Thermoplastic composite corrugated sandwich structure and method of welding the same

Abstract

The application discloses a thermoplastic composite corrugated sandwich structure and a welding method thereof, and relates to the technical field of ultrasonic welding. The corrugated sandwich structure comprises a thermoplastic composite upper panel, a thermoplastic composite core layer and a thermoplastic composite lower panel. The thermoplastic composite upper panel is welded above the thermoplastic composite core layer through an energy transmission film. The thermoplastic composite lower panel is welded below the thermoplastic composite core layer through an energy transmission film. The application obtains original results in the design, manufacture and mechanical property characterization of the thermoplastic composite sandwich structure, and provides guidance for engineering application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultrasonic welding, and particularly relates to a thermoplastic composite corrugated sandwich structure and a welding method thereof. BACKGROUND

[0002] As a technology for quickly connecting thermoplastic composites, ultrasonic welding has the characteristics of high strength, short cycle, and no interface heterogeneity. By applying 20 kHz high frequency and 20-100 microns low amplitude mechanical vibration to the welding interface, heat is generated on the welding interface through surface friction and viscoelastic heating, which melts the energy guide and forms a weld on the welding surface.

[0003] Previous studies have shown that single lap shear test is the most typical method for characterizing the mechanical properties of ultrasonic welding interfaces. In contrast, other mechanical characterization methods are very rare. The results show that the load-carrying capacity of the spot welding interface can be comparable to that of the high-lock bolt of the same size, and has higher structural connection stiffness. In addition, the failure modes of the welding interface under the two loads are also significantly different. At present, due to the limitations of the welding process on the structure configuration, the experimental characterization method of the mechanical properties of TPC ultrasonic welding structure is still very single. In addition, although TPC has excellent fracture toughness and impact resistance, the study on the dynamic response and failure mechanism of the welded structure under impact load is still a blank. SUMMARY

[0004] The application aims to solve the problems of the prior art, and provides the following scheme:

[0005] A thermoplastic composite corrugated sandwich structure, comprising: a thermoplastic composite upper panel, a thermoplastic composite core layer, and a thermoplastic composite lower panel.

[0006] The thermoplastic composite upper panel is welded above the thermoplastic composite core layer by an energy transmission film.

[0007] The thermoplastic composite lower panel is welded below the thermoplastic composite core layer by an energy transmission film.

[0008] Preferably, the thermoplastic composite core layer is any one of a corrugated structure, a dot matrix structure, and a honeycomb structure.

[0009] Preferably, the material of the energy transmission film is thermoplastic resin or fiber-reinforced thermoplastic composite material.

[0010] The matrix of the thermoplastic resin is any one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide, polyformaldehyde, polycarbonate, polyether ether ketone, polyphenyl ether, polysulfone, and rubber.

[0011] The fiber in the fiber-reinforced thermoplastic composite material is any one of glass fiber, carbon fiber, graphite fiber, boron fiber, ceramic fiber, polyethylene fiber, polyamide fiber, PBO fiber and natural fiber.

[0012] The application further provides a welding method of a thermoplastic composite corrugated sandwich structure, which is used for welding the corrugated sandwich structure according to any one of the above.

[0013] Placing the energy transmission film between the thermoplastic composite upper panel and the thermoplastic composite core layer and between the thermoplastic composite lower panel and the thermoplastic composite core layer;

[0014] Fixing the thermoplastic composite core layer and the thermoplastic composite upper panel and the thermoplastic composite lower panel by a fixture;

[0015] Setting the working parameters of the ultrasonic generator and the thicknesses of the thermoplastic composite upper panel, the thermoplastic composite core layer, the thermoplastic composite lower panel and the energy transmission film based on a preset ultrasonic welding heat-force coupling model;

[0016] Melting the energy transmission film at the interface by the ultrasonic generator and synchronously applying pressure;

[0017] Releasing the fixture to weld the face-core connection to obtain the thermoplastic composite corrugated sandwich structure.

[0018] Preferably, the ultrasonic welding heat-force coupling model comprises:

[0019] In the welding initial stage, the interface friction between the energy transmission film and the composite material surface layer under high-frequency ultrasonic oscillation is expressed by using the Coulomb friction equation:

[0020]

[0021] Wherein, Q fric is the interface friction heat dissipation, α is the hammer coefficient, ω is the vibration frequency, μ is the friction system, σ yy (x) is the vertical stress of the horizontal interface, and u(x) is the displacement.

[0022] When the interface temperature generated after the interface friction is higher than the glass transition temperature of the thermoplastic polymer, the energy transmission film starts to melt, and the heat generation mechanism is converted into the viscoelastic flow of the thermoplastic polymer chain molecules, which is expressed by using the viscoelastic flow equation:

[0023]

[0024] wherein Q visco is the viscoelastic thermal dissipation, E' is the loss modulus of the material, ε * is the strain tensor, and α is the hammer coefficient.

[0025] Preferably, the operating parameters of the ultrasonic generator include: an operating frequency of 20 kHz, an ultrasonic amplitude of 50 μm-100 μm, and the applied pressure is 800 N.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The present application proposes to connect the thermoplastic composite corrugated sandwich structure by using ultrasonic welding technology, establishes a thermal-mechanical coupling model at the interface of the thermoplastic composite corrugated sandwich structure ultrasonic welding, clarifies the influence of process parameters and structural configuration on the interface thermodynamic behavior, develops the process mechanics and quality evaluation method of the thermoplastic composite corrugated structure ultrasonic welding, reveals the internal response law between the welding process and the structural strength, carries out the out-of-plane compression and drop hammer impact experiment to characterize the mechanical properties of the welded corrugated structure, and reveals the failure mode and failure mechanism of the structure; the present application obtains original results in the design and manufacture of the thermoplastic composite sandwich structure and the characterization of the mechanical properties, and provides guidance for its engineering application. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the present application, the following briefly introduces the drawings needed in the embodiments. Obviously, the drawings described in the following only some embodiments of the present application, and for those skilled in the art, without paying the creative labor, can also obtain other drawings according to these drawings.

[0029] Figure 1 It is a single corrugated sandwich structure schematic diagram of the embodiment of the present application;

[0030] Figure 2 It is a welding method flowchart schematic diagram of the embodiment of the present application;

[0031] Figure 3 It is a welding method flowchart block diagram of the embodiment of the present application;

[0032] Figure 4 It is a core layer and lower panel welding schematic diagram of the embodiment of the present application;

[0033] Figure 5 It is a core layer and upper panel welding schematic diagram of the embodiment of the present application.

[0034] Explanation of reference signs:

[0035] 1. Ultrasonic generator; 2. Thermoplastic composite upper panel; 3. Energy transmission membrane; 4. Thermoplastic composite core layer; 5. Thermoplastic composite lower panel; 6. Tooling fixture; 7. Support block. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] In this embodiment, as Figure 1 As shown, a thermoplastic composite corrugated sandwich structure includes: a thermoplastic composite upper panel 2, a thermoplastic composite core layer 4, and a thermoplastic composite lower panel 5. The thermoplastic composite upper panel 2 is welded to the top of the thermoplastic composite core layer 4 via an energy transfer membrane 3; the thermoplastic composite lower panel 5 is welded to the bottom of the thermoplastic composite core layer 4 via the energy transfer membrane 3.

[0040] The thermoplastic composite core layer 4 can be any of a corrugated structure, a lattice structure, or a honeycomb structure. The energy transfer membrane 3 is made of thermoplastic resin or fiber-reinforced thermoplastic composite material. The matrix of the thermoplastic resin can be any of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide, polyoxymethylene, polycarbonate, polyetheretherketone, polyphenylene ether, polysulfone, or rubber. The fibers in the fiber-reinforced thermoplastic composite material can be any of glass fiber, carbon fiber, graphite fiber, boron fiber, ceramic fiber, polyethylene fiber, polyamide fiber, PBO fiber, or natural fiber.

[0041] The presence of a core layer between the upper and lower panels gives the sandwich structure a greater specific stiffness than a single-layer solid structure of the same mass, thus enabling it to withstand higher static loads. When subjected to out-of-plane loads such as compression and impact, the core structure undergoes plastic deformation such as bending and buckling, thereby absorbing a large amount of energy. Therefore, the sandwich structure has a better energy absorption effect than the traditional laminated plate structure.

[0042] Example 2

[0043] In this embodiment, as Figure 2 , Figure 3 , Figure 4 andFigure 5 A welding method of a thermoplastic composite corrugated sandwich structure, comprising the following steps:

[0044] S1. Placing an energy transmission film 3 between the thermoplastic composite upper panel 2 and the thermoplastic composite core layer 4, and between the thermoplastic composite lower panel 5 and the thermoplastic composite core layer 4.

[0045] S2. Fixing the thermoplastic composite core layer 4 with the thermoplastic composite upper panel 2 and the thermoplastic composite lower panel 5 by a tooling fixture 6. In this embodiment, a support block 7 is also used to support the thermoplastic composite core layer 4.

[0046] S3. Based on a preset ultrasonic welding thermal-mechanical coupling model, setting the working parameters of the ultrasonic generator 1, and the thicknesses of the thermoplastic composite upper panel 2, the thermoplastic composite core layer 4, the thermoplastic composite lower panel 5 and the energy transmission film 3.

[0047] The ultrasonic welding thermal-mechanical coupling model includes: a welding starting stage, under high-frequency ultrasonic oscillation, the energy transmission film 3 and the composite material surface layer produce interfacial friction, which is expressed by the Coulomb friction equation:

[0048]

[0049] Wherein, Q fric is the interfacial friction heat dissipation, α is the hammer coefficient, ω is the vibration frequency, μ is the friction system, σ yy (x) is the vertical stress of the horizontal interface, u(x) is the displacement; when the interface temperature generated after the interface friction is higher than the glass transition temperature of the thermoplastic polymer, the energy transmission film 3 begins to melt, causing the activation of the thermoplastic polymer chain molecules, and the heat generation mechanism is converted into the viscoelastic flow of the thermoplastic polymer chain molecules, which is expressed by the viscoelastic flow equation:

[0050]

[0051] Wherein, Q visco is the viscoelastic heat dissipation, E' is the loss modulus of the material, ε * is the strain tensor, and α is the hammer coefficient. The working parameters of the ultrasonic generator 1 include: the working frequency is 20 kHz, the ultrasonic amplitude is 50 μm-100 μm, and the applied pressure is 800 N.

[0052] In order to numerically model the face-core connection of the corrugated sandwich structure, the following assumptions are made: Figure 1The model mainly includes three parts: the ultrasonic horn, the TPC upper and lower panels and the core layer, and the energy transfer film 3 at the interface. The composite panel and the core layer use the same material parameters, and the energy transfer film 3 uses the same resin material. Modeling is performed by using the finite element software COMSOL Multiphysics. To improve the calculation efficiency, according to the symmetry of the configuration, a 1 / 2 size two-dimensional model is constructed, which is composed of the upper composite attachment and the lower core layer of 1 / 2 and the energy transfer film 3 of 1 / 2. At the same time, the ultrasonic horn is applied to the top of the panel to exert uniform pressure and vertical displacement. At the same time, the horizontal boundary condition constraint is applied to the panel, and the horizontal and vertical constraints are applied to the core layer to ensure the stability of the structure during vibration. The friction heat source and the elastic thin layer are applied to the contact interface of the energy transfer film 3 and the panel and the core layer, and the viscoelastic heat source is applied to the energy transfer film 3. All couplings are processed by using the Newton iteration method to ensure the strict solution at the convergence. Large geometric changes are processed in the Euler frame, and when the lowest temperature in the thin film exceeds T m ℃, the resolution stops. Under the same welding conditions, that is, the welding pressure is 800 N and the maximum amplitude is 4 μm, we perform numerical simulation on the core layer with different thicknesses (1 mm, 2 mm, 3 mm) and the energy transfer film with different thicknesses (0.2 mm, 0.4 mm, 0.5 mm) to analyze their effects on the temperature field of the corrugated sandwich structure.

[0053] S4. The energy transfer film 3 is melted at the interface by the ultrasonic generator 1, and pressure is applied synchronously.

[0054] S5. The fixture clamp 6 is released, the face-core connection is welded, and the thermoplastic composite corrugated sandwich structure is obtained.

[0055] The above-described embodiments are only descriptions of the preferred modes of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A welding method for a corrugated sandwich structure made of thermoplastic composite material, characterized in that, Includes the following steps: An energy transfer membrane is placed between the upper panel and the core layer of the thermoplastic composite material, and between the lower panel and the core layer of the thermoplastic composite material. The thermoplastic composite core layer is fixed to the thermoplastic composite upper panel and the thermoplastic composite lower panel using tooling fixtures; Based on a preset ultrasonic welding thermo-mechanical coupling model, the working parameters of the ultrasonic generator, as well as the thicknesses of the thermoplastic composite upper panel, the thermoplastic composite core layer, the thermoplastic composite lower panel, and the energy transmission film are set. The ultrasonic welding thermo-mechanical coupling model includes: During the initial welding stage, interfacial friction occurs between the energy transfer membrane and the surface of the composite material under high-frequency ultrasonic oscillation, which is described using the Coulomb friction equation: ， in, For interfacial frictional heat dissipation, The hammer coefficient, The vibration frequency, For friction systems, The vertical stress at the horizontal interface. For displacement; When the interfacial temperature generated by interfacial friction is higher than the glass transition temperature of the thermoplastic polymer, the energy transfer film begins to melt. The heat generation mechanism is transformed into the viscoelastic flow of thermoplastic polymer chain molecules, which is described by the viscoelastic flow equation: ， in, For viscoelastic heat dissipation, The loss modulus of the material. For strain tensor, This is the hammer coefficient; The energy transfer membrane is melted at the interface using an ultrasonic generator, and pressure is applied simultaneously. Remove the tooling fixture and weld the core connection to obtain the corrugated sandwich structure of the thermoplastic composite material.

2. The welding method for a thermoplastic composite corrugated sandwich structure according to claim 1, characterized in that, The operating parameters of the ultrasonic generator include: operating frequency of 20... kHz The ultrasonic amplitude is 50 μm ~100 μm The applied pressure is 800. N .

3. A thermoplastic composite corrugated sandwich structure, wherein the sandwich structure is obtained by welding using the welding method according to any one of claims 1-2, comprising: Thermoplastic composite upper panel, thermoplastic composite core layer, and thermoplastic composite lower panel; The thermoplastic composite upper panel is welded above the thermoplastic composite core layer via an energy transfer membrane; The thermoplastic composite lower panel is welded below the thermoplastic composite core layer via an energy transfer membrane; The thermoplastic composite core layer can be any one of a corrugated structure, a lattice structure, or a honeycomb structure; The energy transfer membrane is made of thermoplastic resin or fiber-reinforced thermoplastic composite material; The matrix of the thermoplastic resin is any one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide, polyoxymethylene, polycarbonate, polyetheretherketone, polyphenylene ether, polysulfone, and rubber. The fibers in the fiber-reinforced thermoplastic composite material are any one of glass fiber, carbon fiber, graphite fiber, boron fiber, ceramic fiber, polyethylene fiber, polyamide fiber, PBO fiber, and natural fiber.

Images