CN115017763A - Method for rapidly predicting fiber shear angle of two-dimensional woven carbon fiber reinforced composite material after compression molding - Google Patents
Method for rapidly predicting fiber shear angle of two-dimensional woven carbon fiber reinforced composite material after compression molding Download PDFInfo
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Abstract
The invention relates to a method for quickly predicting a fiber shear angle of a two-dimensional woven carbon fiber reinforced composite material after compression molding, which comprises the following steps of: unfolding a target part based on a configuration to obtain a plate, and performing grid division on the plate to obtain a first model; meshing a female die of the compression molding die to obtain a second model; vertically projecting the first model onto the second model to obtain a third model; establishing a stress balance equation for the third model, and solving through linear elastic iteration to obtain a fourth model; performing compression molding simulation on the target part, taking a fourth model as an initial solution of iterative computation, and requiring that the shearing angle of the two-dimensional woven carbon fiber reinforced composite material in each grid unit is smaller than a preset shearing locking angle in any iteration step; and after iteration is finished, obtaining the fiber shearing angle distribution cloud picture after compression molding. The method can quickly and accurately predict the fiber shear angle after compression molding on the premise of ensuring the product to be qualified.
Description
Technical Field
The invention relates to a method for quickly predicting a fiber shear angle of a two-dimensional woven carbon fiber reinforced composite material after compression molding, and belongs to the technical field of compression molding of composite materials.
Background
In the aerospace field, composite materials are one of the most important materials, and have a higher status in lightweight manufacturing due to the fact that the composite materials have higher specific strength, specific rigidity, corrosion resistance and the like than traditional metal materials, and are widely used in military equipment and civil equipment. Among the many composite material molding processes, the compression molding process well balances the efficiency and cost of molding and is increasingly focused and applied in the industry.
The compression molding process and the thermoplastic composite material have high adaptability, and the thermoplastic composite material is solidified in a reversible process, so that the compression molding process can fully utilize the characteristic of repeated molding use to improve the production efficiency of parts, shorten the production period and reduce the production cost.
The two-dimensional woven carbon fiber reinforced composite material is a continuous fiber reinforced composite material, the reinforcement is carbon fiber, and the two-dimensional woven carbon fiber reinforced composite material has the advantages of high temperature resistance, high hardness, low density, corrosion resistance, good oxidation resistance, excellent frictional wear performance and the like. In the compression molding of the two-dimensional woven carbon fiber reinforced composite material, how to quickly and accurately predict the configuration and various defects of the molded part is one of the important directions of research of scholars.
In the compression molding process of the two-dimensional woven carbon fiber reinforced composite material, because the allowable range of tensile strain of the fabric in a plane is smaller, the molding of parts can not be completed by changing the thickness like metal, the molding process is more complicated than metal, the two-dimensional woven carbon fiber reinforced composite material is in-plane shear deformation for the shape of a mold designed by fitting, and the quality influence after the molding of the parts is obvious. Therefore, after the two-dimensional woven carbon fiber reinforced composite material is subjected to compression molding, not only the specific product outline needs to be considered, but also the influence of in-plane shear deformation on the product quality needs to be considered, which has important significance for shortening the design period and reducing the trial and error cost, but the applicant searches and finds that the product is still blank at present.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the compression molding method of the two-dimensional woven carbon fiber reinforced composite material is capable of rapidly and accurately predicting the distribution of the fiber shearing angles after compression molding on the premise of ensuring the product to be qualified.
In order to solve the technical problems, the technical scheme provided by the invention is as follows: a method for quickly predicting a fiber shear angle of a two-dimensional woven carbon fiber reinforced composite material subjected to compression molding comprises the following steps:
the method comprises the following steps that firstly, a target part is unfolded based on a configuration to obtain a plate, and the plate is subjected to grid division to obtain a first model; meshing a female die of the compression molding die to obtain a second model;
step two, registering the first model and the second model, and vertically projecting the first model onto the second model to obtain a third model;
step three, establishing a stress balance equation for the third model, and solving through line elastic iteration to obtain a fourth model; when linear elastic iteration is carried out, preset virtual material parameters are adopted;
step four, performing compression molding simulation on the target part based on the plate obtained in the step one, establishing a balance equation according to a virtual work principle to perform iterative computation during simulation, and taking a fourth model as an initial solution of the iterative computation;
during iterative calculation, any iteration step requires that the shearing angle of the two-dimensional woven carbon fiber reinforced composite material in each grid unit is smaller than a preset shearing locking angle, otherwise, the iteration is considered to fail; the shearing angle refers to the variation of an included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material, namely the difference between the included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material in each iteration step and the included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material in the first model;
and after iteration is finished, obtaining a shearing angle distribution cloud picture of the part after compression molding and simultaneously obtaining the contour line of the part after compression molding.
When the compression molding simulation is carried out, the plate is vertically projected onto the female die, and the stress balance equation is established through the virtual material parameters to carry out fairing, so that the initial solution is used as the initial solution during the simulation iterative calculation, and the initial solution is very close to the shape and the structure of a target part, so that compared with large-scale general finite element simulation software and special composite compression molding simulation software, the compression molding simulation method has the advantages of simple and quick modeling, short calculation time and the like under the condition that the precision meets the requirement, the compression molding simulation efficiency can be improved, and the shearing angle distribution cloud pictures and the contour lines of the compression molded part can be quickly obtained, so that the product design period is greatly shortened, and the trial and error cost is reduced.
In addition, during compression molding simulation, the shearing angle of the two-dimensional woven carbon fiber reinforced composite material in each iteration step is required to be smaller than the preset shearing locking angle in the iterative calculation process, so that the final product quality is prevented from being influenced by the overlarge shearing angle in the compression molding deformation process on the premise of meeting the product quality requirement in the compression molding process, the product design period is further shortened, and the test times and the test cost are saved.
Drawings
Fig. 1 is a schematic diagram of a first model.
Fig. 2 is a schematic diagram of a second model.
Fig. 3 is a schematic diagram of the principle of the vertical projection method.
Fig. 4 is a schematic diagram of a third model.
Fig. 5 is a schematic diagram of a fourth model.
FIG. 6 is a cloud of fiber shear angle distributions for ply angles of 0/90.
FIG. 7 is a cloud of fiber shear angle distributions for ply angles of 45/45.
Detailed Description
Examples
This embodiment further illustrates the present invention by taking a double dome element as an example.
The method for rapidly predicting the fiber shear angle of the two-dimensional woven carbon fiber reinforced composite material after compression molding comprises the following steps of:
step one, unfolding a target part based on a configuration to obtain a plate material, and performing grid division on the plate material to obtain a first model, as shown in fig. 1; the female mold of the compression molding mold is gridded to obtain a second model, as shown in fig. 2.
The target part is a theoretically ideal part structure, a female die of the compression molding die is obtained according to the structural design of the target part, and the size of the female die is supplemented to a certain extent based on the size of a plate. The shape of the plate and the structure of the female die are both technical characteristics to be verified and corrected, and the shape of the plate and the structure of the female die are reversely verified and corrected by quickly simulating the profile and the shearing angle of a part subjected to compression molding.
And step two, registering the first model and the second model, and vertically projecting the first model onto the second model to obtain a third model.
Assuming that the first model is parallel to the XY plane, the projection process of the vertical projection method is to solve the intersection point coordinates of the projection of each grid unit node on the first model along the Z-axis direction and the second model after the projection intersects. As shown in fig. 3, dotsAFor any grid cell node in the first model, its coordinates are known: the parallel line passing through the point and taking the Z axis intersects with the second model at the pointBThen point ofBI.e. points on the first modelAVertical projection onto the second model. Calculating the projection of all grid unit nodes on the first model to obtain a vertical projection grid of the plate on the female die, namely a third gridModel, as shown in fig. 4.
Step three, establishing a stress balance equation for the third model, and solving through line elastic iteration to obtain a fourth model; when linear elastic iteration is performed, preset virtual material parameters are adopted, for example, the adopted virtual material parameters are as follows: poisson's ratio =0.5, elastic modulus =1000 MPa. The virtual material parameters have the outstanding advantage that the shape of the fourth model is the same after the material of the part is changed, so that the step one to the step three can be omitted when the shearing angle of the part after the material is changed is predicted, and the prediction speed and efficiency are improved.
In the second step, taking point a as an example, when the included angle between the normal line of the grid cell where point B is located and the Z axis is small, the projection effect is good, but when the included angle between the normal line of the grid cell where point B is located and the Z axis is large, the vertical projection may bring large cell distortion, thereby affecting the accuracy and convergence of the subsequent calculation. Therefore, the third model should be smoothed after the vertical projection is completed.
In the vertical projection, the influence of external load is ignored, so the stress state of the plate is unbalanced, and the stress balance state needs to be solved by linear elasticity iteration. In implementation, preferably, a local coordinate system is established for any grid unit in the third model, a transformation matrix between the local coordinate system and the global coordinate system and a unit node internal force under the global coordinate system can be obtained, then, a newton-raphson iteration method is used for iterative solution, a displacement criterion is used as a convergence judgment criterion, namely, a node displacement norm is calculated, when the node displacement norm is smaller than a convergence judgment factor, iteration convergence is considered, and a fourth model (as shown in fig. 5) obtained after iteration is completed can ensure plate stress balance, the configuration is more accurate, and meanwhile, the quality of the grid unit is better.
And step four, performing compression molding simulation on the target part based on the plate obtained in the step one, establishing a balance equation according to a virtual work principle to perform iterative computation during simulation, and taking a fourth model as an initial solution of the iterative computation. The convergence criterion of the iterative calculation preferably adopts a displacement criterion and a residual force criterion, and the iteration is stopped after any criterion meets the requirement.
For a two-dimensional woven carbon fiber reinforced composite material, when a balance equation is established according to the virtual work principle, a non-orthogonal constitutive equation is required to describe the mechanical properties of the two-dimensional woven carbon fiber reinforced composite material in the deformation process, namely, the fact that the two-dimensional woven carbon fiber reinforced composite material has different strain components, stress components, directional elastic modulus, poisson ratio, shear modulus and the like along the weft direction and the warp direction of fabric fibers is required to be considered. The mechanical properties of the two-dimensional woven carbon fiber reinforced composite material during the deformation process are described by using non-orthogonal constitutive equations, which is the prior art document in the article "A continuous mechanical-based non-orthogonal structural consistent model for the above composite fabric" (author: X.Q. Pen, J.Cao, Composites Part A: Applied Science and Manufacturing, Volume 36, Issue 6, 2005).
During iterative calculation, any iteration step requires that the shearing angle of the two-dimensional woven carbon fiber reinforced composite material in each grid unit is smaller than a preset shearing locking angle, otherwise, the iteration is considered to be failed, and after the iteration is failed, the steps of modifying the mold design, re-placating the process and the like need to be returned for prediction, so that the trial and error efficiency can be further improved, and the product design period can be shortened; the shear angle refers to the variation of an included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material, namely the difference between the included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material in each iteration step and the included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material in the first model.
The calculation of the shear angle is the prior art, for example, refer to "carbon fiber woven composite material stamping test and simulation analysis" (author: gakuliang et al, kinetic energy material, volume 16 (44) of 2013, hereinafter referred to as "reference 1"). The following method is preferably adopted in this embodiment: and calculating the warp direction vector and the weft direction vector of the two-dimensional woven carbon fiber reinforced composite material in each iteration step after deformation according to the warp direction vector and the weft direction vector of the two-dimensional woven carbon fiber reinforced composite material in the first model and the deformation gradient matrix in the iteration process, and further solving the shear angle.
In the iteration process, for the two-dimensional woven carbon fiber reinforced composite material, the stress strain and the shear angle of the two-dimensional woven carbon fiber reinforced composite material are changed while the configuration of the part is changed, so that the stress strain and the shear angle need to be calculated in each iteration step, wherein the shear angle is an important parameter for predicting the forming defects of the two-dimensional woven carbon fiber reinforced composite material. The two-dimensional woven carbon fiber reinforced composite material is in a shape of a die designed for fitting, the main deformation mode is in-plane shearing deformation, the variation quantity of an included angle between radial fibers and latitudinal fibers of the two-dimensional woven carbon fiber reinforced composite material is called a shearing angle when the two-dimensional woven carbon fiber reinforced composite material is subjected to shearing deformation, the shearing angle is increased along with the continuous deformation of parts, meanwhile, the pulling force required by the same shearing angle change of the two-dimensional woven carbon fiber reinforced composite material is increased along with the increase of the pulling force, so that the shearing deformation of a sample is hindered due to the fact that mutual extrusion begins to occur between the two-dimensional woven carbon fiber reinforced composite material, and the integral shearing rigidity is increased. And when the shearing angle of the two-dimensional woven carbon fiber reinforced composite material reaches the shearing locking angle, the load is increased sharply, the interference between fibers is obvious, and the sample is wrinkled at the moment, so that any one iteration step requires that the shearing angle of the two-dimensional woven carbon fiber reinforced composite material in each grid unit is smaller than the preset shearing locking angle. The shear lock angle is related to the properties of the particular material and can be obtained by reference to material parameters.
After iteration is completed, the fiber shearing angle distribution cloud picture after compression molding is obtained, meanwhile, the part contour line after compression molding can be obtained, the shearing angle distribution cloud picture and the contour line are technical features concerned by research and development personnel and can be referred by the research and development personnel, and therefore modification and optimization are conducted on die design, processes and the like. The method for modifying the mold design and the process is the prior art, is mainly executed according to the experience of research and development personnel, relevant specifications and the like, and is not described any more. When the shearing angle is calculated, an orthogonal global coordinate system needs to be set firstly, after the global coordinate system is set, the fact that the weft direction of the fiber is consistent with the X-axis direction of the global coordinate system and is 0 °/90 ° of the ply angle, the included angle between the weft direction of the fiber and the X-axis direction of the global coordinate system is 45 °/45 ° of the ply angle is defined in the embodiment, different fiber shearing angle distribution cloud pictures can be obtained by setting fiber shearing angles of different ply angles, fig. 6 and 7 show the fiber shearing angle distribution cloud pictures when the ply angles are 0 °/90 ° and 45 °/45 ° respectively, and the wrinkling defect after the composite material is formed can be quickly predicted.
The innovation of the invention is that: 1) a relatively accurate initial solution of the compression molding simulation process is obtained through a rapid calculation method, the simulation efficiency is improved, and a shear angle distribution cloud picture can be obtained rapidly; 2) in the simulation process, the shear angle of the two-dimensional woven carbon fiber reinforced composite material is monitored, so that the molding defect caused by the overlarge shear angle is avoided, the product design period can be shortened, and the test times and the test cost are saved.
The invention simulates the compression molding of the two-dimensional woven carbon fiber reinforced composite material quickly, predicts the shear angle quickly, compares large-scale general finite element simulation software with special composite material compression molding simulation software, has the characteristics of simple and quick finite element modeling, short calculation time and the like under the condition that the precision meets the requirement, and can quickly obtain the shear angle distribution cloud chart and the part contour line, thereby effectively serving the compression molding of the two-dimensional woven carbon fiber reinforced composite material, saving the compression molding simulation time, saving the test times and the test cost and shortening the research and development period.
Claims (4)
1. A method for quickly predicting a fiber shear angle of a two-dimensional woven carbon fiber reinforced composite material subjected to compression molding comprises the following steps:
the method comprises the following steps that firstly, a target part is unfolded based on a configuration to obtain a plate, and the plate is subjected to grid division to obtain a first model; meshing a female die of the compression molding die to obtain a second model;
step two, registering the first model and the second model, and vertically projecting the first model onto the second model to obtain a third model;
step three, establishing a stress balance equation for the third model, and solving through line elastic iteration to obtain a fourth model; when linear elastic iteration is carried out, preset virtual material parameters are adopted;
step four, performing compression molding simulation on the target part based on the plate obtained in the step one, establishing a balance equation according to a virtual work principle to perform iterative computation during simulation, and taking a fourth model as an initial solution of the iterative computation;
during iterative calculation, any iteration step requires that the shearing angle of the two-dimensional woven carbon fiber reinforced composite material in each grid unit is smaller than a preset shearing locking angle, otherwise, the iteration is considered to fail; the shearing angle refers to the variation of an included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material, namely the difference between the included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material in each iteration step and the included angle between the warp direction and the weft direction of the two-dimensional woven carbon fiber reinforced composite material in the first model;
and after iteration is finished, obtaining a shearing angle distribution cloud chart of the part after compression molding, and simultaneously obtaining the contour line of the part after compression molding.
2. The method for rapidly predicting the fiber shear angle of the two-dimensional woven carbon fiber reinforced composite material after compression molding according to claim 1, wherein the method comprises the following steps: in the fourth step, the convergence criterion of the iterative computation is a displacement criterion and a residual force criterion, and the iteration is stopped when any criterion meets a preset condition.
3. The method for rapidly predicting the fiber shear angle of the two-dimensional woven carbon fiber reinforced composite material after compression molding according to claim 1, wherein the method comprises the following steps: in the fourth step, during iterative computation, the method for computing the shear angle of the two-dimensional woven carbon fiber reinforced composite material in each grid unit is as follows: and calculating the warp direction vector and the weft direction vector of the two-dimensional woven carbon fiber reinforced composite material in each iteration step after deformation according to the warp direction vector and the weft direction vector of the two-dimensional woven carbon fiber reinforced composite material in the first model and the deformation gradient matrix in the iteration process, and further solving the shear angle.
4. The method for rapidly predicting the fiber shear angle of the two-dimensional woven carbon fiber reinforced composite material after compression molding according to claim 1, wherein the method comprises the following steps: in the third step, a stress balance equation is solved through a Newton-Laplacian iteration method, and a displacement criterion is used as a convergence judgment criterion.
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