A bilayer graded boron carbide composite material, its preparation method and application

Abstract

This invention belongs to the field of ballistic materials technology, specifically relating to a double-layer gradient boron carbide composite material, its preparation method, and its application. The material comprises a boron carbide ceramic layer and a carbon fiber-toughened boron carbide composite material layer, bonded together by a boron carbide deposition layer. The method provided by this invention not only completes the preparation of the carbon fiber-toughened boron carbide composite material layer but also achieves a strong bond between the boron carbide ceramic layer and the carbon fiber-toughened boron carbide composite material layer, improving the ballistic resistance of the double-layer ballistic structure. In the carbon fiber-toughened boron carbide composite material layer, with the increasing thickness of the pyrolytic carbon in the first, second, third, and fourth groups of carbon fiber cloth, as well as the increasing heat treatment temperature and time, the carbon fiber-toughened boron carbide composite material layer exhibits an increasing fracture toughness from the first group to the fourth group of carbon fiber cloth, further enhancing the ballistic resistance of the double-layer ballistic structure.

Description

Technical Field

[0001] This invention belongs to the field of ballistic materials technology, specifically relating to a double-layer gradient boron carbide composite material, its preparation method, and its application. Background Technology

[0002] The open sea environment makes it impossible for ships to evade anti-ship missile attacks; they can only passively resist through their armor and external anti-ballistic devices. With advancements in anti-ship missile warhead technology, the high-speed fragmentation generated by the warhead explosion possesses strong penetration capabilities. Increasing the structural thickness of a ship can improve its penetration resistance to some extent, but it increases the ship's weight and reduces its maneuverability. Therefore, to balance anti-ballistic performance and maneuverability, there is an urgent need to develop anti-ballistic devices that are both highly penetrable and lightweight.

[0003] Ceramics such as alumina, boron carbide, titanium diboride, and silicon carbide have a much lower density than steel and are characterized by high hardness and strength. Ballistic products made from these ceramics can rapidly passivate, erode, and fragment projectiles while resisting their penetration. However, due to their high brittleness and low tensile strength, these ceramics cannot absorb a large amount of energy when resisting projectile penetration, resulting in poor ballistic performance. Therefore, in practical applications, these ceramics are usually used as the faceplate, laminated with a backplate having high fracture toughness to form a double-layered ballistic product.

[0004] Existing double-layer ballistic protection products primarily use fiber-reinforced polymer-based composite materials for their backplates. These composites, due to their high fracture toughness, significantly improve the ballistic resistance of double-layer ballistic protection products. Recent studies have shown that while maintaining high fracture toughness, increasing the hardness, strength, and elastic modulus of the backplate can further enhance the ballistic resistance of double-layer ballistic protection products and reduce the back convexity of the ballistic material. However, polymer-based composite backplates, due to their low hardness and elastic modulus, do not possess the ability to further improve the ballistic resistance of double-layer ballistic protection products. Theoretical calculations indicate that if the fracture toughness of the backplate can be gradually increased while increasing its hardness and strength, there is even greater potential for improving the ballistic resistance of the product. Currently, there are no research reports on gradually increasing the fracture toughness of the backplate. Summary of the Invention

[0005] To address the problems in the background technology, this invention provides a bilayer gradient boron carbide composite material, its preparation method, and its application.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a double-layer gradient boron carbide composite material, comprising a boron carbide ceramic layer and a carbon fiber toughened boron carbide composite material layer, and is formed by bonding boron carbide deposition layers.

[0008] The carbon fiber toughened boron carbide composite material layer is composed of multiple sets of composite carbon fiber cloth. Each set of composite carbon fiber cloth consists of multiple sheets of carbon fiber cloth and pyrolytic carbon and boron carbide deposited sequentially on the surface of the carbon fiber cloth. The thickness of the pyrolytic carbon increases along the direction away from the boron carbide ceramic layer, with each set as a unit.

[0009] Furthermore, the thickness of the boron carbide deposition layer, the boron carbide deposited on the pyrolytic carbon on the surface of the carbon fiber cloth, is 60–90 μm.

[0010] In addition, the thickness of the pyrolytic carbon deposited on the surface of the carbon fiber cloth is 80–200 nm.

[0011] The thickness of the double-layer gradient boron carbide composite material is 26.5–29.8 mm, of which the boron carbide ceramic layer is 20 mm thick and the carbon fiber toughened boron carbide composite material layer is 6.5–9.8 mm thick.

[0012] The composite carbon fiber cloth consists of 4 groups, with each group comprising 6 to 9 sheets of carbon fiber cloth.

[0013] Furthermore, the thickness of pyrolytic carbon in the four groups of composite carbon fiber cloths, along the direction away from the boron carbide ceramic layer, is 80–110 nm, 110–140 nm, 140–170 nm, and 170–200 nm, respectively.

[0014] This invention also provides a method for preparing the aforementioned bilayer gradient boron carbide composite material, comprising the following steps:

[0015] (1) After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and subjected to high temperature heat treatment at 1760-1840℃ for 60-100 min to obtain the first composite carbon fiber cloth, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 80-200 nm.

[0016] (2) The first composite carbon fiber cloth with the same pyrolytic carbon thickness is taken as a group. Multiple groups of first composite carbon fiber cloth are laid on the boron carbide ceramic layer with stripes in sequence according to the order of increasing pyrolytic carbon thickness in the direction away from the boron carbide ceramic layer, and compacted to obtain a preform.

[0017] (3) Boron carbide is deposited by chemical vapor deposition of the preform to obtain a double-layer gradient boron carbide composite material.

[0018] Specifically, the operation is as follows:

[0019] (1) The first composite carbon fiber cloth of the first group includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1760 to 1780℃ for 60 to 70 minutes. The thickness of pyrolytic carbon on the surface of each carbon fiber cloth is 80 to 110 nm.

[0020] The second group of first composite carbon fiber cloth includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1780 to 1800℃ for 70 to 80 minutes. The thickness of pyrolytic carbon on the surface of each carbon fiber cloth is 110 to 140 nm.

[0021] The third group of first composite carbon fiber cloth includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1800 to 1820℃ for 80 to 90 minutes. The thickness of pyrolytic carbon on the surface of each carbon fiber cloth is 140 to 170 nm.

[0022] The first composite carbon fiber cloth in the fourth group includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1820 to 1840℃ for 90 to 100 minutes. The thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 170 to 200 nm.

[0023] (2) The four groups of first composite carbon fiber cloths are laid on the striped boron carbide ceramic layer in sequence according to the increasing thickness of pyrolytic carbon along the direction away from the boron carbide ceramic layer, and compacted to obtain a preform.

[0024] (3) Boron carbide is deposited by chemical vapor deposition on the preform, with a boron carbide thickness of 60-90 μm, to obtain a double-layer gradient boron carbide composite material.

[0025] In step (2), the cross-section of the stripe is an isosceles trapezoid with a height of 0.5-0.8 mm, an upper side length of 0.3-0.5 mm, and a lower side length of 0.9-1.2 mm.

[0026] The present invention also provides an application of the aforementioned double-layer gradient boron carbide composite material in ballistic materials.

[0027] Beneficial effects

[0028] The method provided by this invention not only completes the preparation of the carbon fiber toughened boron carbide composite material layer, but also achieves a firm bond between the boron carbide ceramic layer and the carbon fiber toughened boron carbide composite material layer. The resulting double-layer gradient boron carbide composite material can effectively prevent the back plate from separating from the front plate when the projectile penetrates the front plate (i.e., the boron carbide ceramic layer) and reaches the back plate (i.e., the carbon fiber toughened boron carbide composite material layer), thereby improving the ballistic resistance of the double-layer ballistic structure.

[0029] In the carbon fiber toughened boron carbide composite material layer provided by the present invention, as the pyrolytic carbon thickness of the first, second, third, and fourth groups of carbon fiber cloths, as well as the heat treatment temperature and time increase, the carbon fiber toughened boron carbide composite material layer can exhibit the characteristic of increasing fracture toughness from the first group to the fourth group of carbon fiber cloths, which helps to further improve the ballistic effect of the double-layer ballistic structure.

[0030] The present invention can significantly improve the surface smoothness of carbon fibers by depositing pyrolytic carbon on carbon fiber cloth, thereby improving the fracture toughness of the prepared carbon fiber toughened boron carbide composite material. In addition, high temperature heat treatment can improve the graphitization degree of pyrolytic carbon, thereby improving the lubricity of pyrolytic carbon, which helps to further improve the fracture toughness of the prepared composite material. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the preparation process of the bilayer gradient boron carbide composite ballistic product of the present invention.

[0032] Figure 2 This is a cross-sectional geometry of the stripes processed on the back of the boron carbide ceramic panel of the present invention.

[0033] Figure 3 This is an electron micrograph of the cross-section of the carbon fiber before pyrolytic carbon deposition on the surface of the carbon fiber cloth of the present invention.

[0034] Figure 4 This is an electron micrograph of the cross-section of carbon fiber after pyrolytic carbon deposition on the surface of the carbon fiber cloth of the present invention.

[0035] Figure 5 This is a cross-sectional electron micrograph of the carbon fiber toughened boron carbide composite material prepared by chemical vapor deposition in this invention.

[0036] Figure 6 This is a high-resolution transmission image of the interface of the carbon fiber toughened boron carbide composite material prepared by chemical vapor deposition in this invention. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] To address the issues of low hardness and elastic modulus of fiber-reinforced polymer composites, which prevent them from fully utilizing the ballistic effect of the double-layer structure when used as backing plates, and the lack of information on the gradual increase in fracture toughness of backing plates, this invention provides a double-layer gradient boron carbide composite material, comprising a boron carbide ceramic layer and a carbon fiber-reinforced boron carbide composite material layer, and is formed by bonding boron carbide deposition layers.

[0039] The carbon fiber toughened boron carbide composite material layer is composed of multiple sets of composite carbon fiber cloth. Each set of composite carbon fiber cloth consists of multiple sheets of carbon fiber cloth and pyrolytic carbon and boron carbide deposited sequentially on the surface of the carbon fiber cloth. The thickness of the pyrolytic carbon increases along the direction away from the boron carbide ceramic layer, with each set as a unit.

[0040] Furthermore, the thickness of the boron carbide deposition layer, the boron carbide deposited on the pyrolytic carbon on the surface of the carbon fiber cloth, is 60–90 μm.

[0041] In addition, the thickness of the pyrolytic carbon deposited on the surface of the carbon fiber cloth is 80–200 nm.

[0042] The thickness of the double-layer gradient boron carbide composite material is 26.5–29.8 mm, of which the boron carbide ceramic layer is 20 mm thick and the carbon fiber toughened boron carbide composite material layer is 6.5–9.8 mm thick.

[0043] The composite carbon fiber cloth consists of 4 groups, with each group comprising 6 to 9 sheets of carbon fiber cloth.

[0044] The thickness of pyrolytic carbon in the four groups of composite carbon fiber cloths, along the direction away from the boron carbide ceramic layer, is 80–110 nm, 110–140 nm, 140–170 nm, and 170–200 nm, respectively.

[0045] The aforementioned double-layer gradient boron carbide composite material can effectively prevent the back plate from separating from the front plate when the projectile penetrates the front plate (i.e., the boron carbide ceramic layer) and reaches the back plate (i.e., the carbon fiber toughened boron carbide composite material layer and the boron carbide deposition layer, referred to as the carbon fiber toughened boron carbide ceramic matrix composite material), thereby improving the ballistic resistance of the double-layer ballistic structure.

[0046] Among them, the boron carbide ceramic panel is made by hot pressing or pressureless sintering and can be purchased commercially.

[0047] The present invention also provides a method for preparing the bilayer gradient boron carbide composite material as described in claim 1, comprising the following steps:

[0048] (1) After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and subjected to high-temperature heat treatment at 1760-1840℃ for 60-100 min to obtain the first composite carbon fiber cloth, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 80-200 nm.

[0049] (2) The first composite carbon fiber cloth with the same pyrolytic carbon thickness is taken as a group. Multiple groups of first composite carbon fiber cloth are laid on the boron carbide ceramic layer with stripes in sequence according to the increasing pyrolytic carbon thickness in the direction away from the boron carbide ceramic layer, and compacted to obtain a preform.

[0050] The cross-section of the stripes is an isosceles trapezoid, such as... Figure 2 As shown, the height of the isosceles trapezoid is 0.5–0.8 mm, the length of the upper side is 0.3–0.5 mm, and the length of the lower side is 0.9–1.2 mm.

[0051] (3) Boron carbide is deposited by chemical vapor deposition of the preform to obtain a double-layer gradient boron carbide composite material.

[0052] like Figure 1 As shown, the specific operation of the preparation method is as follows:

[0053] (1) The first composite carbon fiber cloth of the first group includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1760 to 1780℃ for 60 to 70 minutes. The thickness of pyrolytic carbon on the surface of each carbon fiber cloth is 80 to 110 nm.

[0054] The second group of first composite carbon fiber cloth includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1780 to 1800℃ for 70 to 80 minutes. The thickness of pyrolytic carbon on the surface of each carbon fiber cloth is 110 to 140 nm.

[0055] The third group of first composite carbon fiber cloth includes 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon and heat-treated at 1800 to 1820℃ for 80 to 90 minutes. The thickness of pyrolytic carbon on the surface of each carbon fiber cloth is 140 to 170 nm.

[0056] The first composite carbon fiber cloth in Group 4 consists of 6 to 9 carbon fiber cloths. After chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, it is placed in argon gas and heat-treated at 1820 to 1840°C for 90 to 100 minutes. The thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 170 to 200 nm.

[0057] The cross-sectional morphology of carbon fibers before pyrolytic carbon deposition on the surface of carbon fiber cloth is as follows: Figure 3 As shown, the cross-sectional morphology of the carbon fiber after pyrolytic carbon deposition on the surface of the carbon fiber cloth in Group 2 is as follows. Figure 4 As shown, the surface of the original carbon fiber is relatively rough before pyrolytic carbon deposition. Figure 3 ), depositing pyrolytic carbon can significantly improve the surface smoothness of carbon fibers. Figure 4 This improves the fracture toughness of the prepared composite material layer.

[0058] In addition, high-temperature heat treatment can increase the graphitization degree of pyrolytic carbon, thereby improving the lubricity of pyrolytic carbon, which helps to further improve the fracture toughness of the prepared composite material.

[0059] (2) The four groups of first composite carbon fiber cloths are laid on the striped boron carbide ceramic layer in sequence according to the increasing thickness of pyrolytic carbon in the direction away from the boron carbide ceramic layer, and compacted to obtain a preform.

[0060] As the pyrolytic carbon thickness of the carbon fiber cloths in groups 1, 2, 3, and 4 increases, as well as the heat treatment temperature and time, the carbon fiber toughened boron carbide composite material backing plate prepared by this invention exhibits an increasing fracture toughness from group 1 to group 4, which helps to further improve the ballistic effect of the double-layer ballistic structure.

[0061] (3) Preform chemical vapor deposition of boron carbide with a thickness of 60-90 μm, followed by grinding and smoothing to obtain a double-layer gradient boron carbide composite material.

[0062] The method provided by this invention not only completes the preparation of the carbon fiber toughened boron carbide composite material layer, but also achieves a firm bond between the boron carbide ceramic layer and the carbon fiber toughened boron carbide composite material layer. The resulting double-layer gradient boron carbide composite material can effectively prevent the back plate from separating from the front plate when the projectile penetrates the front plate (i.e., the boron carbide ceramic layer) and reaches the back plate (i.e., the carbon fiber toughened boron carbide composite material layer and the boron carbide deposited layer, referred to as the carbon fiber toughened boron carbide ceramic matrix composite material), thereby improving the ballistic resistance of the double-layer ballistic structure.

[0063] Compared with other preparation methods, the bilayer gradient boron carbide composite material prepared by chemical vapor deposition has the advantage of strong designability of mechanical properties. By adjusting the process parameters, the mechanical properties of the prepared composite material can be effectively adjusted to meet the ballistic requirements of ballistic materials.

[0064] In addition, since chemical vapor deposition has the characteristic of net-size molding, the preparation method of the present invention has the advantage of high yield.

[0065] The present invention also provides an application of the aforementioned double-layer gradient boron carbide composite material in ballistic materials.

[0066] The aforementioned double-layer gradient boron carbide composite material, used as a ballistic product, wherein the boron carbide ceramic layer serves as the face plate, and the carbon fiber toughened boron carbide composite material layer and the boron carbide deposition layer, referred to as the carbon fiber toughened boron carbide ceramic matrix composite material, serve as the back plate, exhibiting excellent ballistic resistance.

[0067] The present invention will be described below with reference to embodiments. The boron carbide ceramic panel used in the examples was purchased from Shandong Huaen New Material Technology Co., Ltd., and its density was tested to be 2.51 g / cm³. 3 It has a compressive strength of 2900 MPa, a Vickers hardness of 29.5 GPa, and a fracture toughness of 2.43 MPa·m. 1 / 2The carbon fiber cloth (hereinafter referred to as carbon cloth) without deposited pyrolytic carbon used in the examples was purchased from Weihai Guangwei Composite Materials Co., Ltd. The carbon cloth is woven from carbon fiber with the code TZ300. The carbon fiber has a tensile strength of 3530MPa, a tensile elastic modulus of 230GPa, an elongation at break of 1.5%, and a linear density of 198g / km.

[0068] Example 1

[0069] (1) Stripes are uniformly processed on the back of the boron carbide ceramic panel. The cross-section of the stripes is an isosceles trapezoid with a height of 0.5 mm, an upper side length of 0.5 mm, and a lower side length of 1.2 mm.

[0070] (2) The carbon cloth is divided into 4 groups, each group includes 9 carbon cloths. Pyrolytic carbon is deposited on each carbon cloth by chemical vapor deposition. The pyrolytic carbon thicknesses of the carbon cloths in the 1st, 2nd, 3rd and 4th groups are 80, 110, 140 and 170 nm, respectively.

[0071] (3) The carbon cloth with pyrolytic carbon deposited was heat-treated in argon gas. The heat treatment processes for the first, second, third and fourth groups of carbon cloth were 1780℃ for 60 min, 1800℃ for 70 min, 1820℃ for 80 min and 1840℃ for 90 min, respectively.

[0072] (4) With the back of the boron carbide ceramic panel facing up, lay the first, second, third and fourth groups of carbon cloth obtained in step (3) on the boron carbide ceramic panel one after another.

[0073] (5) Place a graphite block on the carbon cloth in step (4) to compact the carbon cloth and the boron carbide ceramic panel, and perform chemical vapor deposition of boron carbide on the carbon cloth and the boron carbide ceramic panel in step (4) to control the boron carbide deposition thickness on the surface of the carbon cloth to be 60 μm.

[0074] (6) The surface of the sample obtained in step (5) is polished and smoothed using a grinding machine to obtain the double-layer gradient boron carbide composite ballistic product of the present invention.

[0075] The cross-sectional morphology of boron carbide deposited by chemical vapor deposition is as follows: Figure 5 As shown, the high-resolution transmission images of the interface in the second group are as follows: Figure 6 As shown.

[0076] Example 2

[0077] (1) Stripes are uniformly processed on the back of the boron carbide ceramic plate. The cross-section of the stripes is an isosceles trapezoid with a height of 0.6 mm, an upper side length of 0.4 mm, and a lower side length of 1.1 mm.

[0078] (2) The carbon cloth is divided into 4 groups, each group includes 8 carbon cloths. Pyrolytic carbon is deposited on each carbon cloth by chemical vapor deposition. The pyrolytic carbon thicknesses of the carbon cloths in the 1st, 2nd, 3rd and 4th groups are 90, 120, 150 and 180 nm, respectively.

[0079] (3) The carbon cloth with pyrolytic carbon deposited was heat-treated in argon gas. The heat treatment processes for the first, second, third and fourth groups of carbon cloth were 1760℃ for 70 min, 1790℃ for 75 min, 1810℃ for 85 min and 1820℃ for 100 min, respectively.

[0080] (4) With the back of the boron carbide ceramic panel facing up, lay the first, second, third and fourth groups of carbon cloth obtained in step (3) on the boron carbide ceramic panel one after another.

[0081] (5) Place a graphite block on the carbon cloth in step (4) to compact the carbon cloth and the boron carbide ceramic panel, and perform chemical vapor deposition of boron carbide on the carbon cloth and the boron carbide ceramic panel in step (4) to control the boron carbide deposition thickness on the surface of the carbon cloth to be 70 μm.

[0082] (6) The surface of the sample obtained in step (5) is polished and smoothed using a grinding machine to obtain the double-layer gradient boron carbide composite ballistic product of the present invention.

[0083] Example 3

[0084] (1) Stripes are uniformly processed on the back of the boron carbide ceramic plate. The cross-section of the stripes is an isosceles trapezoid with a height of 0.7 mm, an upper side length of 0.4 mm, and a lower side length of 1.0 mm.

[0085] (2) The carbon cloth is divided into 4 groups, each group includes 7 carbon cloths. Pyrolytic carbon is deposited on each carbon cloth by chemical vapor deposition. The thickness of pyrolytic carbon in the 1st, 2nd, 3rd and 4th groups of carbon cloth is 100, 130, 160 and 190 nm, respectively.

[0086] (3) The carbon cloth with pyrolytic carbon deposited was heat-treated in argon gas. The heat treatment processes for the first, second, third and fourth groups of carbon cloth were 1770℃ for 65 min, 1780℃ for 80 min, 1800℃ for 90 min and 1830℃ for 95 min, respectively.

[0087] (4) With the back of the boron carbide ceramic panel facing up, lay the first, second, third and fourth groups of carbon cloth obtained in step (3) on the boron carbide ceramic panel one after another.

[0088] (5) Place a graphite block on the carbon cloth in step (4) to compact the carbon cloth and the boron carbide ceramic panel, and perform chemical vapor deposition of boron carbide on the carbon cloth and the boron carbide ceramic panel in step (4) to control the boron carbide deposition thickness on the surface of the carbon cloth to be 80 μm.

[0089] (6) The surface of the sample obtained in step (5) is polished and smoothed using a grinding machine to obtain the double-layer gradient boron carbide composite ballistic product of the present invention.

[0090] Example 4

[0091] (1) Stripes are uniformly processed on the back of the boron carbide ceramic plate. The cross-section of the stripes is an isosceles trapezoid with a height of 0.8 mm, an upper side length of 0.3 mm, and a lower side length of 0.9 mm.

[0092] (2) The carbon cloth is divided into 4 groups, each group includes 6 carbon cloths. Pyrolytic carbon is deposited on each carbon cloth by chemical vapor deposition. The pyrolytic carbon thicknesses of the carbon cloths in the 1st, 2nd, 3rd and 4th groups are 110, 140, 170 and 200 nm, respectively.

[0093] (3) The carbon cloth with pyrolytic carbon deposited was heat-treated in argon gas. The heat treatment processes for the first, second, third and fourth groups of carbon cloth were 1770℃ for 65 min, 1780℃ for 80 min, 1820℃ for 80 min and 1820℃ for 100 min, respectively.

[0094] (4) With the back of the boron carbide ceramic panel facing up, lay the first, second, third and fourth groups of carbon cloth obtained in step (3) on the boron carbide ceramic panel one after another.

[0095] (5) Place a graphite block on the carbon cloth in step (4) to compact the carbon cloth and the boron carbide ceramic panel, and perform chemical vapor deposition of boron carbide on the carbon cloth and the boron carbide ceramic panel in step (4) to control the boron carbide deposition thickness on the surface of the carbon cloth to be 90 μm.

[0096] (6) The surface of the sample obtained in step (5) is polished and smoothed using a grinding machine to obtain the double-layer gradient boron carbide composite ballistic product of the present invention.

[0097] In particular, in the above embodiments, steps (1) and (2) both belong to the material preparation stage and there is no strict order between them.

[0098] Experimental results

[0099] Since the mechanical properties of the panel are fixed, in order to accurately determine the mechanical properties of the carbon fiber toughened boron carbide ceramic composites prepared in Examples 1-4, the panels of the samples prepared in Examples 1-4 were removed, and only the mechanical properties of the back plate (i.e., the carbon fiber toughened boron carbide composite layer and the boron carbide deposition layer, denoted as carbon fiber toughened boron carbide ceramic matrix composite) were tested. The density was tested using Archimedes' displacement method, and the tensile strength was tested using a universal testing machine.

[0100] The test results are shown in Table 1.

[0101] Table 1 Backplate performance test results

[0102]

[0103] The density of dense boron carbide ceramics is approximately 2.52 g / cm³. 3 The linear density of the carbon fiber used in this invention is 198 g / km. Since carbon fiber has a lower density than boron carbide, from Example 1 to Example 4, as the number of carbon cloth layers decreases and the thickness of the chemically vapor-deposited boron carbide increases, the density of the composite material decreases from 1.92 g / cm³. 3 Gradually increased to 2.01 g / cm³ 3 Furthermore, the physical and mechanical properties of the composite material are also gradually changing, specifically: the interlaminar tensile strength gradually increases from 243 MPa to 298 MPa, and the maximum fracture toughness increases from 14.3 MPa·m. 1 / 2 Gradually increased to 15.3 MPa·m 1 / 2 The minimum fracture toughness is 11.5 MPa·m 1 / 2 Gradually increased to 12.4 MPa·m 1 / 2 It can be seen that the composite material backing plate has a much higher fracture toughness than the boron carbide ceramic face plate, and the fracture toughness of the composite material backing plate has a gradient-like characteristic.

[0104] The double-layered gradient boron carbide composite ballistic products of Examples 1-4 were subjected to target firing tests. During the tests, the boron carbide ceramic plate was used as the projectile-facing surface, and the carbon fiber-toughened boron carbide ceramic composite material was used as the projectile-backing surface. A Type 56 semi-automatic rifle and a 7.62mm armor-piercing incendiary round were used, with an initial bullet velocity of approximately 650 m / s and a firing distance of 15 m. Three samples were tested for each example, and the sample with the worst performance was conservatively used as the ballistic resistance evaluation result.

[0105] In addition, three comparative examples were set up to compare the shooting effects with those of Examples 1 to 4.

[0106] Comparative Example 1: A boron carbide ceramic plate with a thickness of 20 mm was subjected to a target impact test.

[0107] Comparative Example 2: A boron carbide ceramic plate with a thickness of 30 mm was subjected to a target impact test.

[0108] Comparative Example 3, compared with Example 1, did not use a panel, each group of carbon fiber cloth consisted of 27 sheets, and the treatment of the 4 groups of carbon fiber cloth was the same as in Example 1, to prepare a carbon fiber toughened boron carbide ceramic composite material with a thickness of 30 mm, and the composite material was subjected to target hitting test.

[0109] The test results are shown in Table 2.

[0110] Table 2 Target shooting test results

[0111] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Total thickness (mm) 29.8 28.7 27.6 26.5 20 30 30 Panel thickness (mm) 20 20 20 20 20 30 - Back panel thickness (mm) 9.8 8.7 7.6 6.5 0 0 30 Back convexity (mm) 3.6 4.1 4.5 4.7 - - 13.2 Implementation effect Not penetrated Not penetrated Not penetrated Not penetrated penetrate penetrate penetrate

[0112] As shown in Comparative Example 1, the bullet can penetrate a 20mm thick boron carbide ceramic plate. From Example 1 to Example 4, as the number of carbon cloth layers in each group decreased, although the back plate thickness of the samples gradually decreased from 9.8mm to 6.5mm, and the total thickness of the samples gradually decreased from 29.8mm to 26.5mm, all samples exhibited excellent ballistic resistance. Specifically, none of the samples were penetrated by the bullet, and the back convexity was very small; from Example 1 to Example 4, the back convexity of the samples only gradually increased from 3.6mm to 4.7mm.

[0113] As shown in Comparative Example 2, increasing the thickness of the boron carbide ceramic plate from 20mm to 30mm still failed to resist bullet penetration. Furthermore, as shown in Comparative Example 3, the 30mm thick composite material not only failed to resist bullet penetration but also exhibited a back convexity as high as 13.2mm.

[0114] As can be seen from the above embodiments and comparative examples, the double-layer gradient boron carbide composite ballistic product prepared by the method described in this invention not only has excellent ballistic performance, but also has the characteristics of being thinner and lighter.

Claims

1. A double-layered structure gradient boron carbide composite material, characterized by, The double-layer gradient boron carbide composite material comprises a boron carbide ceramic layer and a carbon fiber toughened boron carbide composite material layer, and is formed by combining boron carbide deposition layers. The carbon fiber toughened boron carbide composite material layer is composed of multiple groups of composite carbon fiber cloths, each group of composite carbon fiber cloths is composed of multiple carbon fiber cloths and pyrolytic carbon and boron carbide deposited on the surface of the carbon fiber cloths in sequence, and the thickness of the pyrolytic carbon increases in the direction away from the boron carbide ceramic layer in units of groups.

2. The dual-layer structured gradient boron carbide composite of claim 1, wherein, The thickness of the boron carbide deposited on the pyrolytic carbon on the surface of the carbon fiber cloth is 60-90 μm.

3. The dual-layer structured gradient boron carbide composite of claim 1, wherein, The thickness of the pyrolytic carbon deposited on the surface of the carbon fiber cloth is 80-200 nm.

4. The dual-layer structured gradient boron carbide composite of claim 1, wherein, The thickness of the double-layer gradient boron carbide composite material is 26.5-29.8 mm, wherein the thickness of the boron carbide ceramic layer is 20 mm, and the thickness of the carbon fiber toughened boron carbide composite material layer is 6.5-9.8 mm.

5. The dual-layer structured gradient boron carbide composite of claim 1, wherein, The composite carbon fiber cloth is 4 groups, and each group of composite carbon fiber cloth comprises 6-9 carbon fiber cloths.

6. The dual-layer structured gradient boron carbide composite of claim 5, wherein, The thickness of the pyrolytic carbon in the 4 groups of composite carbon fiber cloths is 80-110 nm, 110-140 nm, 140-170 nm and 170-200 nm in sequence in the direction away from the boron carbide ceramic layer.

7. A method of producing the double-layer structure gradient boron carbide composite material according to claim 1, characterized by, The method comprises the following steps: (1) after chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, the first composite carbon fiber cloth is obtained by high-temperature heat treatment at 1760-1840 ℃ for 60-100 min in argon, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 80-200 nm; (2) the first composite carbon fiber cloths with the same thickness of pyrolytic carbon are taken as a group, and multiple groups of the first composite carbon fiber cloths are sequentially laid on the boron carbide ceramic layer processed with stripes in the order of increasing thickness of the pyrolytic carbon in the direction away from the boron carbide ceramic layer, and then compacted to obtain a preform; (3) the preform is subjected to chemical vapor deposition of boron carbide to obtain a double-layer gradient boron carbide composite material.

8. The method of claim 7, wherein the boron carbide composite material is prepared by the steps of: providing a first layer of boron carbide; providing a second layer of boron carbide; and applying a gradient of boron carbide between the first and second layers. The operation is as follows: (1) the first group of first composite carbon fiber cloths comprises 6-9 carbon fiber cloths, and after chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, the first composite carbon fiber cloth is obtained by heat treatment at 1760-1780 ℃ for 60-70 min in argon, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 80-110 nm; the second group of first composite carbon fiber cloths comprises 6-9 carbon fiber cloths, and after chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, the first composite carbon fiber cloth is obtained by heat treatment at 1780-1800 ℃ for 70-80 min in argon, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 110-140 nm; the third group of first composite carbon fiber cloths comprises 6-9 carbon fiber cloths, and after chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, the first composite carbon fiber cloth is obtained by heat treatment at 1800-1820 ℃ for 80-90 min in argon, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 140-170 nm; the fourth group of first composite carbon fiber cloths comprises 6-9 carbon fiber cloths, and after chemical vapor deposition of pyrolytic carbon on the surface of each carbon fiber cloth, the first composite carbon fiber cloth is obtained by heat treatment at 1820-1840 ℃ for 90-100 min in argon, wherein the thickness of the pyrolytic carbon on the surface of each carbon fiber cloth is 170-200 nm; (2) 4 groups of the first composite carbon fiber cloth are laid on the boron carbide ceramic layer processed with the stripes in the order of increasing thickness of pyrolytic carbon away from the boron carbide ceramic layer, and compacted to obtain a preform; (3) the preform is subjected to chemical vapor deposition of boron carbide, and the thickness of the boron carbide is 60-90 μm, to obtain a double-layer structure gradient boron carbide composite material.

9. The method of claim 7, wherein the boron carbide composite material is prepared by the steps of: providing a first layer of boron carbide; providing a second layer of boron carbide; and applying a gradient of boron carbide between the first and second layers. In the step (2), the cross section of the stripe is isosceles trapezoid, the height of the isosceles trapezoid is 0.5-0.8 mm, the upper base length is 0.3-0.5 mm, and the lower base length is 0.9-1.2 mm.

10. Application of the double-layer structure gradient boron carbide composite material according to claim 1 to bulletproof materials.

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