Simulation analysis method of interlaced ply composite laminate

Abstract

The simulation analysis method of the interlaced ply composite laminate is closer to the characteristics of the interlaced ply composite laminate. According to the embodiment of the present application, the simulation analysis method of the interlaced ply composite laminate comprises a multi-layer grid generation, wherein a single-layer grid model of the interlaced ply composite laminate is applied, and a three-dimensional grid of the multi-layer interlaced ply is created according to parameters including ply sequence, fiber tape width and ply offset, wherein the local single-layer thickness of the fiber reinforced resin-based composite laminate is considered to be smoothly thinned due to the flow of the ply fiber tape during the curing forming process, and the offset displacement of the filling ply is taken as the sum of the fiber tape width, the fiber interval and the offset displacement of the interval ply, so as to ensure that the filling ply can fill the gap between the interval plies.

Description

Technical Field

[0001] This invention relates to a simulation analysis method for structures, and more particularly to a simulation analysis method for interlaced composite laminates. Background Technology

[0002] Fiber-reinforced thermosetting composites have attracted widespread attention due to their unique design and application advantages. However, their poor interlaminar properties, low thickness direction strength, and low compressive-tensile strength ratio limit their further development. Experiments have shown that developing traditional 2D ply structures into 2.5D interlaced ply structures can significantly improve interlaminar properties and impact resistance. Currently, interlaced ply technology has broad application prospects in composite structures for the cold ends of aero-engines, such as fan blades, housings, and nacelle systems, while also posing new challenges to the analysis and simulation techniques of composite materials.

[0003] The patent specification with publication number CN110826284A discloses a method for modeling and analyzing interwoven and laminated composite material laminates, which includes the following steps:

[0004] S1: Design a hybrid layered structure combining interlacing and lamination;

[0005] S2: Based on the interwoven and laminated hybrid ply structure designed in step S1, generate the basic laminated ply model and the basic interwoven ply model respectively;

[0006] S3: Based on the basic laminated ply model and basic interwoven ply model designed in step S1, establish a 3D model of the interwoven and laminated mixed ply composite material laminate.

[0007] S4: Set the material properties, boundary conditions and loading methods for the established 3D model of the interwoven and laminated composite laminate to achieve finite element analysis of the mechanical properties of the interwoven and laminated composite laminate.

[0008] The patent specification with publication number CN110941922A discloses a simulation method for predicting interlaminar and interfiber band damage in composite laminates, including the following steps:

[0009] S1: Establish grid unit cells;

[0010] S2: Based on the single-layer basic mesh model established in step S1;

[0011] S3: Based on the layup angle, layup quantity, and layup sequence, call and combine the base laminate model of the pre-set fiber strip interface unit. Then, generate a composite material laminate 3D model of the pre-set interlayer interface unit and the fiber strip interface unit in the adjacent interlayer pre-set interface unit of the base laminate model of the pre-set fiber strip interface unit.

[0012] S4: Design the material properties of each fiber strip of the composite laminate 3D model of the pre-set interlayer interface unit and fiber strip interface unit generated in step S3 to generate fiber reinforced composite laminate.

[0013] S5: Predict the strength and damage of fiber-reinforced composite laminates using simulation methods.

[0014] According to the inventors' research, the ply cross-sectional features obtained by the aforementioned simulation method still differ from those of real interwoven ply composite laminates, and it is also difficult to simulate the performance divergence of laminates. Summary of the Invention

[0015] The purpose of this invention is to provide a simulation analysis method for interlaced laminate composite material laminates, the analysis results of which are closer to the characteristics of real interlaced laminate composite material laminates.

[0016] According to an embodiment of the present invention, the simulation analysis method for interlaced ply composite laminates includes multi-layer mesh generation. A parameterized single-layer mesh model of the interlaced ply composite laminate is applied, and a three-dimensional mesh of the multi-layer interlaced ply is created based on parameters including ply sequence, fiber band width, and ply offset. Considering the localized thinning of the single-layer thickness caused by fiber band flow during the curing process of the fiber-reinforced resin matrix composite laminate, to ensure that unidirectional filling ply can fill the gaps between interleaved ply, the offset displacement of the filling ply is taken as the sum of the fiber band width, fiber spacing, and the offset displacement of the interleaved ply.

[0017] In one embodiment, the single-layer mesh of the parametric interlaced composite laminate includes a denser region and a thicker region, and a transition region between the denser and thicker regions is designed, wherein the mesh density of the transition region is reduced in both the longitudinal and transverse directions relative to the denser region, and the mesh density of the thicker region is reduced in both the longitudinal and transverse directions relative to the transition region.

[0018] In one embodiment, after generating a three-dimensional model of the interwoven laminate composite material, models of different sample sizes are selected from different positions on the three-dimensional model. Their microstructures will be different, and their predicted performances will also be different. This accurately simulates the performance divergence caused by microstructure deviations in actual test pieces.

[0019] According to an embodiment of the present invention, the simulation analysis method for interlaced ply composite laminates, after generating a three-dimensional model of the interlaced ply composite laminate, obtains the magnification or reduction correction coefficient of each ply thickness by statistically analyzing the total ply thickness at each unit node and comparing it with the theoretical thickness. The single-layer thickness profile at each node is adjusted to increase the curvature of the internal ply so that the model surface is restored to a plane, making the curvature characteristics inside the three-dimensional model smoother and closer to the real ply cross-sectional features.

[0020] On the one hand, it is recommended that the offset displacement of the filler ply be the sum of the fiber ply bandwidth, the ply fiber spacing, and the offset displacement of the interleaved ply. The ply mesh generated according to this parameter relationship has a flat profile after stacking, but the internal ply is smooth and curved, so the analysis results are closer to the characteristics of real interwoven ply composite laminates.

[0021] On the other hand, when the offset displacement of the filling ply and the offset displacement of the spacer ply do not satisfy the above relationship, defects such as ply gaps and overlaps will occur, causing the ply surface to become uneven due to changes in the total thickness. By statistically analyzing the total ply thickness at each unit node and comparing it with the theoretical thickness, the magnification or reduction correction coefficient of each ply thickness is obtained. The single-layer thickness profile at each node is adjusted, and the curvature of the internal ply is increased to restore the model surface to a flat plane. As a result, the analysis results are closer to the characteristics of the real interlaced ply composite laminate. Attached Figure Description

[0022] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0023] Figure 1 This is a flowchart of the finite element simulation analysis method for interlaced composite laminates;

[0024] Figure 2 This is a schematic diagram of the grid unit cell structure of an interlaced composite laminate.

[0025] Figure 3 is a schematic diagram of the denser grid, thicker grid, and transition grid in a single-layer grid of an interwoven lay-up composite laminate.

[0026] Figure 4 is a schematic diagram of the smooth thinning of local monolayer thickness caused by the flow of the ply fiber strips;

[0027] Figure 5 is a schematic diagram of the three-dimensional multilayer mesh model of the interlaced composite laminate before merging;

[0028] Figure 6 This is a schematic diagram of a three-dimensional model of an interlaced composite laminate.

[0029] Figure 7This is a schematic diagram of the thickness cross-section of an interlaced composite laminate.

[0030] Figure 8 This is a schematic diagram of a representative unit of an interlaced composite laminate.

[0031] Figure 9 This is a schematic diagram showing various loading methods for a representative unit of an interlaced composite laminate.

[0032] Figure 10 These are the predicted results of the mechanical properties of interlaced composite laminates;

[0033] Figure 11 It is an electron microscope image of the cross-section of the actual specimen. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0035] Figure 1 The flowchart of the finite element simulation analysis method for interlaced laminate composite materials is shown, including model mesh generation 1, model generation 2, and mechanical property prediction 3. Model mesh generation 1 includes single-layer mesh generation 11 and multi-layer mesh generation 12. The operation flow of the interlaced laminate composite material model generation toolkit is also shown.

[0036] The aforementioned single-layer mesh generation 11 includes the following steps:

[0037] (1) Define the size of a single-layer mesh, such as width and angle, and define the geometric size of the fiber strip, such as fiber strip width, i.e., parameterized interlaced composite laminate unit;

[0038] (2) Based on the interlacing angle, design the included angle of the diagonals of the finite element mesh unit cell model and the size of the mesh unit cell model, and establish the finite element mesh unit cell model 110 of the interlaced composite laminate, as shown in the schematic diagram. Figure 2 As shown; the grid unit cell model 110 is square, with a grid unit cell length a and a ply angle β, from Figure 2 First, the grid unit cell length *a* is defined, and the horizontal edges are determined. Then, based on the ply angle *β* and the horizontal edges, the diagonals can be determined, and consequently, the vertical edges can be determined. The octagons in the grid unit cell model 110, and the connecting lines between the octagons and the squares, serve as auxiliary lines to ensure the convergence of numerical calculations. In another embodiment, the octagons are replaced with other polygons, and the number of sides varies depending on the calculation accuracy, etc.

[0039] (3) Figure 3A A local section of a single-layer mesh is shown. The single-layer mesh includes a refined region 111 and a thickened region 112, connected by a transition region 113. The thickened region 112 is used in non-critical areas to reduce the number of elements in the mesh unit cell model, thus reducing computational cost. The refined region 111 is used in critical areas to ensure computational accuracy. The transition region 113, where the refined region 111 transitions to the thickened region 112, employs... Figure 3B The finite element mesh unit cell model 13 is shown. The transition region 113, relative to the refined region 111, halves the lateral density and reduces the longitudinal density to 1 / 4 of that in the refined region. Figure 3B The horizontal and vertical dimensions are different, making it appear square but actually rectangular. The dimensional changes of the unit cell model in the transition region from the denser to the thicker region are as follows: Figure 3C As shown. In Figures 3A to 3C In the illustrated embodiment, the unit cell of the encryption region 111 adopts... Figure 2 The unit cell model 110 shown uses the transition region 113 and the thickened region 112 as unit cells. Figure 3B The unit cell model 13 is shown. In unit cell model 13, the intersection of lines is a node. For example, the interior of unit cell model 13 has three nodes 138, 139, and 138, which are located in the middle of the long side. The side with the higher adjacent mesh density is defined as the denser side, and the side with the lower mesh density is defined as the thicker side. The denser side of unit cell model 13 has 5 nodes, while the thicker side has only 3 nodes. The three nodes 138, 139, and 138 in the middle are aligned with the corresponding nodes on the denser and thicker sides, respectively. The unit cell of the denser region 111 is a square with a side length of 'a', and each side has 3 nodes. The unit cell of the transition region 113 is a rectangle with a width of 2a and a length of 4a. The wide side of the cell on the encrypted side of the transition region 113 corresponds to two cells in the encrypted region, sharing an edge with these two cells, thus having 5 nodes. Two nodes 138 are set inside the rectangle, located at the midpoint of the long side and aligned with the corresponding nodes on the wide side of the encrypted side. The connecting lines inside the cell model 13 are auxiliary lines to ensure numerical convergence, and these internal connecting lines adapt to the cell model 110 and its internal auxiliary lines. Similarly, the cell model of the encrypted region 111 is rectangular, with a width of 4a and a length of 8a, again halving the horizontal mesh density of the encrypted region 111 and reducing the vertical mesh density to 1 / 4.

[0040] (4) Run the program in the compilation environment and execute steps (1) to (3) of single-layer mesh generation 11. Output the single-layer mesh of the generated interwoven ply composite laminate model as a file that can be read by software such as LS-Dyna, abaqus, and ansys.

[0041] The generation of multilayer meshes for the aforementioned interlaced composite laminate includes:

[0042] (1) Read files generated by LS-Dyna, abaqus, ansys and other software that can read single-layer meshes;

[0043] (2) Read the input parameter file, apply the single-layer mesh of the parametric interwoven ply composite laminate model, and create the model mesh according to parameters such as ply sequence, fiber band width and ply offset, that is, create a multi-layer interwoven ply three-dimensional mesh. The ply offset parameter here is the parameter of "filling ply position" and "interval ply position" mentioned later, which is mainly the offset distance.

[0044] (3) Considering the local thinning of single-layer thickness caused by the flow of fiber strips during the curing process of fiber-reinforced resin matrix composite laminates, in order to ensure that the filling plies in the same direction can accurately fill the gaps between the inter-plies, the offset distance d of the filling ply position is taken as the sum of the ply width g, the ply interval f, and the offset distance e of the inter-ply position. Figure 4A The relationships between these four dimensions are described. Figure 4B This describes the profile morphology of the ply edge considering outward fiber flow. During ply compaction and curing, the edge fibers will flow outward a distance w2, causing thinning of the ply within a range of w1. Figure 4B The diagram shows the width w1 of the thinning region at the ply edge, the width w2 of the outward flow region at the ply edge, and the profile of the overall ply thickness variation hx following a cosine curve with a cycle period of 2*w3.

[0045] h is the ply thickness before the change, x is the width of the thinned ply edge region calculated starting from the thinned region adjacent to the unthinned region at the ply edge, and w3 is the total width of the ply edge thickness change region.

[0046] The outline of the overlaid mesh generated according to this parameter relationship is as follows: Figure 4C As shown, its surface is flat but the internal layers have a smooth and curved cross-sectional shape. Figure 4 also shows the initial spacing width of the fiber strip and the area where the fiber strip width varies.

[0047] When the offset displacement of the fill ply and the offset displacement of the spacer ply do not satisfy the above relationship, defects such as ply gaps and overlaps will occur, causing the ply surface to become uneven due to changes in the total thickness. This invention automatically calculates the total ply thickness at each unit node and compares it with the theoretical thickness to obtain an amplification or reduction correction factor for the thickness of each ply layer. This adjusts the single-layer thickness profile at each node, increases the curvature of the internal ply layers to restore the model surface to a flat plane, and makes the internal curvature characteristics of the model smoother, closely resembling the real ply cross-sectional features. Figure 11 As shown;

[0048] (5) Output the generated three-dimensional multilayer mesh model of the interwoven ply composite laminate as a file that can be read by software such as LS-Dyna, abaqus, and ansys.

[0049] Back Figure 1 The generation of the interwoven laminate model includes interface layer setting and 3D model generation. The interface layer setting includes intralayer interface layer elements 61 to simulate the initiation and propagation of cracks within the layer, and interlayer interface layer elements 62 to simulate the effects of delamination initiation and propagation between layers. Figure 5B As shown.

[0050] 3D model generation includes:

[0051] (1) Software such as LS-Dyna, abaqus, and ansys can read files generated by three-dimensional multi-layer mesh models;

[0052] (2) Read the input parameter file, merge the multi-layer plywood mesh units according to the input parameters including the interface layer thickness, and generate a three-dimensional model of the interwoven plywood composite material laminate.

[0053] (3) Based on the grid angle and layup sequence, fiber tape width and layup offset designed according to the layup angle, an example of layup design is as follows: Figure 5A As shown, the final interlaced laminate model is as follows: Figure 6 As shown;

[0054] by Figure 5A The ply design shown is an example, which includes a three-way, three-cross interlaced ply structure as follows:

[0055] [60 a / -60 a / 60 b / 0 a / -60 b / 60 a / 0 b ] n

[60] a / -60 a / 60 a / 60b / -60 b / 0 b ] n

[0056] and four-way four-way interlaced ply structures including

[0057] [0 a / 45 a / 90 a / 0 b / -45 a / 45 b / 90 b / 0 a / -45 b / 45 a / 90 a / 0 b / -45 a / 45 b / 90 b / -45 b ]and

[0058] [0 a / 45 b / -45 a / 90 b / 0 a / 0 b / 90 a / -45 b / 45 a / 0 b ].

[0059] Here, subscript 'a' indicates that the layup starts from the origin (each layer of adjacent fiber strips is shifted by a certain distance before layup), subscript 'b' indicates the filling layup, and subscript 'n' indicates the adjustment of the layup quantity. This parameter can be adjusted according to the thickness requirements. This type of interlaced layup does not have a theoretically periodic repeating structure.

[0060] (4) Output the generated interwoven ply composite laminate model as a file that can be read by software such as LS-Dyn, abaqus, and ansys.

[0061] Back to Figure 1 The mechanical property prediction includes representative element extraction, mechanical property prediction calculation, and finally evaluation of the calculation results. The mechanical property prediction calculation includes setting material properties, boundary conditions, and loading methods.

[0062] The aforementioned representative unit model extraction includes:

[0063] (1) Software such as LS-Dyna, abaqus, and ansys can read the files generated by the model of the interwoven ply composite laminate.

[0064] (2) Read the input parameter file and extract the representative element model from the interwoven ply composite laminate model according to the input parameters, including the representative element coordinates and dimensions.

[0065] (3) The three-dimensional multi-directional layup and the automatically generated interface layer are merged to generate a finite element model of the interlaced layup composite material laminate, which satisfies the characteristic of uniform thickness of the interlaced layup composite material laminate. Its thickness direction cross-sectional schematic diagram is shown below. Figure 7 As shown; the interface layer is generated by automatically matching the coordinates of the mesh nodes of each layer that are stacked layer by layer. When the planar coordinate distance between two adjacent ply surface nodes is less than a given error value, they are a pair of nodes of the interface layer unit. The node pairs of each ply surface are found through a loop algorithm. The four node pairs of a surface can generate the corresponding intra-layer and inter-layer interface layer units.

[0066] (4) The interlaced composite laminate model can be cut according to coordinates and representative unit dimensions, and multiple locations can be selected to simultaneously divide multiple representative units for analysis. A preferred implementation is as follows: Figure 8 The diagram shows a representative element 8 extracted from a densely interwoven plywood model. Since the bandwidth of the 0-degree and 90-degree plywoods is *g*, and the bandwidth of the ±α plywood is also *g*, but the projected width of the ±α plywood bandwidth in the 0- and 90-degree directions is *g / sinα*, the interwoven structure can only exhibit periodicity within the least common multiple of (g, g / sinα). However, sinα is irrational at most angles α, and there is no least common multiple of (g, g / sinα). Therefore, in principle, most interwoven plywood structures are non-periodic. Thus, selecting different sample sizes from different positions on the 3D model will result in different microstructures and predicted performances. This allows for accurate simulation of performance divergence caused by microstructural deviations in actual test specimens.

[0067] (5) Selecting the layup material model, setting material properties, boundary conditions and loading methods, and identifying the best implementation, for example... Figure 9 As shown, the arrows represent element node displacements and load application directions. Loads in the model are extracted by applying displacements along the arrow directions, or boundary node displacements are extracted by applying loads. The load-displacement curve of the model is obtained by combining this with the formulas: stress = load / model cross-sectional area and strain = displacement / model dimension along the loading direction. Figure 10 The stress-strain curve shown can be obtained from the load-displacement curves in different directions. Figure 9The fiber direction modulus E11, strength X11, Poisson's ratio v12, v13, perpendicular fiber direction modulus E22, strength X22, Poisson's ratio v21, v31, thickness direction modulus E33, strength X33, Poisson's ratio v31, v32, longitudinal and transverse shear modulus G12, shear strength S12, out-of-plane shear modulus G31, shear strength S31, out-of-plane shear modulus G32, shear strength S32 are shown.

[0068] (6) Run the program in the compilation environment and output the generated representative unit model as a file that can be read by software such as LS-Dyna, abaqus, and ansys.

[0069] The aforementioned mechanical property prediction calculations include:

[0070] (1) Read the files generated by software such as LS-Dyna, abaqus, and ansys, which are representative unit models;

[0071] (2) Read the material model properties, model boundary conditions, and operation control conditions, etc.;

[0072] (3) Run the model under various loading modes, obtain the corresponding stress-strain curves, obtain the performance parameters of the interwoven ply composite material, and output the data as a file that can be read by software such as LS-Dyna, abaqus, and ansys.

[0073] The evaluation of the aforementioned calculation results includes:

[0074] (1) The results file is processed and analyzed to obtain the mechanical properties of the representative unit of the interwoven ply composite laminate, including modulus, Poisson's ratio, stress-strain curve and failure mode (conclusion). Using this toolkit, the performance of interwoven ply composites can be accurately predicted. The predicted average modulus and strength are within 10% of the experimental error.

[0075] (2) The finite element simulation results can be directly compared and verified with experimental results, and the mechanical property prediction is better implemented, for example... Figure 10 As shown;

[0076] (3) Combining beam and classical laminate theory, the effectiveness of the finite element simulation results is evaluated and error is analyzed.

[0077] Based on the aforementioned analytical method, computer software is used to automatically generate models that reflect the internal detailed structure of interlaced ply parameters. These models include the smooth thinning of local monolayer thickness caused by the flow of ply fiber bands and the interface layer units between ply layers. This can simulate the process and performance changes of crack initiation, propagation, and eventual failure within the interlaced structure. The generated models can be used to systematically study the impact of interlacing parameters on performance, such as the process and performance changes of crack initiation, propagation, and eventual failure within the interlaced structure. The model generation tool is highly efficient, low-cost, and can handle the details in the model more meticulously, making it closer to the actual part state, with lower prediction errors.

[0078] The bandwidth, ply gap, single-layer thickness, ply sequence, and ply phase of interlaced layups all affect layup performance. Interlaced layups lack a theoretically periodic repeating structure, and the performance of test specimens at different locations on the layup plate will vary. To simulate the influence of layup parameters and specimen sampling location on the performance of interlaced layup composites, the detailed structure of the interlaced layup needs to be considered in the model. The aforementioned implementation method considers the influence of parameters such as fiber bandwidth, ply gap, single-layer thickness, ply sequence, and ply phase on laminate thickness and layup performance in interlaced layup composites. It studies the influence of detailed structure on 2D and 3D interlaced layup composites through 3D modeling, providing support for the design of 3D composite laminate structures. Simultaneously, it provides guidance for the process of preparing interlaced layup composites using automated fiber / tape placement technology, effectively reducing process costs.

[0079] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A simulation analysis method for interlaced composite laminates, including multi-layer mesh generation, characterized in that, A parametric interlaced composite laminate single-layer mesh model is applied. A three-dimensional mesh of multiple interlaced layups is created based on parameters including layup sequence, fiber band width, and layup offset. Considering the localized thinning of single-layer thickness caused by fiber band flow during the curing process of the fiber-reinforced resin composite laminate, the offset displacement of the filling layup is taken as the sum of the fiber band width, fiber spacing, and offset displacement of the interlaced layup to ensure that unidirectional filling layups can fill the gaps between interlaced layups. After generating the three-dimensional model of the interlaced composite laminate, the total layup thickness at each unit node is statistically analyzed and compared with the theoretical thickness to obtain the magnification or reduction correction coefficient for each layup thickness. The single-layer thickness profile at each node is adjusted to increase the curvature of the internal layups, restoring the model surface to a flat plane. This makes the curvature characteristics inside the three-dimensional model smoother and closer to the real layup cross-sectional features.

2. The simulation analysis method for interlaced composite laminates as described in claim 1, characterized in that, The single-layer mesh of the parametric interlaced composite laminate includes a dense region and a thickened region, and a transition region between the dense and thickened regions is designed. The mesh density of the transition region is reduced in both the longitudinal and transverse directions relative to the dense region, and the mesh density of the thickened region is reduced in both the longitudinal and transverse directions relative to the transition region.

3. The simulation analysis method for interlaced composite laminates as described in claim 1, characterized in that, After generating a three-dimensional model of the interwoven laminate composite material, selecting a sample size model from different positions on the three-dimensional model will result in different microstructures and predicted performances. This allows for accurate simulation of the performance divergence caused by microstructure deviations in actual test pieces.

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