JP7176432B2 - Fiber orientation method and fiber orientation device - Google Patents

Description

The present invention relates to a fiber orientation method and a fiber orientation device.

For example, in composite materials containing fibers, it is necessary to design the fiber orientation to optimize the stiffness of the molded article. For example, Non-Patent Document 1 discloses a method of optimizing the fiber orientation by using the fiber orientation angle for each design point as a design variable. As another method, as shown in Non-Patent Document 2, a method is disclosed in which the streamline of the potential flow is set in the flow direction of the fiber and the fiber orientation is optimized so that the fracture index is minimized.

Shinya Honda, “Study on optimal design of curvilinear fiber composites and smart composites”, [online], June 8, 2013, The Japan Society of Mechanical Engineers Computational Mechanics Division, Design Informatics Study Group, [June 25, 2018 day search], Internet (URL: http://www.ifs.tohoku.ac.jp/cmd/reference/LS4_PDF/DI4_honda.pdf) Yusuke Yamanaka, 4 others, “Fiber Line Optimization in Single Ply for 3D Printed Composites Vol.6 No.4 p.121-131”, [online], October 2016, Open Journal of Composite Materials, 2016 October, [searched July 4, 2018], Internet (URL: http://file.scirp.org/pdf/OJCM_2016101214324183.pdf)

In the method shown in Non-Patent Document 1, discontinuous solutions may be obtained for the fiber orientation angles at adjacent design points, and actual molding by design fiber orientation may not be possible. In addition, in the method shown in Non-Patent Document 2, it may be difficult to show the fiber orientation with streamlines when the molded product has a complicated shape. Therefore, in any method, depending on conditions such as shape, design is difficult, and fiber orientation that achieves both rigidity and strength cannot be achieved.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and an object of the present invention is to provide a fiber orientation that is easy to design and achieves both rigidity and strength.

The present invention, as a first means relating to a fiber orientation method for solving the above problems, is a fiber orientation method for determining the fiber orientation of a molding of a material containing fibers, wherein the shape and load state of the molding are a pointing stress vector calculating step of calculating a pointing stress vector indexing the stress of the molding, and a fiber orientation based on the load path and the pointing stress vector and a fiber orientation step for determining the configuration.

As a second means relating to the fiber orientation method, in the first means, a vector calculated based on a stress tensor is used as the pointing stress vector in the pointing stress vector calculation step.

As a third means related to the fiber orientation method, in the first or second means, in the fiber orientation step, a fiber orientation vector is calculated by combining the load path and the pointing stress vector using a weighting factor. , is adopted.

As a fourth means relating to the fiber orientation method, in the third means, the weighting factor is the stress component of the molding.

As a fifth means relating to the fiber orientation method, in the third means, the weighting factor is the fracture index of the molding.

As a sixth means related to the fiber orientation method, in any one of the first to fifth means, in the fiber orientation step, whether or not the determined fiber orientation is larger than a predetermined minimum radius of curvature of the fiber A configuration is adopted in which a curvature determination step for determining is provided.

As a seventh means related to the fiber orientation method, in any one of the first to sixth means, convergence by determining whether a convergence parameter calculated based on the determined fiber orientation is equal to or less than a predetermined value A configuration is adopted in which a determination step is provided.

As an eighth means relating to the fiber orientation method, in the seventh means, a configuration is adopted in which the convergence parameter is determined based on the amount of deformation.

As a first means related to a fiber orientation device, a fiber orientation device for determining the fiber orientation of a molding of a material containing fibers, wherein the load path is calculated according to the shape and load state of the molding A setting unit, a pointing stress vector calculating unit that calculates a pointing stress vector indexing the stress of the molding, and a fiber orientation unit that determines fiber orientation based on the load path and the pointing stress vector, configuration is adopted.

As a second means related to the fiber orientation device, a configuration is adopted in which the Pointing Stress Vector calculator calculates the Pointing Stress Vector based on a stress tensor.

According to the present invention, the fiber orientation is determined based on the load path and the Pointing Stress Vector. Therefore, the fiber orientation of the molded article is closer to the load path and the pointing stress vector, allowing the load to be transmitted along the fibers in the molded article, i.e. increasing the stiffness and strength of the molded article. . Also, the load path and the pointing stress vector are continuously connected from the load point to the support point. Therefore, it is easy to continuously determine the fiber orientation based on the load path.

1 is a block diagram showing a fiber orientation device according to one embodiment of the present invention; FIG. FIG. 4 is a schematic diagram showing a method of calculating a stiffness index in one embodiment of the present invention; 1 is a flow chart showing a fiber orientation method according to an embodiment of the present invention; It is a figure showing an example of a stiffness index and a load course in one embodiment of the present invention. (a) is a graph showing the correlation between the amount of change and the number of calculations, and (b) is an example of fiber orientation for each number of calculations. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the fiber orientation display in one Embodiment of this invention, (a) is a cross-sectional perspective view, (b) is a whole perspective view.

An embodiment of a fiber orientation method and a fiber orientation device according to the present invention will be described below with reference to the drawings.

The fiber orientation device 1 according to the present embodiment includes a stress analysis unit 2, a stiffness index calculation unit 3, a load path setting unit 4, a pointing stress vector calculation unit 5, a fiber orientation unit 6, and a convergence determination unit 7. , and a fiber orientation output section 8 . The fiber orientation device 1 is provided as one function of a computer having a CPU, hard disk and memory. Such a fiber orientation device 1 determines fiber orientation when molding a composite material composed of resin and fibers molded by a 3D printer, an AFP device, an ATL device, or the like.

The stress analysis unit 2 acquires the design shape of the molding and the load applied to the molding, and analyzes the stress state of the molding.

Based on the strain energy, the stiffness index calculator 3 analyzes the stress at all nodes determined by the design shape of the molded product and the load state of the molded product, and calculates the stiffness index U*. Specifically, as shown in FIG. 2, the load point A and the support point B are determined, and the strain energy U when the point C is not fixed as shown in FIG. By calculating the strain energy U' when point C is fixed using a method such as the finite element method, the stiffness index U* at an arbitrary point C (node) is expressed as in the following equation (1). be done. The stiffness index U* is a parameter that indicates the strength of the connection between the load point A and the arbitrary point C. The stiffness index calculation unit 3 calculates stiffness indices U* at all nodes based on the following equation (1).

The load path setting unit 4 calculates the load path based on the design shape of the molding and the stiffness index U* of all the nodes. The load path setting unit 4 calculates a load transmission path (load path) based on the design shape of the molding and the distribution of the stiffness index U* in the loaded state. Specifically, the load path setting unit 4 plots a load path by sequentially connecting locations strongly coupled to the load point (locations with a large stiffness index U*), as indicated by white broken lines in FIG. 4 . set as In FIG. 4, the color density indicates the magnitude of the stiffness index U*, and the lighter the color (whiter), the greater the stiffness index U*. Such a load path is formed continuously from the load point to the support point. Note that the load path is output as a vector at each node.

The pointing stress vector calculation unit 5 calculates a pointing stress vector based on the stress tensor (see formula (2)) at each node from the design shape and load state of the molding. Specifically, the Pointing Stress Vector calculator 5 derives the vector expressions Vx, Vy, and Vz shown in Expression (3) from the stress tensor at each node based on the design shape of the molding and the load state. The Pointing Stress Vector calculator 5 defines the directions along the vector formulas Vx, Vy, and Vz as Pointing Stress Vectors. Such a pointing stress vector is a parameter calculated to optimize the strength of the molding, and visualizes how stress is concentrated. Therefore, by orienting the fibers along the pointing stress vector, it is possible to improve the strength of the molding.

The fiber orientation section 6 determines the fiber orientation based on the calculated load path. Specifically, the fiber orientation section 6 calculates the fiber orientation vector by weighting the load path and the pointing stress vector based on the following formula (4). In equation (4), V _ustar represents the load path and V _stress represents the Pointing Stress Vector. Also, the weighting factor α in equation (4) is, for example, a stress component, and a function represented by a variable that changes for each coordinate in the molding is used. Furthermore, the fiber orientation section 6 calculates the radius of curvature of the fiber when the fiber is oriented along the fiber orientation vector. Then, the fiber orientation unit 6 determines whether or not the radius of curvature of the fiber is larger than a predetermined minimum radius of curvature in order to orient the fiber in the design shape to such an extent that the strength of the fiber is not impaired.

The convergence determination unit 7 calculates and stores the deformation amount in the fiber orientation determined by the fiber orientation unit 6, and calculates the rate of change (convergence parameter) between the deformation amount calculated last time and the deformation amount calculated this time. Then, the convergence determination unit 7 determines whether or not the change rate of the deformation amount is smaller than a predetermined determination value.

The fiber orientation output unit 8 outputs the determined fiber orientation to the monitor. In addition, the fiber orientation output unit 8 outputs data on fiber orientation to a control device such as a 3D printer, an AFP device, and an ATL device.

A fiber orientation method by the fiber orientation device 1 according to this embodiment will be described.
First, in the fiber orientation device 1, the stress analysis unit 2 analyzes the stress of the molding, and the stiffness index calculation unit 3 calculates the stiffness index U* based on the above equation (1) (step S1). In the fiber orientation device 1, the load path setting section 4 calculates the load path based on the stiffness index U* (step S2). Note that step S2 corresponds to the load path calculation step in the present invention.

Then, the fiber orientation device 1 calculates a stress tensor in the Pointing Stress Vector calculator 5 (step S3). Then, the pointing stress vector calculator 5 of the fiber orientation device 1 calculates the pointing stress vector based on the above equation (3) (step S4). Note that steps S3 and S4 correspond to the Pointing Stress Vector calculation step in the present invention.

Subsequently, the fiber orientation device 1 calculates the fiber orientation vector by weighting the load path and the pointing stress vector based on the above equation (4) in the fiber orientation unit 6 (step S5). Further, the fiber orientation device 1 determines whether or not the radius of curvature of the defined fiber orientation vector is larger than the minimum radius of curvature in the fiber orientation section 6 (step S6). Then, if the curvature radius of the fiber orientation vector is smaller than the minimum curvature radius, that is, if the determination is NO, the step is performed again to calculate a new stiffness index U* and Pointing Stress Vector to change the fiber orientation. Return to S1. Note that step S7 corresponds to the curvature determination step in the present invention.

When the curvature radius of the fiber orientation is larger than the minimum curvature radius, that is, when the determination is YES, the fiber orientation device 1 determines whether or not the fiber orientation converges in the convergence determination unit 7. (Step S7). Specifically, the convergence determination unit 7 calculates the rate of change from the previously calculated deformation amount due to the fiber orientation. The convergence determination unit 7 determines that the fiber orientation has converged when the change rate of the deformation amount is equal to or less than a predetermined value. For example, as shown in FIG. 5, the fiber orientation gradually becomes constant in deformation each time the flow of steps S1 to S8 is repeated. Then, if the fiber orientation has not converged, that is, if the determination in step S7 is NO, the process returns to step S1 to change the fiber orientation by calculating a new stiffness index U* and pointing stress vector. return. Note that step S7 corresponds to the convergence determination step in the present invention. Moreover, step S6 corresponds to the fiber orientation step in the present invention.

When the fiber orientation converges, that is, when the determination in step S7 is YES, the fiber orientation device 1 causes the fiber orientation output unit 8 to , the defined orientation of the fiber F is displayed and output to an external device (step S8). In addition, FIG. 6 shows a case where fibers F are oriented in a molded article having a plurality of openings on a substantially hemispherical spherical surface. .
The fiber orientation device 1 determines the fiber orientation of the molded product by repeating the flow of steps S1 to S8.

According to the fiber orientation method according to this embodiment, the fiber orientation is determined based on the load path and the pointing stress vector. Therefore, the fiber orientation of the molded product becomes close to the load path and densely oriented at the site where stress is concentrated. As a result, in the molded article, the load can be transmitted along the fibers, and deformation can be prevented in areas where stress is concentrated, ie, the rigidity and strength of the molded article can be increased.

Moreover, according to the fiber orientation method according to the present embodiment, the Pointing Stress Vector is calculated based on the stress tensor. That is, it is possible to calculate the pointing stress vector based on the nodes used to calculate the stiffness index U*. Therefore, it is easy to calculate the pointing stress vector of the molding.

Further, according to the fiber orientation method according to the present embodiment, the weighting factor α between the pointing stress vector and the load path is a function that changes according to the coordinates in the molded article. This, for example, weights the Pointing Stress Vector at locations where stress is concentrated, and weights the load path at locations where stress is low, so that the location in the molding determines the proper fiber orientation and orientation. It is possible to Therefore, it is possible to appropriately increase the rigidity and strength of the molded product.

Moreover, according to the fiber orientation method according to the present embodiment, the curvature determination step of determining whether or not the radius of curvature of the fiber orientation is larger than the minimum radius of curvature is provided. When the fibers are bent beyond a certain curvature, they are unable to transmit the load, compromising the stiffness of the molded article. However, in the fiber orientation method according to the present embodiment, the fiber orientation does not exceed the bendable radius of curvature of the fibers. Therefore, it is possible to orient the fibers without impairing their rigidity, that is, to increase the rigidity and strength of the molded product.

Moreover, according to the fiber orientation method according to the present embodiment, it is provided with a convergence determination step of determining whether or not the amount of deformation of the fiber orientation has converged. Thereby, the fiber orientation is determined so as to optimize the amount of deformation. Furthermore, by providing the convergence determination step after the curvature determination step, it is possible to obtain a fiber orientation having suitable rigidity and strength while achieving a reasonable fiber orientation.

Although the preferred embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the above embodiments. The various shapes, combinations, and the like of the constituent members shown in the above-described embodiment are merely examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.

In the above embodiment, in the convergence determination step, convergence is determined based on the change rate of the deformation amount, but the present invention is not limited to this. In the convergence determination step, the convergence may be determined using the stiffness change rate as the convergence parameter. Further, in the convergence determination step, the convergence may be determined based on the stress change rate. Further, in the convergence determination step, the convergence may be determined based on the change rate of the fracture index. In this case, the convergence determination unit 7 calculates the stiffness, stress, and fracture index based on the determined fiber orientation, and similarly determines convergence based on the rate of change from the previous stiffness, stress, and fracture index.

In the above embodiment, the weighting factor α is the stress component, but the present invention is not limited to this. For example, the weighting factor α can also use the breaking index. The fracture index is a variable that indicates the degree of stress in a composite stress field. Similar to the stress component, the value is large at locations where stress is high in the molded product, and the value is small at locations where stress is low in the molded product. As a result, the pointing stress vector is weighted at the position where the stress is concentrated, and the load path is weighted at the position where the stress is small. It is possible.

In the above embodiment, the curvature determination step is performed, but it may be omitted depending on the shape of the molded product.

In the above embodiments, the fiber orientation method was described as the operation of the fiber orientation device, but the present invention is not limited to this. The fiber orientation method can also be a function in a 3D printer, AFP machine, ATL machine, or computer that designs the part.

1 Fiber orientation device 2 Stress analysis unit 3 Stiffness index calculation unit 4 Load path setting unit 5 Pointing stress vector calculation unit 6 Fiber orientation unit 7 Convergence determination unit 8 Fiber orientation output unit A Load point B Support point C Arbitrary point F Fiber

Claims (10)

A fiber orientation method for determining the fiber orientation of a molding of a fiber-containing material, comprising:
a load path calculation step of calculating a load path according to the shape and load state of the molding;
a Pointing Stress Vector calculating step of calculating a Pointing Stress Vector indexing the stress of the molding;
and a fiber orientation step of determining the fiber orientation based on the load path and the pointing stress vector. 2. The fiber orientation method according to claim 1, wherein, in said Pointing Stress Vector calculating step, a Pointing Stress Vector calculated based on a stress tensor is used as said Pointing Stress Vector. 3. The fiber orientation method according to claim 1, wherein in said fiber orientation step, a fiber orientation vector is calculated by combining said load path and said pointing stress vector using a weighting factor. 4. The method of claim 3, wherein the weighting factor is a stress component of the molding. 4. The method of claim 3, wherein the weighting factor is the fracture index of the molding. 6. The fiber orientation step comprises a curvature determination step of determining whether or not the determined fiber orientation is larger than a predetermined minimum radius of curvature of the fibers. The fiber orientation method described in . The fiber according to any one of claims 1 to 6, further comprising a convergence determination step of determining whether a convergence parameter calculated based on the determined fiber orientation is equal to or less than a predetermined value. Orientation method. 8. The fiber orientation method according to claim 7, wherein the convergence parameter is determined based on the amount of deformation. A fiber orientation device for determining the fiber orientation of a molding of a material containing fibers,
a load path setting unit that calculates a load path according to the shape and load state of the molding;
a Pointing Stress Vector calculator that calculates a Pointing Stress Vector indexing the stress of the molding;
A fiber orientation device, comprising: a fiber orientation unit that determines fiber orientation based on the load path and the pointing stress vector. 10. The fiber orientation device according to claim 9, wherein the Pointing Stress Vector calculator calculates the Pointing Stress Vector based on a stress tensor.

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