Method for obtaining fiber-reinforced composite materials

Abstract

The present invention relates to a method for obtaining a flame-retardant fiber-reinforced composite material or a laminate of fiber-reinforced composite materials, a) a step of obtaining an inorganic matrix, comprising: 70% to 80% by weight of an alkali silicate component, preferably selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, and more preferably potassium (K) silicate, wherein the silicate component is present in an aqueous solution; and a mixture of 70% to 80% by weight of an alkali silicate component, an amorphous silica component, and an aluminosilicate component, such as reactive aluminosilicate powder, in an amount of 20% to 30% by weight. The present invention includes the steps of: a) obtaining an inorganic matrix by mixing a mixture of amorphous silica and aluminosilicate components in a weight ratio of 5:1 to 25:1, where the weight ratio of silica to aluminosilicate components is 20% to 30% by weight; b) obtaining a prepreg composite material by pre-impregnating reinforcing fibers, preferably selected from the group consisting of carbon fibers, basalt fibers, and glass fibers, and more preferably carbon fibers, with the inorganic matrix obtained in step a); and c) exposing the prepreg composite material obtained in step b) to a pressure of 3 to 20 bar and a temperature of 180°C to 220°C for a period of 90 to 12 minutes. The present invention also relates to a composite material obtained by the method defined above, a method for producing an inorganic matrix for the manufacture of a flame-retardant fiber-reinforced composite material, and an inorganic matrix obtained by the method described above.

Description

[Technical Field]

[0001] The present invention relates to a method for obtaining fiber-reinforced composite materials.

[0002] In particular, the present invention relates to a method for obtaining and curing a flame-retardant fiber-reinforced composite material containing an inorganic matrix. [Background technology]

[0003] It is well known that the phases (or base materials) of a composite material consist of at least one reinforcing material and at least one matrix.

[0004] The reinforcing material may be, for example, reinforcing fibers, but is represented by a dispersed phase that has the function of ensuring rigidity and mechanical strength and bearing most of the load.

[0005] Generally, the matrix consists of a homogeneous phase that encloses the reinforcing material, ensures the aggregation of the composite material, homogenizes the dispersion of particles or reinforcing fibers within the composite, and avoids separation phenomena.

[0006] It is well known that fiber-reinforced composite materials having an inorganic matrix, particularly a ceramic matrix, are resistant to high temperatures.

[0007] For example, Patent Document 1 describes a method for obtaining an inorganic matrix for producing a fiber-reinforced composite material resistant to high temperatures. The composite material obtained from the above matrix is ​​characterized by having good mechanical properties, limited weight and thickness, and structural resistance to oxidation characteristic of high-temperature environments. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2018 / 179019 [Overview of the project]

[0009] However, known methods for producing fiber-reinforced composite materials containing inorganic matrices, particularly those belonging to the alkali-polycyate type aqueous inorganic polymer group also known as geopolymers or preceramic polymers, are known to involve very long and burdensome heat and pressure curing cycles.

[0010] In particular, known curing processes involve a first low-temperature curing and a subsequent high-temperature curing (or post-curing).

[0011] In the first low-temperature curing process, the material is slowly dried at a temperature of 40°C to 80°C for more than 8 hours, always below the boiling point of the aqueous solution (for example, in the specific case of potassium silicate, the boiling point is approximately 103°C). In this process, the aqueous base is slowly evaporated with the aim of gradually initiating the polymerization crosslinking process by dispersing the inorganic powder.

[0012] After the drying process is complete, a post-curing process, also defined as "ceramicization," is typically carried out at temperatures ranging from 600°C to over 1000°C, initiating the ceramicization of the matrix components. The ceramicization process is necessary to impart refractory properties to the product, more commonly, resistance to temperatures above 800°C. This process is carried out in the presence of an inert gas to prevent oxidation of the fiber reinforcement components, typically consisting of carbon fibers or silicon carbide fibers. Nevertheless, partial oxidation of the reinforcing fibers can occur during the ceramicization process under any circumstances.

[0013] More specifically, the conventional cycle for curing a laminate using a fiber-reinforced material and a matrix consisting of a pre-ceramic polymer or geopolymer is: a) A first curing step which is carried out in an autoclave or under pressure at a pressure value between 2 bar and 10 bar, or at atmospheric pressure at a temperature between 40°C and 80°C, and which may be carried out under vacuum for 12 hours, b) A second air drying process carried out at a temperature of 80°C for 6 hours, c) A third post-curing step, wherein the material is ceramicized at a temperature between 700°C and 1000°C, Includes.

[0014] For example, Patent Document 1 described above describes a specific curing process that includes a first curing step performed at a temperature between 40°C and 80°C and a pressure of 1 bar to 10 bar, a second post-curing step performed at a temperature between 100°C and 900°C to obtain a material characterized by a porosity of 20% to 30%, a third impregnation step, a fourth curing step, and a fifth post-curing step performed at a temperature between 250°C and 900°C.

[0015] As described above, by applying the known process described above, a laminate with a porosity of 20-30% can be obtained. In this regard, Patent Document 1 states that in order to obtain a lower porosity value which is more advantageous because it reduces the hygroscopicity of the material, the third impregnation step, the fourth curing step, and the fifth post-curing step can be repeated a certain number of times until the desired porosity is obtained. Therefore, in the prior art, in order to obtain a lower porosity, it is necessary to repeat the standard curing step, which is already a very long and energy-intensive process, many times.

[0016] Therefore, obtaining fiber-reinforced materials that can withstand high temperatures, especially around 1000°C, through long curing at low temperatures and potential post-curing makes the commercialization of such products difficult. This is particularly true for the following reasons, namely, - Due to the long curing cycle, the productivity per machine produced is low. - In particular, the energy cost of the curing cycle is high because it requires a dedicated post-curing oven that operates in the presence of an inert gas and at high operating temperatures (600°C or higher), which is expensive and has high operating costs. by.

[0017] Therefore, the above fiber reinforced products receive high commercial interest due to their lightweight and very high temperature resistance properties. However, in fields characterized by high productivity, such as the automotive and aviation industries, especially in the aviation structure industry, such materials are not applicable. In particular, fiber reinforced materials using carbon fiber and geopolymers are advantageously applied in these fields, but the use of the above curing cycle lengthens the production time and is particularly burdensome. In fact, such fields are characterized by the need to produce large quantities of products. As an example, Airbus manufactures approximately 500 aircraft per year, requires 4 hatches per aircraft, and thus a total of 2,000 products per year. In contrast, in the automotive industry, the cycle time of molded products is known to be at most 15 minutes per piece, typically 3 - 12 minutes. As is well known, this is determined by the need to meet production needs that can be quantified from 20,000 to 100,000 pieces per year only in the luxury car segment.

[0018] In light of the above, it is clear that there is a need to provide new composite materials and methods for manufacturing composite materials that can overcome the drawbacks of known materials and methods.

[0019] The solution according to the present invention is suitable in this context. That is, the solution according to the present invention aims to provide a new method for manufacturing fiber reinforced composite materials containing an inorganic matrix.

[0020] In particular, according to the present invention, by using a preceramic inorganic matrix characterized by a new composition and subjecting a provisional composite material (so-called prepreg material, i.e., a material composed of a reinforcing material and an inorganic matrix) to a single curing process under predetermined temperature and pressure conditions, it has been found that a flame-retardant fiber reinforced composite material characterized by better mechanical properties and lower porosity than materials obtained by known methods can be obtained.

[0021] More specifically, according to the method of the present invention, the provisional composite material is not subjected to a conventional ceramization process. Instead, it is subjected to a single curing process characterized by very low pressure values and temperature values compared to the values used in known methods. The preceramic inorganic matrix used according to the present invention can advantageously impart to the final product the same flame retardancy as that imparted by a conventionally known curing cycle when subjected to the curing process according to the present invention. Furthermore, the final composite material obtained according to the present invention is advantageously characterized by a porosity of 1.5% to 4%. According to the regulations, the lower the porosity, the lower the hygroscopicity of the material. In fact, the saturation absorption of the material obtained according to the present invention is about 1.80%.

[0022] Furthermore, the composite material obtained according to the present invention is characterized by better mechanical properties compared to products obtained by known methods. For example, when using a T700 twill 2x2 type carbon fabric according to the ASTM D3039 standard along the fiber axis, the elastic modulus obtained according to the present invention is 40 GPa, while using the same material, the elastic modulus obtained by known methods is 30 GPa. Furthermore, the composite material according to the present invention is characterized by a tensile strength of 250 GPa to 280 GPa, while in a known curing process, a material characterized by a tensile strength of about 160 MPa is obtained.

[0023] The better mechanical properties of the material according to the present invention are partly determined by an increase in density. In fact, the specific gravity of products obtained by known methods is included in the range of 1.10 g / cm 3 ~1.4 g / cm 3 whereas in the method of the present invention, products with a specific gravity of 1.55 g / cm 3 ~1.65 g / cm 3 are obtained. However, considering the resistivity of the material, it can be seen that the products obtained by the method according to the present invention are more advantageous overall compared to known products.

[0024] Furthermore, according to the present invention, by eliminating the ceramicization process, the reinforcing fibers are not partially oxidized, in contrast to the results obtained by known methods.

[0025] Therefore, according to the present invention, compared to known methods, - Characterized by an extremely short curing time, - The final material can be given good mechanical properties, - Can be used in environments characterized by contact with liquids (this property depends on a lower porosity, and therefore a lower possibility of absorption of the liquid the material comes into contact with). A new method for manufacturing fiber-reinforced composite materials is provided.

[0026] Therefore, the method according to the present invention is extremely advantageous compared to known curing processes used for preceramic polymers.

[0027] Therefore, the first specific object of the present invention is a) A step to obtain an inorganic matrix, - Preferably, an alkali silicate component selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, more preferably potassium (K) silicate, in an amount of 70% to 80% by weight, wherein the silicate component is present in an aqueous solution, and - A mixture of amorphous silica component and an aluminosilicate component, such as reactive aluminum silicate powder, in a weight ratio of 5:1 to 25:1, wherein the mixture of amorphous silica component and aluminosilicate component is 20% to 30% by weight, A process of obtaining an inorganic matrix by mixing, b) A step of obtaining a prepreg composite material, for example, a laminate of prepreg composite materials, by pre-impregnating reinforcing fibers, which are preferably selected from the group consisting of carbon fibers, basalt fibers, and glass fibers, and more preferably carbon fibers, with the inorganic matrix obtained in step a), c) The prepreg composite material obtained in step b) is subjected to a pressure of 3 to 20 bar and a temperature of 180°C to 220°C for a period of 90 to 12 minutes. This is a method for obtaining a flame-retardant fiber-reinforced composite material or a laminate of fiber-reinforced composite materials that includes [the specified element].

[0028] According to one embodiment of the present invention, step c) is, - Expose the material to a temperature of approximately 220°C for approximately 12 minutes, or, according to an alternative embodiment, to a temperature of approximately 180°C for approximately 90 minutes. Includes.

[0029] Furthermore, according to the present invention, step a) may further include mixing 1% to 3.5% by weight of beta-silicate, preferably in the form of nanoparticles, in addition to the alkali silicate component, the amorphous silica component, and the aluminosilicate component.

[0030] Preferably, according to the present invention, the amorphous silica component has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, molten silica, or calcined silica, and is preferably molten silica.

[0031] According to a preferred embodiment of the present invention, the amorphous aluminosilicate component is chemically controlled by the Al2O3×2SiO2 composition.

[0032] Accordingly, according to the method of the present invention, in step a), an alkali polysialate-type original aqueous inorganic polymer belonging to the geopolymer (which can also be defined as a preceramic polymer) group is prepared, then in step b), it is impregnated with reinforcing fibers such as woven or nonwoven carbon fibers, and finally, the prepreg composite material is subjected to the curing step described in step c).

[0033] The present invention is further obtained by the method defined above, and, - Reinforcement fibers, preferably selected from the group consisting of carbon fibers, basalt fibers, and glass fibers, and preferably carbon fibers, amounting to 40% to 60% by weight, - An inorganic matrix containing an alkali silicate component selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, preferably potassium (K) silicate, and 70% to 80% by weight, - A mixture of amorphous silica component and an aluminosilicate component, such as reactive aluminosilicate powder, in an amount of 20% to 30% by weight. This also applies to flame-retardant fiber-reinforced composite materials, Preferably, the inorganic matrix further comprises 1% to 3.5% by weight of beta-silicon carbide nanoparticles.

[0034] According to the present invention, the amorphous silica component preferably has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, fused silica, or calcined silica, with fused silica being preferred. Furthermore, the composite material has a density of 1.4 g / cm³. 3 ~1.7g / cm 3 For example, 1.55 g / cm³ 3 ~1.65g / cm 3 It may have a specific gravity and a porosity of 2-4%.

[0035] A further specific subject of the present invention is a method for obtaining an inorganic matrix for the production of flame-retardant fiber-reinforced composite materials, - 70% to 80% by weight of an alkali silicate component in aqueous solution form, selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, more preferably potassium (K) silicate, - A mixture of amorphous silica component and an aluminosilicate component, such as reactive aluminosilicate powder, wherein the weight ratio of silica component to aluminosilicate component is 5:1 to 25:1, and the mixture of amorphous silica component and aluminosilicate component is 20 to 30% by weight. This method involves mixing the ingredients.

[0036] In particular, according to the present invention, the method may further include mixing 1% to 3.5% by weight of beta-silicate, preferably in the form of nanoparticles, with the alkali silicate component and the mixture of amorphous silica and aluminosilicate components.

[0037] Furthermore, according to the present invention, the amorphous silica component preferably has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, molten silica, or calcined silica, and is preferably molten silica.

[0038] According to a preferred embodiment of the present invention, the aluminosilicate component is stoichiometrically controlled by the Al2O3×2SiO2 composition.

[0039] The present invention further relates to an inorganic matrix obtained by the method defined above. The matrix comprises 70% to 80% by weight of an alkali silicate component selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, preferably potassium (K) silicate; an amorphous silica component; and a mixture of 20% to 30% by weight of an aluminosilicate component, such as reactive aluminosilicate powder.

[0040] Preferably, according to the present invention, the inorganic matrix further comprises 1% to 3.5% by weight of beta-silicon carbide, more preferably in the form of nanoparticles, and the amorphous silica component has an average particle size of 0.01 to 15 microns and is selected from the group consisting of thermal silica, fused silica, or calcined silica, preferably fused silica. [Brief explanation of the drawing]

[0041] [Figure 1] This is an exploded view of a lithium-ion battery pack container equipped with a battery separator made of the composite material according to the present invention, as described in Example 3. [Modes for carrying out the invention]

[0042] The present invention will be described below by non-limiting illustrations, particularly with reference to examples and figures in the accompanying drawings, according to its preferred embodiments. - Figure 1 is an exploded view of a lithium-ion battery pack container equipped with a battery separator made of the composite material according to the present invention, as described in Example 3.

[0043] Example 1: An example of a method for manufacturing and curing a composite material according to the present invention.

[0044] An inorganic matrix was obtained by mixing 23% fused silica and 1%-2% metakaolin (amorphous aluminosilicate component) in a 75% solution of potassium silicate. Here, the percentages are weight percentages relative to the total weight of the resulting matrix.

[0045] Next, a provisional composite material, also known as a prepreg material, was obtained by impregnating the T7003K twill 2x2 carbon fabric with the previously obtained inorganic matrix.

[0046] Next, the prepreg composite material was exposed to a pressure of 7 to 70 bar and a temperature of 220°C for 12 minutes.

[0047] The laminate of the obtained composite material was characterized by the following mechanical properties. - Specific gravity: 1.6 g / m 3 - Elastic modulus: 40 GPa - Tensile strength: 280 MPa - Thermal conductivity: 0.3 W / mK - Porosity 2.5%

[0048] Example 2 Example of a method for manufacturing and curing a composite material according to the present invention

[0049] 21% by weight of molten silica and 1% by weight of metakaolin in a solution of 75.5% by weight of cesium silicate (cesium silicate) were mixed with 2.5% by weight of Beta SiC (beta silicon carbide) to obtain an inorganic matrix. Here, the percentages are weight percentages based on the total weight of the resulting matrix.

[0050] Next, the previously obtained inorganic matrix was impregnated into a T7003K twill 2×2 carbon fabric to obtain a provisional composite material, also called a prepreg material.

[0051] Next, the prepreg composite material was exposed to a pressure of 7 bar and a temperature of 220 °C for a period of 12 minutes.

[0052] The laminate of the obtained composite material was characterized by the following mechanical properties. - Specific gravity: 1.6 g / m 3 - Elastic modulus: 40 GPa - Tensile strength: 295 MPa - Thermal conductivity: 0.27 W / mK

[0053] The introduction of beta SiC has the advantage that the thermal conductivity decreases from 0.3 W / mK to 0.27 W / mK and the heat insulation property becomes better compared to the mixture obtained in Example 1.

[0054] Example 3 Example of application of the composite material according to the present invention

[0055] Using the composite material obtained in Example 2, several components of the lithium-ion battery pack container were fabricated.

[0056] In particular, Figure 1 shows a container for a lithium-ion battery pack 100, which comprises a container 1 consisting of two side walls 1a, 1b, an upper wall 1c, a lower wall or base wall 1d, a rear wall, and a front closing wall 1e, and includes a lithium-ion battery separator 2.

[0057] The lithium-ion battery separator 2 is placed between one battery pack and another battery pack and consists of walls 2a, 2b, and 2c supported by the structure 3. The separator is intended to prevent adjacent battery packs from suffering the same fate in the event of an explosion of one battery pack.

[0058] The front of the battery pack releases the explosion towards the pressure chamber (plenum chamber) through exhaust passage 4.

[0059] All of the walls 2a, 2b, and 2c of the separator 2 placed between the lithium battery packs, and all of the walls 1a, 1b, 1c, 1d, and 1e of the container, were fabricated using the materials and methods of Example 2.

[0060] The composite material of the present invention ensures that in the event of an explosion of a battery pack, a single battery, or all batteries, there will be no contamination of the surrounding environment with smoke or malodorous gases, and that the external temperature of the battery container will be 220°C or lower.

[0061] Such an explosion typically results in pressures between 4 and 10 bar, temperatures between 1400°C and 1800°C, and the release of molten lithium at the surface. Conservatively speaking, thermofluid dynamics calculations suggest that the separator and its cover of a lithium-ion battery pack must withstand internal pressures between 4 and 6 bar for 6 seconds, and up to 8 seconds, at temperatures between 1400°C and 1800°C, without degradation.

[0062] The material according to the present invention possesses resistance to high temperatures after exposure to the temperature properties of an explosion as specified above. It was confirmed that no morphological changes occurred in the material, even in zones where molten lithium accumulated after an explosion due to thermal runaway. To verify its resistance to fire events, a flame exposure test was performed on a sample at 1200°C and 120KW / m². 2 When exposed to a heat flow, the thermal conductivity remained unchanged at 0.27 W / mK. Tests using a universal testing machine showed that the material exhibited a decrease of approximately 60% in its mechanical properties.

[0063] Although the present invention has been described by non-limiting examples according to its preferred embodiments, it should be understood that modifications and / or changes may be introduced by those skilled in the art without departing from the scope of protection, as defined by the appended claims.

Claims

1. a) A process for obtaining an inorganic matrix, - A 70% to 80% by weight alkali silicate component, preferably selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, and more preferably potassium (K) silicate, wherein the silicate component is present in an aqueous solution, and the 70% to 80% by weight alkali silicate component, - A mixture of amorphous silica component and aluminosilicate component in an amount of 20% to 30% by weight, wherein the weight ratio of silica component to aluminosilicate component is 5:1 to 25:1, and A step of obtaining the inorganic matrix by mixing the following: b) A step of obtaining a prepreg composite material by pre-impregnating reinforcing fibers, preferably selected from the group consisting of carbon fibers, basalt fibers, and glass fibers, and more preferably carbon fibers, with the inorganic matrix obtained in step a), c) The prepreg composite material obtained in step b) is subjected to a pressure of 3 to 20 bar and a temperature of 180°C to 220°C for a period of 90 to 12 minutes. A method for obtaining a flame-retardant fiber-reinforced composite material containing [a specific substance].

2. Step a) further includes mixing 1% to 3.5% by weight of beta-silicon carbide in addition to the alkali silicate component, the amorphous silica component, and the aluminosilicate component. The method according to claim 1.

3. The amorphous silica component has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, fused silica, or calcined silica, preferably fused silica. The method according to claim 1 or 2.

4. - Reinforcement fibers, preferably selected from the group consisting of carbon fibers, basalt fibers, and glass fibers, and preferably carbon fibers, amounting to 40% to 60% by weight, - An inorganic matrix containing 70% to 80% by weight of an alkali silicate component, selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, preferably potassium (K) silicate, - A mixture of amorphous silica component and aluminosilicate component in an amount of 20% to 30% by weight, wherein the weight ratio of silica component to aluminosilicate component is 5:1 to 25:1, and Flame-retardant fiber-reinforced composite material containing [the specified element].

5. The inorganic matrix further comprises 1% to 3.5% by weight of beta-silicon carbide nanoparticles. The composite material according to claim 4.

6. The amorphous silica component has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, molten silica, or calcined silica, preferably molten silica. The composite material according to claim 4 or 5.

7. The composite material has a concentration of 1.4 g / cm³. ３ ~1.7 g / cm ３ For example, 1.55 g / cm³ ３ ~1.65 g / cm ３ Having a specific gravity, The composite material according to any one of claims 4 to 6.

8. The composite material has a porosity of 2% to 4%. The composite material according to any one of claims 4 to 7.

9. A method for obtaining an inorganic matrix for the manufacture of flame-retardant fiber-reinforced composite materials, - 70% to 80% by weight of an alkali silicate component in aqueous solution form, selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, more preferably potassium (K) silicate, - A mixture of amorphous silica component and aluminosilicate component in a weight ratio of 20 to 30% by weight, wherein the weight ratio of silica component to aluminosilicate component is 5:1 to 25:1, A method that includes mixing.

10. The present invention further includes mixing 1% to 3.5% by weight of beta-silicate in addition to the alkali silicate component and the mixture of the amorphous silica component and the aluminosilicate component. The method according to claim 9.

11. The amorphous silica component has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, molten silica, or calcined silica, preferably molten silica. The method according to claim 9 or 10.

12. An inorganic matrix for the manufacture of a flame-retardant fiber-reinforced composite material, wherein the matrix comprises 70% to 80% by weight of an alkali silicate component selected from the group consisting of cesium (Cs) silicate, sodium (Na) silicate, or potassium (K) silicate, preferably potassium (K) silicate, and 20% to 30% by weight of a mixture of amorphous silica component and aluminosilicate component, wherein the weight ratio of silica component to aluminosilicate component is 5:1 to 25:

1. Inorganic matrix for the manufacture of flame-retardant fiber-reinforced composite materials.

13. Further containing 1% to 3.5% by weight of beta-silicon carbide, The inorganic matrix according to claim 12.

14. The amorphous silica component has an average particle size of 0.01 microns to 15 microns and is selected from the group consisting of thermal silica, molten silica, or calcined silica, preferably molten silica. The inorganic matrix according to claim 12 or 13.

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