Preparation method of CNT in-situ growth modified energy-conducting rib, energy-conducting rib and method for preparing reinforced composite material ultrasonic welding head by utilizing energy-conducting rib

Abstract

The invention discloses a preparation method of a CNT in-situ growth modified energy-conducting rib, the energy-conducting rib and a method for preparing a reinforced composite material ultrasonic welding joint by using the energy-conducting rib, and the preparation method of the energy-conducting rib comprises the following steps: uniformly spraying a catalyst aqueous solution on the surface of a metal wire mesh, and drying to obtain the metal wire mesh loaded with the catalyst; the metal wire mesh loaded with the catalyst is placed in combustion flames to grow a CNT array on the surface of the metal wire mesh, and the CNT array modified energy-conducting rib is obtained; the surface of the obtained metal wire mesh modified by the CNT array is more uniform in heating, the effective heat transfer area is increased, and improvement of the molten state of resin in a welding area is facilitated; meanwhile, due to the CNT nano-enhancement effect, the interface bonding strength between the metal wire mesh and the resin is remarkably improved, and then the strength of a welding joint is improved. The method not only can be applied to connection of thermoplastic composite materials, but also can be applied to connection of surface plasticized and modified thermosetting composite materials.

Description

Technical Field

[0001] The present invention disclosure relates to the technical field of composite material connection preparation, in particular to a preparation method of CNT in-situ growth modified energy guiding ribs, an energy guiding rib, and a method for preparing an enhanced composite material ultrasonic welded joint by using the same. Background Art

[0002] "Lightweight, long life, high reliability, high efficiency, high stealth, low cost" is the development goal of the new generation of aircraft. Using advanced composite materials as aircraft structures is an important way to achieve this goal. This is because advanced composite materials have the advantages of light weight, high strength, designability, fatigue resistance, and easy realization of structure / function integration. Therefore, after aluminum, titanium, and steel, they have rapidly developed into one of the four major aircraft structural materials. Structural lightweighting is an eternal theme in the development of aerospace vehicles. Replacing metal materials such as aluminum alloy with advanced polymer matrix composites (APC) with high specific strength, high specific modulus, excellent fatigue resistance, and corrosion resistance to manufacture load-bearing structures, such as aircraft skins, frames, panels, etc., and solid rocket motor casings, missile bodies, satellite load-bearing cylinders, etc., is the key technical approach to achieve the structural lightweighting and improve the comprehensive efficiency of aerospace vehicles. In the 1950s of the last century, in order to further break through the load-carrying capacity of aircraft, composite materials were first applied to aircraft structures, realizing a milestone leap in aircraft structural materials from metal materials to composite materials.

[0003] Designability and integral molding are the prominent advantages of APC structures; however, there are problems such as many defects induced in the manufacturing process, serious dimensional tolerances, and low manufacturing fault tolerance and low finished product rate due to the non-detachable secondary bonding structure when manufacturing complex structural parts such as APC stiffened panels using co-curing and co-bonding technologies. The assembly process of APC components usually adopts mechanical connection methods such as bolt connection and rivet connection. Drilling is a necessary prerequisite for APC mechanical connection; drilling cuts off the fiber reinforcements in APC, reducing the mechanical properties of the body; at the same time, there is a great stress concentration in the joint area of mechanical connections, and this effect has a far greater impact on APC with mechanical anisotropy and laminated structure characteristics than on metal materials; the weight gain effect of mechanical connection components also has a serious negative impact on the structural lightweighting of APC. According to statistics, the cost of mechanical connection in aircraft manufacturing accounts for 19%-42% of the total manufacturing cost. If APC welding technology is adopted, more than 61% of the labor cost can be saved. Therefore, the assembly connection between structural parts is indispensable, and its connection technology has also become a crucial part of future aircraft manufacturing processes.

[0004] There are many connection technologies for composite materials, mainly including three categories, namely mechanical fastening connection, adhesive bonding connection, and fusion welding. Among them, both mechanical fastening connection and adhesive bonding are borrowed from metal structure connection methods, and directly applying them to the connection of APC resin matrix composite material structures will cause many defects. For example, when mechanically connecting anisotropic APC, drilling holes will inevitably damage the continuity of the reinforcing fibers, cause local delamination of the laminate, and affect the overall mechanical properties of the structural member. In addition, the introduction of bolts and rivets will cause problems such as local electrochemical corrosion, stress concentration, and loose joint connection caused by temperature changes due to different thermal expansion coefficients in the APC structure. However, due to the isotropic nature of metal materials, the process of drilling and inserting bolts and rivets will not cause serious local damage to the metal structure.

[0005] Therefore, neither mechanical connection nor adhesive bonding is the optimal connection technology for APC materials. In order to overcome the problems existing in the adhesive bonding process and mechanical connection of composite materials, the composite material welding technology that has emerged in recent years provides a new solution for the efficient connection of composite material structural parts. Since thermoplastic composite materials can be melted when heated to a certain temperature and recover their initial properties after cooling, thermoplastic composite materials can be welded.

[0006] Composite material welding technology (also known as composite material fusion bonding technology) mainly converts energy such as electricity, light, electromagnetic, and ultrasonic into heat to heat two or more same or different materials, causing the surface of the base material containing thermoplastic resin matrix to melt or undergo plastic deformation, and connecting them into one body through the combination and diffusion between atoms or molecules. Different from mechanical connection, the composite material welding process will not damage the structural properties of the base material, will not introduce foreign materials into the weld, and will not increase the weight after welding. It can fully utilize the original mechanical properties of the base material, thereby obtaining a welded joint with strength close to that of the base material. In addition, it also has the advantages of short welding time (usually within 0.5s - 5s), low welding cost, green energy-saving, simple operation, and no additional weight increase. Therefore, composite material welding technology is a fast, efficient, and low-cost connection technology in the field of assembly and repair of aerospace composite material parts.

[0007] Ultrasonic welding was first applied to the connection between metal materials in 1956. By applying ultrasonic vibration to metal parts, a large amount of heat is gradually generated by friction in the welding area, thus realizing the welding between metal parts. Ultrasonic welding utilizes high-frequency vibration waves (20 kHz - 40 kHz) transmitted to the surfaces of two overlapping objects to be welded. Under the action of pressure, the overlapping bonding surfaces rub against each other to generate heat, and then the thermoplastic resin melts to form a fusion between molecular layers. Ultrasonic vibration is the main energy source of ultrasonic welding. High temperature is only generated locally in the welding area, and the entire welding process can be completed in a very short time (a few seconds). Since ultrasonic welding does not damage the reinforcing fibers in the composite material and does not require pretreatment of the surface of the welded parts, it just makes up for the shortcomings of mechanical connection and adhesive bonding. Moreover, ultrasonic welding can not only connect the same thermoplastic composite materials, but also connect thermoplastic composite materials and thermosetting composite materials or metal materials. And ultrasonic welding can be used in the forming process of complex laminates and the additive manufacturing of composite laminates.

[0008] Therefore, ultrasonic welding has great research value and development prospects for connecting composite materials. Summary of the Invention

[0009] In view of this, the present invention publicly provides a preparation method of CNT in-situ growth modified energy guiding ribs, the energy guiding ribs, and a method for preparing an ultrasonic welded joint of a reinforced composite material using the same, so as to prepare a welded joint with high interfacial strength.

[0010] On the one hand, the present invention provides a preparation method of CNT in-situ growth modified energy guiding ribs, including:

[0011] Spray the catalyst aqueous solution evenly on the surface of the metal wire mesh and dry it to obtain the metal wire mesh loaded with the catalyst;

[0012] Place the metal wire mesh loaded with the catalyst in a combustion flame and keep it at 800 - 1100 °C for 3 - 20 min. An array of CNTs will grow on the surface of the metal wire mesh to obtain CNT array modified energy guiding ribs;

[0013] Among them, the fuel used for the combustion flame is one or several of C1 - C7 hydrocarbons.

[0014] Preferably, in the catalyst aqueous solution, the amount of substance of the catalyst is 0.5 - 2 mol / L, and the catalyst is selected from one or several of ferric chloride, nickel nitrate, and cobalt nitrate.

[0015] Preferably, the combustion flame is selected from one of ethanol flame, methanol flame, methane flame, butane flame, heptane flame, acetone flame, acetylene flame, and ethylene flame.

[0016] Preferably, the wire mesh is one of stainless steel mesh, nickel-chromium alloy wire mesh, iron-chromium-aluminum alloy wire mesh, and nickel-copper alloy wire mesh, with a thickness of 0.4 mm - 0.8 mm; a wire diameter of 0.1 mm - 0.2 mm; and a wire spacing of 0.16 mm - 0.5 mm.

[0017] In a second aspect, the present invention also provides an energy guiding rib obtained by the preparation method. The energy guiding rib is a wire mesh with a CNT array grown on its surface. Among them, the CNT array is composed of multi-walled CNTs, and the average length of the CNT array is 8 - 30 μm.

[0018] In a third aspect, the present invention provides a method for preparing an enhanced composite ultrasonic welding joint using the energy guiding rib, including:

[0019] Using a thermoplastic composite laminate as the welding base material, a CNT in-situ growth modified energy guiding rib as the composite ultrasonic energy guiding element, and a thermoplastic resin film as the molten binder;

[0020] Coating the upper and lower surfaces of the energy guiding rib with the thermoplastic resin film;

[0021] Inserting the energy guiding rib coated with the thermoplastic resin film into the overlapping area of two thermoplastic composite laminates,

[0022] Applying ultrasonic vibration to the overlapping contact surface in the overlapping area to bond the energy guiding rib coated with the thermoplastic resin film to the thermoplastic composite laminate, obtaining a high-quality welding joint;

[0023] Wherein the thermoplastic resin film is the same as or has a similar polarity to the resin in the welding base material.

[0024] Preferably, the thermoplastic composite laminate is a thermoplastic resin-based composite laminate reinforced with a reinforcing material or a surface plasticized thermosetting composite laminate. Among them, the reinforcing material is one or more of inorganic particles, whiskers, short fibers, or continuous fibers; the surface plasticizing treatment: using a layer of thermoplastic resin film or a layer of thermoplastic prepreg to perform surface plasticizing treatment on the thermoplastic resin.

[0025] The thermoplastic resin film is one of polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), nylon (PA), polyphenylene sulfide (PPS), polyetherimide (PEI), polyether ketone (PEK), polyether ether ketone (PEKK), polyether ether ketone (PEEK), polyarylether nitrile (PEN), polyether ketone with phthaloyl side groups (PEK-C), polyether sulfone with phthaloyl side groups (PEK-S), and polyarylether sulfone ketone with a heteroarylene biphenyl structure (PPESK);

[0026] The thickness of the thermoplastic resin film is 0.1 - 0.3 mm.

[0027] Applying ultrasonic vibration to the lap contact surface in the lap region includes: the amplitude of the ultrasonic vibration is 15 - 30 μm, the welding pressure is 0.2 - 0.6 MPa, and the ultrasonic time is 1 - 10 s;

[0028] After the ultrasonic vibration ends, apply a pressure of 0.2 - 0.6 MPa above the welding area through the ultrasonic vibration head, and keep the pressure after the vibration head generates ultrasonic waves. The pressure-holding time is 1 - 10 s.

[0029] The preparation method of the CNT in-situ growth modified energy guiding rib, the energy guiding rib and the method for preparing an enhanced composite ultrasonic welding joint using the same provided by the present invention grow a CNT array in-situ on the surface of a metal wire mesh through a flame synthesis process, and then use the metal wire mesh modified by the CNT array as a heating element for ultrasonic welding of composites. Using the flame method to grow a CNT array on the surface of a metal wire mesh and using the ultrasonic welding method to prepare a composite material welding joint, both preparation processes have the advantages of being simple, fast, low-cost, high-efficiency, highly flexible, strong adaptability, and easy to industrialize and promote, and have a wide application prospect in the field of composite material connection such as aviation, aerospace, and automobiles.

[0030] The present invention utilizes the conductive heat generation and heat transfer effects of CNTs, making the surface of the metal wire mesh modified by the CNT array generate heat more uniformly and increasing the effective heat transfer area, which is beneficial to improving the molten state of the resin in the welding area; at the same time, due to the CNT nano-reinforcement effect, the interfacial bonding strength between the metal wire mesh and the resin is significantly improved, thereby improving the strength of the welding joint.

[0031] The present invention can not only be applied to the connection of thermoplastic composites, but also be used for the connection of thermosetting composites with surface plasticization modification; at the same time, it can be applied to the connection and assembly of large composite material structures with complex curved surfaces.

[0032] The method of the present invention is simple, fast, and extremely low-cost, and has a wide application prospect in the field of thermoplastic composite material connection such as aviation, aerospace, and automobiles.

[0033] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the disclosure of the present invention. Brief Description of the Drawings

[0034] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments in accordance with the present invention, and are used together with the specification to explain the principles of the present invention.

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 Schematic diagram of the process for preparing carbon nanotubes (CNTs) on a stainless steel mesh in the disclosed embodiments of the present invention;

[0037] Figure 2 Schematic diagram of the method flow for preparing an enhanced composite ultrasonic welding joint by in-situ growth modification of energy-conducting ribs using CNTs in the disclosed embodiments of the present invention. Detailed implementation manners

[0038] The following further explains and illustrates the present invention in combination with specific implementation schemes, but does not limit the protection scope of the present invention.

[0039] Aiming at problems such as low in-plane heat transfer efficiency of the implanted surface of the stainless steel mesh (SSM) and poor interfacial bonding strength with the resin during the ultrasonic welding process of composites;

[0040] First of all, the present invention provides a preparation method for in-situ growth modification of energy-conducting ribs using CNTs, including:

[0041] (1) Spraying the catalyst

[0042] Adopt the spraying process to uniformly spray the catalyst aqueous solution on the surface of the metal mesh, and dry it to obtain a metal wire mesh loaded with the catalyst;

[0043] (2) Preparation by the flame method

[0044] Place the metal wire mesh coated with the catalyst in the combustion flame, keep it at 800 - 1100 °C for 3 - 20 min, preferably keep it at 1000 °C for 10 min, and a CNT array will grow on the surface of the metal wire mesh to obtain an energy-conducting rib modified with a CNT array; among them, the fuel used for the combustion flame is one or several of C1 - C7 hydrocarbons.

[0045] In the catalyst solution, the catalyst is selected from one or several of ferric chloride, nickel nitrate, and cobalt nitrate, preferably nickel nitrate.

[0046] In the catalyst solution, the amount of substance of the catalyst is 0.5 - 2 mol / L, preferably 1 mol / L.

[0047] The combustion flame is selected from one of ethanol flame, methanol flame, methane flame, butane flame, heptane flame, acetone flame, acetylene flame, and ethylene flame, preferably ethanol flame.

[0048] Among them, the fuel used for the combustion flame is one or more of hydrocarbons with C1 - C7.

[0049] The metal wire mesh is selected from one of stainless steel mesh, nickel - chromium alloy wire mesh, iron - chromium - aluminum alloy wire mesh, and nickel - copper alloy wire mesh. Preferably, the metal mesh is 304 stainless steel mesh; the thickness is 0.4 mm - 0.8 mm; the wire diameter is 0.1 mm - 0.2 mm; and the wire spacing is 0.16 mm - 0.5 mm.

[0050] The CNT array is in - situ grown on the surface of the metal wire mesh by the flame method. The CNT array can not only improve the heat - generating and heat - transfer characteristics of the metal wire mesh, thereby improving the temperature uniformity of the welding area and the melting state of the resin, and enhancing the welding efficiency; at the same time, due to the nano - reinforcement effect, the interfacial bonding strength between the metal wire mesh and the resin is increased; these two beneficial effects significantly improve the mechanical properties of the composite material welding joint.

[0051] In the second aspect, the CNT in - situ growth - modified energy - guiding rib prepared by the above method is a metal wire mesh with a CNT array grown on its surface. Among them, the CNT array is composed of multi - wall CNTs, and the average length of the CNT array is 8 - 30 μm.

[0052] In the third aspect, the present embodiment provides a preparation method for a CNT in - situ growth - modified energy - guiding rib - enhanced composite material ultrasonic welding joint. The ultrasonic welding joint includes a thermoplastic composite material, the above - mentioned CNT in - situ growth - modified energy - guiding rib, and a thermoplastic resin film; among them, the thermoplastic composite material is the welding base material, the CNT in - situ growth - modified energy - guiding rib is the composite material ultrasonic energy - guiding element, and the thermoplastic resin film is the melting binder.

[0053] The thermoplastic composite material is a thermoplastic resin - based composite material reinforced by a reinforcing material, or a surface - plasticized thermosetting composite material. Among them, the reinforcing material is one or more of inorganic particles, whiskers, short fibers, or continuous fibers; the surface plasticization treatment is carried out by using a layer of thermoplastic resin film or a layer of thermoplastic prepreg.

[0054] Preferably, the size of the thermoplastic composite material laminate is: length: 50 mm, width: 10 mm, thickness: 2 mm.

[0055] The thermoplastic resin film is prepared from a thermoplastic resin that is the same as or has a similar polarity to the welding base material, specifically one of polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), nylon (PA), polyphenylene sulfide (PPS), polyetherimide (PEI), polyether ketone (PEK), polyether ether ketone (PEKK), polyether ether ketone (PEEK), polyarylether nitrile (PEN), phthaloyl side group-containing polyether ketone (PEK-C), phthaloyl side group-containing polyether sulfone (PEK-S), and poly(phthalazinone ether sulfone ketone) with heterophthalyl structure (PPESK). The thickness of the thermoplastic resin film is 0.1 - 0.3 mm.

[0056] The preparation method of the ultrasonic welding joint includes the following steps:

[0057] Wrap the upper and lower surfaces of the CNT in-situ growth modified energy guiding rib with a thermoplastic resin film, and then embed it in the overlapping area of two thermoplastic composite materials. Utilize the high-frequency vibration of ultrasonic waves. Under the action of pressure, the overlapping contact surfaces rub against each other to generate heat, causing the fiber-reinforced thermoplastic resin matrix composite material to rapidly melt and form a fusion between molecular layers. And utilize the self-melting of the fiber-reinforced thermoplastic resin matrix composite material coating to achieve the welding purpose and obtain a high-quality welding joint. By modifying the energy guiding rib with CNT in-situ growth, the interfacial strength of the joint is improved, and a high-quality welding joint is formed.

[0058] Preferably, ultrasonic vibration is applied for welding. Among them, the amplitude is 15 - 30 μm, the welding pressure is 0.2 - 0.6 MPa, and the ultrasonic time is 1 - 10 s; after the ultrasonic vibration ends, pressure is maintained. The pressure of 0.2 - 0.6 MPa is applied above the welding area by the ultrasonic vibration head. After the vibration head generates ultrasonic waves, pressure is maintained, and the pressure maintaining time is 1 - 10 s. Preferably, the size of the composite energy guiding rib during ultrasonic welding is 10 mm * 10 mm.

[0059] For the composite material ultrasonic welding joint enhanced by the CNT in-situ growth modified energy guiding rib prepared by the present invention, depending on the different thermoplastic resin matrices, the single-lap welding joint tensile shear strength (LSS) of various composite materials reaches 30 - 50 MPa.

[0060] When using high-performance thermoplastic resins such as PEI, PPS, and PEEK, the metal screen (SSM) is more conducive to the full flow and infiltration of the high-viscosity resin melt, and the strength of the formed welding joint is higher than that of carbon fiber (CF) and its fabric.

[0061] In-situ growth of CNT arrays on the surface of SSM by flame method, and the microscopic interface strength between the energy-conducting ribs and the resin is improved by the principle similar to "riveting". The excellent electrical and thermal conductivity of the CNT arrays will improve the heat generation characteristics of the SSM surface and the heat transfer efficiency in the interface region. At the same time, high thermal conductivity continuous carbon fibers (CCF) are added to the thermoplastic resin (TPF) matrix to construct a multi-dimensional heat transfer channel at the micron scale, which helps to improve the heat transfer efficiency of the SSM mesh and more remote areas, and significantly improve the uniformity of the temperature field.

[0062] The present invention will be further explained and illustrated below in conjunction with specific embodiments, but it is not intended to limit the protection scope of the present invention.

[0063] Example 1:

[0064] A preparation method of CNT in-situ growth modified energy-conducting ribs includes the following steps:

[0065] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into a sample with a size of 10 mm * 10 mm, and evenly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh by a spray gun to obtain a stainless steel mesh loaded with catalyst.

[0066] (2) Preparation by flame method: Place the stainless steel mesh loaded with catalyst at a position where the alcohol flame temperature is 1000 °C and stay for 10 min to prepare a stainless steel mesh modified with CNT arrays.

[0067] Perform SEM scanning on the stainless steel mesh modified with CNT arrays prepared in this example, and the microscopic morphology of its surface is shown in Figure 1 , from Figure 1 it can be seen that the CNTs on the stainless steel mesh form a regular array, and the average length of the CNT array is 15 μm.

[0068] Use the above-obtained CNT in-situ growth modified energy-conducting ribs to prepare an enhanced composite ultrasonic welded joint, including the following steps:

[0069] Coat the upper and lower surfaces of the stainless steel mesh modified with CNT arrays with a first PEEK film and a second PEEK film respectively, and embed it in the lap joint area of the carbon fiber reinforced PEEK composite material to be welded to obtain a workpiece to be processed and welded;

[0070] Place the lap joint in the device (see Figure 2) In it, the ultrasonic vibration head is placed on the welded part to be processed in the welding fixture, and ultrasonic vibration is applied to the upper side of the area to be welded; during the welding process, the vibration frequency of 15 kHz, the amplitude of 24 μm, the welding pressure of 0.25 MPa, the ultrasonic time of 2.5 s, and the pressure holding time of 10 s are applied through the ultrasonic vibration head; after cooling, an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite material is obtained, and its LSS value reaches 48.8 Mpa. At this time, the average length of the CNT array is 15 μm.

[0071] Example 2:

[0072] A preparation method of CNT in-situ growth modified energy guiding ribs includes the following steps:

[0073] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into a sample with a size of 10 mm * 10 mm, and evenly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh through a spray gun to obtain a stainless steel mesh loaded with catalyst.

[0074] (2) Preparation by flame method: Place the stainless steel mesh loaded with catalyst at a position where the alcohol flame temperature is 1000 °C and stay for 15 min to prepare a stainless steel mesh modified with CNT array.

[0075] A method for preparing an enhanced composite ultrasonic welded joint by using the above CNT in-situ growth modified energy guiding ribs includes the following steps:

[0076] Wrap the upper and lower surfaces of the stainless steel mesh modified with CNT array with PEEK films respectively, and embed it in the overlapping area of the carbon fiber reinforced PEEK composite material to be welded to obtain the welded part to be processed;

[0077] Place the ultrasonic vibration head on the welded part to be processed in the welding fixture, and apply ultrasonic vibration to the upper side of the area to be welded; during the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.25 MPa, an ultrasonic time of 2.5 s, and a pressure holding time of 10 s through the ultrasonic vibration head; after cooling, an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite material is obtained, and its LSS value reaches 44.6 MPa.

[0078] Example 3:

[0079] A preparation method of CNT in-situ growth modified energy guiding ribs includes the following steps:

[0080] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into samples with a size of 10 mm * 10 mm. Uniformly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh through a spray gun to obtain a stainless steel mesh loaded with the catalyst;

[0081] (2) Preparation by flame method: Place the stainless steel mesh loaded with the catalyst at a position where the temperature of the alcohol flame is 1000 °C and stay for 10 min to prepare a stainless steel mesh modified with a CNT array.

[0082] Using the above-prepared CNT in-situ growth modified energy guiding rib to prepare an enhanced composite ultrasonic welded joint, including the following steps:

[0083] Wrap the upper and lower surfaces of the stainless steel mesh modified with the CNT array with PEEK films respectively, and embed it in the lap joint area of the carbon fiber reinforced PEEK composite material to be welded;

[0084] Place the workpiece to be welded in the welding fixture with an ultrasonic vibration head, and apply ultrasonic vibration on the upper side of the area to be welded; During the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.25 MPa, an ultrasonic time of 2.5 s, and a holding pressure time of 10 s through the ultrasonic vibration head; After cooling, an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite material is obtained, and its LSS value reaches 46.3 MPa.

[0085] Example 4

[0086] A preparation method of a CNT in-situ growth modified energy guiding rib, including the following steps:

[0087] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into samples with a size of 10 mm * 10 mm. Uniformly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh through a spray gun to obtain a stainless steel mesh loaded with the catalyst;

[0088] (2) Preparation by flame method: Place the stainless steel mesh loaded with the catalyst at a position where the temperature of the alcohol flame is 1000 °C and stay for 10 min to prepare a stainless steel mesh modified with a CNT array.

[0089] Applying the above-prepared CNT in-situ growth modified energy guiding rib to prepare an enhanced composite ultrasonic welded joint, including the following steps:

[0090] Wrap the upper and lower surfaces of the stainless steel mesh modified with the CNT array with PEEK films respectively, and embed it in the lap joint area of the carbon fiber reinforced PEEK composite material to be welded to obtain a workpiece to be welded;

[0091] Place the ultrasonic vibration head on the welding fixture for the workpiece to be welded, and apply ultrasonic vibration on the upper side of the area to be welded; during the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.3 MPa, an ultrasonic time of 2.5 s, and a pressure holding time of 10 s through the ultrasonic vibration head; after cooling, obtain an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite, and its LSS value reaches 45.7 MPa.

[0092] Example 5

[0093] A preparation method of CNT in-situ growth modified energy guiding ribs includes the following steps:

[0094] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into a sample with a size of 10 mm * 10 mm, and evenly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh through a spray gun to obtain a stainless steel mesh loaded with catalyst.

[0095] (2) Preparation by flame method: Place the stainless steel mesh loaded with catalyst at a position where the alcohol flame temperature is 800 °C and stay for 10 min to prepare a stainless steel mesh modified with CNT arrays.

[0096] Apply a CNT in-situ growth modified energy guiding rib to enhance the preparation of an ultrasonic welded joint of a composite material, including the following steps:

[0097] Wrap the upper and lower surfaces of the stainless steel mesh modified with CNT arrays with PEEK films respectively, and embed it in the lap joint area of the carbon fiber reinforced PEEK composite material to be welded to obtain a workpiece to be welded.

[0098] Place the ultrasonic vibration head on the welding fixture for the workpiece to be welded, and apply ultrasonic vibration on the upper side of the area to be welded; during the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.25 MPa, an ultrasonic time of 2.5 s, and a pressure holding time of 10 s through the ultrasonic vibration head; after cooling, obtain an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite, and its LSS value reaches 41.1 MPa.

[0099] Example 6

[0100] A preparation method of CNT in-situ growth modified energy guiding ribs includes the following steps:

[0101] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into a sample with a size of 10 mm * 10 mm, and evenly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh through a spray gun to obtain a stainless steel mesh loaded with catalyst.

[0102] (2) Preparation by flame method: Place the stainless steel mesh loaded with catalyst at a position where the temperature of the alcohol flame is 800 °C and stay for 15 min to prepare a stainless steel mesh modified with CNT arrays.

[0103] A method for preparing an enhanced composite ultrasonic welded joint by in-situ growth modification of a CNT energy guiding rib includes the following steps:

[0104] Coat the upper and lower surfaces of the stainless steel mesh modified with CNT arrays with PEEK films respectively, and embed them in the overlapping area of the carbon fiber reinforced PEEK composite material to be welded to obtain a workpiece to be processed and welded;

[0105] Place the workpiece to be processed and welded in the ultrasonic vibration head of the welding fixture, and apply ultrasonic vibration on the upper side of the area to be welded; During the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.25 MPa, an ultrasonic time of 2.5 s, and a pressure holding time of 10 s through the ultrasonic vibration head; After cooling, an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite material is obtained, and its LSS value reaches 40.3 MPa.

[0106] Example 7

[0107] A preparation method of an in-situ growth modified CNT energy guiding rib includes the following steps:

[0108] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into samples with a size of 10 mm * 10 mm, and evenly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh to obtain a stainless steel mesh loaded with catalyst;

[0109] (2) Preparation by flame method: Place the stainless steel mesh loaded with catalyst at a position where the temperature of the alcohol flame is 800 °C and stay for 10 min to prepare a stainless steel mesh modified with CNT arrays.

[0110] A preparation method of an ultrasonic welded joint of a composite material enhanced by an in-situ growth modified CNT energy guiding rib includes the following steps:

[0111] Coat the upper and lower surfaces of the stainless steel mesh modified with CNT arrays with PEEK films respectively, and embed them in the overlapping area of the carbon fiber reinforced PEEK composite material to be welded to obtain a workpiece to be processed and welded;

[0112] Place the ultrasonic vibration head on the welded part to be processed in the welding fixture, and apply ultrasonic vibration on the upper side of the welding area; during the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.3 MPa, an ultrasonic time of 2.5 s, and a pressure holding time of 10 s through the ultrasonic vibration head; after cooling, obtain an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite, and its LSS value reaches 37.7 MPa.

[0113] Example 8

[0114] A preparation method of a CNT in-situ growth modified energy guiding rib, comprising the following steps:

[0115] (1) Spraying catalyst: Cut a stainless steel mesh with a wire diameter of 0.19 mm and a pore diameter of 0.32 mm into a sample with a size of 10 mm * 10 mm, and evenly spray the prepared nickel nitrate solution with a molar concentration of 1 mol / L on the surface of the stainless steel mesh through a spray gun to obtain a stainless steel mesh loaded with the catalyst;

[0116] (2) Preparation by flame method: Place the stainless steel mesh loaded with the catalyst at a position where the alcohol flame temperature is 800 °C and stay for 15 min to prepare a stainless steel mesh modified with a CNT array.

[0117] A preparation method of an ultrasonic welded joint of a composite material reinforced by a CNT in-situ growth modified energy guiding rib, comprising the following steps:

[0118] Wrap the upper and lower surfaces of the stainless steel mesh modified with the CNT array with PEEK films respectively, and embed it in the lap joint area of the carbon fiber reinforced PEEK composite material to be welded to obtain a welded part to be processed;

[0119] Place the ultrasonic vibration head on the welded part to be processed in the welding fixture, and apply ultrasonic vibration on the upper side of the welding area; during the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.3 MPa, an ultrasonic time of 2.5 s, and a pressure holding time of 10 s through the ultrasonic vibration head; after cooling, obtain an ultrasonic welded joint of CF / PEEK thermoplastic resin matrix composite, and its LSS value reaches 35.3 MPa.

[0120] As can be seen from Examples 1-8, the ultrasonic welding joint obtained in Example 1 has the highest LSS value. This is because based on the existing experiments, the metal mesh coated with the catalyst can ensure the full cracking of the carbon source when calcined at 1000°C for 10 min, resulting in a high crystallinity of CNT; when the ultrasonic vibration head applies a vibration frequency of 15 kHz and an amplitude of 24 μm, the tip effect of CNT is fully activated to promote the interface temperature rise; under a welding pressure of 0.25 MPa, the interface has good contact, high energy transfer efficiency, and the energy guiding rib structure will not be damaged; under an ultrasonic time of 2.5 s and a holding pressure time of 10 s, the interface diffusion is sufficient and the bonding force is significantly improved.

[0121] Comparative Example 1

[0122] Embed the metal mesh without loading CNT into the lap joint area of the carbon fiber reinforced PEEK composite material to be welded to obtain the workpiece to be processed. Place the workpiece to be processed in the welding fixture with the ultrasonic vibration head, and apply ultrasonic vibration on the upper side of the area to be welded; during the welding process, apply a vibration frequency of 15 kHz, an amplitude of 24 μm, a welding pressure of 0.25 MPa, an ultrasonic time of 2.5 s, and a holding pressure time of 10 s through the ultrasonic vibration head; after cooling, obtain the ultrasonic welding joint of the CF / PEEK thermoplastic resin matrix composite material, and its LSS value reaches 37.2 Mpa.

[0123] Compared with Comparative Example 1, the metal mesh modified with CNT as the energy guiding rib in Example 1 can greatly improve the strength of the ultrasonic welding joint. The reason is that both carbon nanotubes and the metal mesh have excellent thermal conductivity, and the metal mesh modified with CNT can further accelerate the conversion of ultrasonic vibration energy (mechanical energy) into heat energy, promote the local temperature rise at the welding interface, and optimize the energy distribution through the thermal conduction network. And CNT as the reinforcing phase can improve the overall shear resistance and fatigue resistance of the metal mesh. Finally, through the method of the present invention, CNT can be evenly distributed on the surface of the metal mesh to form a microscopic "anchoring effect", and strong interface bonding is achieved through chemical bonding + mechanical interlocking to form an ultrasonic welding joint with higher strength.

[0124] Those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and the practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field not disclosed in the present invention. The specification and examples are only regarded as exemplary, and the true scope and spirit of the present invention are pointed out by the following claims.

[0125] It should be understood that the present invention is not limited to the content described above and can be modified and changed without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A method for preparing CNT in-situ growth modified energy conducting ribs, characterized in that: include: The catalyst aqueous solution is evenly sprayed on the surface of the metal mesh, and then dried to obtain the metal mesh loaded with the catalyst; The metal wire mesh loaded with the catalyst is placed in a combustion flame and kept at 800-1100° C. for 3-20 minutes, and a CNT array is grown on the surface of the metal wire mesh to obtain a CNT array modified energy conducting rib; The fuel used for the combustion flame is one or more of C1 to C7 hydrocarbons.

2. The method for preparing CNT in-situ growth modified energy conductors according to claim 1, characterized in that: In the catalyst aqueous solution, the amount of the catalyst substance is 0.5-2 mol / L, and the catalyst is selected from one or more of ferric chloride, nickel nitrate, and cobalt nitrate.

3. The method for preparing CNT in-situ growth modified energy conductors according to claim 1, characterized in that: The combustion flame is selected from one of ethanol flame, methanol flame, methane flame, butane flame, heptane flame, acetone flame, acetylene flame and ethylene flame.

4. The method for preparing CNT in-situ growth modified energy conductors according to claim 1, characterized in that: The metal wire mesh is one of stainless steel wire mesh, nickel-chromium alloy wire mesh, iron-chromium-aluminum alloy wire mesh, and nickel-copper alloy wire mesh, with a thickness of 0.4mm-0.8mm and a wire diameter of 0.1mm-0.2mm; The wire spacing is 0.16mm-0.5mm.

5. The energy conducting rib obtained by the preparation method according to claims 1-4, characterized in that: The energy conducting ribs are metal wire meshes with CNT arrays grown on the surface, wherein the CNT arrays are composed of multi-walled CNTs, and the average length of the CNT arrays is 8-30 μm.

6. A method for preparing a reinforced composite ultrasonic welded joint using the energy conducting ribs according to claim 1, characterized in that: include: Thermoplastic composite laminates are used as welding base materials, CNT in-situ growth modified energy-conducting ribs are used as composite ultrasonic energy-conducting elements, and thermoplastic resin films are used as molten adhesives. Covering the upper and lower surfaces of the energy conducting ribs with a thermoplastic resin film; The energy-conducting ribs coated with thermoplastic resin films are embedded in the overlapping area of ​​two thermoplastic composite laminates. Ultrasonic vibration is applied to the overlapping contact surface of the overlapping area to combine the energy conducting ribs coated with the thermoplastic resin film with the thermoplastic composite laminate to obtain a high-quality welded joint; The thermoplastic resin film has the same polarity or a similar polarity to the resin in the welding base material.

7. The method for preparing a reinforced composite ultrasonic welded joint according to claim 6, characterized in that: The thermoplastic composite laminate is a thermoplastic resin-based composite laminate reinforced with a reinforcing material, or a thermosetting composite laminate with a surface plasticized treatment, wherein the reinforcing material is one or more of inorganic particles, whiskers, short fibers or continuous fibers; the surface plasticization treatment: a layer of thermoplastic resin film or a layer of thermoplastic prepreg is used to perform surface plasticization treatment on the thermoplastic resin.

8. The method for preparing a reinforced composite ultrasonic welded joint according to claim 6, characterized in that: The thermoplastic resin film is one of polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyacrylonitrile-butadiene-styrene (ABS), nylon (PA), polyphenylene sulfide (PPS), polyetherimide (PEI), polyetherketone (PEK), polyetheretherketone (PEKK), polyetheretherketone (PEEK), polyarylethernitrile (PEN), polyetherketone containing phthalide side groups (PEK-C), polyethersulfone containing phthalide side groups (PEK-S), and polyarylethersulfoneketone containing phthalide structure (PPESK); The thickness of the thermoplastic resin film is 0.1 to 0.3 mm.

9. The method for preparing a reinforced composite ultrasonic welded joint according to claim 6, characterized in that: The step of applying ultrasonic vibration to the overlapping contact surface of the overlapping area includes: the amplitude of the ultrasonic vibration is 15-30 μm, the welding pressure is 0.2-0.6 MPa, and the ultrasonic time is 1-10 s; After the ultrasonic vibration is completed, a pressure of 0.2-0.6MPa is applied above the welding area through the ultrasonic vibration head. After the vibration head generates ultrasonic waves, the pressure is maintained for 1-10s.

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