Demoulding cloth, composite material and preparation method

Abstract

The invention provides demolding cloth, a composite material and a preparation method, and belongs to the technical field of composite materials. The release cloth includes: a support substrate; the magnetic fiber array penetrates into the supporting base material in an upright state, and at least part of magnetic fibers in the magnetic fiber array are exposed out of the supporting base material; wherein the demolding cloth is used for being placed between a mold and a composite material, the composite material is prevented from being adhered to the mold after being cured and formed, when the demolding cloth is separated from the composite material after the composite material is cured and formed, the magnetic fiber array is separated from the interior of the supporting base material and remains in the composite material, and the mechanical property of the composite material is improved through the magnetic fiber array.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a release cloth, a composite material and a preparation method thereof. Background Art

[0002] Composite materials are composed of two or more different materials that complement each other in performance to achieve performance that is difficult to achieve with a single material. The advantages of composite materials include: light weight, high strength, corrosion resistance, fatigue resistance, and designability. They are widely used in many modern industrial and technological fields such as aerospace, military, transportation, and construction. In the use of composite materials in the above-mentioned industrial and technological fields, different composite parts are mostly connected by bonding or hybrid connection when forming composite materials. After the composite parts are cured and formed, the surface is covered with a resin layer, so it is relatively smooth and flat. When different composite parts are bonded for the second time, the bonding strength of the resin bonding surface is weaker than the strength of the composite parts themselves, which easily leads to debonding and failure of the bonding surface.

[0003] At present, the commonly used treatment method is to perform secondary treatment on the surface of the composite material parts after curing and forming through technical means such as sandblasting, grinding, plasma treatment, laser etching, etc., in order to improve the bonding strength of the bonding surface. However, the sandblasting and grinding treatments in the above treatment methods are often easy to cause different degrees of damage to the composite material parts; plasma treatment or laser etching treatment has high requirements for equipment and is not easy to be applied on a large scale in industrialization. Therefore, although the above technical means can improve the mechanical properties of composite materials to a certain extent, there are additional processing costs, equipment costs, etc., which make it difficult to promote and apply them in a variety of different scenarios.

[0004] In summary, there is currently a lack of a convenient, efficient and universal technical solution to improve the secondary bonding strength of composite materials. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a release cloth, a composite material and a preparation method, in order to at least partially solve the above technical problems. Therefore, the specific technical solutions provided by the present invention are as follows.

[0006] As a first aspect of the present invention, a release cloth is provided, comprising: a supporting substrate; and a magnetic fiber array, which is inserted into the interior of the supporting substrate in an upright state, and the magnetic fibers in the magnetic fiber array are at least partially exposed outside the supporting substrate; wherein the release cloth is used to be placed between the mold and the composite material to prevent the composite material from sticking to the mold after solidification and molding, and when the release cloth is separated from the composite material after the composite material is solidified and molded, the magnetic fiber array detaches from the interior of the supporting substrate and remains in the interior of the composite material, thereby improving the mechanical properties of the composite material through the magnetic fiber array.

[0007] As a second aspect of the present invention, a method for preparing a release cloth is provided, comprising: impregnating a supporting substrate with a rubber resin solution to obtain a pre-impregnated supporting substrate; placing the pre-impregnated supporting substrate in a magnetic field and uniformly dropping magnetic fibers from above the pre-impregnated supporting substrate, wherein under the action of the magnetic field and gravity, the magnetic fibers penetrate into the interior of the supporting substrate in an upright state to form a magnetic fiber array, while the magnetic fibers are at least partially exposed outside the supporting substrate, and heating and curing to obtain a release cloth.

[0008] As a third aspect of the present invention, a composite material is provided, comprising: a first base material, a magnetic fiber array is inserted into the interior of the first base material, and the magnetic fibers in the magnetic fiber array are at least partially exposed outside the first base material; and a second base material, which is bonded to the first base material by a resin glue, and the magnetic fiber array and the resin glue form a pinning effect; wherein the magnetic fiber array is obtained using the above-mentioned release cloth.

[0009] As a fourth aspect of the present invention, a method for preparing a composite material is provided, comprising: placing a demolding cloth in a mold; pouring a prepreg into a mold with a demolding cloth placed thereon; curing and molding the prepreg to obtain a first base material; separating a supporting substrate of the demolding cloth from the first base material, and allowing the magnetic fiber array to detach from the inside of the supporting substrate and remain in the first base material; bonding the second base material to the first base material loaded with the magnetic fiber array by resin glue and curing the same to obtain a composite material.

[0010] Based on the above technical solution, a release cloth, a composite material and a preparation method provided by the present invention have at least one of the following beneficial effects.

[0011] (1) In an embodiment of the present invention, the present invention provides a demoulding cloth loaded with magnetic fibers, which can play a role in the curing and molding process of the composite material, and effectively prevent the composite material and the mold from adhering to each other during the curing and molding process. After the composite material is cured and molded, the magnetic fibers exposed on the surface of the demoulding cloth are fixed inside the composite material. When the demoulding cloth is separated, the supporting substrate of the demoulding cloth is removed, and the magnetic fibers in the demoulding cloth remain inside the composite material. When the composite material is bonded for the second time, the magnetic fibers are used to improve the mechanical properties of the bonding point during the second bonding of the composite material. At the same time, since the magnetic fibers penetrate into the interior of the composite material, the mechanical properties of the composite material body can also be improved. The demoulding cloth provided by the present invention can be used in the curing and molding process of various composite materials, has no special requirements for the curing and molding process, and does not cause surface damage to the composite material. In addition, the interlayer shear performance after the second bonding is good and the peel strength is high.

[0012] (2) In the embodiment of the present invention, the support substrate is firstly infiltrated with a rubber resin solution, and then the magnetic fibers are distributed in an upright state on the surface of the support substrate to form a magnetic fiber array. The magnetic fibers pass through the support substrate but do not pass out of the support substrate under the action of the magnetic field and gravity. After curing, the magnetic fibers are stably fixed inside the support substrate by the rubber resin, and the magnetic fibers are partially exposed outside the support substrate. The method for preparing the release cloth provided by the present invention can realize the high-efficiency and continuous preparation of the release cloth, which is convenient for industrial production.

[0013] (3) In an embodiment of the present invention, the above-mentioned demoulding arrangement is placed in a mold, and then the prepreg is cured and molded to obtain a first base material. When the demoulding cloth is separated, the magnetic fiber array in the demoulding cloth is separated from the supporting substrate and remains inside the first base material. The second base material is bonded to the first base material loaded with the magnetic fiber array by a resin glue and cured to obtain a composite material. When the first base material and the second base material are combined, the interaction between the magnetic fibers and the resin glue enhances the interface bonding force in the composite material, so that the overall mechanical properties of the composite material are significantly improved, and the tensile and shear resistance are enhanced to meet the needs of more complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the continuous release cloth preparation process in Example 1 of the present invention;

[0015] Figure 2 This is a scanning electron microscope (SEM) image of the release cloth in Example 1 of the present invention;

[0016] Figure 3 This is a scanning electron microscope (SEM) image of stainless steel fibers exposed on the surface of the composite laminate in Example 1 of the present invention;

[0017] Figure 4 1 is a comparison diagram of load-displacement curves of mode I interlaminar fracture tests of different composite laminates in Example 1 of the present invention.

[0018] Description of reference numerals:

[0019] 01-1 demoulding cloth roller, 01-2 dry demoulding cloth, 01-3 first guide roller, 01-4 silicone rubber resin solution, 01-5 second guide roller, 01-6 scraper roller, 01-7 third guide roller, 01-8 fourth guide roller, 01-9 fifth guide roller, 01-10 sixth guide roller, 01-11 conveyor belt, 01-12 take-up roller;

[0020] 02-1 vibrating screen, 02-2 vibrating motor;

[0021] 03-1 stainless steel fiber, 03-2 stainless steel fiber in a vertical state, 03-3 stainless steel fiber partially inserted into the silicone rubber layer, 03-4 stably fixed stainless steel fiber;

[0022] 04-1 first magnet, 04-2 second magnet;

[0023] 05-1 heating power supply, 05-2 first conductor, 05-3 second conductor, 05-4 heating pad, 05-5 thermocouple;

[0024] 11-1 stainless steel fiber, 11-2 nylon mesh, 11-3 silicone rubber layer;

[0025] 12-1 Stainless steel fiber, 12-2 Surface resin layer of composite laminate. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0027] In order to improve the secondary bonding strength of composite materials and solve the problem of low interface fracture energy after secondary bonding of composite materials, the present invention provides a release cloth composed of a supporting substrate and a magnetic fiber array, which can be used in the curing and molding process of composite materials, and the magnetic fiber array is left in the composite material, while part of the magnetic fiber is exposed outside the composite material, and the mechanical properties of the bonding point during the secondary bonding of the composite material are improved by the magnetic fiber.

[0028] As a first aspect of the present invention, a release cloth is provided, comprising: a supporting substrate; and a magnetic fiber array, which is inserted into the interior of the supporting substrate in an upright state, and the magnetic fibers in the magnetic fiber array are at least partially exposed outside the supporting substrate; wherein the release cloth is used to be placed between the mold and the composite material to prevent the composite material from sticking to the mold after solidification and molding, and when the release cloth is separated from the composite material after the composite material is solidified and molded, the magnetic fiber array detaches from the interior of the supporting substrate and remains in the interior of the composite material, thereby improving the mechanical properties of the composite material through the magnetic fiber array.

[0029] In an embodiment of the present invention, the present invention provides a demoulding cloth loaded with magnetic fibers, which can play a role in the curing and molding process of the composite material, and effectively avoid the adhesion between the composite material and the mold during the curing and molding process. After the composite material is cured and molded, the magnetic fibers exposed on the surface of the demoulding cloth are fixed inside the composite material, and the supporting substrate of the demoulding cloth is removed when the demoulding cloth is separated, while the magnetic fibers in the demoulding cloth remain inside the composite material. When the composite material is bonded for the second time, the mechanical properties of the bonding point of the composite material during the second bonding are improved by the magnetic fibers. At the same time, since the magnetic fibers penetrate into the interior of the composite material, the mechanical properties of the composite material body can also be improved. The demoulding cloth provided by the present invention can be used in the curing and molding process of various composite materials, has no special requirements for the curing and molding process, and does not cause surface damage to the composite material, and has good interlayer shear performance and high peel strength after the second bonding.

[0030] According to an embodiment of the present invention, the loading amount of magnetic fibers on the supporting substrate is 10-100 fibers / cm 2 , for example, 10 pieces / cm 2 , 30 / cm 2 , 50 / cm 2 , 80 / cm 2 , 100 pieces / cm 2 . The distribution density of the magnetic fibers is determined according to the material type and density of the magnetic fibers actually used. Due to the large differences between different types of magnetic fibers, the number of roots per unit area is used as the distribution density counting method. At lower loads, the pinning points of the magnetic fibers are relatively sparse, and they mainly inhibit microscopic cracks and small deformations. As the load increases, on the one hand, more magnetic fibers provide more pinning points, which strengthens the ability to hinder crack propagation. On the other hand, the interaction between the magnetic fibers is enhanced, forming a synergistic pinning effect similar to a "fiber cluster".

[0031] According to an embodiment of the present invention, the magnetic fiber is bonded to the supporting substrate by rubber resin, and the rubber resin includes any one of nitrile rubber, hydrogenated nitrile rubber, fluororubber, silicone rubber, ethylene propylene rubber, fluorosilicone rubber, and acrylate rubber. Considering that the resin of the release cloth should be easily separated from the surface of the composite material prepared from thermosetting or thermoplastic resin materials, rubber resin is selected, preferably silicone rubber resin with lower cost, and the viscosity of the silicone rubber resin is not more than 8000. If the viscosity is too high, it is difficult for the magnetic fiber to fall to the bottom of the rubber resin by gravity and magnetic field in a short time.

[0032] According to an embodiment of the present invention, the pore size of the supporting substrate is 50 μm-1 mm, for example, it can be 50 μm, 200 μm, 500 μm, 800 μm, 1 mm. The thickness of the supporting substrate is 0.05-2.5 mm, for example, it can be 0.05 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm. The diameter of the magnetic fiber is 5-300 μm, for example, it can be 5 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm. The length of the magnetic fiber is 0.2-5 mm, for example, it can be 0.2 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm. The length of the magnetic fiber exposed outside the supporting substrate is 0.15-2.5 mm, for example, it can be 0.15 mm, 0.5 mm, 1 mm, 2 mm, 2.5 mm. The pore size of the support substrate is larger than the diameter of the magnetic fiber, so that the magnetic fiber can fall into the pores of the support substrate under the action of gravity and magnetic field. At this time, the magnetic fiber is fixed by rubber resin to make the magnetic fiber stably attached to the support substrate. For example, when the pore size of the support substrate is 50μm, the diameter of the magnetic fiber is 5-10μm; when the pore size of the support substrate is 500μm, the diameter of the magnetic fiber is 5-100μm. In the subsequent preparation of the composite material, the magnetic fiber exposed outside the support substrate is retained inside the composite material. Since the magnetic fiber falls to the bottom of the pores of the support substrate by gravity and magnetic field, and the thickness of the rubber resin is also taken into account, the length of the magnetic fiber is controlled to be about two to three times the thickness of the support substrate to keep the length of the magnetic fiber inside and outside the support substrate consistent. For example, the thickness of the support substrate is 0.5mm, the length of the magnetic fiber is 1-1.5mm; the thickness of the support substrate is 2mm, and the length of the magnetic fiber is 4-4.5mm.

[0033] According to an embodiment of the present invention, the supporting substrate includes any one of a metal mesh and a non-metal mesh; the metal mesh includes any one of a stainless steel mesh, an aluminum mesh, and a copper mesh; the non-metal mesh includes any one of a nylon mesh, a polyester mesh, a polypropylene mesh, a polyethylene mesh, and a polyethylene fiber mesh. The supporting substrate provides a stable support for the magnetic fiber and can be reused. The magnetic fiber includes at least one of a stainless steel fiber, a nickel-plated fiber, and a fiber coated with a ferroferric oxide layer; the nickel-plated fiber includes at least one of a nickel-plated carbon fiber, a nickel-plated glass fiber, a nickel-plated basalt fiber, a nickel-plated aramid fiber, a nickel-plated liquid crystal fiber, and a nickel-plated nylon fiber; the fiber coated with a ferroferric oxide layer includes at least one of a carbon fiber coated with ferroferric oxide, a glass fiber coated with ferroferric oxide, a basalt fiber coated with ferroferric oxide, an aramid fiber coated with ferroferric oxide, a liquid crystal fiber coated with ferroferric oxide, and a nylon fiber coated with ferroferric oxide. Since the magnetic fibers are subsequently retained inside the composite material, the fiber material that is the same or similar to the composite material can be nickel-plated or coated with ferroferric oxide to obtain magnetic fibers, which can meet the practical application of the composite material and have magnetism, and remain upright during the preparation of the release cloth.

[0034] As a second aspect of the present invention, a method for preparing a release cloth is provided, comprising: impregnating a supporting substrate with a rubber resin solution to obtain a pre-impregnated supporting substrate; placing the pre-impregnated supporting substrate in a magnetic field and uniformly dropping magnetic fibers from above the pre-impregnated supporting substrate, wherein under the action of the magnetic field and gravity, the magnetic fibers penetrate into the interior of the supporting substrate in an upright state to form a magnetic fiber array, while the magnetic fibers are at least partially exposed outside the supporting substrate, and heating and curing to obtain a release cloth.

[0035] In the embodiment of the present invention, the support substrate is first soaked with a rubber resin solution, and then the magnetic fibers are distributed in an upright state on the surface of the support substrate to form a magnetic fiber array. The magnetic fibers pass through the support substrate under the action of the magnetic field and gravity but do not pass out of the support substrate. After curing, the magnetic fibers are stably fixed inside the support substrate by the rubber resin, and the magnetic fibers are partially exposed outside the support substrate. The method for preparing the release cloth provided by the present invention can realize the high-efficiency and continuous preparation of the release cloth, which is convenient for industrial production.

[0036] As a third aspect of the present invention, a composite material is provided, comprising: a first base material, a magnetic fiber array is inserted into the interior of the first base material, and the magnetic fibers in the magnetic fiber array are at least partially exposed outside the first base material; and a second base material, which is bonded to the first base material by a resin glue, and the magnetic fiber array and the resin glue form a pinning effect; wherein the magnetic fiber array is obtained using the above-mentioned release cloth.

[0037] In an embodiment of the present invention, the first base material is prepared by using the above-mentioned demoulding cloth, so that the magnetic fiber array is inserted into the first base material, and the magnetic fibers in the magnetic fiber array are partially exposed outside the first base material. The surface of the first base material with the magnetic fiber array distributed thereon is bonded to the second base material by a resin adhesive, and the pinning effect formed by the magnetic fiber array and the resin adhesive hinders the initiation and expansion of cracks in the resin adhesive, thereby improving the mechanical properties of the composite material.

[0038] According to an embodiment of the present invention, the length of the magnetic fiber exposed outside the first base material is 0.05-2.5mm, for example, it can be 0.05mm, 0.5mm, 1mm, 2mm, 2.5mm. When preparing a multi-layer composite material, the exposed magnetic fiber can "pin" adjacent material layers together like a "nail". The shorter exposed length will not protrude excessively while ensuring a certain pinning effect, so as to avoid affecting the surface flatness of the composite material. The longer exposed length can provide a deeper pinning effect when a stronger bonding force is required, such as when manufacturing aerospace materials or high-performance sports equipment that have extremely high requirements for interlayer bonding, to ensure that the layers can work together and withstand greater external forces.

[0039] According to an embodiment of the present invention, the resin adhesive includes at least one of a thermosetting resin and a thermoplastic resin; the thermosetting resin includes at least one of an epoxy resin, a polyurethane, an unsaturated polyester, and a phenolic resin; the thermoplastic resin includes at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl acetate, polyester, polyacrylate, rosin-modified alkyd resin, polyvinyl chloride, chlorinated polypropylene, and alcohol-soluble polyamide. When the first base material and the second base material are bonded by the resin adhesive, the magnetic fibers exposed outside the first base material form a pinning effect with the resin adhesive to hinder the initiation and expansion of cracks in the resin adhesive, thereby improving the mechanical properties of the composite material.

[0040] In an embodiment of the present invention, when the second base material is also prepared by the above-mentioned release cloth, the surface of the second base material loaded with magnetic fibers is bonded to the surface of the first base material loaded with magnetic fibers by resin glue. At this time, the magnetic fibers exposed outside the first base material and the magnetic fibers exposed outside the second base material both form a pinning effect with the resin glue, further improving the mechanical properties of the composite material.

[0041] As a fourth aspect of the present invention, a method for preparing a composite material is provided, comprising: placing a demolding cloth in a mold; pouring a prepreg into a mold with a demolding cloth placed thereon; curing and molding the prepreg to obtain a first base material; separating a supporting substrate of the demolding cloth from the first base material, and allowing the magnetic fiber array to detach from the inside of the supporting substrate and remain in the first base material; bonding the second base material to the first base material loaded with the magnetic fiber array by resin glue and curing the same to obtain a composite material.

[0042] In an embodiment of the present invention, the above-mentioned demoulding arrangement is placed in a mold, and then the prepreg is cured and molded to obtain a first base material. When the demoulding cloth is separated, the magnetic fiber array in the demoulding cloth is separated from the supporting substrate and remains inside the first base material. The second base material is bonded and cured to the first base material loaded with the magnetic fiber array by resin glue to obtain a composite material. When the first base material and the second base material are combined, the interaction between the magnetic fiber and the resin glue enhances the interface bonding force in the composite material, so that the overall mechanical properties of the composite material are significantly improved, and the tensile and shear resistance are enhanced to meet more complex working conditions.

[0043] The present invention is further described below by examples and related test experiments. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined into other feasible embodiments at will. All instruments, consumables and reagents in the following examples, if not otherwise specified, may be obtained from commercial sources.

[0044] Example 1

[0045] In this embodiment 1, a release cloth was prepared by the following method, and the prepared release cloth was used to prepare a composite material.

[0046] In this embodiment 1, the supporting substrate is a nylon mesh with a pore size of 0.2 The thickness is 0.2 mm and 200 μm. The magnetic fiber is a stainless steel fiber with a length of 1000 μm and a diameter of 40 μm. The adhesive resin solution is a silicone rubber resin solution, and a certain proportion of ethanol solvent is added to dilute the solution.

[0047] Figure 1 This is a schematic diagram of the continuous release cloth preparation process in Example 1 of the present invention.

[0048] like Figure 1 As shown, the release cloth was prepared by the following method.

[0049] Take the 80 mesh nylon mesh belt 01-2 and pull it off from the demoulding cloth roller 01-1. Pass it through the first guide roller 01-3, the silicone rubber resin solution 01-4, the second guide roller 01-5, the scraper roller 01-6, and the third guide roller 01-7. The nylon mesh belt impregnated with the silicone rubber resin solution is transported forward through the conveyor belt 01-11. The conveyor belt 01-11 passes through the third guide roller 01-7, the fourth guide roller 01-8, the fifth guide roller 01-9, and the sixth guide roller 01-10. The nylon mesh belt reaches the bottom of the vibrating mesh screen 02-1. Vibrating motors 02-2 are installed on both sides of the vibrating mesh screen 02-1. After the vibration motors 02-2 are started, the stainless steel fibers 03-1 are scattered from the vibrating mesh screen 02-1 and fall in the air. Under the action of the first magnet 04-1, the stainless steel fibers 03-2 oriented along the magnetic force line and in a vertical state are distributed on the silicone rubber layer on the surface of the nylon mesh belt. The stainless steel fibers 03-2 are oriented along the magnetic force line and in a vertical state under the action of the first magnet 04-1. Under the action of field attraction, it is inserted into the silicone rubber layer and directly inserted into the bottom of the silicone rubber layer, so that the stainless steel fiber 03-3 partially inserted into the silicone rubber layer is obtained. The nylon mesh belt moves forward under the traction of the winding roller 01-7 and reaches the middle of the first magnet 04-1 and the second magnet 04-2. Under the action of the high orientation magnetic field established between the two magnets, the stainless steel fiber obtains a higher uprightness; turn on the heating power supply 05-1, heat the heating pad 05-4 through the first wire 05-2, and connect it to the thermocouple 05-5 through the second wire 05-3. The thermocouple 05-5 is placed inside the heating pad 05-4 to sense the temperature signal of the heating pad 05-4 in real time. The signal is fed back to the heating power supply 05-1, thereby realizing the temperature regulation of the heating pad 05-4. The silicone rubber resin in the nylon mesh belt is quickly cured after heating, and the stably fixed stainless steel fiber 03-4 is obtained after the resin is cured. After the demolding cloth is dried, it is wound into a roller by the winding roller 01-12.

[0050] Figure 2 This is a scanning electron microscope (SEM) image of the release cloth in Example 1 of the present invention.

[0051] from Figure 2 It can be seen that the stainless steel fibers are stably and uprightly distributed in the nylon cloth wrapped with silicone rubber.

[0052] Furthermore, the release cloth is used in the composite vacuum bag hot pressing process, using 0.15mm thick unidirectional carbon fiber prepreg, 10 layers of prepreg are laid, and then a layer of release cloth with vertically oriented stainless steel fibers is laid on the surface, and hot pressing and curing are performed to obtain a 1.5mm thick composite laminate. The release cloth is torn off, and the stainless steel fibers in the release cloth are separated from the nylon cloth wrapped with silicone rubber and remain in the composite laminate. After the side with the stainless steel fibers is coated with resin adhesive, the two laminates are pressed together. After the resin is cured, the peeling load of the composite laminate after secondary bonding is tested according to the ASTM D5528 double cantilever beam type I interlaminar fracture toughness test method.

[0053] Figure 3 This is a scanning electron microscope (SEM) image of stainless steel fibers exposed on the surface of the composite laminate in Example 1 of the present invention.

[0054] from Figure 3 It can be seen that the stainless steel fibers have been completely transferred from the surface of the release cloth to the surface of the composite laminate and are partially exposed outside the composite laminate.

[0055] Figure 4 The figure is a comparison of load displacement curves of the mode I interlaminar fracture test of different composite laminates in Example 1 of the present invention. In addition to the composite laminate prepared by using the release cloth loaded with stainless steel fibers, a composite laminate without a release cloth and a composite laminate without a release cloth but polished with sandpaper before bonding were also prepared.

[0056] from Figure 4 It can be seen that sandpaper polishing the surface of the composite laminate only slightly improves the interlaminar fracture performance of the composite laminate, but the interlaminar fracture toughness of the composite laminate using the release cloth is significantly improved. The three typical curves are area-integrated, and the work done in the peeling process of the untreated composite laminate is 1.25J, the work done in the peeling process of the composite laminate obtained by sandpaper polishing is 1.44J, and the work done in the peeling process of the composite laminate obtained by the release cloth is 2.27J. The results show that the composite laminate obtained by the release cloth prepared by the present invention has an improvement of 81.6% in the peeling work compared with the untreated composite laminate.

[0057] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A release cloth, comprising: a supporting substrate; as well as A magnetic fiber array is inserted into the supporting substrate in an upright state, and the magnetic fibers in the magnetic fiber array are at least partially exposed outside the supporting substrate; Among them, the release cloth is used to be placed between the mold and the composite material to prevent the composite material from sticking to the mold after solidification and forming. When the release cloth is separated from the composite material after solidification and forming, the magnetic fiber array detaches from the inside of the supporting substrate and remains in the inside of the composite material, and the mechanical properties of the composite material are improved by the magnetic fiber array.

2. The release cloth according to claim 1, wherein: The loading amount of the magnetic fibers on the supporting substrate is 10-100 fibers / cm 2 ; The magnetic fibers are bonded to the supporting substrate via rubber resin.

3. The release cloth according to claim 1, wherein The pore size of the support substrate is 50 μm-1 mm, and the thickness of the support substrate is 0.05-2.5 mm; The diameter of the magnetic fiber is 5-300 μm, and the length of the magnetic fiber is 0.2-5 mm; The length of the magnetic fiber exposed outside the supporting substrate is 0.15-2.5 mm.

4. The release cloth according to claim 2, wherein: The rubber resin includes any one of nitrile rubber, hydrogenated nitrile rubber, fluororubber, silicone rubber, ethylene-propylene rubber, fluorosilicone rubber, and acrylate rubber; The supporting substrate includes any one of a metal wire mesh and a non-metal wire mesh; The magnetic fiber comprises at least one of stainless steel fiber, nickel-plated fiber, and fiber coated with a ferroferric oxide layer.

5. The release cloth according to claim 4, wherein: The metal wire mesh includes any one of a stainless steel wire mesh, an aluminum mesh, and a copper mesh; The non-metallic wire mesh includes any one of a nylon mesh, a polyester mesh, a polypropylene mesh, a polyethylene mesh, and a polyethylene fiber mesh; The nickel-plated fiber includes at least one of nickel-plated carbon fiber, nickel-plated glass fiber, nickel-plated basalt fiber, nickel-plated aramid fiber, nickel-plated liquid crystal fiber, and nickel-plated nylon fiber; The fiber coated with the ferroferric oxide layer includes at least one of carbon fiber coated with ferroferric oxide, glass fiber coated with ferroferric oxide, basalt fiber coated with ferroferric oxide, aramid fiber coated with ferroferric oxide, liquid crystal fiber coated with ferroferric oxide, and nylon fiber coated with ferroferric oxide.

6. A method for preparing a release cloth according to any one of claims 1 to 5, comprising: impregnating the support substrate with the rubber resin solution to obtain a pre-impregnated support substrate; The prepreg support substrate is placed in a magnetic field and magnetic fibers are evenly dropped from above the prepreg support substrate. Under the action of the magnetic field and gravity, the magnetic fibers are in an upright state and penetrate into the interior of the support substrate to form a magnetic fiber array. At the same time, the magnetic fibers are at least partially exposed outside the support substrate, heated and cured to obtain a release cloth.

7. A composite material comprising: A first base material, wherein a magnetic fiber array is inserted into the first base material, and magnetic fibers in the magnetic fiber array are at least partially exposed outside the first base material; as well as The second base material is bonded to the first base material through a resin adhesive, and the magnetic fiber array and the resin adhesive form a pinning effect; Wherein, the magnetic fiber array is obtained using the release cloth as described in any one of claims 1-5.

8. The composite material according to claim 7, wherein The length of the magnetic fiber exposed outside the first base material is 0.05-2.5 mm; The resin glue includes at least one of a thermosetting resin and a thermoplastic resin.

9. The composite material according to claim 7, wherein: The thermosetting resin includes at least one of epoxy resin, polyurethane, unsaturated polyester and phenolic resin; The thermoplastic resin includes at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl acetate, polyester, polyacrylate, rosin-modified alkyd resin, polyvinyl chloride, chlorinated polypropylene, and alcohol-soluble polyamide.

10. A method for preparing a composite material as claimed in any one of claims 7 to 9, comprising: placing a demoulding arrangement in a mold; pouring the prepreg into the mold with the release cloth placed thereon; Curing and molding the prepreg to obtain a first base material; Separating the support substrate of the release cloth from the first base material, so that the magnetic fiber array is detached from the inside of the support substrate and remains in the first base material; The second base material and the first base material loaded with the magnetic fiber array are bonded and cured by resin glue to obtain a composite material.

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