Method for rapidly predicting I-type interlayer fracture toughness of hybrid pultrusion plate
By combining the Puck failure criterion and finite element simulation, a Type I interlaminar fracture toughness model for hybrid pultruded plates was established, which solved the problem of difficulty in efficiently predicting crack propagation in existing technologies, achieved rapid and accurate prediction results, and reduced the risk of production accidents in wind turbine blades.
Patent Information
- Application Number
- CN202510948628.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-10
- Publication Date
- 2025-11-07
AI Technical Summary
Existing technologies make it difficult to predict the Type I fracture toughness of hybrid pultruded plates in an efficient and low-cost experimental manner, which makes wind turbine blades prone to crack propagation during use and poses a risk of production accidents.
A test model of interlaminar fracture toughness of hybrid pultruded plates was established by using the Puck failure criterion and finite element simulation software. The crack propagation behavior was quickly predicted through simulation calculation, and the fiber failure mode was determined by the Puck criterion and the energy release rate GIC was calculated.
This method enables rapid prediction of the interlaminar fracture toughness of hybrid pultruded plates, reducing the risk of crack propagation in wind turbine blades, saving manpower and resources, and improving the accuracy and efficiency of prediction.
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Figure CN120911173A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of composite material type I fracture simulation, in particular, to a kind of hybrid pultruded plate type I interlaminar fracture toughness fast prediction method combined with Puck failure criterion, suitable for the research of composite material crack propagation behavior and type I fracture toughness G ⅠC Prediction in the field of composite materials. BACKGROUND
[0002] With the development of offshore wind resources and onshore ultra-low wind resources, the development of wind power blades at home and abroad has accelerated. At present, the wind power industry is in the era of bidding, and the price parity project is rapidly advancing. Lightweight, high strength and low cost are becoming the goal of blade development. Hybrid fiber composite material, as an important manufacturing material for wind power blades, retains the advantages of single fiber composite material, and improves certain properties of composite material by selecting fiber types, hybrid ratio, laying angle and hybrid method, etc. It has the advantages of high performance and low cost, and is a difficult problem that needs to be solved for the development of wind power generation. Several common fibers of hybrid composite material include carbon fiber, glass fiber and aramid fiber. The currently widely used material is carbon fiber / glass fiber pultruded plate. Due to the high straightness of fiber yarn in the production process, the performance of glass fiber yarn can be fully utilized, and the performance in the axial direction of the product is more excellent
[0003] During use, wind power blades may produce delamination damage, and micro cracks invisible to the naked eye may occur between hybrid pultruded plates. Under the coupling of various loads in subsequent work, the micro cracks will continue to expand, and the crack propagation will have a great influence on the load-bearing capacity of wind power blades, which is prone to production accidents in work. In order to reduce production accidents caused by crack propagation of wind power blades, experiments are generally used to test the performance of hybrid pultruded plates in this direction, and certain safety standards are formulated to develop work specifications. However, the study of this failure behavior through experiments and other methods requires a large amount of manpower and material resources. SUMMARY
[0004] According to the deficiencies and urgent needs of existing engineering applications and simulation calculations, with the wide application of finite element simulation software, the structure is analyzed by finite element, and the type I fracture toughness of hybrid pultruded plate and the crack propagation behavior of the structure can be more accurately predicted by the simulation method using Puck inter-fiber failure criterion. The present application provides a simulation model combined with Puck failure criterion for studying the type I fracture toughness fast prediction method of hybrid pultruded plate.
[0005] The simulation method mentioned includes the following steps:
[0006] Step 1, establish a hybrid pultruded plate type I interlaminar fracture toughness test geometric model, and divide the model into hexahedral grid processing.
[0007] Step 2, extract the grid components, establish the attribute assignment required unit set.
[0008] Step 3, according to the established unit set to grid unit material model definition material properties,
[0009] Step 4, according to ASTM5528 standard measurement of composite interlaminar fracture toughness of type I loading, determine the boundary conditions and load,
[0010] Step 5, the finite element model for calculation, get the calculation results, extraction load-opening displacement curve, calculation of hybrid pultruded plate interlaminar fracture toughness of type I G ⅠC .
[0011] It should be noted that in step 1, the hybrid pultruded plate interlaminar fracture toughness test geometry model can be modeled according to different hybrid ratio.
[0012] It should be noted that in step 1, in order to adapt to different geometric models and obtain high-quality hexahedral grid, the grid can be divided after the geometric model is divided into regions.
[0013] It should be noted that in step 3, the grid unit material model is defined as follows:
[0014] 3.1, give the grid unit of fiber laminate property which is not in the crack propagation area;
[0015] 3.2, give the grid unit in the crack propagation area user-defined material properties calling Puck criterion, start the element deletion function;
[0016] 3.3, the unit material parameters required in simulation calculation are obtained by test such as strength, stiffness, Poisson's ratio.
[0017] It should be noted that in step 4, the loading method for measuring the interlaminar fracture toughness of composite type I may be different according to different standards, which can be loaded according to the specific standard or reasonably simplified.
[0018] It should be noted that in step 5, the Puck criterion is introduced based on the VUMAT user-defined subroutine to judge the crack propagation behavior of hybrid pultruded plate, and the method is as follows:
[0019] 5.1, in Puck criterion, the failure between fibers includes any matrix crack or fiber / matrix debonding; Puck criterion identifies three different failure modes between fibers, which are called mode A, B and C; the three failure modes between fibers can be distinguished by the orientation of the fracture plane relative to the reinforcing fibers;
[0020] 5.2, three failure modes
[0021] Failure mode A between fibers:
[0022] Mode A corresponds to a 0° angle of fracture; this criterion is invoked if the transverse stress in the composite is greater than 0 (which implies that the transverse crack is perpendicular to the transverse load);
[0023]
[0024] Failure mode B between fibers:
[0025] Mode B corresponds to a transverse compressive stress (which inhibits crack formation) with a longitudinal shear stress lower than the fracture resistance (an empirical constant);
[0026]
[0027] The above criteria will be evaluated in the following cases
[0028]
[0029] Failure mode C between fibers:
[0030] Mode C corresponds to a transverse compressive stress (which inhibits crack formation) with a longitudinal shear stress significantly too large to cause a fracture in an oblique plane to the fiber axis; the failure criterion for mode C is
[0031]
[0032] The above criteria will be evaluated in the following cases
[0033]
[0034] 5.3. Where the physical meaning of each parameter is as follows, σ1 is the stress in the fiber direction, σ2 and σ3 are the normal stresses perpendicular to the fiber direction, τ 21 is the shear stress, S 21 is the longitudinal shear strength of the composite, Y T is the transverse tensile strength of the composite, Y C is the transverse compressive strength, τ 21C is the critical shear stress, equals the crack resistance strength against failure of the plane of action by the transverse shear stress, is the slope of the (σ2, τ 21 ) fracture envelope, to be linked to and the following relationships are assumed to remain constant:
[0035]
[0036] where It is equal to the crack resistance strength that resists failure of the surface where the transverse shear stress τ⊥⊥ is located.
[0037] therefore, Represented as
[0038]
[0039] in, Assuming it is with S 21 The same, this will allow Represented as
[0040]
[0041] Puck and Mannignal (2007) The following recommended values are provided.
[0042]
[0043] For resin-based fiber-reinforced composites, glass fiber is typically used at 0.25 and 0.3, while carbon fiber is typically used at 0.3 and 0.35.
[0044] Puck will also τ 21C Defined as
[0045]
[0046] Define σ 1D Degraded stress in composite materials causes pre-fiber failure warping in individual fibers, leading to microcracks and debonding damage in these areas. To mitigate this weakening effect, Puck uses a weakening factor f... w This reduces fracture resistance; Puck defined two equations for this purpose, the first of which is used for the generalized weakening factor.
[0047]
[0048] The second expression is used to provide another expression for the weakening factor to make the fracture condition similar, and is also used to provide a linear expression for stress;
[0049]
[0050] The Helius PFA implementation of the Puck criterion utilizes only the in-plane stress components of the three-dimensional stress state; in this case, the two equations above should be equivalent expressions because there are no iterative calculations on the fracture plane to be performed, thus yielding...
[0051]
[0052] n is an empirical exponent, according to Puck's recommendation, Helius PFA uses n = 6 for the exponent, and by 1.1X T or -1.1X C Empirical calculation sigma 1d Depending on the sign of sigma1, the Helius PFA implementation of Puck's criteria only uses the in-plane components of the three-dimensional stress and strain, i.e.sigma13, sigma23, sigma33, for calculating material failure.
[0053] 6. The method according to claim 1, wherein the calculation method of the interlaminar fracture toughness of the hybrid pultruded plate I is characterized in that, in step 5, the calculation method of the interlaminar fracture toughness is:
[0054] The load application surface is coupled with the established reference point Rp, and the support reaction-displacement curve, i.e., the load-opening displacement curve, of the extractable reference point can be extracted through the history output, and the energy release rate G of the I-type fracture can be calculated according to the calculation formula of the fracture toughness. ⅠC .
[0055] The strain energy release rate of the I-type static delamination specimen is calculated by using the modified beam theory (Modified Beam Theory Method, MBT), and the calculation formula is:
[0056]
[0057] Wherein, P is the load applied in the test, d is the displacement of the loading point, b and a are the width and delamination length of the DCB specimen respectively, and |Delta| is the delamination length correction amount, which is used to consider the displacement and rotation of the cantilever at the crack tip due to material anisotropy. The correction amount can be obtained by data fitting of the flexibility C measured by the I-type delamination test and the delamination length a as shown in the figure Figure 6 , wherein the flexibility C = d / P.
[0058] The beneficial effects of the present application compared with the prior art are:
[0059] The present application introduces Puck criterion for failure judgment; and the I-type interlaminar toughness of the hybrid pultruded plate is quickly predicted through simulation calculation. BRIEF DESCRIPTION OF DRAWINGS
[0060] Figure 1 is a flowchart of a hybrid pultruded plate I-type interlaminar fracture toughness rapid prediction method of the present application;
[0061] Figure 2 is a schematic diagram of each model of Puck criterion;
[0062] Figure 3 is a support reaction-displacement curve diagram extracted in the example;
[0063] Figure 4 for the crack propagation process diagram of the hybrid pultruded plate;
[0064] Figure 5 for G ⅠC with the curve of crack propagation (R curve);
[0065] Figure 6 for the data fitting diagram of the compliance C and the delamination length a measured by the mode I delamination test. DETAILED DESCRIPTION
[0066] The present application will be described in detail below in conjunction with examples and drawings, further illustrating its purposes, technical solutions and advantages. The described embodiments are only some examples of the present application, and by adjusting the model parameters, the fracture toughness of different hybrid ratios and hybrid modes can be calculated. Any improvement and deformation based on the examples of the present application belongs to the protection scope of the present application.
[0067] A flowchart of a mode I interlaminar fracture toughness rapid prediction method of a hybrid pultruded plate. Referring to Figure 1 , the specific steps of the mode I interlaminar fracture toughness rapid prediction method are as follows:
[0068] Step 1, establish a mode I interlaminar fracture toughness test geometric model of the hybrid pultruded plate, and divide the model into hexahedral mesh processing.
[0069] In the example, step 1, draw a geometric model with a prefabricated 30mm crack, divide the geometric model into 24 layers, arrange 6 layers of carbon fiber laminated plates above and below the hybrid pultruded plate geometric model, arrange 12 layers of glass fiber laminated plates in the middle, and divide the grid attribute as C3D8R.
[0070] Step 2, extract the grid components, and establish the attribute assignment required unit set.
[0071] In this example, step 2, establish the carbon fiber laminated plate grid unit set Set1 and the glass fiber laminated plate grid unit set Set2 of the non-crack propagation area, and the carbon fiber laminated plate grid unit set Set3 and the glass fiber laminated plate grid unit set Set4 of the crack propagation area.
[0072] Step 3, define the material model according to the established unit set of the grid unit material model.
[0073] In this example, step 3, the grid unit sets Set1, Set2, Set3 and Set4 are respectively assigned with corresponding material properties. Step 4, according to the loading mode for measuring the mode I interlaminar fracture toughness of the composite material according to the ASTM5528 standard, determine the boundary conditions and apply the load.
[0074] In this example, step 4, the upper face of the left side crack region is coupled with Rp1, and a U2 displacement condition is applied to Rp1 and all but the four degrees of freedom of UR3 are constrained. The lower face of the crack region is coupled with Rp2, and a displacement constraint is applied to Rp2, and all but the four degrees of freedom of UR3 are constrained.
[0075] Step 5, calculate the finite element model, obtain the calculation results, and extract the load-opening displacement curve Figure 5 , and obtain the interlaminar fracture toughness of the hybrid pultruded plate type I.
[0076] In this embodiment, step 3: the strength initiation criterion of the crack propagation region adopts the Puck criterion, see Figure 2 The Puck criterion is introduced based on the VUMAT user-defined subroutine to judge the crack propagation behavior of the hybrid pultruded plate, and the method is as follows:
[0077] 5.1, in the Puck criterion, the failure between fibers includes any matrix cracking or fiber / matrix debonding; the Puck criterion identifies three different failure modes between fibers, which are referred to as modes A, B and C; the three failure modes between fibers can be distinguished by the orientation of the fracture plane relative to the reinforcing fibers;
[0078] 5.2, three failure modes
[0079] Failure mode A between fibers:
[0080] Mode A corresponds to a 0° fracture angle; if the transverse stress in the composite is greater than 0 (which indicates that the transverse crack is perpendicular to the transverse load), this criterion is called;
[0081]
[0082] Failure mode B between fibers:
[0083] Mode B corresponds to transverse compressive stress (suppressing crack formation) with longitudinal shear stress lower than the fracture resistance (an empirical constant);
[0084]
[0085] The above criteria will be evaluated in the following cases
[0086]
[0087] Failure mode C between fibers:
[0088] Mode C corresponds to transverse compressive stress (suppressing crack formation) with longitudinal shear stress significantly too large, resulting in a fracture on an inclined plane to the fiber axis; the failure criterion for mode C is
[0089]
[0090] The above criteria will be evaluated in the following situations.
[0091]
[0092] 5.3 The physical meanings of each parameter are as follows: σ1 is the stress in the fiber direction, σ2 and σ3 are the normal stresses perpendicular to the fiber direction, and τ... 21 It is shear stress, S 21 For the longitudinal shear strength of composite materials, Y T For the transverse tensile strength of composite materials, Y C Lateral compressive strength, τ 21C For critical shear stress, Equal to the crack resistance strength against failure caused by transverse shear stress on the working surface. For (σ2, τ) 21 The slope of the broken envelope should be... and When establishing a connection, the following relationship is assumed to remain unchanged:
[0093]
[0094] in It is equal to the crack resistance strength that resists failure of the surface where the transverse shear stress τ⊥⊥ is located.
[0095] therefore, Represented as
[0096]
[0097] in, Assuming it is with S 21 The same, this will allow Represented as
[0098]
[0099] Puck and Mannignal (2007) The following recommended values are provided.
[0100]
[0101] For resin-based fiber-reinforced composites, glass fiber is typically used at 0.25 and 0.3, while carbon fiber is typically used at 0.3 and 0.35.
[0102] Puck will also τ 21C Defined as
[0103]
[0104] Definition of σ 1D degradation stress in the composite, so that each fiber appears pre-fiber failure buckling, which in turn leads to the appearance of micro-cracks and debonding forms of damage in these areas; for consideration of this weakening effect, Puck defines a weakening factor f w reduces the fracture resistance; Puck defines two equations for this purpose, the first for the generalized weakening factor;
[0105]
[0106] The second is used to provide another expression of the weakening factor to make the fracture condition homogeneous, and also to provide a first-order expression for stress;
[0107]
[0108] The Helius PFA implementation of the Puck criterion only uses the in-plane stress components of the three-dimensional stress state; in this case, the above two equations should be equivalent expressions, because there is no iterative calculation on the fracture plane to be performed, so
[0109]
[0110] n is an empirical index, according to Puck's suggestion, Helius PFA uses n = 6 for the index, and 1.1X T or -1.1X C Empirical calculation of σ 1d , depending on the sign of σ1, the Helius PFA implementation of the Puck criterion only uses the in-plane components of the three-dimensional stress and strain, i.e. σ13, σ23, σ33, which are not used to calculate material failure.
[0111] It should be noted that in step 5, the method for calculating the fracture toughness is as follows: in this embodiment, the support reaction-displacement curve of the reference point is extracted, and the energy release rate G ⅠC is obtained according to the formula for calculating the type I fracture toughness:
[0112] Referring to Figure 3 , the support reaction-displacement curve of the reference point is extracted;
[0113] Referring to Figure 4 , the corresponding delamination length of the applied load and the loading point displacement is obtained;
[0114] The strain energy release rate of the type I static delamination specimen is calculated by the modified beam theory (Modified Beam Theory Method, MBT), and the calculation formula is:
[0115]
[0116] wherein P is the load applied in the test, d is the displacement of the loading point, b and a are the width and delamination length of the DCB specimen respectively, and |Δ| is the correction of the delamination length for considering the displacement and rotation of the cantilever at the crack tip due to the material anisotropy. The correction can be obtained by data fitting of the compliance C measured in the type I delamination test and the delamination length a as shown in the graph of Figure 6 wherein the compliance C = d / P.
[0117] Referring to Figure 5 , G ⅠC is obtained by the calculation formula. The curve of the crack propagation (R curve) is obtained.
[0118] The present application can more accurately predict the crack propagation behavior of the hybrid pultruded plate, prevent the dangerous damage that may occur in the actual work of the wind power blade, and save manpower and material resources compared with the experimental method.
[0119] The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall be considered as the protection scope of the present application.
Claims
1. A method for quickly predicting interlaminar fracture toughness of a hybrid pultruded plate type I, characterized in that, The method comprises the following steps: Step 1, a hybrid pultruded plate type I interlaminar fracture toughness test geometric model is established, and hexahedral grids are divided for the model; Step 2, grid components are extracted, and a unit set required by attribute assignment is established; Step 3, material properties are defined for the grid unit material model according to the established unit set; Step 4, boundary conditions are determined and loads are applied according to the loading mode for measuring the interlaminar fracture toughness of the composite material I according to the ASTM5528 standard; Step 5, calculate the finite element model, obtain the calculation results, extract the load-opening displacement curve, and calculate the interlaminar fracture toughness G of the hybrid pultrusion plate type I ⅠC .
2. The method according to claim 1, wherein the method is characterized by: In step 1, the hybrid pultruded plate is made of carbon fiber laminated plates and glass fiber laminated plates interlaminarly laid, and a 30mm wedge-shaped crack is preset in the hybrid pultruded plate.
3. The method of claim 1, wherein the method is characterized by: In step 3, the material model of the grid unit is defined as follows: 3.1, the grid unit not in the crack propagation area is assigned with the fiber laminated plate attribute; 3.2, the grid unit in the crack propagation area is assigned with the user-defined material attribute calling the Puck criterion, and the unit deletion function is enabled; 3.3, the unit material parameters required in the simulation calculation are obtained by test, including strength, stiffness and Poisson's ratio.
4. The method of claim 1, wherein the method is characterized by: In step 4, the loading mode process for measuring the interlaminar fracture toughness of the composite material I includes the following steps: The upper and lower end faces of the left pre-crack are coupled with reference points Rp1 and Rp2 respectively, the displacement boundary condition is applied to Rp1, and the displacement constraint is applied to Rp2.
5. The method of claim 1, wherein the method is characterized by: In step 5, the Puck criterion is introduced based on the VUMAT user-defined subroutine to judge the delamination propagation behavior of the hybrid pultruded plate: 5.1, in the Puck criterion, the failure between fibers includes any matrix crack or fiber / matrix debonding; the Puck criterion identifies three different failure modes between fibers, which are referred to as modes A, B and C; the three failure modes between fibers can be distinguished by the orientation of the fracture plane relative to the reinforcing fibers; 5.2, three failure modes Failure mode A between fibers: Mode A corresponds to a 0° fracture angle; if the transverse stress in the composite material is greater than 0 (which indicates that the transverse crack is perpendicular to the transverse load), the criterion is called; Failure mode B between fibers: Mode B corresponds to transverse compressive stress (inhibiting crack formation) with longitudinal shear stress lower than the fracture resistance (an empirical constant); The above criterion will be evaluated under the following conditions σ2< 0 and Failure mode C between fibers: Mode C corresponds to transverse compressive stress (inhibiting crack formation) with longitudinal shear stress significantly too large, resulting in a fracture on an inclined plane to the fiber axis; the failure criterion for mode C is The above criterion will be evaluated under the following conditions σ2< 0 and 5.3, where the parameters have the following physical meanings, σ1 is the stress in the fiber direction, σ2 and σ3 are the normal stresses perpendicular to the fiber direction, τ 21 is the shear stress, S 21 is the longitudinal shear strength of the composite, Y T is the transverse tensile strength of the composite, Y C is the transverse compressive strength, τ 21C is the critical shear stress, is the fracture strength resisting failure of the plane on which the transverse shear stress acts, is the slope of the (σ2, τ 21 ) fracture envelope, and the following relationships are assumed to hold: and wherein is equal to the cracking strength that resists failure of the action surface by the transverse shear stress τ⊥⊥. Thus, is represented as wherein Assuming that the S 21 same, this will allow is represented as Puck will also tau 21C defined as Definition of σ 1D degrading stresses in the composite, such that each fiber experiences a pre-fiber failure buckling, which in turn leads to the formation of micro-cracks and debonding type of damage in these regions; in view of this weakening effect, Puck defines a weakening factor f w reduces the resistance to fracture; for this purpose, Puck defines two equations, the first for the generalized weakening factor; A second expression for providing a weakening factor is used to make the fracture condition homogeneous, and also to provide a first-order expression for stress; The Helius PFA implementation of the Puck criterion only utilizes the in-plane stress components of the three-dimensional stress state; in this case, the above two equations should be equivalent expressions, because there is no iterative calculation on the fracture plane to be performed, so it follows that n is an empirical exponent, according to Puck's recommendation, Helius PFA uses n = 6 for the exponent and by 1.1X T or -1.1X C Empirical calculation of σ 1d Depending on the sign of σ1, the Helius PFA implementation of Puck's criterion uses only the in-plane components of the three-dimensional stress and strain, i.e. σ13, σ23, σ33, for the calculation of material failure.
6. The method of claim 1, wherein the method is characterized by: In Step 5, the load opening displacement curve of the reference point Rp1 is extracted to calculate the mode I fracture toughness G of the hybrid pultruded plate ⅠC : The strain energy release rate of the I-type static delamination specimen is calculated by using the modified beam theory (MBT), and the calculation formula is as follows: Wherein, P is the load applied in the test, d is the displacement of the loading point, b and a are the width and delamination length of the DCB specimen respectively, |Δ| is the correction of the delamination length, which is used to consider the displacement and rotation of the cantilever at the crack tip due to the anisotropy of the material; the correction can be obtained by data fitting of the flexibility C measured by the type I delamination test and the delamination length a.