Low-halogen flame-retardant fiber-reinforced sandwich composite material and preparation method thereof

Abstract

The application discloses a low-halogen flame-retardant fiber-reinforced sandwich composite material and a preparation method thereof. The composite material comprises, from bottom to top, a lower panel layer, a core material layer and an upper panel layer. Low-halogen flame-retardant adhesive film layers are arranged between the lower panel layer and the core material layer, between the core material layer and the upper panel layer, and between the core material layers. The application adopts a one-stage temperature control and segmented pressurization process, reduces the difficulty of equipment control and energy consumption, solves the problems of bubble residues in the sandwich structure through segmented pressurization, and improves the production efficiency. Carbon fiber mats and other sandwich materials are added to achieve the balance between lightweight and mechanical properties through gradient layering. The fiber resin prepreg panel, the core material and the low-halogen flame-retardant adhesive film layering sequence are changed to achieve the synergy of lightweight and high strength through gradient layering. Carbon fiber mats / bamboo fiber mats are used to replace part of the fiber resin prepreg layer to achieve weight reduction and optimize material cost. The core material flame-retardant and low-halogen flame-retardant adhesive film synergistic effect is adopted to improve the flame-retardant effect of the composite material.

Description

Technical Field

[0001] This invention relates to a composite material, specifically to a low-halogen flame-retardant fiber-reinforced sandwich composite material and its preparation method. Background Technology

[0002] With the increasing demand for lightweight materials in modern industry, especially the urgent need for high-strength lightweight structural materials in industries such as aerospace and new energy vehicles, traditional carbon fiber composites are facing insurmountable technical bottlenecks. Existing carbon fiber composites suffer from numerous problems in their preparation: traditional sandwich composites, when cured at a single temperature, are prone to thermal deformation of the sandwich foam, resulting in uneven resin impregnation and high porosity; improper processing of UD unidirectional tapes can easily lead to fiber damage, causing a significant decrease in mechanical properties; traditional carbon fiber laminates typically use multiple layers of UD (unidirectional) carbon fiber, which, while improving mechanical properties by increasing the number of UD layers, also increases material density, making it difficult to meet lightweight design requirements; furthermore, the preparation of traditional carbon fiber composites consumes a large amount of UD carbon fiber, leading to increased material costs, and their recycling is difficult, making them unsuitable for sustainable development.

[0003] Currently, the industry has explored some new directions: by adding short-cut carbon fibers to form a disordered porous network structure, the surface density of the material can be reduced while retaining certain mechanical properties; by introducing high specific strength and high closed-cell rate foam as core material, the overall structural stiffness can be improved after being combined with the board, providing a new idea for lightweighting.

[0004] Although foam sandwich structures have been widely used, single-temperature curing can easily cause thermal deformation of the foam, resulting in poor interfacial bonding between the foam and the upper and lower composite materials. At the same time, the performance of the carbon fiber mesh laminate structure (CFN) and the sandwich structure has not been fully coordinated, resulting in the overall material performance and lightweight effect not meeting expectations. It is difficult to balance flame retardancy and appearance quality, and cannot meet the multi-dimensional requirements of high-end equipment for low cost, high performance, and high aesthetics. Summary of the Invention

[0005] The purpose of this invention is to provide a low-halogen flame-retardant fiber-reinforced sandwich composite material and its preparation method. Through segmented pressure control process, synergistic layup design and innovation of low-halogen flame-retardant materials, the composite material achieves a synergistic improvement in lightweight, high mechanical properties, high flame retardancy and environmental protection, while reducing production costs.

[0006] The objective of this invention is achieved through the following technical solution: A low-halogen flame-retardant fiber-reinforced sandwich composite material adopts a sandwich structure, consisting of a lower panel layer, a core material layer, and an upper panel layer from bottom to top, wherein: Both the lower panel layer and the upper panel layer are made of fiber resin prepreg. The core material layer is made of one or more of the following: carbon fiber needle-punched felt, chopped carbon fiber felt (nonwoven), carbon fiber nonwoven fabric, carbon fiber paper, carbon fiber multiaxial fabric, carbon fiber-glass fiber hybrid fabric, bamboo fiber needle-punched felt, aramid fiber cloth, aramid needle-punched felt (Kevlar felt), ultra-high molecular weight polyethylene (UHMWPE) felt, basalt fiber cloth, basalt fiber needle-punched felt, glass fiber needle-punched felt, PMI (polymethacrylamide) foam, POM (polyoxymethylene) foam, PVC (polyvinyl chloride) foam, PET (polyethylene terephthalate) foam, PU (polyurethane) foam, phenolic foam, etc. The core material layer is at least one layer; A low-halogen flame-retardant adhesive film layer is provided between the lower panel layer and the core material layer, between the core material layer and the upper panel layer, and between the core material layers.

[0007] A method for preparing the above-mentioned low-halogen flame-retardant fiber-reinforced sandwich composite material includes the following steps: Step 1, Raw material processing: Cut and clean each layer of material; Step 2, Lamination: Prepare composite materials using a one-step / two-step process. One-step method: The fiber resin prepreg, low-halogen flame retardant film, core material, low-halogen flame retardant film, and fiber resin prepreg are laid out in the mold in one go, and the whole thing is hot-pressed and cured in one step. Two-step method: First, lay out the core material and low-halogen flame-retardant film separately according to the required design, and then lay out the panel layer, low-halogen flame-retardant film and core material a second time. Step 3: Hot pressing and curing molding: The stacked sandwich structure is placed in a hot press mold for curing, using a one-stage temperature control and segmented pressurization process to ensure that the resin is completely cured and forms a dense structure. Step 4: Cooling and demolding: After curing, stop heating, maintain constant pressure, cool to room temperature, release pressure, demold, and remove the part.

[0008] This invention prepares a low-halogen flame-retardant fiber-reinforced sandwich composite material with a single-stage temperature-controlled and segmented pressure-curing process. By optimizing the layup design of the composite material, weight reduction and material cost optimization are achieved while significantly improving the flame-retardant effect. Compared with the prior art, this invention has the following advantages: 1. The use of a segmented temperature control and pressurization process reduces the difficulty of equipment control and energy consumption. The segmented pressurization process solves problems such as residual air bubbles in the sandwich structure and improves production efficiency. 2. Add core materials such as carbon fiber felt, and achieve a balance between lightweight and mechanical properties through gradient layup; 3. By changing the layup sequence of fiber resin prepreg panel, core material, and low-halogen flame retardant film, lightweight and high strength are achieved through gradient layup; 4. A two-step molding process is adopted. First, the adhesive film and sandwich structure are prepared, and then the prepreg is laminated with it to complete the board molding.

[0009] 5. Use carbon fiber felt / bamboo fiber felt to replace part of the fiber resin prepreg layer to reduce weight and optimize material costs; 6. Enhanced interfacial synergy: Through the synergistic effect of the adhesive film layer and the prepreg layer, the interfacial bonding strength between the panel layer and the core layer is optimized, thereby improving the overall mechanical stability. 7. The synergistic effect of flame-retardant core material and low-halogen flame-retardant adhesive film is used to improve the flame-retardant effect of composite materials; 8. It can be applied to consumer electronics casings, lightweight automotive components, aerospace components, high-end equipment, transportation, and automotive interiors. Attached Figure Description

[0010] Figure 1 Flowchart for the preparation of low-halogen flame-retardant fiber-reinforced sandwich composite materials; Figure 2 This is a schematic diagram of the low-halogen flame-retardant fiber-reinforced sandwich composite material in Example 1; Figure 3 This is a schematic diagram of the low-halogen flame-retardant fiber-reinforced sandwich composite material in Example 2; Figure 4 This is a schematic diagram of the low-halogen flame-retardant fiber-reinforced sandwich composite material in Example 3; Figure 5 This is a schematic diagram of the low-halogen flame-retardant fiber-reinforced sandwich composite material in Example 4; Figure 6 This is a schematic diagram of the low-halogen flame-retardant fiber-reinforced sandwich composite material in Example 5; Figure 7 This is a schematic diagram of the low-halogen flame-retardant fiber-reinforced sandwich composite material in Example 6. Detailed Implementation

[0011] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0012] This invention provides a low-halogen flame-retardant fiber-reinforced sandwich composite material, wherein the composite material has a sandwich structure, consisting of a lower panel layer, a core material layer, and an upper panel layer from bottom to top, wherein: Both the lower panel layer and the upper panel layer are made of fiber resin prepreg. The resin in the fiber resin prepreg is one or more of the following: epoxy resin (bisphenol A type epoxy resin, phenolic epoxy resin, flexible epoxy resin), bismaleimide, phenolic resin (thermosetting phenolic resin, boron-modified phenolic resin), thermoplastic resin (polycarbonate (PC), polyamide (PA6 / PA66), polyetheretherketone (PEEK), polyphenylene sulfide (PPS)), unsaturated polyester resin (phthalic, isophthalic, vinyl ester resin), cyanate ester resin (bisphenol A type cyanate ester, modified cyanate ester), vinyl ester, polypropylene resin, polycarbonate, bio-based resin (soybean oil-based epoxy, polylactic acid (PLA) modified epoxy, bamboo fiber derived resin), polyetheretherketone, etc.; the fiber is one or more of the following: carbon fiber (conventional domestic and international benchmarks for Toray T300, T700, T800, M40x, M46J, etc. with equivalent performance), glass fiber, aramid fiber, basalt fiber, etc. The core material layer is made of one or more of the following: carbon fiber needle-punched felt, chopped carbon fiber felt (nonwoven), carbon fiber nonwoven fabric, carbon fiber paper, carbon fiber multiaxial fabric, carbon fiber-glass fiber hybrid fabric, bamboo fiber needle-punched felt, aramid fiber cloth, aramid needle-punched felt (Kevlar felt), ultra-high molecular weight polyethylene (UHMWPE) felt, basalt fiber cloth, basalt fiber needle-punched felt, glass fiber needle-punched felt, PMI (polymethacrylamide) foam, POM (polyoxymethylene) foam, PVC (polyvinyl chloride) foam, PET (polyethylene terephthalate) foam, PU (polyurethane) foam, phenolic foam, etc. The core material layer is at least one layer; A low-halogen flame-retardant adhesive film layer is provided between the lower panel layer and the core material layer, between the core material layer and the upper panel layer, and between the core material layers. The low-halogen flame-retardant adhesive film layer is made of resin and flame retardant, wherein the mass ratio of resin to flame retardant is 5~3:1; The flame retardants are mainly one or more of the following: phosphorus-based flame retardants (such as red phosphorus, ammonium polyphosphate (APP), triphenyl phosphate (TPP), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)), nitrogen-based flame retardants (such as guanidines, melamine cyanurate (MCA), melamine polyphosphate (MPP)), inorganic flame retardants (aluminum hydroxide (ATH), magnesium hydroxide (MH), montmorillonite (MMT), nano-calcium carbonate, graphene, nano-silica, nano-zinc borate (ZB)), intumescent flame retardants (pentaerythritol PER), silicon-based low-halogen flame retardants (polysiloxane), boron-based low-halogen flame retardants (zinc borate, metaborate), bio-based flame retardants (phytic acid, chitosan, cellulose and its derivatives, lignin-based flame retardants, cyclotriphosphazene derivatives, starch phosphate, bamboo charcoal derivatives), and phosphazenes (hexaphenoxycyclotriphosphazene, polydichlorophosphazene). The thickness of the composite material is 0.4~1mm; The thickness of the low-halogen flame-retardant adhesive film layer is 0.2~0.8mm; The density of the low-halogen flame-retardant adhesive film layer and the core material layer is 0.05~0.8 g / cm³. 3 The low-halogen flame-retardant adhesive film layer accounts for 20-45% of the entire board component.

[0013] This invention also provides a method for preparing the above-mentioned low-halogen flame-retardant fiber-reinforced sandwich composite material. The method involves changing the molding process and layup design to prepare the composite material, such as... Figure 1 As shown, the specific steps include the following: Step 1, Raw material processing: Cut the core material, low-halogen flame retardant film and fiber resin prepreg to the required size and clean their surfaces.

[0014] Step 2, Lay-up: Prepare sandwich composite materials using a one-step / two-step process: One-step method: The fiber resin prepreg, low-halogen flame retardant film, core material, low-halogen flame retardant film, and fiber resin prepreg are laid out in the mold in one go, and the whole thing is hot-pressed and cured in one step.

[0015] Two-step method: First, lay up the core material and low-halogen flame-retardant film separately according to the required design. Then, lay up the panel layer, low-halogen flame-retardant film and core material a second time and hot press them together.

[0016] Step 3: Hot pressing and curing molding: The stacked sandwich structure is placed in a hot press mold for curing. A one-stage temperature control and segmented pressurization process is adopted, with the curing temperature set at 80~160℃. First, it is pre-pressed at 0.3~0.5MPa for about 1~5 minutes to remove residual air between layers and compact the layers. After the pre-pressing is completed, the pressure is gradually increased to 0.5~1MPa and cured at constant temperature and pressure for 3~10 minutes to ensure that the resin fully wets the interface between the fiber and the core material and completes the curing and molding. Step 4: Cooling and demolding: After curing, stop heating, maintain constant pressure, cool to room temperature, release pressure and demold, remove the part and process and trim it.

[0017] Example 1 (1) Raw material processing The UD unidirectional tape prepreg, PMI foam, low-halogen flame retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and the surfaces are cleaned. The UD unidirectional tape prepreg includes carbon fiber and epoxy resin, and the low-halogen flame retardant film is made of epoxy resin and melamine cyanurate.

[0018] (2) One-step layup First, apply a release agent to the mold surface, then lay up the layers in one continuous, symmetrical sequence (from the mold surface upwards): The mold surface is coated with a release agent layer—two layers of UD unidirectional tape prepreg (0° / 90° alternating layup)—low halogen flame retardant film layer—carbon fiber felt—low ​​halogen flame retardant film layer—PMI foam core material—low halogen flame retardant film layer—carbon fiber felt—low ​​halogen flame retardant film layer—two layers of UD unidirectional tape prepreg (0° / 90° alternating layup) are laid up in one go in the mold; During the layup process, after every two layers of material, use a rubber roller to evenly press and vent air along the fiber direction. The pressing pressure should be controlled at 0.1~0.2MPa to avoid residual air bubbles between layers.

[0019] (3) Hot pressing and curing molding The sandwich structure is placed in a hot press mold, and a one-stage temperature control process is adopted, with the curing temperature set at 135℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress for 5 minutes under a pressure of 0.5 MPa to remove residual air between layers and compact the ply structure; Curing stage: After pre-pressurization, gradually increase the pressure to 1MPa and cure at constant temperature and pressure for 10 minutes to ensure that the resin fully wets the interface between the fiber and the core material and completes the curing process.

[0020] (4) Post-processing After curing, stop heating, maintain mold pressure, and cool to 50°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired result. Figure 1 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0021] Result: Density approximately 0.7 g / cm³ 3 It has a flame retardant rating of UL94 V-0, a low-halogen environmentally friendly halogen content of less than 900ppm, a molding cycle that is 42% shorter than the traditional segmented temperature control process, and tight interlayer bonding with no bubbles or delamination defects.

[0022] Example 2 (1) Raw material processing The UD unidirectional prepreg tape, POM foam, low-halogen flame retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and their surfaces are cleaned. The UD unidirectional prepreg tape consists of carbon fiber and epoxy resin, and the low-halogen flame retardant film is made of epoxy resin and aluminum hydroxide flame retardant.

[0023] (2) One-step layup First, apply a release agent to the mold surface, then lay up the layers in one continuous, symmetrical sequence (from the mold surface upwards): The mold surface is coated with a release agent layer—3 layers of UD unidirectional tape prepreg (0° / 90° alternating layup)—low halogen flame retardant film layer—carbon fiber felt—low ​​halogen flame retardant film layer—POM foam core material—low halogen flame retardant film layer—carbon fiber felt—low ​​halogen flame retardant film layer—3 layers of UD unidirectional tape prepreg (0° / 90° alternating layup) are laid up in one go in the mold; During the layup process, after every 3 layers of material, use a rubber roller to evenly press and vent air along the fiber direction. The pressing pressure should be controlled at 0.1~0.2MPa to avoid residual air bubbles between layers.

[0024] (3) Hot pressing and curing molding The sandwich structure is placed in a hot press mold, and a one-stage temperature control process is adopted, with the curing temperature set at 120℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress for 5 minutes under a pressure of 0.3 MPa to remove residual air between layers and compact the ply structure; Curing stage: After pre-pressurization, gradually increase the pressure to 0.5MPa and cure at constant temperature and pressure for 15 minutes to ensure that the resin fully wets the interface between the fiber and the core material and completes the curing process.

[0025] (4) Post-processing After curing, stop heating, maintain mold pressure, and cool to 50°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired result. Figure 2 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0026] Result: Density is 0.9 g / cm³ 3 It has a flame retardant rating of UL94V-0, a low-halogen environmentally friendly halogen content of less than 900ppm, a molding cycle that is 42% shorter than the traditional segmented temperature control process, and tight interlayer bonding with no bubbles or delamination defects.

[0027] Example 3 (1) Raw material processing The UD unidirectional prepreg tape, PMI foam, low-halogen flame retardant film, and bamboo fiber needle-punched felt are cut to the design dimensions and their surfaces are cleaned. The UD unidirectional prepreg tape consists of carbon fiber and epoxy resin, and the low-halogen flame retardant film is made of epoxy resin and APP flame retardant.

[0028] (2) One-step layup First, apply a release agent to the mold surface, then lay up the layers in one continuous, symmetrical sequence (from the mold surface upwards): The mold surface is coated with a release agent layer—3 layers of UD unidirectional tape prepreg (0° / 90° alternating layup)—low halogen flame retardant film layer—bamboo fiber felt—low ​​halogen flame retardant film layer—PMI foam core material—low halogen flame retardant film layer—bamboo fiber felt—low ​​halogen flame retardant film layer—3 layers of UD unidirectional tape prepreg (0° / 90° alternating layup) are laid up in one go in the mold; During the layup process, after every 3 layers of material, use a rubber roller to evenly press and vent air along the fiber direction. The pressing pressure should be controlled at 0.1~0.2MPa to avoid residual air bubbles between layers.

[0029] (3) Hot pressing and curing molding The sandwich structure is placed in a hot press mold, and a one-stage temperature control process is adopted, with the curing temperature set at 135℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress for 2 minutes under a pressure of 0.4 MPa to remove residual air between layers and compact the ply structure; Curing stage: After pre-pressurization, gradually increase the pressure to 0.6MPa and cure at constant temperature and pressure for 17 minutes to ensure that the resin fully wets the interface between the fiber and the core material and completes the curing process.

[0030] (4) Post-processing After curing, stop heating, maintain mold pressure, and cool to 50°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired result. Figure 3 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0031] Result: Density is 1.4 g / cm³ 3 It has a flame retardant rating of UL94 V-0, is low in halogens and environmentally friendly with halogen content below 900ppm, and has a molding cycle that is 42% shorter than the traditional segmented temperature control process. It has a tight interlayer bond and is free of bubbles and delamination defects.

[0032] Example 4 (1) Raw material processing The UD unidirectional prepreg tape, low-halogen flame-retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and their surfaces are cleaned. The UD unidirectional prepreg tape consists of carbon fiber and epoxy resin, and the low-halogen flame-retardant film is made of epoxy resin and DOPO.

[0033] (2) Two-step layup (sandwich preparation + hot pressing) ① Sandwich preparation: Lay out carbon fiber felt, low-halogen flame retardant film, PMI foam, low-halogen flame retardant film and carbon fiber felt in sequence, roll evenly with a rubber roller to remove air, ensure that there are no air bubbles or wrinkles between layers, align the edges of the layers with an error of ≤±0.5mm, and then cut for later use.

[0034] ②Hot pressing First, the UD unidirectional tape prepreg is laid out in a [0° / ±45° / 90°]s layer design, with a total of 6 layers. A release agent layer is applied to the mold surface. Then, 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°), a low-halogen flame-retardant film layer, a core assembly, another low-halogen flame-retardant film layer, and another 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°) are stacked and placed in a hot press mold. A one-stage temperature control process is used, with the curing temperature set at 135℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress at 0.5MPa pressure for 2 minutes to compact the sandwich structure and remove residual air; Curing stage: After pre-pressurization, gradually increase the pressure to 1MPa and cure at constant temperature and pressure for 5 minutes to ensure that the resin film melts and the resin is fully impregnated, so as to achieve a firm bond between the panel layer and the core material and complete the curing process. (3) Post-processing After curing, stop heating, maintain mold pressure, and cool to 50°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired result. Figure 4 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0035] Result: Density is 1.25 g / cm³ 3 It has a flame retardant rating of UL94V-0, is low in halogens and environmentally friendly with halogen content below 900ppm, and is free of wrinkles and delamination defects, making it suitable for the fabrication of complex curved surface components.

[0036] Example 5 (1) Raw material processing The UD unidirectional prepreg tape, POM foam, low-halogen flame retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and their surfaces are cleaned. The UD unidirectional prepreg tape consists of carbon fiber and epoxy resin, and the low-halogen flame retardant film is made of epoxy resin and APP flame retardant.

[0037] (2) Two-step layup (sandwich preparation + hot pressing) ① Sandwich preparation: Lay out carbon fiber felt, low-halogen flame retardant film, POM foam, low-halogen flame retardant film and carbon fiber felt in sequence, roll evenly with a rubber roller to remove air bubbles, ensure that there are no air bubbles or wrinkles between the layers, align the edges of the layers with an error of ≤±0.5mm, and then cut for later use.

[0038] ②Hot pressing First, the UD unidirectional tape prepreg is laid out in a [0° / ±45° / 90°]s layer design, for a total of 6 layers. A release agent layer is applied to the mold surface. Then, 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°), a low-halogen flame-retardant film layer, a core assembly, another low-halogen flame-retardant film layer, and another 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°) are stacked and placed in a hot press mold. A one-stage temperature control process is used, with the curing temperature set at 120℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress for 5 minutes under a pressure of 0.3MPa to compact the sandwich structure and remove residual air; Curing stage: After pre-pressurization, gradually increase the pressure to 0.8MPa and cure at constant temperature and pressure for 5 minutes to ensure that the resin film melts and the resin is fully impregnated, so as to achieve a firm bond between the panel layer and the core material and complete the curing process. (3) Post-processing After curing, stop heating, maintain constant mold pressure, and cool to 38°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired product. Figure 4 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0039] Result: Density is 1.3 g / cm³ 3 It has a flame retardant rating of UL94V-0, is low in halogens and environmentally friendly, and is free of wrinkles and delamination defects, making it suitable for the fabrication of complex curved surface components.

[0040] Example 6 (1) Raw material processing The UD unidirectional prepreg tape, POM foam, low-halogen flame retardant film, and bamboo fiber needle-punched felt are cut to the design dimensions and their surfaces are cleaned. The UD unidirectional prepreg tape consists of carbon fiber and epoxy resin, and the low-halogen flame retardant film is made of epoxy resin and DOPO.

[0041] (2) Two-step layup (sandwich preparation + hot pressing) ① Sandwich preparation: Lay out bamboo fiber felt, low-halogen flame retardant film, POM foam, low-halogen flame retardant film and bamboo fiber felt in sequence, roll evenly with a rubber roller to remove air bubbles, ensure that there are no air bubbles or wrinkles between the layers, align the edges of the layers with an error of ≤±0.5mm, and then cut for later use.

[0042] ②Hot pressing First, the UD unidirectional tape prepreg is laid out in a [0° / ±45° / 90°]s layer design, for a total of 6 layers. A release agent layer is applied to the mold surface. Then, 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°), a low-halogen flame-retardant film layer, a core assembly, another low-halogen flame-retardant film layer, and another 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°) are stacked and placed in a hot press mold. A one-stage temperature control process is used, with the curing temperature set at 120℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress at 0.4MPa pressure for 1 minute to compact the sandwich structure and remove residual air; Curing stage: After pre-pressurization, gradually increase the pressure to 1MPa and cure at constant temperature and pressure for 10 minutes to ensure that the resin film melts and the resin is fully impregnated, so as to achieve a firm bond between the panel layer and the core material and complete the curing process. (3) Post-processing After curing, stop heating, maintain constant mold pressure, and cool to 38°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired product. Figure 4 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0043] Result: Density is 1.1 g / cm³ 3 It has a flame retardant rating of UL94V-0, is low in halogens and environmentally friendly, and is free of wrinkles and delamination defects, making it suitable for the fabrication of complex curved surface components.

[0044] Example 7 (1) Raw material processing The UD unidirectional prepreg tape, PMI foam and POM foam, low-halogen flame retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and the surfaces are cleaned. The UD unidirectional prepreg tape includes carbon fiber and epoxy resin, and the low-halogen flame retardant film is made of epoxy resin and DOPO.

[0045] (2) Two-step layup (sandwich preparation + hot pressing) ① Sandwich preparation: Lay out carbon fiber felt, low-halogen flame retardant film, PMI foam, low-halogen flame retardant film, POM foam, low-halogen flame retardant film, and carbon fiber felt in sequence. Use a rubber roller to evenly press and remove air bubbles, ensuring that there are no air bubbles or wrinkles between the layers, and that the edges of the layers are aligned with an error of ≤±0.5mm. Then cut the layers for later use.

[0046] ②Hot pressing First, the UD unidirectional tape prepreg is laid out in a [0° / ±45° / 90°]s layer design, for a total of 6 layers. A release agent layer is applied to the mold surface. Then, 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°), a low-halogen flame-retardant film layer, a core assembly, another low-halogen flame-retardant film layer, and another 3 layers of UD unidirectional tape prepreg (alternating layups of 0° / ±45° / 90°) are stacked and placed in a hot press mold. A one-stage temperature control process is used, with the curing temperature set at 120℃. The segmented pressurization process is as follows: Pre-compression stage: Pre-compress at 0.5MPa pressure for 3 minutes to compact the sandwich structure and remove residual air; Curing stage: After pre-pressurization, gradually increase the pressure to 1MPa and cure at constant temperature and pressure for 9 minutes to ensure that the resin film melts and the resin is fully impregnated, so as to achieve a firm bond between the panel layer and the core material and complete the curing process. (3) Post-processing After curing, stop heating, maintain constant mold pressure, and cool to 38°C to prevent material deformation and cracking due to thermal stress. After cooling, release pressure, demold, and remove the part to obtain the desired product. Figure 4 The low-halogen flame-retardant fiber-reinforced sandwich composite material shown is an example.

[0047] Result: Density is 0.8 g / cm³ 3 It has a flame retardant rating of UL94V-0, is low in halogens and environmentally friendly, and is free of wrinkles and delamination defects, making it suitable for the fabrication of complex curved surface components.

[0048] Example 8 (1) Raw material processing The UD unidirectional tape prepreg, bamboo fiber needle-punched felt, low-halogen flame-retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and their surfaces are cleaned. The UD unidirectional tape prepreg includes carbon fiber and epoxy resin, and the low-halogen flame-retardant film is made of epoxy resin and melamine cyanurate.

[0049] (2) One-step layup The mold surface is coated with a release agent layer—two layers of UD unidirectional tape prepreg (0° / 90° alternating layup)—low halogen flame retardant film layer—carbon fiber felt—low ​​halogen flame retardant film layer—bamboo fiber needle-punched felt—low ​​halogen flame retardant film layer—carbon fiber felt—low ​​halogen flame retardant film layer—two layers of UD unidirectional tape prepreg (0° / 90° alternating layup) are laid up in one go in the mold; During the layup process, after every two layers of material, use a rubber roller to evenly press and vent air along the fiber direction. The pressing pressure should be controlled at 0.1~0.2MPa to avoid residual air bubbles between layers.

[0050] Pre-compression stage: Pre-compress for 5 minutes under a pressure of 0.5 MPa to remove residual air between layers and compact the ply structure; Curing stage: After pre-pressurization, gradually increase the pressure to 1MPa and cure at constant temperature and pressure for 10 minutes to ensure that the resin fully wets the interface between the fiber and the core material and completes the curing process.

[0051] (3) Post-processing Result: Density approximately 1.2 g / cm³ 3 It has a flame retardant rating of UL94 V-0, a low-halogen environmentally friendly halogen content of less than 900ppm, a molding cycle that is 42% shorter than the traditional segmented temperature control process, and tight interlayer bonding with no bubbles or delamination defects.

[0052] Example 9 (1) Raw material processing The UD unidirectional tape prepreg, low-halogen flame-retardant film, and carbon fiber needle-punched felt are cut to the design dimensions and then surface-cleaned. The UD unidirectional tape prepreg consists of carbon fiber and epoxy resin, and the low-halogen flame-retardant film is made of epoxy resin and APP flame retardant. (2) One-step layup The mold surface is coated with a release agent layer, followed by two layers of UD unidirectional tape prepreg (0° / 90° alternating layup), a low-halogen flame-retardant film layer, a carbon fiber felt, a low-halogen flame-retardant film layer, a carbon fiber felt, a low-halogen flame-retardant film layer, and two layers of UD unidirectional tape prepreg (0° / 90° alternating layup), all of which are laid up in one go within the mold. During the layup process, after every two layers of material, use a rubber roller to evenly press and vent air along the fiber direction. The pressing pressure should be controlled at 0.1~0.2MPa to avoid residual air bubbles between layers.

[0053] Pre-compression stage: Pre-compress for 5 minutes under a pressure of 0.5 MPa to remove residual air between layers and compact the ply structure; Curing stage: After pre-pressurization, gradually increase the pressure to 1MPa and cure at constant temperature and pressure for 10 minutes to ensure that the resin fully wets the interface between the fiber and the core material and completes the curing process.

[0054] (3) Post-processing Result: Density approximately 1.0 g / cm³ 3 It has a flame retardant rating of UL94 V-0, a low-halogen environmentally friendly halogen content of less than 900ppm, a molding cycle that is 42% shorter than the traditional segmented temperature control process, and tight interlayer bonding with no bubbles or delamination defects.

Claims

1. A low-halogen flame-retardant fiber-reinforced sandwich composite material, characterized in that... The composite material adopts a sandwich structure, consisting of a lower panel layer, a core material layer, and an upper panel layer from bottom to top, wherein: Both the lower panel layer and the upper panel layer are made of fiber resin prepreg. The core material layer is made of one or more of the following: carbon fiber needle-punched felt, chopped carbon fiber felt, carbon fiber nonwoven fabric, carbon fiber paper, carbon fiber multiaxial fabric, carbon fiber-glass fiber hybrid fabric, bamboo fiber needle-punched felt, aramid fiber cloth, aramid needle-punched felt, ultra-high molecular weight polyethylene felt, basalt fiber cloth, basalt fiber needle-punched felt, glass fiber needle-punched felt, PMI foam, POM foam, PVC foam, PET foam, PU foam, and phenolic foam. The core material layer is at least one layer; A low-halogen flame-retardant adhesive film layer is provided between the lower panel layer and the core material layer, between the core material layer and the upper panel layer, and between the core material layers.

2. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 1, characterized in that... In the fiber resin prepreg, the resin is one or more of epoxy resin, bismaleimide, phenolic resin, thermoplastic resin, unsaturated polyester resin, cyanate ester resin, vinyl ester, polypropylene resin, polycarbonate, bio-based resin, and polyetheretherketone resin; the fiber is one or more of carbon fiber, bamboo fiber, glass fiber, aramid fiber, and basalt fiber.

3. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 2, characterized in that... The epoxy resin is one or more of bisphenol A type epoxy resin, phenolic epoxy resin, and flexible epoxy resin; the phenolic resin is one or two of thermosetting phenolic resin and boron-modified phenolic resin; the thermoplastic resin is one or more of polycarbonate, polyamide, polyetheretherketone, and polyphenylene sulfide; the unsaturated polyester resin is one or more of orthophthalic, isophthalic, and vinyl ester resin; the cyanate ester resin is one or two of bisphenol A type cyanate ester and modified cyanate ester; and the bio-based resin is one or more of soybean oil-based epoxy, polylactic acid-modified epoxy, and bamboo fiber-derived resin.

4. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 1, characterized in that... The low-halogen flame-retardant adhesive film layer is made of resin and flame retardant, wherein the mass ratio of resin system to flame retardant is 5~3:

1.

5. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 4, characterized in that... The flame retardant is mainly one or more of the following: phosphorus-based flame retardants, nitrogen-based flame retardants, inorganic flame retardants, intumescent flame retardants, boron-based low-halogen flame retardants, bio-based flame retardants, and phosphazene flame retardants.

6. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 5, characterized in that... The phosphorus-based flame retardant is one or more of red phosphorus, ammonium polyphosphate, triphenyl phosphate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the nitrogen-based flame retardant is one or more of guanidine, melamine cyanurate, and melamine polyphosphate; the inorganic flame retardant is one or more of aluminum hydroxide, magnesium hydroxide, montmorillonite, nano-calcium carbonate, graphene, nano-silica, and nano-zinc borate; the intumescent flame retardant is pentaerythritol (PER); the silicon-based low-halogen flame retardant is polysiloxane; the boron-based low-halogen flame retardant is one or two of zinc borate and metaborate; the bio-based flame retardant is one or more of phytic acid, chitosan, cellulose and its derivatives, lignin-based flame retardants, cyclotriphosphazene derivatives, starch phosphate, and bamboo charcoal derivatives; and the phosphazene is one or two of hexaphenoxycyclotriphosphazene and polydichlorophosphazene.

7. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 1, characterized in that... The thickness of the composite material is 0.4~1mm; the thickness of the low-halogen flame-retardant adhesive film layer is 0.2~0.8mm.

8. The low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 1, characterized in that... The density of the low-halogen flame-retardant adhesive film layer and the core material layer is 0.05~0.5 g / cm³. 3 The low-halogen flame-retardant adhesive film layer accounts for 20-45% of the entire part.

9. A method for preparing a low-halogen flame-retardant fiber-reinforced sandwich composite material according to any one of claims 1-8, characterized in that... The method includes the following steps: Step 1, Raw material processing: Cut and clean each layer of material; Step 2, Lay-up: Prepare sandwich composite materials using a one-step or two-step process. One-step method: The fiber resin prepreg, low-halogen flame retardant film, core material, low-halogen flame retardant film, and fiber resin prepreg are laid out in the mold in one go, and the whole thing is hot-pressed and cured in one step. Two-step method: First, lay out the core material and low-halogen flame-retardant film separately according to the required design. Then, lay out the panel layer, low-halogen flame-retardant film and core material a second time and hot press them into shape. Step 3: Hot pressing and curing molding: The stacked sandwich structure is placed in a hot press mold for curing, using a one-stage temperature control and segmented pressurization process to ensure that the resin is completely cured and forms a dense structure. Step 4: Cooling and demolding: After curing, stop heating, maintain constant pressure, cool to room temperature, release pressure, demold, and remove the part.

10. The method for preparing the low-halogen flame-retardant fiber-reinforced sandwich composite material according to claim 9, characterized in that... In step 3, the curing temperature is 80~160℃. First, pre-compress at 0.3~0.5MPa for 1~5 minutes to remove residual air between layers and compact the layers. After pre-compression, gradually increase the pressure to 0.5~1MPa and cure at constant temperature and pressure for 3~10 minutes.

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