System and method for predicting strength of multilayer materials

Abstract

The present invention provides a system and method for predicting the strength of a multi-layer material in which two or more films are laminated.

Description

[Technical Field]

[0001] This patent application claims the benefit of priority based on Korean Patent Application No. 10-2022-0071405 dated June 13, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a system and method for predicting the strength of multilayer materials, particularly multilayer films. [Background technology]

[0003] Polymer films are non-fiber, flat plastic moldings with a thickness of 0.25 mm or less. They are lightweight, have good barrier properties, are highly transparent, and are relatively inexpensive, making them used in almost all fields, including packaging materials, household goods, electronic devices, automobiles, and aircraft.

[0004] However, it is difficult to satisfy the multiple required physical properties with a single film. To solve this problem, multilayer materials with a structure in which two or more films are laminated have been developed.

[0005] During the development process of a multilayer material, the physical properties, particularly strength, of the multilayer material cannot be calculated simply by combining the physical properties of the individual films. Conventionally, to evaluate the physical properties, particularly strength, of a multilayer material, test pieces of the multilayer material are manufactured for each film combination pattern, and the manufactured test pieces are evaluated. This method of manufacturing multilayer material test pieces not only takes time to manufacture, but also makes it difficult to evaluate all of the various film types and physical properties.

[0006] Therefore, there is a need for a method that allows prediction of the physical properties, particularly strength, of multilayer materials without directly manufacturing the multilayer materials. Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, an object of the present invention is to provide a system and method that are capable of predicting the physical properties, particularly the strength, of a multilayer material in a simulation step. [Means for solving the problem]

[0008] To achieve the above-mentioned object, the present invention provides a strength prediction system for multilayer materials.

[0009] In one embodiment, the present invention relates to a strength prediction system for a multilayer material in which n (n is an integer of 2 or more) films are laminated, and the strength prediction system predicts the elastic modulus (E k ), Poisson's ratio (ν k ), shear modulus (G k ), thickness (Z k ), stacking angle (θ k ), principal stress direction strength ([F] k ), an input unit into which the total thickness (h) of the multilayer material is input, a control unit that calculates the strength of the multilayer material using the value input into the input unit, a display connected to the control unit, and a storage unit connected to the control unit.

[0010] The control unit calculates the stress of each layer based on the value input to the input unit, and applies the stacking angle (θ k ) to apply the principal direction stress ([σ] k ), Strength in the principal stress direction of each layer ([F] k ) is the strength discrimination parameter ([f] k ) and Principal direction stress of each layer ([σ] k ) and intensity discrimination parameter ([f] k ) to calculate the safety coefficient for each layer, The minimum value of the calculated safety factors for each layer is extracted and defined as the strength value of the multi-layer material.

[0011] In one specific embodiment, determining the strength value of the multi-layer material from the calculated safety factors of each layer comprises: The minimum value of the calculated safety factor for each layer is extracted, If the safety factor satisfies the preset ULF (Ultimate Laminate Failure) standard, the extracted minimum value is determined as the strength value of the multilayer material.

[0012] In one embodiment, the control unit repeats a cycle of calculating the safety factor of each layer based on the values ​​input to the input unit n times. The value calculated in the kth cycle is reflected in the input value to perform the k+1th cycle, and the strength of the multilayer material is determined as the strength when all n layers forming the multilayer material break. Here, k is an integer from 1 to n-1, and n is the number of layers constituting the multilayer material.

[0013] In another embodiment, the control unit repeats a cycle of calculating a safety factor for each layer based on values ​​input to the input unit, performs the (k+1)th cycle by reflecting the value calculated in the (k)th cycle as the input value, and determines the value calculated in the (k+1)th cycle as the strength of the multilayer material when the strength determined by comparing the value calculated in the (k)th cycle with the value calculated in the (k+1)th cycle no longer increases, where k is an integer from 1 to n-1 and n is the number of layers constituting the multilayer material.

[0014] In one embodiment, the control unit calculates the stress of each layer based on the value input to the input unit, The stiffness matrix of each layer ([Q]) is calculated by applying the input elastic modulus, Poisson's ratio, and shear modulus of each layer. k , stiffness matrix) is derived, The derived stiffness matrix value is calculated by adding the layer angle (θ k ) and reset the stiffness matrix of each layer, The thickness of each layer (Z k ) Calculate the stiffness matrix of the multilayer material using the stiffness matrix value reset in response to the information; Set the compliance matrix for the calculated multi-layer material stiffness matrix; Calculate mid-plane strains and curvatures using a compliance matrix for arbitrary forces (F) and moments (M), The calculated mid-plane strain and curvature and the thickness of each layer (Z K ) information and calculate the strain of each layer, Strain and stiffness matrix of each layer ([Q] k ) is used to calculate the stress in each layer.

[0015] The present invention also provides a method for predicting the strength of a multilayer material. In one embodiment, the present invention relates to a method for predicting the strength of a multilayer material in which n films (n is an integer of 2 or more) are laminated, comprising the steps of: The elastic modulus of each layer (E k ), Poisson's ratio (ν k ), shear modulus (G k ), thickness (Z k ), stacking angle (θ k ), the total thickness (h) of the multilayer material is input to calculate the stress of each layer; The calculated stress of each layer is added to the stacking angle of each layer (θ k ) is applied to each layer to calculate the principal direction stress ([σ] k ), and Strength in the principal stress direction of each layer ([F] k ) is used as the strength discrimination parameter ([f] k ) Principal direction stress of each layer ([σ] k ) and intensity discrimination parameter ([f] k ) to calculate the safety factor of each layer; and extracting the minimum value from the calculated safety factors of each layer and determining it as the strength value of the multilayer material.

[0016] In a specific embodiment, the step of extracting the minimum value of the calculated safety factors of each layer and determining it as the strength value of the multilayer material includes: The minimum value of the calculated safety factor for each layer is extracted, If the safety factor satisfies the preset ULF (Ultimate Laminate Failure) standard, the extracted minimum value is determined as the strength value of the multilayer material.

[0017] In one embodiment, the present invention calculates the stress of each layer and combines them to calculate a safety factor for each layer, repeating this step n times. The value calculated in the kth cycle is reflected as an input value in the k+1th cycle, and the strength when all n layers forming the multilayer material break is defined as the strength of the multilayer material. Here, k is an integer from 1 to n-1, and n is the number of layers constituting the multilayer material.

[0018] In another example, the present invention repeatedly performs steps of calculating the stress of each layer and combining them to calculate the safety factor of each layer. The value calculated in the kth cycle is applied to the input value to perform the k+1th cycle. If the strength of the multilayer material determined by comparing the value calculated in the kth cycle with the value calculated in the k+1th cycle no longer increases, the value calculated in the kth cycle is defined as the strength of the multilayer material. Here, k is an integer from 1 to n-1, and n is the number of layers constituting the multilayer material.

[0019] In one example, the step of calculating the stress for each layer comprises: The stiffness matrix of each layer ([Q]) is calculated by applying the input elastic modulus, Poisson's ratio, and shear modulus of each layer. k , stiffness matrix); The derived stiffness matrix value is calculated by adding the layer stacking angle (θk ) to reconfigure the stiffness matrix of each layer; The thickness of each layer (Z k Calculating the stiffness matrix of the multi-layer material using the stiffness matrix values ​​reset in response to the information; establishing a compliance matrix for the calculated stiffness matrix of the multi-layer material; Calculating mid-plane strain and curvature using a compliance matrix for any force (F) and moment (M); The calculated mid-plane strain and curvature, and the thickness of each layer (Z K ) information and calculating the strain of each layer using the information; Strain and stiffness matrix of each layer ([Q] k ) to calculate the stress of each layer. [Effects of the Invention]

[0020] The system and method for predicting the strength of a multilayer material according to the present invention makes it possible to predict the physical properties, particularly the strength, of a multilayer material without producing a multilayer material test piece. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a configuration diagram of a system for predicting properties of a multilayer material according to an embodiment of the present invention. [Figure 2] 1 is a flowchart of a method for predicting the strength of a multilayer material according to an embodiment of the present invention. [Figure 3] 1 is a flowchart of a method for predicting the strength of a multilayer material according to an embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram of a multilayer material with designated orientation. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention provides a strength prediction system for a multilayer material in which n films (n is an integer of 2 or more) are laminated.

[0023] In one embodiment, the strength prediction system for a multilayer material according to the present invention calculates the elastic modulus (E k ), Poisson's ratio (ν k ), shear modulus (G k ), thickness (Z k ), stacking angle (θ k ), strength in the principal stress direction ([F] k ), and the total thickness (h) of the multilayer material; a control unit that calculates the strength of the multilayer material by applying the values ​​input to the input unit; a display coupled to the control unit; and a storage coupled to the controller.

[0024] The control unit calculates the stress of each layer based on the value input to the input unit, and applies the stacking angle (θ k ) is applied to each layer to calculate the principal direction stress ([σ] k ) and the strength in the principal stress direction of each layer ([F] k ) is the strength discrimination parameter ([f] k ) and the principal direction stress of each layer ([σ] k ) and intensity discrimination parameter ([f] k ) is combined to calculate the safety factor for each layer, and the smallest value of the calculated safety factors for each layer is extracted and determined as the strength value of the multilayer material.

[0025] The present invention also provides a method for predicting the strength of a multilayer material. In one embodiment, the present invention relates to a method for predicting the strength of a multilayer material in which n films (n is an integer of 2 or more) are laminated, comprising the steps of: The elastic modulus of each layer (E k ), Poisson's ratio (ν k ), shear modulus (G k ), thickness (Z k ), stacking angle (θk ), and the total thickness (h) of the multilayer material are input, and a step (step a) is performed to calculate the stress of each layer; The calculated stress of each layer is added to the stacking angle of each layer (θ k ) is applied to each layer to calculate the principal direction stress ([σ] k ) (step b), Strength in the principal stress direction of each layer ([F] k ) is used as the strength discrimination parameter ([f] k ) (step c), Principal direction stress of each layer ([σ] k ) and intensity discrimination parameter ([f] k ) to calculate the safety factor for each layer (step d); and a step (step e) of extracting the minimum value from the calculated safety factors of each layer and determining it as the strength value of the multilayer material.

[0026] As an example, the steps for predicting the strength of a multi-layer material in the present invention are as follows.

[0027] The information to be input is the elastic modulus (E) in the machine direction (MD, 1) and transverse direction (TD, 2) of each layer (k). k 1,2 ) and the Poisson's ratio (ν k 1,2 ) and the shear modulus (G) in the machine direction (1) and transverse direction (2) of each layer (k) K 1,2 ) and the angle (θ k ) and the thickness of each layer (k) (Z k ) and the total thickness (h) of the multilayer material. Also, the strength of each layer in the principal stress direction ([F] k ) is also included in the input information.

[0028] First, using the input information, the stress (σ k x,y ) is calculated. Then, the calculated stress (stress, σ k x,y ) and the layering angle (θ k ) is applied to each layer to calculate the principal direction stress ([σ] k 1,2 )

[0029] In addition, the strength in the principal stress direction of each layer ([F] k 1,2 ) is used as the strength discrimination parameter ([f] k 1,2 ) and the principal direction stress of each layer ([σ] k 1,2 ) and intensity discrimination parameter ([f] k 1,2 ) to calculate the safety factor for each layer (S k f For example, the safety factor of each layer (S k f To calculate the stress-to-fracture ratio (SFR), the Tsai-Wu criterion can be applied, or the Maximum Stress criterion, Maximum Strain criterion, or Tsai-Hill criterion, etc., can be applied as appropriate.

[0030] The calculated safety factor for each layer (S k f ) the smallest value ((S k f ) min ) to extract the strength value of the multilayer material (

number

number

number

[0031] The calculated safety factor for each layer (S k f ) the smallest value ((S k f ) min ) to extract the strength value of the multilayer material (

number

[0032] In the first method, the steps from calculating the stress of each layer (step a) to calculating the safety factor of each layer (step d) are repeated once, and the calculated safety factor of each layer (S k f ) the smallest value ((S k f ) min ) to extract the strength value of the multilayer material (

number

number

number

[0033] In the second method, steps from calculating the stress of each layer (step a) to calculating the safety factor of each layer (step d) are repeated n times. Here, the value calculated in the kth cycle is reflected in the input value and the k+1th cycle is performed. The strength when all n layers that make up the multilayer material break is taken as the strength value of the multilayer material (

number

number

number

[0034] In the third method, the steps from calculating the stress of each layer (step a) to calculating the safety factor of each layer (step d) are repeated. Here, the value calculated in the kth cycle is reflected in the input value and the k+1th cycle is performed. If the strength of the multilayer material determined by comparing the value calculated in the kth cycle with the value calculated in the k+1th cycle does not increase any more, the value calculated in the kth cycle is defined as the strength of the multilayer material. Here, k is an integer between 1 and n-1, and n means the number of layers constituting the multilayer material. In each cycle, the calculated safety factor of each layer (S k f ) the smallest value ((S k f ) min ) is extracted, and the strength value (

number

[0035] In another embodiment, the calculated safety factor (S k f ) the smallest value ((S k f ) min ) to extract the strength value of the multilayer material (

number

number

[0036] Strength values ​​of multi-layer materials ( [Number] ) If the determined value satisfies the pre-set ULF (Ultimate Laminate Failure) criterion, this is taken as the strength value of the final multi-layer material ( [Number] ) and is determined.

[0037] Conversely, if the strength value of the multi-layer material ( [Number] ) does not satisfy the pre-set ULF (Ultimate Laminate Failure) criterion, the elastic modulus of the broken layer determined in that cycle is adjusted and recalculated. As a specific example, a coefficient r is applied to the elastic modulus of the broken layer for adjustment. For example, when r = 0, it is assumed that the broken layer in that cycle has lost its stress-bearing capacity in that direction in the next loading cycle. When 0 < r < 1, it is assumed that the broken layer in that cycle has partially lost its stress-bearing capacity in the next loading cycle. At the same time, the strength of the broken layer is changed to infinity so that no breakage occurs in the same layer in the next loading cycle.

[0038] In another embodiment, the step (step a) of calculating the stress of each layer by inputting any one or more of the elastic modulus (E k ), Poisson's ratio (ν k ), shear modulus (G k ), thickness (Z k ), stacking angle (θ k ), and total thickness (h) of the multi-layer material of each layer can be performed as follows.

[0039] First, the information to be input is the elastic modulus (E) in the machine direction (MD, 1) and transverse direction (TD, 2) of each layer (k). k 1,2 ), Poisson's ratio (ν k 1,2 ), shear modulus (G) in the machine direction (1) and cross direction (2) of each layer (k) K 1,2 ), the angle (θ k ), the thickness of each layer (k) (Z k ), the total thickness (h) of the multilayer material, etc.

[0040] Elastic modulus (E k 1,2 ), Poisson's ratio (ν k 1,2 ), Shear modulus (G k 1,2 ) to calculate the stiffness matrix ([Q]) for each layer (k) in the machine direction (1) and cross direction (2). k 1,2 ) and calculate the stiffness matrix ([Q]) in the machine direction (1) and cross direction (2) of each layer (k). k 1,2 ) compliance matrix ([S] k 1,2 ) and set the stiffness matrix ([Q] k 1,2 ) and the stacking angle (θ k ) and the stiffness matrix ([Q] k x,y ) and set the thickness (Z k ) information, the stiffness matrix of the multilayer material is recalculated using the stiffness matrix value ([A] x,y , [B] x,y , [D] x,y) is calculated. Then, the stiffness matrix ([A] x,y , [B] x,y , [D] x,y ) compliance matrix ([a] x,y , [b] x,y , [c] x,y , [d] x,y ) to set the

[0041] Next, the mid-plane strain and curvature are calculated using the compliance matrix for any force ( / F) and moment ( / M), and the calculated mid-plane strain and curvature and the thickness of each layer (Z K ) information and the strain in each layer will be calculated using this.

[0042] Specifically, any force ( / F) and moment ( / M) are assumed to be hypothetical external forces, and can be determined using the total thickness value to hypothetically apply a unit normal stress to the multilayer material.

[0043] The above forces ( / N) and moments ( / M) and the stiffness matrix of the multilayer material ([A] x,y , [B] x,y , [D] x,y ) compliance matrix ([a] x,y , [b] x,y , [c] x,y , [d] x,y ) to calculate the mid-plane strain (ε 0 x,y ) and curvatures (k x,y,s ) and calculate the mid-plane strain (ε 0 x,y ) and curvature (k x,y,s ) and the thickness of each layer (k) (Z k) information to calculate the strain (ε k x,y ) and calculate the strain of each layer (k) and the stiffness matrix of each layer (k) ([Q] k x,y ) to calculate the stress (σ k x,y ) is calculated. Then, the calculated stress (stress, σ k x,y ) and the layering angle (θ k ) is applied to each layer to calculate the principal direction stress ([σ] k 1,2 )

[0044] The present invention will be described in more detail below with reference to the drawings and embodiments, but the scope of the present invention is not limited thereto.

[0045] (First embodiment) FIG. 1 is a configuration diagram of a strength prediction system for a multilayer material according to a first embodiment of the present invention.

[0046] As shown in FIG. 1, the configuration of the strength prediction system for a multilayer material according to the first embodiment of the present invention is such that a user can estimate the elastic modulus (E) of each layer (k) in the machine direction (MD, hereinafter referred to as “1” and meaning the main direction) and the transverse direction (TD, hereinafter referred to as “2”). k 1,2 ), Poisson's ratio (ν k 1,2 ), the shear modulus (G) of each layer (k) in the machine direction (1) and cross direction (2) K 1,2 ), the angle (θ k ), the thickness of each layer (k) (Z k), a physical property calculation unit 21 connected to the input unit 10, a control unit 20, a display 30 connected to the control unit 20, and a storage 40 connected to the control unit 20.

[0047] In the present invention, the term "multilayer materials" refers to a laminate having a structure in which two or more materials are laminated, and may refer to a multilayer film of a polymer or the like, or a composite material made of different materials such as FRP (fiber reinforced plastics) and aluminum pouches. For example, the multilayer material may refer to a multilayer film.

[0048] (Second embodiment) 2 and 3 are flowcharts of a method for predicting the strength of a multilayer material according to an embodiment of the present invention.

[0049] Referring to FIG. 2, in a multilayer material in which two or more materials are laminated, Elastic modulus (E) of each layer (k) in the machine direction (1) and cross direction (2) k 1,2 ), Poisson's ratio (ν k 1,2 ), the shear modulus (G) of each layer (k) in the machine direction (1) and cross direction (2) K 1,2 ), the angle (θ k ), the thickness of each layer (k) (Z k ) is input (S11).

[0050] Elastic modulus (E k 1,2 ), Poisson's ratio (ν k 1,2 ), Shear modulus (G k 1,2) to calculate the stiffness matrix ([Q]) for each layer (k) in the machine direction (1) and cross direction (2). k 1,2 ) is calculated using the following formula (1) (S12).

number

[0051] The stiffness matrix ([Q]) in the machine direction (1) and cross direction (2) of each layer (k) calculated in this way is k 1,2 ) compliance matrix ([S] k 1,2 ) is set (S13).

[0052] The derived stiffness matrix ([Q] k 1,2 ) and the stacking angle (θ k ) and the stiffness matrix ([Q] k x,y ) is reset as shown in the following equation (2) (S14).

number

[0053] Using the thickness information and the reset stiffness matrix value of each layer (k), the stiffness matrix of the entire laminate, i.e., the multilayer material ([A] x,y , [B] x,y , [D] x,y ) is calculated as in the following formula (3) (S15).

number

[0054] The stiffness matrix of the entire laminate, i.e., the multilayer material, calculated in this way ([A] x,y , [B] x,y , [D] x,y) compliance matrix ([a] x,y , [b] x,y , [c] x,y , [d] x,y ) is set as shown in the following equation (4) (S16).

number

[0055] In the present invention, in order to virtually apply a unit normal stress to the entire multilayer material, it can be determined using the total thickness value as shown in the following equation (5) or equation (6) (S17). Here, equation (5) is applied when calculating the strength of the multilayer material in the x direction, and equation (6) is applied when calculating the strength of the multilayer material in the y direction.

number

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[0056] The input total force ( / N) and total moment ( / M) and the stiffness matrix of the entire laminate, i.e., the multi-layer material ([A] x,y , [B] x,y , [D] x,y) Compliance matrix for ([a] x,y , [b] x,y , [c] x,y , [d] x,y ) to calculate the mid-plane strain (ε 0 x,y ) and curvatures (k x,y,s ) is calculated as shown in the following formula (7) (S18).

number

[0057] Mid-plane strain (ε0 x,y ) and curvature (k x,y,s ) and the thickness (Z k ) information, strain (ε k x,y ) is calculated as shown in the following formula (8) (S19).

number

[0058] The strain of each layer (k) and the stiffness matrix of each layer (k) ([Q] k x,y ) to calculate the stress (σ k x,y ) is calculated as shown in the following equation (9) (S20).

number

[0059] Next, referring to FIG. 3, the calculated stress (σ k x,y ) is the layer angle (θ k ) information for each layer, the MD and TD (principal direction) stress ([σ] k 1,2 ) (S21). Here, the following formula (10) is used.

number

[0060] In addition, the strength in the principal stress direction of each layer k ([F] k 1,2 ) would be input as follows, for example (S22):

[0061] Tensile strength of each layer (k) in direction 1: F k 1t , Compressive strength in direction 1: F k 1c Tensile strength of each layer (k) in direction 2: F k 2t , Compressive strength in direction 2: F k 2c Tensile strength of each layer (k) in direction 6: F k 6. Biaxial tensile strength in direction 1-2: F k 12 Here, the orientation of each layer is as shown in Figure 4. Referring to Figure 4, the horizontal direction of the multilayer material is set as direction 1 or x-direction, the vertical direction is set as direction 2 or y-direction, and the diagonal direction is set as direction 6 or s-direction.

[0062] Using the input strength of each layer (k), a parameter for determining the strength of the entire multilayer material is constructed as shown in the following formula (11) (S23). The following formula (11) is an example of applying the Tsai-Wu criterion.

number

[0063] Here, if experimental biaxial tensile strength values ​​cannot be used, the following equation (12) can be assumed.

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[0064] Principal direction stress of each layer ([σ] k 1,2 ) and intensity discrimination parameter ([f] k 1,2 ) to calculate the safety factor (S k f ) is calculated (S24). For example, when the Sai-U criteria are applied, the safety factor is calculated as shown in the following formula (13).

number

[0065] By solving the quadratic equation in equation (12), the safety factor (S k f ) two solutions are obtained, and the positive values ​​(S k fa ) is the tensile strength, negative values ​​(S k fr ) represents the compressive strength. Comparing the safety factors of each layer, the layer with the smallest safety factor (k i ) can be defined as the fracture layer (S25).

[0066] At this time, the safety factor of the fracture layer is set to the strength value (

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[0067] Furthermore, when a unit normal stress is applied in the previous step S17 using equation (6), the y-direction strength of the multilayer material is derived using equation (15).

number

[0068] If the result of the loading cycle satisfies the preset ULF (Ultimate Laminate Failure) criteria (S27), a predetermined strength value (

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[0069] If it does not meet the ULF criteria, steps S29 and S30 will be performed and the entire algorithm cycle will be reapplied.

[0070] Here, the ULF criteria can be selected and applied by choosing any one of Examples 1 to 3 below (S27).

[0071] (Example 1) In the loading cycle (i = 1), when any one of the layers constituting the multilayer material reaches breakage, the strength at that time is taken as the final strength of the multilayer material.

[0072] (Example 2) In the loading cycle (i = n), when all the layers (n) forming the multilayer material break, the strength at that time is taken as the final strength of the multilayer material.

[0073] (Example 3) When comparing the result of the i-th loading cycle with the result of the i + 1-th loading cycle, if the strength does not increase, the strength selected in the i-th loading cycle is taken as the final strength.

[0074] The strength value of the multilayer material determined in S26 (

Number

[0075] At the same time, the strength of the broken layer is changed to infinity so that breakage of the same layer does not occur in the next loading cycle (S30). [

[0076] (Third embodiment) In another embodiment of the present invention, if an input value input to an input unit is not readily available, it can be derived through a conversion process using other property values.

[0077] In one embodiment, the modulus of elasticity (E k ) and Poisson's ratio (ν k ) is the first Lame constant (λ k ), shear modulus (G k ), bulk modulus (K k ) can be calculated using one or more physical properties. For example, the elastic modulus (E k ) and Poisson's ratio (ν k ) can be converted to

[0078] The available combinations are (λ k , G k ), then the following formula 1 is used.

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[0079] The available combinations are (λ k , E k ), then the following formula 2 is used.

number

[0080] The available combinations are (λ k , ν k ), then the following formula 3 is used.

number

[0081] The available combinations are (λ k, K. k ), then the following formula 4 is used.

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[0082] The available combinations are (G k , E k ), then the following formula 5 is used.

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[0083] The available combinations are (G k , ν k ), then the following formula 6 is used.

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[0084] The available combinations are (G k , K. k ), then the following formula 7 is used.

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[0085] The available combinations are (K k , E k ), then the following formula 8 is used.

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[0086] The available combinations are (K k , ν k ), then it is determined by the following formula 9.

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[0087] The above formulas 1 to 9 are merely examples, and two or more formulas can be combined as needed. [Explanation of symbols]

[0088] 10: Input section 20: Control unit 21: Physical property calculation section for the entire laminate 22: Strain and stress calculation section for each film layer 30: Display 40: Storage 100: Multilayer material

Claims

1. A strength prediction system for a multilayer material in which n (n is an integer of 2 or more) films are laminated, The elastic modulus (E ｋ ), Poisson's ratio (ν ｋ ), thickness (Z ｋ ), stacking angle (θ ｋ an input unit to which the user inputs the a control unit that calculates the strength of the multilayer material by applying the values ​​input to the input unit; a display coupled to the control unit; a storage coupled to the controller; The control unit Calculating the stress of each layer based on the value input to the input unit; The stress of each layer is applied to the stacking angle of each layer (θ ｋ ) is applied to each layer to determine the principal direction stress ([σ] ｋ ) and The strength in the principal stress direction of each layer ([F] ｋ ) is used as a strength discrimination parameter ([f] ｋ ) and Principal direction stress of each layer ([σ] ｋ ) and intensity discrimination parameter ([f] ｋ ) to calculate the safety factor for each layer, A system that extracts the minimum value of the calculated safety factors for each layer and determines it as the strength value of the multi-layer material.

2. The input value input to the input unit is Shear modulus of each layer (k) (G ｋ ), strength in the principal stress direction ([F] ｋ ), and a total thickness (h) of the multilayer material.

3. Determining the strength value of the multi-layer material from the calculated safety factor of each layer is Extracting the minimum value of the calculated safety factor for each layer; and determining the extracted minimum value as the strength value of the multilayer material if the extracted minimum value satisfies a predetermined ULF standard as a safety factor.

4. The control unit repeating a cycle of calculating a safety factor for each layer based on the values ​​input to the input section n times; performing a (k+1)th cycle by reflecting the value calculated in the kth cycle as an input value, and determining the strength of the multilayer material as the strength of the multilayer material when all of the n layers forming the multilayer material are broken; The system according to any one of claims 1 to 3, wherein k is an integer from 1 to n-1, and n represents the number of layers constituting the multilayer material.

5. The control unit Repeating a cycle of calculating a safety factor for each layer based on the values ​​input to the input section; The value calculated in the kth cycle is reflected in the input value, and the k+1th cycle is performed; If the strength of the multilayer material determined by comparing the value calculated in the kth cycle with the value calculated in the k+1th cycle no longer increases, determine the value calculated in the kth cycle as the strength of the multilayer material; The system according to any one of claims 1 to 3, wherein k is an integer from 1 to n-1, and n represents the number of layers constituting the multilayer material.

6. The control unit calculates the stress of each layer based on the value input to the input unit, The stiffness matrix ([Q]) of each layer is calculated by applying the input elastic modulus, Poisson's ratio, and shear modulus of each layer. ｋ ) and The derived stiffness matrix value is calculated by adding the layering angle (θ ｋ ) and reset the stiffness matrix of each layer, The thickness of each layer (Z ｋ ) calculating a stiffness matrix of the multilayer material using the reset stiffness matrix values ​​received from the information; establishing a compliance matrix for the calculated stiffness matrix of the multilayer material; Calculating mid-plane strain and curvature using compliance matrices for arbitrary forces (F) and moments (M); The calculated midplane strain and curvature and the thickness of each layer (Z Ｋ ) information, and calculating the strain of each layer using the information; Strain of each layer and stiffness matrix of each layer ([Q] ｋ and calculating the stress in each layer using the stress distribution function.

7. A method for predicting the strength of a multilayer material in which n (n is an integer of 2 or more) films are laminated, comprising the steps of: The elastic modulus of each layer (E ｋ ), Poisson's ratio (ν ｋ ), thickness (Z ｋ ), stacking angle (θ ｋ ) calculating the stress in each layer based on the The calculated stress of each layer is applied to the stacking angle of each layer (θ ｋ ) is applied to each layer to determine the principal direction stress ([σ] ｋ ), The strength in the principal stress direction of each layer ([F] ｋ ) is used as a strength discrimination parameter ([f] ｋ ) Principal direction stress of each layer ([σ] ｋ ) and intensity discrimination parameter ([f] ｋ ) to calculate the safety factor of each layer; and extracting the minimum value from the calculated safety factors of each layer and determining it as the strength value of the multi-layer material.

8. The step of calculating the stress of each layer includes: Shear modulus of each layer (k) (G ｋ ), strength in the principal stress direction ([F] ｋ 8. The method of claim 7, further comprising at least one of: (a) a thickness of the multilayer material; (b) a total thickness of the multilayer material;

9. The step of extracting the minimum value of the calculated safety factors of each layer and determining it as the strength value of the multi-layer material includes: Extracting the minimum value of the calculated safety factor for each layer; 8. The method of claim 7, further comprising: determining the extracted minimum value as the strength value of the multilayer material if the extracted minimum value satisfies a predetermined ULF standard as a safety factor.

10. Repeating the steps of calculating the stress of each layer and combining the calculated stresses of each layer to calculate a safety factor of each layer n times; and performing the (k+1)th cycle by reflecting the value calculated in the kth cycle as an input value, and determining the strength of the multilayer material as the strength of the multilayer material when all of the n layers forming the multilayer material are broken, 10. The method according to any one of claims 7 to 9, wherein k is an integer from 1 to n-1, and n represents the number of layers constituting the multilayer material.

11. Repeating the steps of calculating the stress of each layer and combining the calculated stresses of each layer to calculate a safety factor for each layer; The value calculated in the kth cycle is reflected in the input value, and the k+1th cycle is performed; and when the strength of the multilayer material determined by comparing the value calculated in the kth cycle with the value calculated in the k+1th cycle no longer increases, determining the value calculated in the kth cycle as the strength of the multilayer material.

10. The method according to any one of claims 7 to 9, wherein k is an integer from 1 to n-1, and n represents the number of layers constituting the multilayer material.

12. The step of calculating the stress of each layer includes: The stiffness matrix ([Q]) of each layer is calculated by applying the input elastic modulus, Poisson's ratio, and shear modulus of each layer. ｋ ) and The derived stiffness matrix value is calculated by adding the layering angle (θ ｋ ) and reset the stiffness matrix of each layer, The thickness of each layer (Z ｋ ) calculating the stiffness matrix of the multilayer material using the reset stiffness matrix value in response to the information; setting a compliance matrix for the calculated stiffness matrix of the multi-layer material; calculating mid-plane strain and curvature using a compliance matrix for any force (F) and moment (M); The calculated midplane strain and curvature and the thickness of each layer (Z Ｋ ) information to calculate the strain in each layer; Strain of each layer and stiffness matrix of each layer ([Q] ｋ 10. The method according to claim 7, further comprising the step of calculating the stress in each layer using the stress distribution function.

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