Multi-layer composite structure, preparation method, battery cover, and electronic device

Abstract

The present application provides a multi-layer composite structure, a preparation method, a battery cover, and an electronic device. The multi-layer composite structure consists of a plurality of fiber layers that are arranged in stack, each fiber layer being formed by a fiber sheet being impregnated in a prepolymerization solution and then cured, and the fiber sheet in at least one fiber layer being made of poly(p-phenylene-2,6-benzobisoxazole) fiber, i.e., PBO fiber. In this way, the multi-layer composite structure can be provided with a higher strength and modulus, such that energy can be absorbed and dispersed when the multi-layer composite structure is impacted, thus not affecting the reliability thereof upon impact on the basis of thinning and making said structure lightweight, and providing good puncture resistance to a battery cover formed by the multi-layer composite structure.

Description

Multilayer composite structure, preparation method, battery cover and electronic device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on December 17, 2023, with application number 202311751031.6 and invention name “Multi-layer composite structure, preparation method, battery cover and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of terminal technology, and in particular to a multi-layer composite structure, a preparation method, a battery cover, and an electronic device. Background Art

[0003] Casings for consumer electronic devices like mobile phones, tablets, and PCs primarily serve to enhance the appearance and protect the safety of components like the built-in battery. Currently, consumer electronics, especially foldable devices, are experiencing strong demand for reduced weight, thickness, and reliability, and battery covers are a prime example of where these components can be reduced in weight and thickness.

[0004] Under the current battery cover structure design of folding devices, traditional glass fiber composite materials can no longer meet the design requirements of thinning and weight reduction, and the battery cover made of glass fiber composite materials has a high reliability risk, especially in the scenario where the whole device falls, the puncture resistance performance is poor, and it is impossible to complete the design of thinning and weight reduction of the battery cover on the basis of providing reliable drop protection.

[0005] Summary of the Invention

[0006] The present application provides a multi-layer composite structure, a preparation method, a battery cover and an electronic device to solve the problem that the battery cover of the electronic device cannot provide reliable drop protection after being thinned and reduced in weight.

[0007] According to a first aspect of an embodiment of the present invention, a multilayer composite structure is provided, comprising: a plurality of stacked fiber layers, each fiber layer being formed by impregnating fiber sheets in a prepolymerized adhesive and then curing; wherein the fiber sheets in at least one fiber layer are made of poly(p-phenylene benzobisoxazole) (PBO) fibers. This structure, due to the higher strength and higher modulus of PBO fibers compared to glass fibers, can better absorb and disperse energy when the multilayer composite structure is subjected to an impact, thereby reducing thickness and weight without compromising its reliability under impact.

[0008] In one feasible embodiment, at least one of the multiple fiber layers is a first fiber layer; the fiber sheets in each first fiber layer are composed of straightened PBO fiber tows extending in the same direction. This unidirectional arrangement of the PBO fiber tows increases the density of the PBO fiber tows in the first fiber layer, thereby reducing the effect of the pre-polymerized adhesive in the fiber layer on the strength and modulus of the fiber layer.

[0009] In one feasible embodiment, each of the multiple fiber layers is a first fiber layer; the PBO fiber tows in adjacent first fiber layers extend in different directions. This can enhance the energy absorption and dispersion of the formed multi-layer composite structure, improving its puncture resistance.

[0010] In a feasible embodiment, the angle between the extension directions of the PBO fiber bundles in adjacent first fiber layers is a right angle.

[0011] In one feasible embodiment, each of the multiple fiber layers is a first fiber layer; the PBO fiber tows in the topmost and bottommost first fiber layers of the multilayer composite structure extend in a first direction; and the PBO fiber tows in the remaining first fiber layers of the multilayer composite structure extend in a second direction; the first direction and the second direction are different. This can enhance the energy absorption and dispersion of the resulting multilayer composite structure, improving its puncture resistance.

[0012] In a feasible implementation manner, the angle between the first direction and the second direction is a right angle.

[0013] In one feasible embodiment, the pre-polymerized adhesive accounts for 30% to 45% by weight of each first fiber layer, and the thickness of each first fiber layer is 0.04 mm to 0.2 mm. This allows the first fiber layer to be cured by the pre-polymerized adhesive while reducing the pre-polymerized adhesive content in the first fiber layer, thereby improving the strength and modulus of the first fiber layer.

[0014] In one feasible embodiment, the other fiber layers in the plurality of fiber layers, excluding the first fiber layer, constitute a third fiber layer. The fiber sheets in the third fiber layer are composed of first fiber tows extending in the same direction and in a straightened state. The first fiber tows may be any of glass fiber, aramid fiber, ceramic fiber, and carbon fiber. The plurality of third fiber layers are stacked, with at least one first fiber layer disposed between adjacent third fiber layers. This allows the PBO fibers to be combined with other fibers to enhance the bonding strength between the different fiber layers, thereby increasing the overall strength of the multilayer composite structure.

[0015] In one feasible embodiment, the PBO fiber tows in the first fiber layer extend in a third direction; the first fiber tows in the third fiber layer adjacent to the first fiber layer extend in a fourth direction; the first fiber tows in the adjacent third fiber layers extend in different directions; and the third direction is different from the fourth direction. In this way, the strength of the fiber layers can be increased by weaving the fibers, thereby enhancing the puncture resistance of the multi-layer composite structure.

[0016] In a feasible implementation manner, the angle between the third direction and the fourth direction is a right angle.

[0017] In one feasible embodiment, at least one of the plurality of fiber layers is a second fiber layer; the fiber sheets in each second fiber layer are woven from PBO fiber tows extending in a fifth direction and a sixth direction, where the fifth direction is different from the sixth direction. In this way, the fiber layers can be formed from the woven fiber sheets, thereby preventing the fiber sheets formed from the PBO fiber tows from becoming untidy.

[0018] In a feasible embodiment, each of the multiple fiber layers is a second fiber layer; and the angle between the fifth direction and the sixth direction is a right angle.

[0019] In a feasible implementation manner, the mass proportion of the pre-polymerized adhesive in each second fiber layer is 45% to 55%; and the thickness of each second fiber layer is 0.1 mm to 0.2 mm.

[0020] In one feasible embodiment, the fiber layers other than the second fiber layer in the plurality of fiber layers constitute a fourth fiber layer. The fiber sheets in the fourth fiber layer are woven from second fiber tows extending in fifth and sixth directions, wherein the second fiber tows are any of glass fibers, aramid fibers, ceramic fibers, and carbon fibers. The plurality of fourth fiber layers are stacked, with at least one second fiber layer disposed between adjacent fourth fiber layers. This allows the PBO fibers to be combined with other fibers to enhance the bonding strength between the different fiber layers, thereby increasing the overall strength of the multilayer composite structure.

[0021] In a feasible embodiment, the mass proportion of the pre-polymerized adhesive in each fiber layer is 30% to 60%, and the thickness of each fiber layer is greater than or equal to 0.03 mm and less than or equal to 0.3 mm.

[0022] According to a second aspect of an embodiment of the present invention, a method for preparing a multilayer composite structure is provided, comprising: placing an epoxy resin monomer, a curing agent, a accelerator, a dispersant, and a filler in a prepreg, stirring the mixture thoroughly, and pre-curing the mixture to form a prepolymer adhesive; immersing a fiber sheet in the prepolymer adhesive and curing the mixture to obtain a fiber layer; and cutting, stacking, and pressing the plurality of fiber layers to obtain a multilayer composite structure; wherein the fiber sheet in at least one fiber layer is made of PBO fiber.

[0023] In a feasible embodiment, the fiber sheet is immersed in a prepolymer adhesive and cured to obtain a fiber layer, including: placing the fiber bobbin yarn in place, and arranging the fiber bundles in one direction by swinging the yarn to form a plurality of fiber sheets; the fiber bundles in at least one fiber sheet are PBO fiber bundles; the plurality of fiber sheets are immersed in the prepolymer adhesive respectively; the mass proportion of the prepolymer adhesive in the plurality of impregnated fiber sheets and the thickness of the plurality of impregnated fiber sheets are controlled; and the plurality of impregnated fiber sheets are cured respectively to obtain a plurality of fiber layers.

[0024] In a feasible embodiment, multiple fiber layers are cut, stacked, and pressed to obtain a multi-layer composite structure, including: cutting the multiple fiber layers separately to obtain multiple fiber layers of preset sizes; stacking the multiple cut fiber layers; wherein the fiber bundles in adjacent fiber layers have different extension directions, or the fiber bundles in the topmost and bottommost fiber layers extend in a first direction, and the fiber bundles in the fiber layers other than the topmost and bottommost layers extend in a second direction, and the first direction is different from the second direction; pressing the multiple stacked fiber layers to obtain a multi-layer composite structure.

[0025] In a feasible embodiment, the mass proportion of the pre-polymerized adhesive in each fiber layer is 30% to 45%; and the thickness of each fiber layer is 0.04 mm to 0.2 mm.

[0026] In a feasible embodiment, the fiber sheet is immersed in a pre-polymer glue and cured to obtain a fiber layer, including: making a plurality of woven fiber sheets by weaving fiber bundles; the fiber bundle in at least one woven fiber sheet is a PBO fiber bundle; the plurality of woven fiber sheets are immersed in the pre-polymer glue respectively; the mass proportion of the pre-polymer glue in the plurality of woven fiber sheets after impregnation and the thickness of the plurality of woven fiber sheets after impregnation are controlled; and the plurality of woven fiber sheets after impregnation are cured respectively to obtain a plurality of fiber layers.

[0027] In a feasible embodiment, multiple fiber layers are cut, stacked, and pressed to obtain a multi-layer composite structure, including: cutting the multiple fiber layers separately to obtain multiple fiber layers of preset sizes; stacking the cut multiple fiber layers; and pressing the stacked multiple fiber layers to obtain a multi-layer composite structure.

[0028] In a feasible implementation manner, the mass proportion of the pre-polymerized adhesive in each fiber layer is 45% to 55%; and the thickness of each fiber layer is 0.1 mm to 0.2 mm.

[0029] In a feasible embodiment, the fiber sheet has a gram weight of 30 g / m2 to 140 g / m2.

[0030] In a feasible embodiment, the pressing treatment includes a hot pressing treatment, the hot pressing treatment temperature is 100° C. to 200° C., the hot pressing time is 10 min to 30 min, and the hot pressing pressure is 0.2 MPa to 0.7 MPa.

[0031] In a feasible embodiment, the mass proportion of the pre-polymerized adhesive in the fiber layer is 30% to 60%, and the thickness of the fiber layer is 0.03 mm to 0.3 mm.

[0032] In a feasible implementation, the cutting method may be laser cutting.

[0033] According to a third aspect of an embodiment of the present invention, a battery cover is provided, comprising: a substrate layer, the substrate layer comprising any one of the multi-layer composite structures described above; a decorative layer, the decorative layer being arranged on one side of the substrate layer; through holes being provided on the substrate layer and the decorative layer; and a camera lens, the camera lens cover being provided on the through hole, and the camera lens being provided on the side of the battery cover provided with the decorative layer.

[0034] According to a fourth aspect of an embodiment of the present invention, an electronic device is provided, comprising: a front panel; a middle frame, the middle frame being arranged on one side of the front panel and having a battery slot provided therein; a battery, the battery being arranged in the battery slot; and a battery cover as described above, the battery cover being arranged on a side of the middle frame away from the front panel and being used to protect the battery arranged in the battery slot.

[0035] This application provides a multilayer composite structure, preparation method, battery cover, and electronic device. The multilayer composite structure is constructed by stacking multiple fiber layers, wherein each fiber layer is formed by impregnating fiber sheets in a prepolymerized adhesive solution and then curing the fiber sheets. At least one fiber layer comprises fiber sheets made of poly(p-phenylene benzobisoxazole) (PBO). This allows the multilayer composite structure to have higher strength and modulus. When the multilayer composite structure is impacted, it absorbs and dissipates energy, thereby reducing thickness and weight without compromising its reliability under impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a schematic structural diagram of a battery cover;

[0037] FIG2 is a schematic structural diagram of a battery cover substrate layer;

[0038] FIG3 is a schematic structural diagram of another battery cover substrate layer;

[0039] FIG4 is a schematic structural diagram of another battery cover substrate layer;

[0040] FIG5 is a schematic structural diagram of another mobile phone cover substrate layer;

[0041] FIG6 is a schematic diagram of a multi-layer composite structure according to an embodiment of the present application;

[0042] FIG7 is a schematic diagram of a multilayer composite structure provided with a first fiber layer in an embodiment of the present application;

[0043] FIG8 is a schematic diagram of another multilayer composite structure provided with a first fiber layer according to an embodiment of the present application;

[0044] FIG9 is a schematic diagram of a multilayer composite structure provided with a second fiber layer in an embodiment of the present application;

[0045] FIG10 is a schematic diagram of another multilayer composite structure provided with a second fiber layer according to an embodiment of the present application;

[0046] FIG11 is a schematic diagram of a multi-layer composite structure having multiple fiber layers according to an embodiment of the present application;

[0047] FIG12 is a schematic diagram of another multi-layer composite structure provided with multiple fiber layers according to an embodiment of the present application;

[0048] FIG13 is a schematic diagram of a preparation process of a multi-layer composite structure according to an embodiment of the present application;

[0049] FIG14 is a schematic structural diagram of a battery cover according to an embodiment of the present application;

[0050] FIG15 is a schematic structural diagram of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0051] The following will clearly describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, other embodiments obtained by ordinary technicians in this field without making any creative work are all within the scope of protection of this application.

[0052] Hereinafter, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified with "first," "second," etc., may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0053] In addition, in this application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to changes in the orientation of the components in the drawings.

[0054] The following explains the professional terms mentioned in the embodiments of the present application to facilitate understanding by those skilled in the art.

[0055] PBO fiber, short for poly-p-phenylene benzobisoxazole fiber, is a polyamide containing heterocyclic aromatic groups.

[0056] Casings for consumer electronic devices like mobile phones, tablets, and PCs primarily serve to enhance the appearance and protect the safety of internal components like batteries and processors. Currently, consumer electronics, especially foldable devices, are experiencing strong demand for reduced weight, thickness, and reliability, and battery covers are a prime example of where these components can be reduced in weight and thickness.

[0057] The foldable models described in the embodiments of the present application include but are not limited to foldable fixed terminals or mobile terminals such as mobile phones, foldable screen mobile phones, laptops, foldable stands, foldable PADs, laptops, personal digital assistants or wearable devices.

[0058] It should be understood that foldable electronic devices include inward-folding electronic devices and outward-folding electronic devices. Inward-folding electronic devices are electronic devices whose flexible screen is located on the inside of the device when the device is folded, while outward-folding electronic devices are electronic devices whose flexible screen covers the outside of the device when the device is folded.

[0059] Under the current battery cover structure design of folding devices, traditional glass fiber composite materials can no longer meet the design requirements of thinning and weight reduction, and the battery cover made of glass fiber composite materials has a high reliability risk, especially in the scenario where the whole device falls, the battery cover has poor puncture resistance. Weight reduction and thinning conflict with protection, resulting in poor weight reduction and thinning effects and poor puncture resistance.

[0060] Figure 1 is a schematic diagram of the structure of a battery cover. As shown in Figure 1, taking the battery cover of a smartphone as an example, the battery cover 1 may include a substrate layer 10 and a decorative layer 20, wherein the substrate layer 10 is formed by stacking multiple layers of prepreg 11 composed of glass fiber, aramid or other fibers, and the decorative layer 20 may be made of ceramic, glass, leather or other materials, which are not limited in this application. Since the decorative layer 20 is a structure provided on the surface of the substrate layer 10 for appearance decoration, the thickness of the decorative layer 20 is thinner than that of the substrate layer 10. Therefore, in the process of thinning and reducing the weight of the battery cover 1, the main structural design is the substrate layer 10. At the same time, the substrate layer 10 is also an important component that affects the puncture resistance of the battery cover 1.

[0061] Figure 2 is a schematic diagram of the structure of one battery cover substrate layer, and Figure 3 is a schematic diagram of the structure of another battery cover substrate layer. As shown in Figure 2, the commonly used substrate layer 10 is a laminated structure of E-glass prepreg 11a, which is primarily composed of E-glass. E-glass is a type of glass fiber composed of aluminoborosilicate glass. The E-glass fibers in each layer of E-glass prepreg 11a are woven into a mesh structure, thereby providing puncture resistance.

[0062] As shown in FIG3 , in one embodiment, the glass fiber in the substrate layer 10 can be replaced with S-glass fiber, that is, the substrate layer 10 is a structure in which S-glass prepreg 11 b with S-glass as the main body is stacked.

[0063] S-glass is a type of aluminum-magnesium silicate glass fiber. Compared to E-glass, S-glass has a higher modulus and strength. The S-glass in S-glass prepreg 11b is also woven into a mesh structure. During stacking, the S-glass in adjacent S-glass prepregs 11b extend in different directions through cross-stacking, improving the impact resistance of substrate layer 10. The overlapping structure also reduces cracking during drops, achieving puncture resistance.

[0064] However, since S-glass fiber only offers approximately 20% better mechanical properties than E-glass fiber, the actual improvement in puncture resistance is limited. Furthermore, since both S-glass fiber and E-glass fiber are glass fibers, their densities do not differ significantly. Therefore, the weight of the battery cover 1 constructed using substrate layers 10 composed of different glass fibers is essentially the same, making it impossible to optimize the weight of the battery cover 1.

[0065] FIG4 is a schematic diagram of the structure of another battery cover substrate layer. As shown in FIG4 , in some embodiments, the substrate layer 10 can also be made by mixing and stacking multiple fiber prepregs. For example, the substrate layer 10 can be provided with five layers of prepreg 11, which may include glass fiber prepreg 11c, ceramic fiber prepreg 11d, and aramid fiber prepreg 11e. The upper and lower sides of the ceramic fiber prepreg 11d are respectively provided with a layer of glass fiber prepreg 11c, and the side of the two layers of glass fiber prepreg 11c away from the ceramic fiber prepreg 11d can be provided with a layer of aramid fiber prepreg 11e, thereby forming a five-layer substrate layer 10.

[0066] By using a mixed stack of aramid fibers and ceramic fibers, the toughness of the aramid fibers and the high modulus of the ceramic fibers can be used to improve the stiffness and toughness of the substrate layer 10, thereby increasing the impact resistance and puncture resistance of the substrate layer 10 and improving the puncture resistance of the battery cover 1.

[0067] However, due to the high density of ceramic fibers, the weight of the substrate layer 10 containing ceramic fibers increases, affecting the overall weight of the battery cover 1 and hindering weight reduction. Furthermore, although ceramic fibers have a high modulus, they are relatively brittle compared to glass fibers, resulting in limited improvement in puncture resistance.

[0068] Figure 5 is a schematic diagram of the structure of another mobile phone cover substrate layer. As shown in Figure 5, in some embodiments, due to the high density of glass fiber itself, in order to reduce weight and thickness, hollow glass microspheres 12 can be added to the prepreg 11 of the substrate layer 10 to reduce the overall density of the prepreg 11.

[0069] Taking the example of a substrate layer 10 including five layers of glass fiber prepreg, hollow glass microspheres with a density of about 0.4 g / cm3 can be added to the glass fiber prepreg except the top and bottom layers, so as to reduce the density of the substrate layer 10 from 1.9 g / cm3 to about 1.4 g / cm3, thereby reducing the weight of the battery cover 1.

[0070] It should be understood that in order to add hollow glass microspheres to the substrate layer 10, they must be added to the resin used to prepare the prepreg 11 during the preparation of the prepreg 11. Furthermore, to accommodate the glass microspheres, the resin content of the prepreg 11 needs to be increased. However, since the strength of the resin is significantly different from that of the fiber, this can lead to a decrease in the safety properties of the substrate layer 10, such as puncture resistance. Furthermore, since the glass microspheres are inherently brittle, their addition can reduce the toughness of the substrate layer 10. This can easily lead to edge chipping during processing, especially during cutting operations, reducing the yield rate of the battery cover 1.

[0071] To solve the above problems, the embodiments of the present application provide a multi-layer composite structure, a preparation method, a battery cover and an electronic device, which can achieve the thinning and weight reduction of the battery cover itself, and can also optimize the puncture resistance of the battery cover, reduce the risk of damage to internal components of the electronic device in falling or other scenarios, and improve the application safety of the electronic device.

[0072] FIG6 is a schematic diagram of a multilayer composite structure according to an embodiment of the present application. As shown in FIG6 , the present embodiment provides a multilayer composite structure 100 comprising a plurality of stacked fiber layers 110. Each fiber layer 110 is formed by impregnating fiber sheets in a prepolymerized adhesive solution and then curing the fiber sheets. The fiber sheets in at least one fiber layer 110 are made of PBO fibers.

[0073] In the embodiment of the present application, in order to solidify the fiber sheets to form the fiber layers 110, the mass ratio of the pre-polymerized adhesive in each fiber layer 110 needs to be controlled. Specifically, in order to shape the fiber layers 110 and enable operations such as hot pressing, the mass ratio of the pre-polymerized adhesive in the fiber layers 110 needs to be greater than or equal to 30%.

[0074] However, since the physical properties such as structural strength of the cured pre-polymerized adhesive are somewhat different from those of the fiber sheet, excessive pre-polymerized adhesive will cause the structural strength of the formed fiber layer 110 to decrease, which is not conducive to improving the puncture resistance of the multi-layer composite structure 100. Therefore, the mass proportion of the pre-polymerized adhesive in the fiber layer 110 needs to be less than or equal to 60%, that is, the mass proportion of the pre-polymerized adhesive in the fiber layer 110 needs to be controlled within 30% to 60%. This will reduce the influence of the pre-polymerized adhesive on the strength of the fiber layer 110 while being able to shape the fiber layer 110, thereby improving the structural strength of the obtained multi-layer composite structure 100.

[0075] It should be understood that the mass proportion of the pre-polymerized adhesive in the fiber layer 110 refers to the mass proportion of the solid structure formed by curing the pre-polymerized adhesive in the fiber layer 110 after curing.

[0076] At the same time, in order to meet the structural design of thinning and weight reduction, the thickness of each fiber layer 110 is greater than or equal to 0.03 mm and less than or equal to 0.3 mm, so that the fiber layer 110 has a thinner thickness on the basis of providing a certain structural strength, thereby facilitating the structural design of the thinning and weight reduction battery cover through the multi-layer composite structure 100.

[0077] PBO fiber has density, strength, and modulus similar to carbon fiber, and possesses the same toughness as aramid fiber, while also possessing the material properties of lightness and high strength. Therefore, the fiber layer 110 composed of PBO fiber has the aforementioned advantages, which can improve the overall structural strength of the multilayer composite structure 100 while reducing its weight. This, in turn, improves the structural strength and reduces the weight of the battery cover formed by the multilayer composite structure 100, achieving a thinner and lighter battery cover.

[0078] It should be noted that the pre-polymerized adhesive is primarily used to shape and solidify the fiber layer 110, and to facilitate post-stacking processing to form the multi-layer composite structure 100. In some embodiments, the pre-polymerized adhesive may include materials such as epoxy monomers, curing agents, accelerators, dispersants, and fillers. This application does not limit the specific types of materials included in the pre-polymerized adhesive.

[0079] For example, during the actual preparation of the multilayer composite structure 100, multiple fiber prepregs may be cut, stacked, and pressed together to obtain the multilayer composite structure 100, wherein at least one fiber prepreg is a PBO fiber prepreg. It should be understood that the fiber prepreg is the fiber layer 110 in the aforementioned embodiment.

[0080] FIG7 is a schematic diagram of a multilayer composite structure provided with a first fiber layer in an embodiment of the present application, and FIG8 is a schematic diagram of another multilayer composite structure provided with a first fiber layer in an embodiment of the present application.

[0081] In some embodiments of the present application, the fibers in the fiber layer 110 may extend in a unidirectional direction. As shown in Figures 7 and 8 , at least one fiber layer 110 among the multiple fiber layers 110 is a first fiber layer 110a. The fiber sheets in each first fiber layer 110a are composed of straightened PBO fiber tows 111 extending in the same direction.

[0082] For example, as shown in FIG7 , a multilayer composite structure 100 may include five fiber layers 110 , each of which is a first fiber layer 110 a . The PBO fiber tows 111 in adjacent first fiber layers 110 a extend in different directions. Due to the different extension directions, the PBO fiber tows 111 in adjacent first fiber layers 110 a form a cross structure, thereby improving the puncture resistance of the multilayer composite structure 100 .

[0083] Therefore, during the preparation of the multilayer composite structure 100 , a plurality of PBO fiber prepregs need to be cut, stacked, and pressed to obtain the multilayer composite structure 100 in which each fiber layer 110 is the first fiber layer 110 a .

[0084] In some embodiments, the angle between the extension directions of the PBO fiber tows 111 in adjacent first fiber layers 110a is a right angle. As shown in FIG7 , if the extension direction of the PBO fiber tows 111 in the topmost first fiber layer 110a is 0°, then the extension direction of the PBO fiber tows 111 in the adjacent first fiber layer 110a can be 90°. The PBO fiber tows 111 in the five first fiber layers 110a can be arranged in the order of 0° / 90° / 0° / 90° / 0°, thereby improving the overall strength of the multilayer composite structure 100.

[0085] As shown in Figure 8, in some embodiments of the present application, the multilayer composite structure 100 may also include four fiber layers 110, and each fiber layer 110 is a first fiber layer 110a, wherein the PBO fiber bundles 111 in the uppermost and lowermost first fiber layers 110a extend in a first direction, and the PBO fiber bundles 111 in other first fiber layers 110a in the multilayer composite structure 100 extend in a second direction, and the first direction is different from the second direction.

[0086] Compared to the multilayer composite structure 100 in the previous embodiment, the multilayer composite structure 100 in this embodiment eliminates one first fiber layer 110a, thereby further reducing the thickness and weight of the battery cover formed by the multilayer composite structure 100. For example, the angle between the first direction and the second direction can also be a right angle. For example, if the first direction is 0°, the second direction can be 90°. Therefore, the PBO fiber tows 111 in the four first fiber layers 110a can be arranged in the order of 0° / 90° / 90° / 0°, thereby improving the overall strength of the multilayer composite structure 100.

[0087] It should be understood that the fiber density shown in FIG. 7 and FIG. 8 is merely an example for illustrating the arrangement of the PBO fiber tows.

[0088] In practical applications, the unidirectionally arranged fibers have a higher density, which reduces the mass of pre-polymerized adhesive required to form the first fiber layer 110 and better preserves the strength and modulus of the PBO fiber tows. Furthermore, the PBO fiber tows in each first fiber layer 110a are straightened, allowing for better control of the thickness of the first fiber layer 110a and reducing surface irregularities. This facilitates thinning and weight reduction of the battery cover through the multi-layer composite structure 100.

[0089] In some embodiments of the present application, the pre-polymerized adhesive includes resin to shape the fiber layer 110. In the first fiber layer 110a, since the PBO fiber tows 111 in the same first fiber layer 110a are in a straightened state and have a high fiber density, the mass proportion of the pre-polymerized adhesive in the first fiber layer 110a is relatively low.

[0090] Exemplarily, the mass proportion of the pre-polymerized adhesive in each first fiber layer 110a ranges from 30% to 45%, thereby reducing the impact of the pre-polymerized adhesive on the strength of the first fiber layer 110a, better preserving the strength and modulus of the PBO fiber tows 111, and improving their puncture resistance. Furthermore, the unidirectional and straightened PBO fiber tows 111 enable more precise control of the thickness of the resulting first fiber layer 110a. Exemplarily, to ensure the strength of the multi-layer composite structure 100, the thickness of each first fiber layer 110a can be 0.1 mm.

[0091] It should be noted that the mass proportion of the pre-polymerized glue in the first fiber layer 110a and the thickness of the first fiber layer 110a are both feasible implementation methods in the present application. The mass proportion of the pre-polymerized glue in the first fiber layer 110a and the thickness of the first fiber layer 110a can also be other values. The present application does not limit the specific values ​​of the mass proportion of the resin and the thickness of the first fiber layer 110a.

[0092] By extending the PBO fiber tows 111 in the same direction to form the first fiber layer 110a, a first fiber layer 110a with higher single-layer strength and modulus than glass fiber can be obtained, thereby improving the puncture resistance of the battery cover composed of the multi-layer composite structure 100. Compared to battery covers composed of glass fiber, the resulting battery cover can be reduced in weight by 1g to 1.5g while improving puncture resistance by 100% to 200%.

[0093] FIG9 is a schematic diagram of a multilayer composite structure provided with a second fiber layer in an embodiment of the present application, and FIG10 is a schematic diagram of another multilayer composite structure provided with a second fiber layer in an embodiment of the present application.

[0094] In a feasible embodiment of the present application, at least one fiber layer 110 among the multiple fiber layers 110 of the multilayer composite structure 100 is a second fiber layer 110b. The fiber sheets in each second fiber layer 110b are woven from PBO fiber tows 111 extending in a fifth direction and a sixth direction, where the fifth direction and the sixth direction are different.

[0095] As shown in Figures 9 and 10 , each fiber layer 110 in the multilayer composite structure 100 is a second fiber layer 110b, and the multilayer composite structure 100 may include four or five second fiber layers 110b. In some embodiments, the angle between the fifth direction and the sixth direction is a right angle, that is, the PBO fiber tows 111 in the second fiber layer 110b are arranged vertically.

[0096] The second fiber layers 110b can be stacked directly to form the multi-layer composite structure 100, or can be cross-stacked to improve the overall strength of the multi-layer composite structure 100. Specifically, as shown in FIG10 , the multi-layer composite structure 100 includes four second fiber layers 110b. The PBO fiber tows 111 in the fifth direction of the second fiber layers 110b are warp fibers, and the PBO fiber tows 111 in the sixth direction are weft fibers. Taking the warp fiber direction of the topmost second fiber layer 110b as 0° as an example, the warp fibers in the four second fiber layers 110b from top to bottom can be arranged in the order of 0° / 45° / 90° / 135°, thereby forming a cross-grid structure, thereby improving the overall strength of the multi-layer composite structure 100.

[0097] It should be noted that the weaving method of the PBO fiber tows 111 shown in Figures 9 and 10 is only an example in this application. In actual applications, the weaving density of the PBO fiber tows 111 is higher and the gaps between the PBO fiber tows 111 are smaller. The second fiber layer 110b formed by weaving has the effect of preventing yarn from falling apart. However, because the weaving process causes the crossed PBO fiber tows 111 to bend, the woven fiber sheet has a certain degree of unevenness. As a result, the weight of the pre-polymerized adhesive will increase to a certain extent during the filling and curing process. The thickness of the second fiber layer 110b is limited by the thickness of the at least two crossed PBO fiber tows 111. Compared with the first fiber layer 110a, the thickness and weight reduction of the multi-layer composite structure 100 constructed using the second fiber layer 110b is limited.

[0098] In some embodiments, the pre-polymerized adhesive used to form the second fiber layer 110b also contains resin. Due to the characteristics of the woven fibers, the mass percentage of the pre-polymerized adhesive in the second fiber layer 110b is higher than that in the first fiber layer 110a. Exemplarily, the mass percentage of the pre-polymerized adhesive in each second fiber layer 110b is 45% to 55%, and the thickness of each second fiber layer 110b ranges from 0.1 mm to 0.2 mm.

[0099] By weaving PBO fiber tows 111 to form the second fiber layer 110b, a second fiber layer 110b with higher single-layer strength and modulus than glass fiber can be achieved, thereby improving the puncture resistance of the battery cover composed of the multi-layer composite structure 100. Compared to battery covers constructed from glass fiber, the resulting battery cover can be 0.5g to 1g lighter and have 50% to 80% higher puncture resistance.

[0100] Figure 11 is a schematic diagram of a multilayer composite structure having multiple fiber layers according to an embodiment of the present application, and Figure 12 is a schematic diagram of another multilayer composite structure having multiple fiber layers according to an embodiment of the present application. Due to the high cost of PBO fibers and their poorer bonding with the resin in the prepolymerized adhesive than fibers such as glass fibers, in some embodiments, to increase the strength and reduce the weight of the multilayer composite structure 100, a third fiber layer 110c may be provided in the multilayer composite structure 100, as shown in Figure 11 .

[0101] Specifically, among the multiple fiber layers 110 in the multilayer composite structure 100, except for at least one first fiber layer 110a, the other fiber layers 110 are all third fiber layers 110c. The fiber sheets in the third fiber layer 110c are arranged by first fiber tows 111a extending in the same direction and in a straightened state. The first fiber tows 111a can be any of glass fibers, aramid fibers, ceramic fibers, and carbon fibers.

[0102] In the multilayer composite structure 100, multiple third fiber layers 110c can be stacked, and at least one first fiber layer 110a can be positioned between adjacent third fiber layers 110c. As shown in FIG11 , the multilayer composite structure 100 includes five fiber layers 110, including one first fiber layer 110a and four third fiber layers 110c. In this case, the four third fiber layers 110c can be stacked, and the first fiber layer 110a can be positioned in the middle of the multilayer composite structure 100, i.e., there are two third fiber layers 110c above and below the first fiber layer 110a.

[0103] It should be noted that the fiber types used in different third fiber layers 110c may be the same or different. As shown in Figure 11, the first fiber layer 110a is disposed in the middle of the multilayer composite structure 100. The first fiber tows 111a in the two third fiber layers 110c above and below the first fiber layer 110a may be aramid fibers. The first fiber tows 111a in the top and bottom third fiber layers 110c of the multilayer composite structure 100 may be glass fibers or carbon fibers.

[0104] It should be understood that the material of the first fiber bundle 111a in the aforementioned third fiber layer 110c and the arrangement of the third fiber layer 110c are only one feasible implementation method. The present application may also include a third fiber layer 110c with other materials and arrangements. Therefore, the material of the first fiber bundle 111a and the stacking arrangement of the fiber layer 110c are not limited in this application.

[0105] In some embodiments, to improve the puncture resistance of the multilayer composite structure 100, the PBO fiber tows 111 in the first fiber layer 110a may extend in a third direction, and the first fiber tows 111a in the third fiber layer 110c adjacent to the first fiber layer 110a may extend in a fourth direction, where the third direction is different from the fourth direction, and the first fiber tows 111a in the adjacent third fiber layer 110c extend in different directions. For example, the angle between the third direction and the fourth direction may be a right angle.

[0106] In this way, the fibers in different fiber layers 110 can be cross-arranged, thereby reducing voids in the multi-layer composite structure 100 and improving the strength of the multi-layer composite structure 100 .

[0107] It should be understood that when using multiple fibers to construct the multilayer composite structure 100, the fibers may also be woven to enhance the strength of the multilayer composite structure 100. As shown in FIG12 , the fiber layer 110 in the multilayer composite structure 100 may include at least one second fiber layer 110b and a plurality of fourth fiber layers 110d.

[0108] Exemplarily, among the multiple fiber layers 110 in the multilayer composite structure 100, except for at least one second fiber layer 110b, the other fiber layers 110 are all fourth fiber layers 110d. The fiber sheets in the fourth fiber layer 110d are woven from second fiber tows 111b extending in the fifth and sixth directions. The second fiber tows 111b can be any one of glass fibers, aramid fibers, ceramic fibers, and carbon fibers.

[0109] In the multilayer composite structure 100, multiple fourth fiber layers 110d may be stacked, and at least one second fiber layer 110b may be disposed between adjacent fourth fiber layers 110d. As shown in FIG12 , the multilayer composite structure 100 includes four fiber layers 110, including one second fiber layer 110b and three fourth fiber layers 110d. In this case, the three fourth fiber layers 110d may be stacked, and the second fiber layer 110b may be disposed between two adjacent fourth fiber layers 110d. That is, there is one fourth fiber layer 110d on one side of the second fiber layer 110b and two fourth fiber layers 110d on the other side.

[0110] It should be understood that the fiber types used in different fourth fiber layers 110d may be the same or different. For example, as shown in FIG12 , the second fiber tows 111b in the three fourth fiber layers 110d may be glass fiber, aramid fiber, and carbon fiber, respectively, or may be glass fiber, aramid fiber, and ceramic fiber, etc. This application does not impose any restrictions on the types of the second fiber tows 111b in the fourth fiber layers 110d.

[0111] FIG13 is a schematic diagram of a preparation process of a multi-layer composite structure in an embodiment of the present application.

[0112] In addition to providing a multi-layer composite structure 100, the present application also provides a method for preparing the multi-layer composite structure. As shown in FIG13 , the preparation method includes:

[0113] S100: Epoxy resin monomer, curing agent, accelerator, dispersant and filler are placed in the prepreg, stirred and pre-cured to form a prepolymer glue solution.

[0114] The epoxy resin monomer can be bisphenol A epoxy resin, the curing agent can be an amine curing agent, the accelerator can be a polyamide resin accelerator, the dispersant can be a surfactant dispersant, and the filler can be talcum powder. After the above reaction solution is fully stirred and pre-cured, a pre-polymerized glue solution can be formed.

[0115] For example, the epoxy resin monomer may be 618 epoxy resin monomer, and the heating temperature during the pre-curing process may be 70° C. It should be understood that the above-mentioned type of epoxy resin monomer and pre-curing temperature are only one feasible embodiment, and other types of epoxy resin monomers and pre-curing temperatures may also be used in this application to achieve the above-mentioned effects.

[0116] S200: Immersing the fiber sheet in a prepolymerized adhesive solution and performing a curing treatment to obtain a fiber layer.

[0117] After obtaining the prepolymer glue, the fiber sheet can be immersed in the prepolymer glue and cured to obtain a fiber layer. It should be noted that in the actual production process, after the fiber sheet is immersed in the prepolymer glue and cured, the product obtained is a fiber prepreg. The fiber prepreg is an intermediate product for making a fiber composite structure. For example, a PBO fiber sheet is immersed in the prepolymer glue and cured to obtain a PBO fiber prepreg. In the embodiment of the present application, a fiber layer 110 can be considered as a fiber prepreg, and the operations performed on multiple fiber layers 110 in subsequent steps can be considered as operations on multiple fiber prepregs.

[0118] As can be seen from the above-described embodiment of the multi-layer composite structure 100, the fiber sheet in the fiber layer 110 can be a fiber sheet with unidirectionally arranged fibers or a woven fiber sheet formed by weaving fibers. Therefore, the preparation process of the fiber layer 110 can include preparing the fiber sheet with unidirectionally arranged fibers or preparing the fiber sheet by weaving fibers.

[0119] For example, in order to prepare a fiber layer 110 in which fibers are arranged unidirectionally in a fiber sheet, the fiber bobbin yarn can be first placed in place and the fiber bundles can be arranged unidirectionally by swinging the yarn to form a plurality of fiber sheets, wherein the fiber bundles in at least one fiber sheet are PBO fiber bundles. It should be understood that the fiber layer 110 in the embodiment of the present application uses a single type of fiber bundle, that is, each fiber layer 110 contains a fiber sheet formed by one and only one type of fiber bundle.

[0120] The obtained multiple fiber sheets are respectively immersed in pre-polymer glue. At the same time, in order to reduce the influence of the pre-polymer glue on the strength of the formed fiber layer 110 and the thickness of the subsequently formed multi-layer composite structure, it is necessary to control the mass proportion of the pre-polymer glue in the multiple immersed fiber sheets and the thickness of the multiple immersed fiber sheets, so as to achieve control over the prepared products.

[0121] After the impregnation is completed, due to the high fluidity of the pre-polymerized adhesive, the impregnated fiber sheets need to be cured separately to obtain multiple fiber layers.

[0122] When the fiber layer 110 is prepared by weaving fiber sheets, a plurality of woven fiber sheets may be prepared by weaving fiber bundles, wherein the fiber bundles in at least one woven fiber sheet are PBO fiber bundles.

[0123] The obtained multiple woven fiber sheets are respectively immersed in pre-polymer glue, and the mass proportion of the pre-polymer glue in the multiple immersed woven fiber sheets and the thickness of the multiple immersed woven fiber sheets are controlled. Finally, the multiple immersed woven fiber sheets are respectively cured to obtain multiple fiber layers.

[0124] Specifically, the impregnated fiber sheets are cured by heating in an oven, and the curing temperature may be 100° C. to 120° C.

[0125] It should be understood that the woven fiber sheet has a certain degree of bending in the fiber bundles relative to the fiber sheet with unidirectional fiber arrangement, and due to the gaps formed in the woven structure, the mass proportion of the prepolymer glue in the woven fiber sheet after impregnation, as well as the thickness of the woven fiber sheet after impregnation, are larger than those of the fiber sheet with unidirectional fiber arrangement.

[0126] In the embodiment of the present application, the gram weight of the fiber sheet in the fiber layer 110 may be in the range of 30 g / m2 to 140 g / m2. It should be understood that the arrangement of the fiber tows affects the gram weight of the fiber layer 110, wherein the gram weight of the fiber sheet with unidirectional arrangement of the fiber tows may be in the range of 30 g / m2 to 140 g / m2, while the gram weight of the woven fiber sheet may be in the range of 50 g / m2 to 140 g / m2. For example, taking the fiber sheet composed of PBO fiber tows as an example, a fiber sheet with a gram weight of 50 g / m2 or a woven fiber sheet with a gram weight of 60 g / m2 may be preferably used to prepare the fiber layer 110.

[0127] At the same time, in order to facilitate the molding of the fiber layer 110 and reduce the influence of the pre-polymerized glue on the strength of the fiber layer 110, the mass proportion of the pre-polymerized glue in the fiber layer 110 is 30% to 60%, and the thickness of the fiber layer 110 is 0.03mm to 0.3mm. Preferably, in the fiber layer 110 prepared by the fiber sheet with unidirectional fiber arrangement, the mass proportion of the pre-polymerized glue in each fiber layer 110 is 30% to 45%, and the thickness of each fiber layer 110 is 0.04mm to 0.2mm. In the fiber layer 110 prepared by the woven fiber sheet, the mass proportion of the pre-polymerized glue in each fiber layer 110 is 45% to 55%, and the thickness of each fiber layer 110 is 0.1mm to 0.2mm. It should be noted that the specific thickness of the fiber layer 110 can be adjusted as needed.

[0128] S300: Cutting, stacking, and pressing multiple fiber layers to obtain a multi-layer composite structure.

[0129] In which, the fiber sheets in at least one fiber layer are made of PBO fibers. Since the multilayer composite structure 100 obtained by processing multiple fiber layers 110 is a composite material, in practical applications, in order to facilitate subsequent operations, it is necessary to control the size of the multilayer composite structure 100 formed during the preparation of the multilayer composite structure 100. For example, taking the preparation of a mobile phone cover using the multilayer composite structure 100 as an example, a rectangular multilayer composite structure 100 with a length and width slightly larger than the mobile phone is required. Therefore, the shape and size of the multilayer composite structure 100 are related to the preset preparation target. Therefore, when preparing the multilayer composite structure 100, it is necessary to cut the multiple fiber layers 110 separately to obtain fiber layers of a preset size, wherein the preset size is related to the structure to be prepared by the multilayer composite structure 100.

[0130] The multiple fiber layers 110 after cutting are then stacked, wherein the fiber bundles in adjacent fiber layers 110 extend in different directions. Furthermore, the angle between the extension directions of the fiber bundles in adjacent fiber layers 110 may be a right angle. Alternatively, the fiber bundles in the topmost and bottommost fiber layers 110 extend in a first direction, and the fiber bundles in the other fiber layers except the topmost and bottommost layers extend in a second direction, and the first direction is different from the second direction. If the first direction is 0°, the second direction may be 45°, 60°, 90° or any other angle. In some embodiments, in order to achieve an arrangement pattern and improve the overall strength of the formed multilayer composite structure 100, the second direction may be 90° based on the first direction being 0°. Finally, the multiple stacked fiber layers 110 may be pressed together to obtain the multilayer composite structure 100.

[0131] In some embodiments, if the fiber sheets in the fiber layer 110 are woven fiber sheets, then during the process of preparing the multi-layer composite structure 100, the plurality of fiber layers 110 may be first cut separately to obtain a plurality of fiber layers 110 of a predetermined size, and then the cut plurality of fiber layers 110 are stacked and arranged, and finally the stacked plurality of fiber layers 110 are pressed together to obtain the multi-layer composite structure 100. The stacking method of the plurality of fiber layers 110 may be as shown in FIG. 10 , which will not be described in detail in this application.

[0132] The cutting method may be laser cutting. The pressing process may include a hot pressing process, wherein the temperature range of the hot pressing process is 100° C. to 200° C., the hot pressing time is 10 minutes to 30 minutes, and the hot pressing pressure is 0.2 MPa to 0.7 MPa.

[0133] FIG14 is a schematic structural diagram of a battery cover in an embodiment of the present application.

[0134] In addition to providing a multilayer composite structure 100 and a method for preparing the multilayer composite structure 100, this application also provides a battery cover 210 in an embodiment. As shown in Figure 14, the battery cover 210 includes a substrate layer 211 and a decorative layer 212. The substrate layer 211 includes the multilayer composite structure 100 described in any of the aforementioned embodiments, and the decorative layer 212 is disposed on one side of the substrate layer 211. The decorative layer 212 can be made of glass, ceramic, resin, or other materials with decorative functions. This application does not limit the material of the decorative layer 212.

[0135] In some embodiments, in order to meet the device installation requirements on some electronic devices, a through hole 213 is provided on the base material layer 211 and the decorative layer 212, and the battery cover 210 also includes a camera lens 214. The shape of the camera lens 214 matches the shape of the through hole 213, and the camera lens 214 is covered on the through hole 213. In order to realize the shooting function of the electronic device, the material of the camera lens 214 can be glass or other transparent materials, and this is not limited in this application.

[0136] It should be understood that the camera lens 214 is disposed on the side of the battery cover 210 where the decorative layer 212 is disposed, thereby providing certain protection for the components within the electronic device.

[0137] The following describes the preparation process of the battery cover 210 through several embodiments.

[0138] Example 1

[0139] (1) Since the substrate layer 211 is the multilayer composite structure 100 in any of the aforementioned embodiments, the preparation process of the substrate layer 211 is the same as the preparation process of the aforementioned multilayer composite structure 100. Exemplarily, the preparation of the substrate layer 211 may include:

[0140] 618 epoxy resin monomer, amine curing agent, polyamide resin accelerator, surfactant dispersant, and talc are placed in the prepreg, fully stirred, and heated to 70°C before pre-curing to form a prepolymer glue solution; wherein the ratio of epoxy resin monomer, amine curing agent, polyamide resin accelerator, surfactant dispersant, and talc is 100:10:20:10:18;

[0141] Place the PBO fiber bobbin in place, and transform the fiber tow into a unidirectional PBO fiber sheet with uniform thickness and width through yarn swinging;

[0142] The unidirectional PBO fiber sheet is impregnated with the prepolymerized adhesive through a prepreg line, and then passed through a hot roller to control the mass proportion of the prepolymerized adhesive in the unidirectional PBO fiber sheet to be 40%, and the thickness of the unidirectional PBO fiber sheet after impregnation is controlled to be 0.05 mm, thereby obtaining a unidirectional PBO fiber sheet impregnated with the prepolymerized adhesive;

[0143] The unidirectional PBO fiber sheet impregnated with the prepolymerized adhesive is placed in an oven at 100°C to 120°C for curing to obtain a unidirectional PBO fiber prepreg;

[0144] Unidirectional PBO fiber prepreg is cut by laser to obtain unidirectional PBO fiber prepreg sheets, and the directions of laser cutting are respectively along the fiber direction and perpendicular to the fiber direction of the unidirectional PBO fiber prepreg, i.e. 0° and 90°;

[0145] According to the design of the 0.4mm battery cover substrate layer, unidirectional PBO fiber prepreg sheets were stacked in four layers at 0° / 90° / 90° / 0° and hot pressed with hot pressing parameters of 150°C / 20min and a pressure of 0.5 MPa. After cooling, a PBO fiber composite sheet with non-profile edges was obtained as the substrate layer 211.

[0146] (2) Preparation of the entire battery cover 210

[0147] The surface of the obtained substrate layer 211 is subjected to appearance treatment to install a decorative layer 212 on the surface of the substrate layer 211. The methods for installing the decorative layer 212 include spraying, rubbing or external PU leather, etc., and then the substrate layer 211 is laser cut to remove the non-profile surface and make a through hole 213 according to the design of the camera lens 214 to obtain the main structure of the battery cover 210.

[0148] The main structure of the obtained battery cover 210 is subjected to auxiliary material bonding and assembly of the camera lens 214 to finally obtain the battery cover 210.

[0149] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 1.5g and improves the puncture resistance by 100% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0150] Example 2

[0151] Example 2 provides a battery cover 210. Example 2 differs from Example 1 in the percentage by mass of the prepolymerized adhesive in the unidirectional PBO fiber sheet, the thickness of the unidirectional PBO fiber sheet after impregnation, and the stacking order and number of layers of the unidirectional PBO fiber prepreg sheets. In this example, the percentage by mass of the prepolymerized adhesive in the unidirectional PBO fiber sheet is 45%, the thickness of the unidirectional PBO fiber sheet after impregnation is controlled to be 0.1 mm, and the unidirectional PBO fiber prepreg sheets are stacked in five layers at a 0° / 90° / 0° / 90° / 0° angle.

[0152] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 1g and improves the puncture resistance by 200% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0153] Example 3

[0154] Example 3 provides a battery cover 210. The difference between Example 3 and Example 1 is that according to the design of the 0.4mm battery cover substrate, the unidirectional PBO fiber prepreg sheet and other unidirectional fiber prepreg sheets are stacked, and the middle layer or layers are unidirectional PBO fiber prepreg sheets. This embodiment adopts unidirectional glass fiber prepreg sheets, unidirectional aramid fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, and unidirectional ceramic fiber prepreg sheets to be stacked in 4 layers at 0° / 90° / 90° / 0° and hot pressed. The hot pressing parameters are 150°C / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer 211.

[0155] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.5g and improves the puncture resistance by 120% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0156] Example 4

[0157] Example 4 provides a battery cover 210. The difference between Example 4 and Example 1 is that according to the design of the 0.4mm battery cover substrate, the unidirectional PBO fiber prepreg sheet and other unidirectional fiber prepreg sheets are stacked, and the middle layer or layers are unidirectional PBO fiber prepreg sheets. This embodiment adopts unidirectional glass fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, and unidirectional carbon fiber prepreg sheets to be stacked in 4 layers at 0° / 90° / 90° / 0° and hot pressed. The hot pressing parameters are 150°C / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-profile edges is obtained as the substrate layer 211.

[0158] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 1g and improves the puncture resistance by 80% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0159] Example 5

[0160] Example 5 provides a battery cover 210. The difference between Example 5 and Example 2 is that according to the design of the 0.4mm battery cover substrate, the unidirectional PBO fiber prepreg sheet and other unidirectional fiber prepreg sheets are stacked, and the middle layer or layers are unidirectional PBO fiber prepreg sheets. This embodiment adopts unidirectional aramid fiber prepreg sheets, unidirectional glass fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, unidirectional carbon fiber prepreg sheets, and unidirectional ceramic fiber prepreg sheets to be stacked in 5 layers at 0° / 90° / 0° / 90° / 0° and hot pressed. The hot pressing parameters are 150°C / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer 211.

[0161] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.6g and improves the puncture resistance by 100% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0162] Example 6

[0163] Example 6 provides a battery cover 210. The difference between Example 6 and Example 2 is that according to the design of the 0.4mm battery cover substrate, the unidirectional PBO fiber prepreg sheet and other unidirectional fiber prepreg sheets are stacked, and the middle layer or layers are unidirectional PBO fiber prepreg sheets. This embodiment adopts unidirectional aramid fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, unidirectional PBO fiber prepreg sheets, and unidirectional ceramic fiber prepreg sheets. They are stacked in 5 layers at 0° / 90° / 0° / 90° / 0° and hot pressed. The hot pressing parameters are 150°C / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer 211.

[0164] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.8g and improves the puncture resistance by 120% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0165] Example 7

[0166] (1) Preparation of substrate layer 211

[0167] 618 epoxy resin monomer, amine curing agent, polyamide resin accelerator, surfactant dispersant, and talc are placed in the prepreg, fully stirred, and heated to 70°C before pre-curing to form a prepolymer glue solution; wherein the ratio of epoxy resin monomer, amine curing agent, polyamide resin accelerator, surfactant dispersant, and talc is 100:10:20:10:18;

[0168] The woven PBO fiber sheet is impregnated with the prepolymerized adhesive through a prepreg, and then passed through a hot roller to control the mass proportion of the prepolymerized adhesive in the woven PBO fiber sheet to be 50%, and the thickness of the woven PBO fiber sheet after impregnation is controlled to be 0.1 mm, thereby obtaining a woven PBO fiber sheet impregnated with the prepolymerized adhesive;

[0169] The woven PBO fiber sheet impregnated with the prepolymerized adhesive is placed in an oven at 100-120° C. for curing to obtain a woven PBO fiber prepreg;

[0170] The woven PBO fiber prepreg was cut by laser to obtain woven PBO fiber prepreg sheets, and the laser cutting directions were 0°, 45°, 90° and 135° along the warp direction respectively;

[0171] According to the design of the 0.4mm battery cover substrate, woven PBO fiber prepreg sheets were stacked in 4 layers at 0° / 45° / 90° / 135° and hot pressed with hot pressing parameters of 150°C / 20min and a pressure of 0.5 MPa. After cooling, a PBO fiber composite sheet with non-profile edges was obtained as the substrate layer 211.

[0172] (2) Preparation of the entire battery cover 210

[0173] The surface of the obtained substrate layer 211 is subjected to appearance treatment to install a decorative layer 212 on the surface of the substrate layer 211. The methods for installing the decorative layer 212 include spraying, rubbing or external PU leather, etc., and then the substrate layer 211 is laser cut to remove the non-profile surface and make a through hole 213 according to the design of the camera lens 214 to obtain the main structure of the battery cover 210.

[0174] The main structure of the obtained battery cover 210 is subjected to auxiliary material bonding and assembly of the camera lens 214 to finally obtain the battery cover 210.

[0175] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 1g and improves the puncture resistance by 50% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0176] Example 8

[0177] Example 8 provides a battery cover 210. Example 8 differs from Example 7 in that the mass percentage of the prepolymerized adhesive in the woven PBO fiber sheet and the thickness of the woven PBO fiber sheet after impregnation are different. The woven PBO fiber prepreg sheets are stacked in different directions and with different layers. In this example, the mass percentage of the prepolymerized adhesive in the woven PBO fiber sheet is 55%, the thickness of the woven PBO fiber sheet after impregnation is controlled to be 0.2 mm, and the woven PBO fiber prepreg sheets are stacked in five layers with an angle of 0° / 45° / 90° / 135° / 0°.

[0178] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.5g and improves the puncture resistance by 80% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0179] Example 9

[0180] Example 9 provides a battery cover 210. The difference between Example 9 and Example 7 is that according to the design of the 0.4mm battery cover substrate, the woven PBO fiber prepreg sheets and other woven fiber prepreg sheets are stacked, and the middle layer or layers are woven PBO fiber prepreg sheets. This embodiment adopts 4 layers of woven aramid fiber prepreg sheets, woven PBO fiber prepreg sheets, woven ceramic fiber prepreg sheets, and woven carbon fiber prepreg sheets at 0° / 45° / 90° / 135° and hot pressing. The hot pressing parameters are 150℃ / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer 211.

[0181] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.8g and improves the puncture resistance by 100% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0182] Example 10

[0183] Example 10 provides a battery cover 210. The difference between Example 10 and Example 7 is that according to the design of the 0.4mm battery cover substrate, the woven PBO fiber prepreg sheet and other woven fiber prepreg sheets are stacked, and the middle layer or layers are woven PBO fiber prepreg sheets. This embodiment adopts 4 layers of woven aramid fiber prepreg sheets, woven PBO fiber prepreg sheets, woven PBO fiber prepreg sheets, and woven ceramic fiber prepreg sheets according to 0° / 45° / 90° / 135° stacking and hot pressing. The hot pressing parameters are 150℃ / 20min, and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer 211.

[0184] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.8g and improves the puncture resistance by 100% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0185] Example 11

[0186] Example 11 provides a battery cover 210. The difference between Example 10 and Example 8 is that according to the design of the 0.4mm battery cover substrate, the woven PBO fiber prepreg sheets and other woven fiber prepreg sheets are stacked, and the middle layer or layers are woven PBO fiber prepreg sheets. This embodiment adopts woven carbon fiber prepreg sheets, woven ceramic fiber prepreg sheets, woven PBO fiber prepreg sheets, woven aramid fiber prepreg sheets, and woven glass fiber prepreg sheets. They are stacked in 5 layers at 0° / 45° / 90° / 135° / 0° and hot pressed. The hot pressing parameters are 150°C / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer 211.

[0187] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.5g and improves the puncture resistance by 120% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0188] Example 12

[0189] Example 12 provides a battery cover 210. The difference between Example 12 and Example 8 is that according to the design of the 0.4mm battery cover substrate, the woven PBO fiber prepreg sheets and other woven fiber prepreg sheets are stacked, and the middle layer or layers are woven PBO fiber prepreg sheets. This embodiment adopts woven ceramic fiber prepreg sheets, woven PBO fiber prepreg sheets, woven PBO fiber prepreg sheets, woven PBO fiber prepreg sheets, and woven aramid fiber prepreg sheets. They are stacked in 5 layers at 0° / 45° / 90° / 135° / 0° and hot pressed. The hot pressing parameters are 150°C / 20min and the pressure is 0.5Mpa. After cooling, a composite laminated plate containing non-shaped edges is obtained as the substrate layer.

[0190] The battery cover 210 produced by this embodiment reduces the weight of the entire device by 0.5g and improves the puncture resistance by 120% compared to a 0.4mm pure woven E-grade glass fiber battery cover.

[0191] FIG15 is a schematic structural diagram of an electronic device in an embodiment of the present application.

[0192] In addition to providing a multi-layer composite structure 100 and a battery cover 210, the present application also provides an electronic device 200 in an embodiment of the present application. As shown in FIG15 , the electronic device 200 may include a front panel 220, a middle frame 230, a battery 240, and a battery cover 210. The middle frame 230 is disposed on one side of the front panel 220, and a battery slot 231 is provided in the middle frame 230. After the electronic device 200 is installed, the battery 240 is located in the battery slot 231. The battery cover 210 is disposed on the side of the middle frame 230 away from the front panel 220. The battery cover 210 can be used to protect the battery 240 disposed in the battery slot 231.

[0193] In an embodiment of the present application, the cavity formed by the front panel 220, the middle frame 230 and the battery cover 210 also includes electronic components, which include but are not limited to processors, antennas, sensors, gyroscopes, speakers and other devices, so that the electronic device 200 can operate normally.

[0194] It should be noted that those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope of this application is indicated by the following claims.

[0195] It should be understood that the present application is not limited to the exact structures described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A multi-layer composite structure, characterized in that, Comprising: A plurality of fiber layers arranged in a stack, each of the fiber layers being formed by curing a fiber sheet impregnated with a prepolymer solution; Wherein, the fiber sheet in at least one of the fiber layers is made of poly(p-phenylene benzobisoxazole) PBO fiber.

2. The multi-layer composite structure according to claim 1, wherein At least one of the plurality of fiber layers is a first fiber layer; The fiber sheet in each first fiber layer is arranged by PBO fiber filaments having the same extending direction and in a straightened state.

3. The multi-layer composite structure according to claim 2, wherein Each of the plurality of fiber layers is the first fiber layer; The extending directions of the PBO fiber filaments in adjacent first fiber layers are different.

4. The multi-layer composite structure according to claim 3, wherein The included angle between the extending directions of the PBO fiber filaments in adjacent first fiber layers is a right angle.

5. The multi-layer composite structure according to claim 2, wherein Each of the plurality of fiber layers is the first fiber layer; The PBO fiber filaments in the first fiber layers of the uppermost and lowermost layers in the multi-layer composite structure extend in a first direction; The PBO fiber filaments in the other first fiber layers in the multi-layer composite structure extend in a second direction; The first direction is different from the second direction.

6. The multi-layer composite structure according to claim 5, wherein The included angle between the first direction and the second direction is a right angle.

7. The multi-layer composite structure according to any one of claims 2 to 6, wherein The mass ratio of the prepolymer solution in each first fiber layer is 30% to 45%; The thickness of each first fiber layer is 0.04 mm to 0.2 mm.

8. The multi-layer composite structure according to claim 2, wherein The other fiber layers in the plurality of fiber layers except the first fiber layer are third fiber layers; The fiber sheet in the third fiber layer is arranged by first fiber filaments having the same extending direction and in a straightened state, and the first fiber filaments are any one of glass fiber, aramid fiber, ceramic fiber and carbon fiber; A plurality of the third fiber layers are arranged in a stack, and at least one first fiber layer is arranged between adjacent third fiber layers.

9. The multi-layer composite structure according to claim 8, wherein The PBO fiber filaments in the first fiber layer extend in a third direction; The first fiber filaments in the third fiber layer adjacent to the first fiber layer extend in a fourth direction; The extending directions of the first fiber filaments in adjacent third fiber layers are different; The third direction is different from the fourth direction.

10. The multi-layer composite structure according to claim 9, wherein The included angle between the third direction and the fourth direction is a right angle.

11. The multi-layer composite structure according to claim 1, wherein At least one of the plurality of fiber layers is a second fiber layer; Each fiber sheet in each of the second fiber layers is formed by weaving PBO fiber bundles with extension directions in a fifth direction and a sixth direction, and the fifth direction is different from the sixth direction.

12. The multi-layer composite structure according to claim 11, wherein each of the fiber layers in the plurality of fiber layers is the second fiber layer; the included angle between the fifth direction and the sixth direction is a right angle.

13. The multi-layer composite structure according to claim 11 or 12, wherein the mass ratio of the prepolymer solution in each of the second fiber layers is 45% - 55%; the thickness of each of the second fiber layers is 0.1 mm - 0.2 mm.

14. The multi-layer composite structure according to claim 11, wherein the other fiber layers in the plurality of fiber layers except the second fiber layer are fourth fiber layers; each fiber sheet in the fourth fiber layer is formed by weaving second fiber bundles with extension directions in the fifth direction and the sixth direction, and the second fiber bundles are any one of glass fiber, aramid fiber, ceramic fiber, and carbon fiber; a plurality of the fourth fiber layers are stacked, and at least one of the second fiber layers is disposed between adjacent fourth fiber layers.

15. The multi-layer composite structure according to any one of claims 1 - 14, wherein the mass ratio of the prepolymer solution in each of the fiber layers is 30% - 60%; the thickness of each of the fiber layers is greater than or equal to 0.03 mm and less than or equal to 0.3 mm.

16. A method for preparing a multi-layer composite structure, characterized in that, Comprising: placing an epoxy resin monomer, a curing agent, an accelerator, a dispersant, and a filler in a prepreg and fully stirring and pre-curing to form a prepolymer solution; immersing a fiber sheet in the prepolymer solution and performing a curing treatment to obtain a fiber layer; performing cutting, stacking, and pressing treatments on a plurality of the fiber layers to obtain a multi-layer composite structure; wherein, the fiber sheet in at least one of the fiber layers is made of PBO fiber.

17. The method for preparing a multi-layer composite structure according to claim 16, wherein the immersing a fiber sheet in the prepolymer solution and performing a curing treatment to obtain a fiber layer comprises: positioning a fiber bobbin, and unidirectionally arranging fiber bundles through yarn laying to make a plurality of the fiber sheets; at least one of the fiber bundles in the fiber sheets is a PBO fiber bundle; immersing the plurality of fiber sheets in the prepolymer solution respectively; controlling the mass ratio of the prepolymer solution in the plurality of impregnated fiber sheets and the thickness of the plurality of impregnated fiber sheets; performing a curing treatment on the plurality of impregnated fiber sheets respectively to obtain a plurality of the fiber layers.

18. The method for preparing a multi-layer composite structure according to claim 17, wherein the performing cutting, stacking, and pressing treatments on a plurality of the fiber layers to obtain a multi-layer composite structure comprises: cutting the plurality of fiber layers respectively to obtain a plurality of the fiber layers with a preset size; Stack the multiple cut fiber layers; wherein, the extending directions of the fiber bundles in adjacent fiber layers are different, or the fiber bundles in the topmost and bottommost fiber layers extend in a first direction, and the fiber bundles in the other fiber layers except the topmost and bottommost fiber layers extend in a second direction, and the first direction is different from the second direction; Perform a pressing process on the multiple stacked fiber layers to obtain the multi-layer composite structure.

19. The method for preparing a multi-layer composite structure according to claim 17 or 18, wherein, The mass ratio of the prepolymer solution in each fiber layer is 30% to 45%; The thickness of each fiber layer is 0.04 mm to 0.2 mm.

20. The method for preparing a multi-layer composite structure according to claim 16, wherein, The step of impregnating the fiber sheet in the prepolymer solution and performing a curing process to obtain a fiber layer includes: Manufacture multiple woven fiber sheets by weaving fiber bundles; the fiber bundles in at least one of the woven fiber sheets are PBO fiber bundles; Respectively impregnate the multiple woven fiber sheets in the prepolymer solution; Control the mass ratio of the prepolymer solution in the multiple impregnated woven fiber sheets and the thickness of the multiple impregnated woven fiber sheets; Perform a curing process on the multiple impregnated woven fiber sheets respectively to obtain multiple fiber layers.

21. The method for preparing a multi-layer composite structure according to claim 20, wherein, The step of cutting, stacking, and pressing the multiple fiber layers to obtain a multi-layer composite structure includes: Respectively cut the multiple fiber layers to obtain multiple fiber layers of a preset size; Stack the multiple cut fiber layers; Perform a pressing process on the multiple stacked fiber layers to obtain the multi-layer composite structure.

22. The method for preparing a multi-layer composite structure according to claim 20 or 21, wherein, The mass ratio of the prepolymer solution in each fiber layer is 45% to 55%; The thickness of each fiber layer is 0.1 mm to 0.2 mm.

23. The method for preparing a multi-layer composite structure according to any one of claims 17 to 22, wherein, The grammage of the fiber sheet is 30 g / m2 to 140 g / m2.

24. The method for preparing a multi-layer composite structure according to claim 16, wherein, The pressing process includes a hot pressing process, the temperature of the hot pressing process is 100°C to 200°C, the hot pressing time is 10 min to 30 min, and the hot pressing pressure is 0.2 MPa to 0.7 MPa.

25. The method for preparing a multi-layer composite structure according to claim 16, wherein, The mass ratio of the prepolymer solution in the fiber layer is 30% to 60%, and the thickness of the fiber layer is 0.03 mm to 0.3 mm.

26. A battery cover, characterized in that, Comprising: A substrate layer, the substrate layer includes the multi-layer composite structure according to any one of claims 1 to 15; A decorative layer, the decorative layer is disposed on one side of the substrate layer; through holes are provided on the substrate layer and the decorative layer; The camera lens covers the through hole, and the camera lens is disposed on the side of the battery cover where the decorative layer is provided.

27. An electronic device, characterized in that, Comprising: The front panel; The middle frame is disposed on one side of the front panel, and a battery slot is provided inside the middle frame; The battery is disposed in the battery slot; The battery cover as claimed in claim 26, the battery cover is disposed on the side of the middle frame away from the front panel, and the battery cover is used to protect the battery disposed in the battery slot.

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