A modeling method for a 2.5-dimensional satin woven composite unit cell geometry model

Abstract

The present invention discloses a modeling method of a 2.5-dimensional satin woven composite unit cell geometric model, comprising the following steps: 1) obtaining a three-dimensional structural image of the internal structure of five satin materials; 2) assuming the cross-sectional shape and direction of the fiber bundle; 3) dividing and obtaining a unit cell image; 4) measuring the geometric parameters required for unit cell modeling; 5) drawing a unit cell two-dimensional model; 6) establishing a unit cell three-dimensional finite element model. The method can characterize the weaving structure and weaving characteristics of the five satin weaves, and in the subsequent study of its stiffness and strength performance, the influence of yarn interlacing in the thickness direction on its performance can be considered, while reducing the size of the unit cell model as much as possible to improve the calculation efficiency; when modeling, it is considered that the weft yarn at the yarn interlacing position is no longer kept straight due to the pressure of the warp yarn, but presents a certain degree of bending, so that the established model is closer to the real model.

Description

Technical Field

[0001] The invention relates to the research field of 2.5-dimensional braided composite materials, in particular to a modeling method of a unit cell geometric model of a 2.5-dimensional satin braided composite material. Background Art

[0002] With the rapid development of material technology, in order to meet the increasingly high requirements for structural materials in the fields of national defense, military industry, aerospace, etc., woven composite materials are also being continuously improved and optimized, and have broad application prospects. 2.5-dimensional woven composite materials are a kind of composite materials with the structural characteristics of reinforcing fiber bundles in the warp, weft and thickness directions. They have excellent mechanical properties such as high specific stiffness and specific strength, good interlayer mechanical properties, impact resistance, and delay of internal cracks. At the same time, the molding cycle and cost reduction are also reduced to a certain extent compared with the three-dimensional woven structure, which has great research potential. However, due to the complex and diverse internal structure of the satin structure and the irregular structural changes caused by the molding process, its microscopic geometric structure is full of inhomogeneity, which increases the difficulty of studying and predicting its mechanical properties. In order to better analyze the damage evolution process and damage mechanism of 2.5-dimensional five-layer satin woven materials, it is necessary to establish a real and effective finite element geometric model, and conduct subsequent analysis on this basis to improve the accuracy of mechanical property prediction. Summary of the invention

[0003] The purpose of the present invention is to provide a modeling method for a unit cell geometric model of a 2.5-dimensional satin woven composite material. By applying reasonable boundary conditions and loads, the stress-strain response can be obtained to complete the prediction of the stiffness and strength of the material and broaden the application of five-layer satin materials in engineering.

[0004] To achieve the above object, according to one aspect of the present invention, the present invention provides the following technical solution:

[0005] A method for modeling a 2.5-dimensional satin woven composite unit cell geometric model comprises the following steps:

[0006] 1) Obtaining three-dimensional structural images of the internal structures of five satin materials;

[0007] 2) Assume the cross-sectional shape and orientation of the fiber bundle;

[0008] 3) Divide and obtain unit cell images;

[0009] 4) Measure the geometric parameters required for unit cell modeling;

[0010] 5) Draw a two-dimensional model of a unit cell;

[0011] 6) Establish a unit cell three-dimensional finite element model.

[0012] The present invention is further configured that the step 1) obtains a three-dimensional structural image of the internal structure of five satin materials, specifically,

[0013] Using X-CT scanning technology, five satin material specimen segments with a length exceeding one cycle were selected, and the segments were scanned layer by layer using X-rays. Three-dimensional structural images of the internal structures of the five satin materials were obtained using imaging software.

[0014] The present invention is further configured that the step 2) assumes the cross-sectional shape and orientation of the fiber bundle, specifically including the following assumptions:

[0015] 1. Assume that the cross section of the weft yarn is elliptical, and the cross sections of the warp yarn and the backing warp yarn are both rectangular;

[0016] 2. The lining warp yarn is straight, the warp yarn direction is a piecewise function, the contact part between the warp yarn and the weft yarn fits the outer contour line of the weft yarn, and the rest is a straight line;

[0017] 3. The weft yarn and the warp yarn are bent where they interweave, and the rest of the yarn remains straight;

[0018] 4. Perfect bonding between fiber bundles and between fiber bundles and matrix without extrusion, ignoring friction, and the cross-sectional area of ​​the yarn is equal everywhere.

[0019] The present invention is further configured that the step 3) divides and obtains the single cell image, specifically,

[0020] The minimum period of the weaving structure cycle, i.e., the unit cell, is found from the three-dimensional structural image of the internal structure of the five-piece satin material, and a unit cell image is obtained. The unit cell can be used to obtain the entire complete five-piece satin structure through translation, symmetry, and cyclic repetition.

[0021] The present invention is further configured that the step 4) measures the geometric parameters required for unit cell modeling, specifically,

[0022] After importing the three-dimensional structure image obtained in step 1 into the computer software, curve fitting is performed on the cross-sectional outer contour lines of the warp yarn, weft yarn, and lining warp yarn, and the length, width, and area of ​​the cross-sectional shape of each component of the warp yarn, weft yarn, and lining warp yarn are measured. Then, the total length of the unit cell in three directions is measured to provide a dimensional basis for the subsequent geometric model establishment.

[0023] The present invention is further configured that the step 5) draws a unit cell two-dimensional model, specifically,

[0024] Using the measured geometric parameters, the entire projection of the unit cell structure on a plane is drawn on a two-dimensional plane through computer software, and stretched into a flat plate structure with thickness to obtain a unit cell two-dimensional model.

[0025] The present invention is further configured that the step 6) establishes a unit cell three-dimensional finite element model, specifically,

[0026] The outer contours of different yarns in the unit cell two-dimensional model are stretched to the actual positions along straight lines, the curved weft yarns are stretched along the oblique lines, and the rest are stretched along the straight lines to obtain the unit cell three-dimensional finite element model.

[0027] Compared with the prior art, the advantages of the present invention are: 1. It can characterize the weaving structure and weaving characteristics of five-piece satin. In the subsequent study of its stiffness and strength performance, it can consider the influence of yarn interweaving in the thickness direction on its performance, while reducing the size of the unit cell model as much as possible to improve the calculation efficiency; 2. When modeling, it is considered that the weft yarn at the yarn interweaving point is no longer kept straight due to the pressure of the warp yarn, but shows a certain degree of bending. The position of the bent weft yarn is directly determined from the two-dimensional model. The established model is closer to the real model, which is superior to the geometric model modeling method that ignores the bending of the weft yarn. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of five satin weave structures;

[0029] Figure 2 Warp CT images of five satin woven composites;

[0030] Figure 3 Weft CT images of five satin woven composite materials;

[0031] Figure 4 Five satin-woven composite geometric model fronts;

[0032] Figure 5 Five satin-weave composite geometric model backs;

[0033] Figure 6 Three-axis projection of five satin woven composite geometric models;

[0034] Figure 7 Five unit cell finite element models of satin woven composites;

[0035] Figure 8 Front view of five satin woven composite unit cell finite element models;

[0036] Fig. 9 Mid-layer section of the finite element model of five satin-woven composite unit cells, including the warp yarns;

[0037] Fig.10 Side view of the finite element model of five satin woven composite unit cells;

[0038] Fig.11 Five straight sections of satin-woven composite single-cell weft yarns;

[0039] Fig.12Five satin-woven composite single-cell weft yarn segments;

[0040] Fig.13 Five satin-weave composite monocell warp yarns;

[0041] Fig.14 Five satin weave composite monocell warp yarns. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings.

[0043] The present invention provides a modeling method for a 2.5-dimensional satin woven composite material unit cell geometric model.

[0044] 1) Obtaining three-dimensional structural images of the internal structures of five satin materials, specifically,

[0045] Using X-CT scanning technology, five satin material specimen segments with a length exceeding one cycle were selected, and the segments were scanned layer by layer using X-rays. The three-dimensional structural images of the internal structures of the five satin materials were obtained using the matching imaging software.

[0046] 2) Assumptions on the cross-sectional shape and orientation of the fiber bundle, including the following assumptions:

[0047] 1. Assume that the cross section of the weft yarn is elliptical, and the cross sections of the warp yarn and the backing warp yarn are both rectangular;

[0048] 2. The lining warp yarn is straight, the warp yarn direction is a piecewise function, the contact part between the warp yarn and the weft yarn fits the outer contour line of the weft yarn, and the rest is a straight line;

[0049] 3. The weft yarn and the warp yarn are bent where they interweave, and the rest of the yarn remains straight;

[0050] 4. Perfect bonding between fiber bundles and between fiber bundles and matrix without extrusion, ignoring friction, and the cross-sectional area of ​​the yarn is equal everywhere.

[0051] 3) Divide and obtain the unit cell image, specifically,

[0052] The minimum period of the weaving structure cycle, i.e., the unit cell, is found from the three-dimensional structural image of the internal structure of the five-piece satin material to obtain a unit cell image. The unit cell can be used to obtain the entire complete five-piece satin structure through translation, symmetry, and cyclic repetition.

[0053] 4) Measure the geometric parameters required for unit cell modeling, specifically,

[0054] After the three-dimensional structural image obtained by X-CT is imported into CAD, the cross-sectional outer contour lines of the warp yarn, weft yarn and lining warp yarn are fitted with curves, the length, width and area of ​​the cross-sectional shape of each component of the warp yarn, weft yarn and lining warp yarn are measured, and then the total length of the unit cell in three directions is measured to provide a dimensional basis for the subsequent geometric model establishment.

[0055] 5) Draw a two-dimensional model of a unit cell, specifically,

[0056] Using the measured geometric parameters, the entire projection of the unit cell structure on a plane is drawn in a two-dimensional plane through the software UG, and stretched into a flat plate structure with thickness to obtain a unit cell two-dimensional model.

[0057] 6) Establish a unit cell three-dimensional finite element model, specifically,

[0058] The outer contours of different yarns in the unit cell two-dimensional model are stretched to the actual position along the straight line, the curved weft yarn is stretched along the oblique line, and the rest are stretched along the straight line to obtain the unit cell three-dimensional finite element model. Because the satin structure is complex, the intertwined yarns make the matrix have a large number of sharp corners, and the bending of the weft yarn also brings certain difficulties to the mesh division. Using the hypermesh software to divide the mesh is also conducive to optimizing the mesh quality.

[0059] Combination Figures 1 to 6 The five-layer satin material and its two-dimensional structure studied by the modeling method of the present invention are described in detail. The present invention establishes an effective geometric model of a 2.5-dimensional five-layer satin woven composite material. Figure 1 The diagram shows the weaving of warp and weft yarns of five satin structures. The horizontal yarn 1 is the warp yarn, and the vertical yarn 2 is the weft yarn. The warp yarns of the five satin materials span five rows of weft yarns in one cycle, and the warp yarns are interlaced between the upper and lower layers of weft yarns. Every four rows of weft yarns, there is an interweaving of the warp and weft yarns, which will cause the weft yarns to be misaligned and bent.

[0060] Figure 2 and Figure 3They are X-CT scans of the warp and weft directions of a 2.5-dimensional five-satin woven composite material. It was observed that the fluctuation of the warp yarn is different from the asymmetry of the ideal five-satin structure. The actual weft yarn arrangement is not aligned up and down, but has a certain degree of offset, which makes the fluctuation of the warp yarn also tend to be symmetrical and stable. The present invention takes this into consideration when establishing the geometric model, assuming that the lower weft yarn is located in the middle of the upper weft yarn. At this point, the division of the unit cell is determined, which is half of the complete cycle. The solid line frame in the figure is the selected unit cell. Draw the gauge in the X-CT imaging software, then import the CT scan image into CAD, fit the outer contour line, measure the cross-sectional dimensions of the yarn, and take the average value of multiple point measurements to determine the geometric parameters of the three fiber bundle cross sections, including the major and minor axes of the weft yarn with an elliptical cross section, the width and height of the warp yarn with a rectangular cross section, and the width and height of the lining warp yarn with a rectangular cross section. At the same time, the three-dimensional dimensions of the entire unit cell are measured.

[0061] Figure 4-Figure 6 It is a two-dimensional model of five satin woven composite materials drawn by UG. In order to make the general geometric model close to the real material structure and appropriately simplify it to improve the calculation efficiency, the following assumptions are made when establishing the model:

[0062] (1) The fiber bundles inside the material are closely arranged, there are no gaps in the interweaving, and no torsion occurs;

[0063] (2) The cross-sectional size and shape of all yarns are consistent everywhere, without considering extrusion deformation;

[0064] (3) Assume that the cross section of the weft yarn is a standard ellipse, and the major and minor axis dimensions are determined by the CT image measurement results; because the cross sections of the warp yarn and the backing warp yarn are both rectangular, and the warp yarn is a single-strand carbon fiber bundle, and the backing warp yarn is a double-strand, it is assumed that the two are of equal height, and the width of the backing warp yarn is twice that of the warp yarn;

[0065] (4) The direction of the warp centerline is assumed to be a piecewise function. The part in contact with the weft yarn is an elliptical curve that fits the weft yarn contour line, and the rest is a straight line tangent to the ellipse. The directions of the lining warp yarn and the weft yarn at the non-interlacing point are both straight lines.

[0066] (5) The weft yarn at the intersection of the warp and weft yarns is compressed and offset by a distance of the weft yarn thickness, and the lower weft yarn is located at the center position of the two weft yarns in the upper layer.

[0067] Figure 4 The middle lining warp yarn 3 runs from left to right, with a rectangular cross section, and the height and width are obtained according to the above measurement. The warp yarn 4 is woven from left to right, and the cross section is also rectangular, and the height and width are obtained according to the above measurement. The weft yarn 5 has two layers, the upper and lower layers, and the cross section is an ellipse, and the major and minor axis dimensions of the ellipse are obtained according to the above measurement. Figure 1The method shown is to weave around the weft yarn, because the weft yarn offset must be considered. The weft yarn position 21 before the offset and the weft yarn position 22 after the offset differ by a weft yarn height of 0.4mm. The warp yarn bypasses the weft yarn current position 22 from the weft yarn position 21 before the offset, and the warp yarn bypasses the weft yarn current position 24 from the weft yarn position 23 before the offset. The straight section is 12, and the length of the straight section is half of the length of the weft yarn section. The curved sections are 11 and 13, which are elliptical and fit the weft yarn section. The upper and lower layers of the lining warp yarn 3 are tangent to the upper and lower layers of the weft yarn 5 respectively. The height of the lining warp yarn is equal to half of the height of the weft yarn. The upper weft yarn on the back of the geometric model is 25, the lower weft yarn is 26, and the back lining warp yarn is 31. Figure 6 Middle front 6 corresponds Figure 5 , back 7 corresponds to the top Figure 4 The three-dimensional finite element model was established by layer-by-layer stretching, and the thickness of a single layer was 0.2 mm.

[0068] Figure 7-14 This is a finite element model of five satin woven composite materials. The model contains one layer of warp yarn, half layers of upper and lower layers, a single layer of lining warp yarn in the middle, two rows of upper and lower weft yarns, and the rest are matrix. Import the UG geometry and perform wire cutting using the Trimwith lines function. Divide the two-dimensional grid on the front view of the imported geometry model (including geometric lines), set the grid size as needed, and the reference size is 0.1mm. Consider that the weft yarn finite element model is divided into two parts: straight weft yarn that is not in contact with the warp yarn and curved weft yarn at the intersection of the warp and weft yarns, as shown in Figure 2. Fig.11 and Fig.12 As shown in the figure. The straight section a of the curved weft yarn is at the same height as the surrounding weft yarns, and the curved section c is lower than the surrounding weft yarns by the thickness of a weft yarn section. The meshes of the non-offset section a and the offset section c are stretched along a straight line, the same as the straight weft yarn. The transition section b is stretched along the oblique line in the hypermesh, and the matrix mesh around the transition section is divided into meshes by face-to-face mapping, as shown in the figure. Fig.10 As shown in FIG. 8 , the matrix mesh is mapped from section 81 to section 82 and section 83. The warp mesh and the backing warp mesh are stretched along the thickness direction of the unit cell model by hypermesh, and finally are respectively as shown in FIG. Fig.13 , Fig.14 shown.

[0069] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for modeling a 2.5-dimensional satin woven composite unit cell geometric model, characterized in that: The following steps are involved: 1) Obtain three-dimensional structural images of the internal structures of five satin materials; 2) Assumptions on the cross-sectional shape and orientation of the fiber bundle, including the following assumptions: (a) Assume that the cross section of the weft yarn is elliptical, and the cross sections of the warp yarn and the backing warp yarn are both rectangular; (b) The warp yarn is straight, the warp yarn direction is a piecewise function, the contact part between the warp yarn and the weft yarn fits the outer contour line of the weft yarn, and the rest is a straight line; (c) The weft yarn is bent where it interweaves with the warp yarn, while the rest of the yarn remains straight; (d) Perfect bonding between fiber bundles and between fiber bundles and matrix without extrusion, ignoring friction, and the cross-sectional area of ​​the yarn is equal everywhere; 3) Divide and obtain unit cell images; 4) Measure the geometric parameters required for unit cell modeling; 5) Draw a two-dimensional model of a unit cell; 6) Establish a unit cell three-dimensional finite element model, specifically, The outer contours of different yarns in the unit cell two-dimensional model are stretched to the actual positions along straight lines, the curved weft yarns are stretched along the oblique lines, and the rest are stretched along the straight lines to obtain the unit cell three-dimensional finite element model.

2. The modeling method of a 2.5-dimensional satin woven composite material unit cell geometric model according to claim 1, characterized in that: The step 1) obtains the three-dimensional structural images of the internal structures of five satin materials, specifically, Using X-CT scanning technology, five satin material specimen segments with a length exceeding one cycle were selected, and the segments were scanned layer by layer using X-rays. Three-dimensional structural images of the internal structures of the five satin materials were obtained using imaging software.

3. The modeling method of a 2.5-dimensional satin woven composite unit cell geometric model according to claim 1, characterized in that: The step 3) divides and obtains the unit cell image, specifically, The minimum period of the weaving structure cycle, i.e., the unit cell, is found from the three-dimensional structural image of the internal structure of the five-piece satin material, and a unit cell image is obtained. The unit cell can be used to obtain the entire complete five-piece satin structure through translation, symmetry, and cyclic repetition.

4. The modeling method of a 2.5-dimensional satin woven composite unit cell geometric model according to claim 3, characterized in that: The step 4) measures the geometric parameters required for unit cell modeling, specifically, After importing the three-dimensional structure image obtained in step 1 into the computer software, curve fitting is performed on the cross-sectional outer contour lines of the warp yarn, weft yarn, and lining warp yarn, and the length, width, and area of ​​the cross-sectional shape of each component of the warp yarn, weft yarn, and lining warp yarn are measured. Then, the total length of the unit cell in three directions is measured to provide a dimensional basis for the subsequent geometric model establishment.

5. The method for modeling a 2.5-dimensional satin woven composite unit cell geometric model according to claim 1, characterized in that: The step 5) draws a unit cell two-dimensional model, specifically, Using the measured geometric parameters, the entire projection of the unit cell structure on a plane is drawn on a two-dimensional plane through computer software, and stretched into a flat plate structure with thickness to obtain a unit cell two-dimensional model.

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