Closed-cell foamed aluminum composite board based on gradient composite structure and preparation method and application of closed-cell foamed aluminum composite board

Abstract

The invention discloses a closed-cell foamed aluminum composite board based on a gradient composite structure and a preparation method and application of the closed-cell foamed aluminum composite board, and belongs to the technical field of new energy automobile power battery protection. The closed-cell foamed aluminum composite board is composed of a continuous fiber reinforced thermoplastic plastic bottom plate, a gradient foamed aluminum core layer and a high-thermal-conductivity top plate. The preparation process comprises the steps of obtaining the gradient foamed aluminum core layer through a blowing foaming method or a melt foaming method, modifying the surface of the foamed aluminum core layer, achieving excellent mechanical interlocking and interface bonding of the fiber reinforced thermoplastic plastic and the foamed aluminum through a segmented low-temperature pressurization process, and meanwhile, achieving high-strength and high-toughness foamed aluminum composite material through the combination of technologies such as microwave welding / ultrasonic brazing and the like. And high-strength combination of the high-thermal-conductivity top plate and the foamed aluminum core layer is realized. The battery box solves the problems of contradiction between light weight and strength of a traditional battery box, poor durability of a foamed aluminum sandwich plate bonding interface and the like, and is suitable for safety protection scenes of new energy automobiles and energy storage systems.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicle power battery protection, and in particular to a closed-cell foam aluminum composite plate based on a gradient composite structure, and a preparation method and application thereof. Background Art

[0002] The lightweight battery system and excellent mechanical safety performance have become the prerequisites for the large-scale popularization and application of new energy vehicles, and determine the vehicle's driving range and safety.

[0003] Currently, the power battery boxes of new energy vehicles are mainly made of aluminum alloy plates (such as 6061-T6) or steel-aluminum hybrid structural plates. The following aspects of battery boxes made of the above two plate structures still need technical improvement: 1. The contradiction between lightness and strength. The aluminum alloy box must maintain a wall thickness of ≥2.5mm to meet the bottom compressive strength requirements (GB / T31467.3 stipulates compressive stiffness ≥10kN / mm). Although the steel bottom plate can be thinned to 1.2mm by stamping, the density is as high as 7.8g / cm 3 . 2. The bottom's ability to resist deformation is insufficient. In the actual use of new energy vehicles, both aluminum profiles and steel battery boxes have bottom collisions that cause mechanical damage to the battery cells, thereby causing thermal runaway problems. Although honeycomb aluminum structures can improve bending stiffness, the production process is complex and the cost is increased. Foamed aluminum has significant characteristics such as high energy absorption capacity, low density, high damping performance and low thermal conductivity. It is an effective means to reduce the weight of the battery box and improve mechanical protection.

[0004] Public patent CN208753404U proposes a battery box with foam aluminum sandwich panels. The foam aluminum sandwich panels are made of foam aluminum core panels and outer aluminum panels bonded together, but there are the following problems: 1) The failure caused by aging and fatigue of the metal / foam aluminum interface adhesive is not solved. The commonly used epoxy resin adhesive hydrolyzes in a wet and hot cycle environment, and the peel strength is reduced. At the same time, due to the difference in thermal expansion coefficients between aluminum and foam aluminum, the interface cracks after temperature shock. 2) The durability of the battery box bottom plate and the enclosure is reinforced by aluminum angle parts and rivets. Existing foam aluminum sandwich structures mostly use adhesives to connect metal panels, which are prone to interface peeling under wet and hot cycle conditions. Based on this, there is an urgent need for a battery box that integrates lightweight, high safety and durability. Summary of the Invention

[0005] The purpose of the present invention is to provide a closed-cell foam aluminum composite plate based on a gradient composite structure, a preparation method and application thereof, and through the innovation of gradient functional composite structure and composite process, a lightweight, highly safe and durable battery box is produced. Thermoplastic composite materials are used to replace the traditional metal bottom plate, combined with the high energy absorption characteristics of gradient foam aluminum, so that the weight of the box is reduced while meeting the bottom pressure resistance and thermal insulation requirements, solving the problems of the contradiction between lightweight and strength, insufficient bottom deformation resistance and so on in the existing technology.

[0006] To achieve the above objectives, the present invention provides a closed-cell foam aluminum composite plate based on a gradient composite structure, wherein the gradient composite structure includes a continuous fiber reinforced thermoplastic plastic bottom plate, a gradient foam aluminum core layer and a high thermal conductivity top plate.

[0007] The gradient composite structure includes a continuous fiber reinforced thermoplastic plastic bottom plate, a gradient foam aluminum core layer and a high thermal conductivity top plate.

[0008] Preferably, the thickness of the continuous fiber reinforced thermoplastic plastic base plate is 0.1-8.0 mm.

[0009] Preferably, the thermoplastic plastic is any one of polyetheretherketone PEEK, polyphenylene sulfide PPS, polyurea, polyamide PA66, polycarbonate PC, polyetherimide PEI, polypropylene PP, polyphenylene ether PPO, thermoplastic polyester PET, and polylactic acid PLA; the continuous fiber is any one of basalt fiber, carbon fiber, glass fiber, aramid fiber, and flax fiber;

[0010] The continuous fiber reinforced thermoplastic plastic base plate is any combination of the thermoplastic plastic and the continuous fiber.

[0011] Preferably, the density of the gradient aluminum foam core layer is 0.3-1.3 g / cm 3 .

[0012] Preferably, the high thermal conductivity top plate is a high thermal conductivity aluminum plate.

[0013] The present invention also provides a method for preparing a closed-cell aluminum foam composite plate based on a gradient composite structure, comprising the following steps:

[0014] (1) Preparation of gradient aluminum foam core layer

[0015] Prepared by air blowing foaming method or melt foaming method;

[0016] (2) Modification of gradient aluminum foam core layer

[0017] The lower surface of the gradient aluminum foam core layer is modified by sandblasting, laser modification or chemical etching;

[0018] (3) Composite

[0019] First, the lower surface of the high thermal conductivity top plate and the upper surface of the gradient foam aluminum core layer are composited by using one of microwave-assisted solid phase welding, ultrasonic-assisted brazing, controlled atmosphere brazing, stir friction welding or ordinary brazing. Then, the upper surface of the pretreated continuous fiber reinforced thermoplastic plastic bottom plate and the lower surface of the modified foam aluminum core layer are composited by segmented low-temperature pressurization.

[0020] Preferably, when adopting segmented pressurization and compounding, pressurization and compounding are carried out in a vacuum or inert gas hot pressing device according to gradient parameters, specifically:

[0021] The first stage: 120-140℃ / 0.5-2MPa / 1-5min;

[0022] Second stage: 140-160℃ / 0.5-2MPa / 1-5min;

[0023] The third stage: 170~450℃ / 1~8MPa / 1~30min.

[0024] The present invention also provides the use of the above-mentioned closed-cell foam aluminum composite board in the manufacture of new energy vehicle battery boxes.

[0025] Therefore, the closed-cell aluminum foam composite plate based on a gradient composite structure provided by the present invention, and its preparation method and application have the following beneficial effects:

[0026] (1) Multi-dimensional lightweight: By combining continuous fiber reinforced thermoplastics with gradient aluminum foam, the box is lighter than traditional metal structures and sandwich composite materials;

[0027] (2) Improved energy absorption: The porous structure of gradient aluminum foam improves absorption performance, and the continuous fiber reinforced plastic and aluminum foam achieve modulus matching, which improves bending resistance.

[0028] (3) Process compatibility: Low-temperature composite process (≤500°C) avoids damage to the foam structure.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of a closed-cell aluminum foam composite plate produced in an embodiment of the present invention;

[0031] Reference numerals:

[0032] 1. High thermal conductivity top plate; 2. Gradient foam aluminum core layer; 3. Continuous fiber reinforced thermoplastic bottom plate. DETAILED DESCRIPTION

[0033] like Figure 1As shown, the present invention provides a closed-cell aluminum foam composite plate based on a gradient composite structure, and the gradient composite structure is composed of the following three functional layers:

[0034] Functional Layer 1: A continuous fiber-reinforced thermoplastic baseplate 3 serves as a composite baseplate, achieving thermal insulation and lightweighting, replacing the original metal aluminum plate. This requires a plastic with high energy absorption and corrosion resistance. The thermoplastic is any one of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyurea, polyamide (PA66), polycarbonate (PC), polyetherimide (PEI), polypropylene (PP), polyphenylene ether (PPO), thermoplastic polyester (PET), and polylactic acid (PLA). The continuous fiber is any one of basalt fiber, carbon fiber, glass fiber, aramid fiber, and flax fiber. The continuous fiber-reinforced thermoplastic baseplate is any combination of the thermoplastic and the continuous fiber. The thickness of the continuous fiber-reinforced thermoplastic baseplate is 0.1-8.0 mm.

[0035] Functional layer 2: density of 0.3-1.3g / cm 3 The gradient foam aluminum core layer 2 is used as the middle layer, the purpose of which is to prevent bottom collisions, achieve lightweight and effectively absorb energy.

[0036] Functional layer three: A high thermal conductivity aluminum plate or other high thermal conductivity material is selected as a composite high thermal conductivity top plate 1 to dissipate the temperature of the battery.

[0037] The present invention also provides a method for preparing the above-mentioned closed-cell foam aluminum composite plate based on the gradient composite structure, which specifically comprises the following steps:

[0038] 1. Preparation of gradient aluminum foam: air blowing foaming method and melt foaming method with gradient temperature control.

[0039] 1) Preparation of gradient aluminum foam core layer by air blowing foaming method

[0040] Melt preparation: Melt aluminum or aluminum alloy in a heating furnace to 680-750℃.

[0041] Thickening treatment: Add a tackifier (such as Al2O3 or SiC powder, added in an amount of 1-10wt%) and disperse it evenly through high-speed stirring (speed 200-1500rpm) to increase the melt viscosity.

[0042] Gradient blowing: Initially, a large aperture (e.g., 3-5 mm) is opened, and high-pressure gas (0.2-0.5 MPa) is blown into the bottom of the melt, forming larger bubbles. Over time or as the position changes, the aperture is reduced (to 0.5-1 mm) and the gas pressure is lowered (0.05-0.1 MPa), generating smaller bubbles. The gas blown in is an inert gas, such as nitrogen or argon.

[0043] Cooling and shaping: Rapid cooling (cooling rate 10-30°C / s) through the spray cooling system to fix the gradient pore structure.

[0044] The adjustment of the aperture can be coordinated with the gas pressure, the vibration frequency of the blowing head and the temperature gradient to ensure a smooth transition of the bubble size gradient.

[0045] 2) Preparation of gradient aluminum foam core layer by melt foaming method

[0046] A. Temperature gradient distribution method

[0047] Mold design: Use segmented heating mold, set different temperatures in different areas (such as 600℃ at the bottom and 550℃ at the top).

[0048] Foaming process: After the melt is injected into the mold, the foaming agent in the bottom high-temperature area decomposes rapidly to form large holes; the foaming in the top low-temperature area is delayed, the bubble growth is restricted, and small holes are formed.

[0049] Cooling and shaping: gradient cooling (bottom cooling first, top cooling later), fixed hole structure.

[0050] B. Foaming agent gradient distribution method

[0051] Preparation of different types of aluminum melts: adding viscosity enhancer to the aluminum melt by adjusting the amount of foaming agent added (0.2wt%, 0.5wt%, 1wt% TiH2) and different types of foaming agents (TiH2, foaming agent pretreated TiH2 / Cu, etc.).

[0052] Different types of aluminum melts are heated to the decomposition temperature of the foaming agent (550-600°C), and gradient foam aluminum is prepared in different layers due to different concentrations and types of foaming agents.

[0053] By regulating the decomposition temperature of the foaming agent and matching the heating gradient of different layers of melt, a more precise porosity gradient of foamed aluminum can be achieved.

[0054] 2. Gradient foam aluminum modification, including physical modification and chemical modification. Physical modification includes sandblasting modification and laser modification. The purpose is to form microchannels on the surface of gradient foam aluminum, provide channels for continuous fiber reinforced thermoplastics after hot melting, and improve the composite effect.

[0055] Sandblasting modification: The closed-cell aluminum foam is modified by sandblasting. The sandblasting method is to spray sand into the aluminum foam at a speed of 20-1000m / s. The sandblasting raw material is selected with a particle size of 10-300 mesh. Sandblasting is used to penetrate the bubble wall of the closed pores of the closed-cell aluminum foam surface to obtain a modified closed-cell foam metal.

[0056] Chemical modification: Use hydrochloric acid or NaOH solution to etch the surface of aluminum foam to form controllable microchannels (pore size 10-50μm) to avoid mechanical damage.

[0057] Laser modification: Use laser to process micro grooves (depth 50-200μm) on the surface of foam aluminum to directionally guide the flow of thermoplastic melt and improve the bonding strength of the composite interface.

[0058] 3. Composite process

[0059] ① First, composite the lower surface of the high thermal conductivity top plate with the upper surface of the gradient foam aluminum core layer.

[0060] The top plate is made of 6061 aluminum alloy, and the top plate and the area with large gradient density are welded by microwave-assisted solid phase welding or ultrasonic-assisted brazing, controlled atmosphere brazing, stir friction welding, or ordinary brazing.

[0061] Microwave-assisted solid-phase welding: For 6061 aluminum plates, low-frequency microwaves (2.45GHz, power 500-800W) are used and short-time irradiation (10-30 seconds) is used to achieve local melting and prevent the foam aluminum core layer from expanding due to heat.

[0062] Ultrasonic assisted brazing: Using Sn-Ag-Cu solder, ultrasonic amplitude 10-20μm, frequency 20kHz, time 2-5 seconds, to achieve low temperature (200-250℃) high-efficiency welding.

[0063] Friction stir welding: rotation speed 750rpm, welding speed 35mm / min, pressing depth shoulder pressing down 0.2mm, ensuring that the stirring needle does not penetrate the foam aluminum to avoid damaging the porous structure.

[0064] Controlled atmosphere brazing: using BAISi-4 brazing filler metal and Nocolok flux; high temperature brazing (600°C) under inert atmosphere (argon) protection.

[0065] Ordinary brazing: use Zn or Zn-based brazing filler metal, temperature 420–430°C, keep warm for 1–5 minutes, argon protection; use Al-based brazing filler metal (such as Al-Si alloy), brazing temperature is about 600°C).

[0066] ② The upper surface of the pretreated continuous fiber reinforced thermoplastic plastic base plate and the lower surface of the modified foam aluminum core layer are composited by segmented pressure.

[0067] The pretreatment process is to pretreat the continuous fiber and thermoplastic matrix respectively. The treatment methods are different for different fibers and matrices. For example, carbon fiber is usually surface modified to increase surface activity and improve the interface bonding strength of the pre-matrix. For example:

[0068] Plasma treatment: Carbon fiber and basalt fiber are treated with low-temperature plasma (power 50-100W, time 5-15 minutes) to increase surface roughness and polar group content, and improve adhesion to the thermoplastic matrix.

[0069] Chemical coupling agent coating: Use silane coupling agent (KH550) to treat the fiber surface to reduce the contact angle (such as the contact angle of basalt fiber from 110° to 67°) and enhance wettability.

[0070] The matrix is typically dried or filled with fillers. Interface optimization is key to continuous fiber-reinforced thermoplastic composites and requires chemical oxidation, coupling agents, or plasma treatment, depending on the fiber type. Matrix modification requires a combination of drying, filler addition, or blending strategies to improve melt flow and interfacial bonding strength.

[0071] Pressurize and compound according to gradient parameters in a vacuum hot pressing furnace, specifically:

[0072] The first stage: 120-140℃ / 0.5-2MPa / 1-5min→Continuous fiber reinforced thermoplastic softening flow filling gradient aluminum foam microtexture;

[0073] Second stage: 140-160℃ / 0.5-2MPa / 1-5min→Mechanical interlocking is formed;

[0074] The third stage: 170-450℃ / 1-8MPa / 1-30min→interface diffusion layer is formed.

[0075] The technical solution of the present invention is further described below by means of the accompanying drawings and examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, and simplifications made without violating the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the protection scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application and belong to the scope of protection of the present invention.

[0076] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0077] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0078] Unless otherwise specified in the present invention, the reagents, instruments, and equipment used are those commonly used by those skilled in the art.

[0079] Example

[0080] This embodiment provides a method for preparing a closed-cell aluminum foam composite plate based on a gradient composite structure, which specifically includes the following steps:

[0081] (1) Preparation of gradient aluminum foam core layer by melt foaming method combined with temperature gradient mold

[0082] The mold is heated in sections, with different temperatures set in different areas (600°C at the bottom and 550°C at the top). After the melt is injected into the mold, the foaming agent in the high-temperature bottom area rapidly decomposes, forming large pores. Meanwhile, foaming in the low-temperature top area is delayed, limiting bubble growth and forming small pores. After gradient cooling (the bottom area cools first, the top area cools later), a fixed pore structure is formed.

[0083] (2) Sandblasting is used to modify the pores on the lower surface of the gradient foam aluminum core layer.

[0084] Sand is sprayed into the foamed aluminum at a speed of 500 m / s. The sandblasting material is selected to have a particle size of 10-300 mesh. The sand is used to penetrate the cell walls of the closed cells of the closed-cell foamed aluminum to obtain a surface-modified closed-cell foamed aluminum core layer.

[0085] (3) Composite process

[0086] Different continuous fibers were treated with low-temperature plasma (power 80W, time 10 minutes) to increase surface roughness and polar group content, and improve adhesion to the thermoplastic matrix. The different thermoplastic plastic matrices were vacuum dried, and then the continuous fibers were immersed in molten thermoplastic resin through an impregnation tank to form a prepreg with uniform fiber impregnation. After compression molding, the pretreated continuous fiber-reinforced thermoplastic plastic base plate was obtained.

[0087] The upper surface of the pretreated continuous fiber-reinforced thermoplastic plastic base plate was composited with the lower surface of the modified foam aluminum core layer. The lower surface of the 6061 aluminum alloy was then composited with the upper surface of the unmodified gradient foam aluminum core layer using microwave-assisted solid-phase welding. Specifically, Sn-Ag-Cu solder was used, with an ultrasonic amplitude of 15 μm, a frequency of 20 kHz, and a duration of 4 seconds to achieve low-temperature and high-efficiency welding.

[0088] The closed-cell aluminum foam composite sheet produced above was used to manufacture battery cases, and its density was measured. By combining continuous fiber-reinforced thermoplastics with gradient aluminum foam, the case is lighter than traditional metal structures. The specific material combinations and their density reductions are shown in Table 1:

[0089] Table 1

[0090]

[0091]

[0092] Furthermore, compared to conventional aluminum foam, the gradient aluminum foam's pore structure offers enhanced absorption performance, and the continuous fiber-reinforced plastic and aluminum foam achieve modulus matching, improving flexural properties. PEEK / CF or polyurea / BF composites offer 10-60% higher peak impact force and 20-80% higher energy absorption. Beyond battery enclosures, the materials produced by this invention can also be used in other applications requiring high energy absorption.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A closed-cell aluminum foam composite plate based on a gradient composite structure, characterized by: The gradient composite structure includes a continuous fiber reinforced thermoplastic plastic bottom plate, a gradient foam aluminum core layer and a high thermal conductivity top plate.

2. The closed-cell aluminum foam composite plate based on a gradient composite structure according to claim 1, characterized in that: The thickness of the continuous fiber reinforced thermoplastic plastic base plate is 0.1-8.0 mm.

3. The closed-cell aluminum foam composite plate based on a gradient composite structure according to claim 1, characterized in that: The thermoplastic plastic is any one of polyetheretherketone, polyphenylene sulfide, polyurea, polyamide, polycarbonate, polyetherimide, polypropylene, polyphenylene ether, thermoplastic polyester, and polylactic acid; the continuous fiber is any one of basalt fiber, carbon fiber, glass fiber, aramid fiber, and flax fiber; The continuous fiber reinforced thermoplastic plastic base plate is any combination of the thermoplastic plastic and the continuous fiber.

4. The closed-cell aluminum foam composite plate based on a gradient composite structure according to claim 1, characterized in that: The density of the gradient aluminum foam core layer is 0.3-1.3 g / cm 3 .

5. The closed-cell aluminum foam composite plate based on a gradient composite structure according to claim 1, characterized in that: The high thermal conductivity top plate is a high thermal conductivity aluminum plate.

6. The method for preparing a closed-cell aluminum foam composite plate based on a gradient composite structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparation of gradient aluminum foam core layer Prepared by air blowing foaming method or melt foaming method; (2) Modification of gradient aluminum foam core layer The lower surface of the gradient aluminum foam core layer is modified by sandblasting, laser modification or chemical etching; (3) Composite First, the lower surface of the high thermal conductivity top plate and the upper surface of the gradient foam aluminum core layer are composited by using one of microwave-assisted solid phase welding, ultrasonic-assisted brazing, controlled atmosphere brazing, stir friction welding or ordinary brazing. Then, the upper surface of the pretreated continuous fiber reinforced thermoplastic plastic bottom plate and the lower surface of the modified foam aluminum core layer are composited by segmented low-temperature pressurization.

7. The method for preparing a closed-cell aluminum foam composite plate based on a gradient composite structure according to claim 6, characterized in that: When using segmented pressurization and compounding, pressurization and compounding are carried out in a vacuum or inert gas hot pressing device according to gradient parameters, specifically: The first stage: 120-140℃ / 0.5-2MPa / 1-5min; Second stage: 140-160℃ / 0.5-2MPa / 1-5min; The third stage: 170~450℃ / 1~8MPa / 1~30min.

8. Application of a closed-cell aluminum foam composite plate based on a gradient composite structure according to any one of claims 1 to 5, characterized in that: The closed-cell aluminum foam composite plate is used in the manufacture of battery boxes for new energy vehicles.

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