shown in fig. 2 (a), then laminating the prepreg 1 as shown in fig. 2 (b) according to a paving scheme, paving on the surface of a die 2, coating by adopting high-temperature-resistant release cloth, a separation film, a vacuum bag and the like, then placing the fiber prepreg and the die 2 into an autoclave together, sealing a tank door, and curing and forming in a high-temperature and high-pressure environment according to a specified curing process system. After the temperature and pressure are reduced and the pressure are relieved, opening a tank door to take out the sample of the thermosetting composite material 3 and the mould together;

step two, unreeling the pure glass fiber cloth roll 4 for cutting as shown in the figure 3 (a), then respectively using absolute ethyl alcohol and acetone to ultrasonically clean the cut reticular glass fiber cloth 4 for 5-10min, removing surface impurities, and then putting the reticular glass fiber cloth 4 into an oven for drying;

step three, as shown in fig. 3 (c), paving the reticular glass fiber cloth 4 treated in the step two on the upper surface of the thermosetting composite material 3, uniformly spraying thermoplastic resin on the surface of the reticular glass fiber cloth 4 by using a spray gun 5, paving a thermoplastic film on the uppermost surface, and finally co-curing the thermoplastic film 6 and the thermosetting composite material 3 by using an autoclave to prepare a fiber reinforced thermosetting composite material 7 with plasticized surface;

step four, as shown in fig. 4 (a), injecting a thermoplastic polymer material 9 in a molten state into a polymer forming mold 10 by using a nozzle 8 under high pressure, and after the material is injected, carrying out vacuumizing and pressurizing treatment on the mold 10, wherein after the material is reduced to a melting point, the thermoplastic polymer in a molten stage is rapidly solidified and formed into an energy guide rib 11;

step five, as shown in fig. 5 (a), firstly placing the energy guiding rib 11 manufactured in the step four on the interface of the area to be welded of the lower welding composite material plate 12 processed in the step three, then singly lapping the area to be welded of the upper welding composite material plate 13 processed in the step three on the interface of the energy guiding rib 11, and adding an aluminum gasket 14 to fix the area to be welded on the anvil 15;

step six, as shown in fig. 5 (b), an ultrasonic welding head 16 is used to apply welding pressure and sinusoidal vibration displacement load perpendicular to the surface of the composite material directly above the area to be welded of the composite material plate 13 in step five, table 1 lists welding parameters in three control modes of travel, energy and time, the welding area is pressurized by the welding head after welding is completed, unloading is performed after the energy guiding ribs are cooled, and ultrasonic welding of the thermosetting composite material is completed.

And step seven, performing a single lap tensile shear test on the welded thermosetting composite material welding sample obtained in the step six by using a universal testing machine, analyzing failure mechanisms of sections, and exploring an optimal welding process.

Step eight, in order to confirm the interfacial inclusion reinforcement of the reticular glass fiber cloth in the surface plasticization, the traditional thermosetting composite material with the surface plasticization is welded by adopting the same welding process, and the tensile strength of the welded joint is checked, and the tensile strength result is shown in table 2.

The results show that the peel strength of the welded joint is achieved by inclusion of a mesh glass cloth on the plasticized surface under almost every welding process.

Table 1 test piece welding process parameters

Table 2 tensile Strength of test piece welded joint

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. An ultrasonic welding method of a fiber reinforced thermosetting composite material is characterized in that: comprises the steps of,

step (1), paving the prepreg lamination on the surface of a die by referring to a paving scheme, and curing and forming the prepreg lamination under the influence of curing and forming factors to prepare a thermosetting laminated plate; the curing and forming factors include temperature, time and pressure;

applying welding pressure and sinusoidal vibration displacement load perpendicular to the surface of the composite material plate to be welded on the second fiber reinforced thermosetting composite material plate overlapped in the step (4) by using an ultrasonic welding head, setting ultrasonic welding parameters in different control modes to realize welding of the composite material plate under different working conditions, and carrying out pressure maintaining on the welding area by using the welding head after welding is completed, unloading after cooling an energy guiding rib, so as to finish ultrasonic welding of the thermosetting composite material;

2. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the fiber reinforced thermosetting composite resin matrix is one of epoxy resin (EP), polyimide (PI) and Bismaleimide (BMI).

3. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the thermoplastic film and the pure glass fiber cloth in the step (2) are required to be cleaned and dried before being laid, so that the influence of impurity doping on welding performance is avoided; the cleaning steps are as follows: respectively ultrasonically cleaning with absolute ethyl alcohol and acetone for 5-10min, removing surface impurities, and then putting into an oven for drying.

4. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the thermoplastic resin film in the step (2) is one of Polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyetherimide (PEI) and polyether nitrile (PEN) polyether ether ketone (PEEK).

5. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the energy-conducting ribs in the step (3) are made of one of Polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyetherimide (PEI) and polyether nitrile (PEN) polyether ether ketone (PEEK).

6. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the thickness of the energy guiding rib in the step (3) is controlled to be 0.1-0.4mm.

7. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the welding pressure in the step (5) is 500N and 1500N respectively;

the welding amplitude in the step (5) is 25 mu m and 40 mu m respectively.

8. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the stroke control parameter in the step (5) is set to be 0.35mm.

9. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: the energy control parameters in the step (5) are respectively set to 930J, 1100J and 1550J.

10. A method of ultrasonic welding a fiber reinforced thermoset composite material as defined in claim 1, wherein: and (5) setting the time control parameters of the step (5) to be 0.5s and 1.6s respectively.