A double-helix cross-ply design method for bionic composite materials

Abstract

The present invention discloses a double - helix cross - ply design method for a bionic composite material, belonging to the field of composite material ply design methods. This method is inspired by the double - helix structure and function of coelacanth scales, and by linearly increasing the laying angle θ of fiber sheets i , a forward - helix unit [0 / θ i / 2θ i / ... / 180 - θ i / 180] and a reverse - helix unit [180 / 180 - θ i / ... / 2θ i / θ i / 0] are respectively formed. Further, by changing the misalignment angle α of the cross - combination between fiber helix units, a series of double - helix cross - ply design schemes are formed. The influence of the double - helix cross - ply design on the mechanical properties of composite laminates is theoretically analyzed, and the misalignment angle α is optimized. The optimal misalignment angle α optimized by the present invention improves the theoretical out - of - plane stiffness of the composite laminate, and at the same time effectively weakens the difference between the equivalent elastic moduli (equivalent bending moduli) in the x - axis and y - axis directions of the fiber - reinforced composite laminate.

Description

Technical Field

[0001] The invention belongs to the field of composite material ply design methods, and in particular relates to a double-helix cross-ply design method for bionic composite materials. Background Art

[0002] In nature, the scales of an ancient fish, the coelacanth, can absorb the load imposed by the outside world, effectively resist the expansion of cracks, and effectively defend against the attacks of carnivores. The scales are composed of a hard mineralized shell surrounding a more resilient core. The core area is mainly composed of a double-helix plywood micro-nano structure composed of mineralized collagen fibrils, and the double-helix units are arranged in a cross-type combination. This biological helical structure is similar to the configuration of the fiber-reinforced resin-based composite laminate structure widely used in actual engineering, both of which are composed of fiber reinforcement and filling phases. However, the traditional fiber-reinforced resin-based composite laminate structure is mainly an orthogonal structure (i.e., the rotation angle between adjacent fiber sheets is 90°), a quasi-isotropic structure (i.e., the rotation angle between adjacent fiber sheets is 45°), and a unidirectional structure (i.e., the fiber orientation is 0°). With the widespread application of composite materials in various fields, the composite laminates designed by traditional ply can no longer meet the growing needs of the engineering field, and the design system for high-performance fiber-reinforced composite materials also needs to be injected with fresh blood. Therefore, this bionic double helix structure design significantly enriches the fiber layup design scheme, and helps to achieve bionic structural composite materials with better mechanical properties, which is of great significance to the development of high-performance fiber-reinforced composite materials in engineering fields such as aerospace. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects in the prior art and provide a double-helix cross-ply design method for bionic composite materials. The present invention introduces a biological helical structure into a traditional composite laminate, with the purpose of enriching the fiber orientation design scheme, providing a simple method starting from the ply design to improve the out-of-plane stiffness of the composite laminate, reduce the in-plane anisotropy of the composite laminate, so as to achieve a bionic structural composite material with better mechanical properties.

[0004] The specific technical solutions adopted by the present invention are as follows:

[0005] The present invention provides a double-helix cross-layer design method for a bionic composite material, which is as follows:

[0006] S1: Determine the rotation angle θ when the fiber sheets are stacked layer by layer;

[0007] S2: According to the determined rotation angle θ, a forward spiral unit [0 / θ / 2θ / ... / 180-θ / 180] and a reverse spiral unit [180 / 180-θ / ... / 2θ / θ / 0] are formed respectively;

[0008] S3: stacking the forward spiral units and the reverse spiral units in a cross-combination manner to form a ply structure in which odd-numbered layers are forward spiral units and even-numbered layers are reverse spiral units; by changing the misalignment angle α when the forward spiral units and the reverse spiral units are cross-combined i , and several ply structures are obtained, and the ply order is expressed as [0 / 180+α i / θ / 180-θ+α i / 2θ / 180-2θ+α i / ... / 180-θ / θ+α i / 180 / 0+α i ];

[0009] S4: According to the misalignment angle α i The bionic composite laminates are cross-combined and the analysis method based on the classical laminate theory is used to predict the in-plane and out-of-plane mechanical properties of the bionic composite laminates.

[0010] S5: Determine each misalignment angle α i The in-plane and out-of-plane mechanical properties of the bionic composite laminates are selected to minimize the difference in the equivalent modulus in the x-axis and y-axis directions of the bionic composite laminates and the out-of-plane stiffness D * The highest misalignment angle α i is the optimal misalignment angle α.

[0011] Preferably, the rotation angle θ satisfies 0°≤θ≤180°, and the misalignment angle α i Satisfy 0°≤α i ≤180°.

[0012] Preferably, the bionic composite laminate material is carbon fiber.

[0013] Preferably, in step S4, the theoretical mechanical properties of the bionic composite laminate in-plane and out-of-plane are as follows:

[0014] The out-of-plane stiffness of a composite laminate can be expressed as:

[0015]

[0016] The equivalent in-plane elastic modulus in the x-axis and y-axis directions can be expressed as:

[0017]

[0018]

[0019] The equivalent bending modulus in the x-axis and y-axis directions can be expressed as:

[0020]

[0021]

[0022] Where h is the thickness of the bionic composite laminate; D ij is the bending stiffness matrix coefficient of bionic composite laminate; d ij is the bending flexibility matrix coefficient of the bionic composite laminate, which can be obtained by inverting the bending stiffness matrix; a ij is the tensile flexibility matrix coefficient of the bionic composite laminate, which can be obtained by the tensile stiffness matrix A ij Get the inverse.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The embodiment of the present invention is based on the light-weight and high-strength characteristics of the internal fiber arrangement structure of the coelacanth fish scale, and integrates the bionic design concept into the ply design of the traditional composite laminate. According to the requirements of the existing engineering technology for light-weight and high-strength materials, the fiber type and ply design are optimized, providing a design method that can not only improve the out-of-plane mechanical properties of the composite laminate, but also effectively weaken the in-plane anisotropy of the composite laminate;

[0025] 2. The embodiments of the present invention solve the complex operability of the current technology for improving the mechanical properties of composite laminates by optimizing the ply design. The bionic double-helix cross-ply design method can provide constructive suggestions for the design and manufacture of composite laminates.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following embodiments of the present invention are described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of a forward fiber spiral unit and a reverse fiber spiral unit provided in an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of the structure of a double helix cross combination is provided for an embodiment of the present invention;

[0029] Figure 3 is the regularized out-of-plane stiffness D that can be obtained in the embodiment of the present invention * With the misalignment angle α i Relationship diagram;

[0030] Figure 4 The equivalent elastic modulus in the x-axis direction and the y-axis direction in the plane and the misalignment angle α can be obtained in the embodiment of the present invention.i Relationship diagram;

[0031] Figure 5 The equivalent bending modulus and misalignment angle α in the x-axis and y-axis directions that can be obtained in the embodiment of the present invention are: i relationship diagram. DETAILED DESCRIPTION

[0032] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0033] The method of the present invention is based on the double helical structure and function of the coelacanth scales. By linearly increasing the angle θ of the fiber layer laying, a forward helical unit [0 / θ / 2θ / ... / 180-θ / 180] and a reverse helical unit [180 / 180-θ / ... / 2θ / θ / 0] are formed respectively, and the staggered angle α of the two fiber helical units for cross-combination is further transformed. i , forming a series of double-helix cross-ply design schemes. The present invention theoretically analyzes the influence of double-helix cross-ply design on the mechanical properties of composite laminates, and optimizes the misalignment angle α. The optimal misalignment angle α optimized by the present invention improves the theoretical out-of-plane stiffness of the composite laminate, while effectively weakening the difference between the equivalent elastic modulus (equivalent bending modulus) of the fiber-reinforced composite laminate in the x-axis and y-axis directions.

[0034] The technical solution adopted by the present invention is specifically as follows:

[0035] S1: Determine the rotation angle θ when the fiber sheets are stacked layer by layer.

[0036] In actual application, the steps are as follows:

[0037] Based on the mechanical properties of the composite laminate structure and the performance of the final composite laminate product, the rotation angle θ when the fiber sheets are stacked layer by layer is preliminarily determined, which should satisfy 0°≤θ≤180°.

[0038] According to the present invention, the method for preliminarily determining the rotation angle θ according to the mechanical properties of the composite laminate structure and the performance of the final composite laminate product is not particularly limited and is based on methods known in the art.

[0039] S2: According to the determined rotation angle θ, a forward spiral unit [0 / θ / 2θ / ... / 180-θ / 180] and a reverse spiral unit [180 / 180-θ / ... / 2θ / θ / 0] are formed respectively.

[0040] S3: stacking the forward spiral units and reverse spiral units obtained in step S2 in a cross-combination manner to form a ply structure in which odd-numbered layers are forward spiral units and even-numbered layers are reverse spiral units; by changing the misalignment angle α when the forward spiral units and reverse spiral units are cross-combined i , a series of new ply structures were designed. Among them, the misalignment angle should satisfy 0°≤α i ≤180°. The ply order of the ply structure can be expressed as [0 / 180+α i / θ / 180-θ+α i / 2θ / 180-2θ+α i / ... / 180-θ / θ+α i / 180 / 0+α i ].

[0041] S4: According to the misalignment angle α i The bionic composite laminates formed by cross-combination are analyzed by the classical laminate theory to predict the in-plane and out-of-plane mechanical properties of the bionic composite laminates.

[0042] In actual use, the classical laminate theory used in the present invention is a method well known in the art and will not be described in detail. The out-of-plane stiffness of the composite laminate can be expressed as:

[0043]

[0044] The equivalent in-plane elastic modulus in the x-axis (y-axis) can be expressed as:

[0045]

[0046]

[0047] The equivalent bending modulus in the x-axis direction (y-axis direction) can be expressed as:

[0048]

[0049]

[0050] In the above formula, h is the thickness of the laminate; D ij is the bending stiffness matrix coefficient of the laminate, d ij is the bending flexibility matrix coefficient of the laminate, which can be obtained by inverting the bending stiffness matrix; a ij is the tensile flexibility matrix coefficient of the laminate, which can be obtained by the tensile stiffness matrix A ij These coefficients can be obtained by inverse calculation according to the classical laminate theory, so I will not go into details.

[0051] S5: Determine each misalignment angle α iThe in-plane and out-of-plane mechanical properties of the bionic composite laminates are selected to minimize the difference in the equivalent modulus in the x-axis and y-axis directions of the bionic composite laminates and the out-of-plane stiffness D * The highest misalignment angle α i is the optimal misalignment angle α.

[0052] In actual use, the steps are as follows:

[0053] According to formula I to formula V, the misalignment angle α to be selected can be determined. i Out-of-plane and in-plane mechanical properties of cross-laminated composite laminates. According to theoretical calculation results, it can be found that the misalignment angle α i The equivalent elastic modulus (equivalent bending modulus) of the composite laminate in the x-axis and y-axis directions is significantly affected, and the reduction in the difference between the two indicates that the inherent anisotropy of the fiber-reinforced composite material is effectively weakened; at the same time, the misalignment angle α i It affects the theoretical out-of-plane stiffness of the composite laminate, and the increase of the out-of-plane stiffness is beneficial to improving the out-of-plane mechanical properties of the fiber-reinforced composite laminate.

[0054] Therefore, the difference between the equivalent modulus in the x-axis and y-axis directions of the laminate in the plane is minimized, and the out-of-plane stiffness D * The highest misalignment angle α is the optimal misalignment angle. According to the optimal misalignment angle and the ply method in step (3), the optimal ply sequence can be designed as [0 / 180+α / θ / 180-θ+α / 2θ / 180-2θ+α / ... / 180-θ / θ+α / 180 / 0+α].

[0055] According to the present invention, the spiral ply design method of bionic composite laminate is not limited to the unified design of the rotation angle θ and the total number of plies (thickness), and the appropriate rotation angle θ and the total number of plies (thickness) can be selected according to actual needs.

[0056] According to the present invention, the composite laminate is not particularly limited, and is preferably a high-performance fiber-reinforced composite material such as carbon fiber.

[0057] The present invention will be further described in detail below in conjunction with specific implementation examples, taking the preparation of a bionic double-helix cross-structure composite laminate made of unidirectional carbon fiber prepreg as an example to illustrate the present invention.

[0058] Example

[0059] This embodiment provides a method for designing a double-helix cross-layer of a bionic composite material, and the steps of the method are as follows:

[0060] (1) Based on the mechanical properties of the composite laminate structure and the performance of the final composite laminate product, the rotation angle θ when the fiber sheets are stacked layer by layer is preliminarily determined to be 12°, and the prepreg specification selected is Weihai Guangwei USN1500 / EPW model, and its single layer thickness after curing is 0.141 mm;

[0061] (2) According to the determined rotation angle θ=12°, a forward spiral unit [0 / 12 / 24 / ... / 168 / 180] and a reverse spiral unit [180 / 168 / ... / 24 / 12 / 0] are formed respectively. Figure 1 As shown, Figure 1 It is a schematic diagram of the structure of the forward fiber spiral unit and the reverse fiber spiral unit provided in an embodiment of the present invention.

[0062] (3) The above two fiber spiral units are further stacked in a cross-combination manner to form a ply structure in which the odd-numbered layers are forward spiral units and the even-numbered layers are reverse spiral units. By changing the misalignment angle α when the two fiber spiral units are cross-combined i , designed a series of new ply structures, such as Figure 2 As shown, the ply order can be expressed as [0 / 180+α i / 12 / 168+α i / 24 / 156+α i / ... / 168 / 12+α i / 180 / 0+α i ], where the misalignment angle α when two fiber helical units are crossed and combined i Should satisfy 0°≤α i ≤180°.

[0063] (3) Based on the classical laminate theory, the misalignment angle α to be selected i Theoretical analysis of cross-combined bionic composite laminates:

[0064] 1. Misalignment angle is 0°≤α i In the range of ≤180°, the regularized out-of-plane stiffness D can be calculated by applying formula I. * With the misalignment angle α i relationship, such as Figure 3 As shown; the equivalent elastic modulus and misalignment angle α in the x-axis and y-axis directions of the laminate plane can be obtained by using formula ⅠI and formula III respectively. i relationship, such as Figure 4 As shown; the equivalent bending modulus and misalignment angle α of the laminate in the x-axis direction and the y-axis direction can be obtained by using formula IV and formula V respectively. i relationship, such as Figure 5 As shown;

[0065] 2. From Figure 3It can be seen that the out-of-plane stiffness increases first and then decreases with the increase of the misalignment angle. i =90° when the maximum value is reached; Figure 4 It can be seen that the equivalent elastic modulus in the x-axis and y-axis directions of the laminate plane is i =90°, they are equal; Figure 5 It can be seen that the equivalent bending modulus of the laminate in the x-axis and y-axis directions is i =90°. Based on the above results, the optimal misalignment angle of the bionic double helix cross structure composite material is α i =90°, therefore the best ply sequence is [0 / 180+90 / 12 / 168+90 / 24 / 156+90 / ... / 168 / 12+90 / 180 / 0+90].

[0066] This bionic structure design method significantly enriches the fiber ply design scheme in the field of composite materials. At the same time, based on the classical laminate theory, the present invention can optimize the optimal misalignment angle and provide the optimal ply design scheme for composite laminates. This effectively weakens the in-plane anisotropy of composite laminates and achieves excellent out-of-plane mechanical response of composite laminates.

[0067] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A double-helix cross-layer design method for bionic composite materials, characterized in that: The details are as follows: S1: Determine the rotation angle θ when the fiber sheets are stacked layer by layer; S2: According to the determined rotation angle θ, a forward spiral unit [0 / θ / 2θ / ... / 180-θ / 180] and a reverse spiral unit [180 / 180-θ / ... / 2θ / θ / 0] are formed respectively; S3: stacking the forward spiral units and the reverse spiral units in a cross-combination manner to form a ply structure in which odd-numbered layers are forward spiral units and even-numbered layers are reverse spiral units; by changing the misalignment angle α when the forward spiral units and the reverse spiral units are cross-combined i , and several ply structures are obtained, and the ply order is expressed as [0 / 180+α i / θ / 180-θ+α i / 2θ / 180-2θ+α i / ... / 180-θ / θ+α i / 180 / 0+α i ]; S4: According to the misalignment angle α i The bionic composite laminates are cross-combined and the analysis method based on the classical laminate theory is used to predict the in-plane and out-of-plane mechanical properties of the bionic composite laminates. S5: Determine each misalignment angle α i The in-plane and out-of-plane mechanical properties of the bionic composite laminates are selected to minimize the difference in the equivalent modulus in the x-axis and y-axis directions of the bionic composite laminates and the out-of-plane stiffness D * The highest misalignment angle α i is the optimal misalignment angle α.

2. The double-helix cross-layer design method for a bionic composite material according to claim 1, characterized in that: The rotation angle θ satisfies 0°≤θ≤180°, and the misalignment angle α i Satisfy 0°≤α i ≤180°.

3. The double-helix cross-layer design method for a bionic composite material according to claim 1, characterized in that: The bionic composite material laminate material is carbon fiber.

4. The double-helix cross-layer design method for a bionic composite material according to claim 1, characterized in that: In step S4, the theoretical mechanical properties of the bionic composite laminate in-plane and out-of-plane are as follows: The out-of-plane stiffness of a composite laminate can be expressed as: The equivalent in-plane elastic modulus in the x-axis and y-axis directions can be expressed as: The equivalent bending modulus in the x-axis and y-axis directions can be expressed as: Where h is the thickness of the bionic composite laminate; D ij is the bending stiffness matrix coefficient of bionic composite laminate; d ij is the bending flexibility matrix coefficient of the bionic composite laminate, which can be obtained by inverting the bending stiffness matrix; a ij is the tensile flexibility matrix coefficient of the bionic composite laminate, which can be obtained by the tensile stiffness matrix A ij Get the inverse.

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