A method for optimizing parameters in the process of automatically laying prepreg tows

Abstract

The present invention provides a method for optimizing parameters in the process of automatically laying prepreg tows on a large-curvature surface structure, which includes establishing a functional relationship between the laying pressure on a planar structure and the indentation depth of a pressure roller based on a selected pressure roller material; dividing each ply into a plurality of strips, each strip being formed by a plurality of prepreg tows; obtaining a projection line by projecting the central axis of the pressure roller onto the strip, for each strip, the intersection point of the projection line and the strip trajectory line is the first intersection point, and the intersection point with the center line of the prepreg tow is the second intersection point, obtaining the reference indentation depth at the first intersection point, the indentation depth and the laying pressure at the second intersection point by using the aforementioned functional relationship according to the reference laying pressure at the first intersection point; obtaining the laying pressure range and the average laying pressure on the strip according to the laying pressures at the first intersection point and the second intersection point; establishing a uniformity function of the laying pressure on each strip, and adjusting the uniformity of the laying pressure on the strip according to the uniformity function.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing composite material structural parts, and more specifically, to a method for optimizing parameters in the process of automatically laying prepreg tows on a large-curvature curved surface structure. Background Art

[0002] The automatic fiber placement technology has the advantages of high material utilization rate and large laying freedom, so it has been widely used in the production and manufacturing of composite material structural parts in the aerospace field. The process of manufacturing composite material structural parts using the automatic fiber placement technology is as follows: under the control of an automatic fiber placement machine, the fiber placement head of the automatic fiber placement machine bundles multiple prepreg tows into a strip under the pressure of a pressure roller according to the layup, direction, and thickness determined by the design requirements, and lays the strip on a mold along the trajectory line of the strip planned by a computer to complete the automatic laying of the layup of the composite material structural part. Then, each layup is heated and softened and compacted and shaped to form a composite material structural part.

[0003] However, as Figures 1-3 shown, for a large-curvature curved surface structure, such as the leading edge panel structure of a wing or a hyperbolic panel structure, the pressure roller 4 conforms to the curved surface shape of the conforming surface 1 during the laying process. Therefore, as Figures 2-3 shown, for each strip 2, the pressure roller 4 generates a greater pressing depth and laying pressure F on the prepreg tow 3 closer to its central axis 41, and a smaller pressing depth and laying pressure F on the prepreg tow 3 farther from its central axis 41. Therefore, along the central axis 41 direction of the pressure roller 4, the distribution of the laying pressure and forming pressure on the prepreg tow 3 in the strip 2 is uneven.

[0004] Currently, for the automatic fiber placement preforming of a similar large-curvature curved surface structure, the number of prepreg tows 3 in the strip 2 is usually set based on engineering experience during the programming stage, and the optimal number of prepreg tows 3 in the strip 2 is finally determined through multiple actual trial layings to obtain a strip 2 with a uniform forming pressure distribution. Moreover, during the actual trial laying process, the bonding quality between the prepreg tow 3 at the edge position and the curved surface 1 is also improved by increasing the laying pressure or raising the laying heating temperature. However, increasing the laying heating temperature will increase the tendency of the fiber placement material to age, and increasing the laying pressure will also cause greater deformation of the fibers of the prepreg tow 3 near the central axis 41 of the pressure roller 4, thereby affecting the quality of the laid and formed composite material structural part.

[0005] At the same time, improving the laying and bonding quality by increasing the laying pressure and laying temperature requires multiple trial layings for verification on the one hand, and on the other hand, it will cause uneven stress and heat on the entire curved surface structure, thereby having a certain impact on the final performance of the formed composite material structural part. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problem of uneven distribution of laying pressure and forming pressure on the prepreg tow in the strip for a large-curvature surface structure in the existing automatic fiber placement technology, and provide a method for optimizing the parameters in the process of automatically laying prepreg tows on a large-curvature surface structure. This method establishes the functional relationship between the laying pressure and the roller indentation depth through a planar structure, analyzes the laying pressure on the prepreg tow of the strip, and obtains the uniformity function of the laying pressure of the strip in a single ply. The optimized number of prepreg tows of the strip is obtained by using the uniformity function, so as to obtain a strip with a uniform laying pressure distribution.

[0007] Specifically, the present invention provides a method for optimizing the parameters in the process of automatically laying prepreg tows on a large-curvature surface structure, characterized in that the method comprises:

[0008] Based on the material and properties of the selected roller material, establish the functional relationship between the laying pressure and the roller indentation depth through the process of automatically laying fibers on a planar structure;

[0009] Divide each ply into multiple strips on a computer, wherein the trace line of each strip corresponds to the path passed by the automatic fiber placement machine to complete the laying of the strip, and each strip is formed by a plurality of prepreg tows arranged side by side;

[0010] Project the central axis of the roller onto the multiple strips to obtain the projection line of the central axis of the roller. For each strip, set the intersection point of the projection line and the trace line of the strip as the first intersection point, set the laying pressure at the first intersection point as the reference laying pressure, and obtain the reference indentation depth at the first intersection point by using the functional relationship between the laying pressure and the roller indentation depth.

[0011] Set the intersection point of the projection line and the center line of each prepreg tow of the strip as the second intersection point, and based on the reference indentation depth, calculate the indentation depth at the second intersection point according to the distance between the second intersection point and the first intersection point, and then obtain the laying pressure corresponding to the indentation depth at the second intersection point by using the functional relationship between the laying pressure and the roller indentation depth.

[0012] Obtain the range of laying pressure and the average laying pressure on the strip according to the laying pressure at the first intersection point and the second intersection point;

[0013] Establish the uniformity function of the laying pressure on each strip by using the ratio of the range of laying pressure and the average laying pressure, and optimize the uniformity of the laying pressure on the strip according to the uniformity function.

[0014] According to an embodiment of the present invention, the roller material is configured as an elastomeric material with elasticity.

[0015] According to an embodiment of the present invention, each ply is divided into a plurality of strips by using automatic fiber placement software or other fiber placement trajectory programming software, and a trajectory line of each strip and a fiber placement trajectory for placing a prepreg tow corresponding to the center line of each prepreg tow in each strip are generated.

[0016] According to an embodiment of the present invention, a plurality of strips corresponding to each ply are divided according to the shape and size of the large curvature surface structure and the shape and size of the pressing roller, and a trajectory line of each strip is generated.

[0017] According to an embodiment of the present invention, the shape and size of the large curvature surface structure include the length, width and curvature of the surface, and the shape and size of the pressing roller include the length and radius of the pressing roller.

[0018] According to an embodiment of the present invention, the trajectory line of each strip is configured to coincide with the center line of each strip.

[0019] According to an embodiment of the present invention, the step of forming a projection line of the central axis of the pressing roller includes:

[0020] Select any point on the trajectory line of the strip as a reference point, make a normal vector of the surface and a tangent vector of the trajectory line at the reference point, construct a sectional plane of the central axis of the pressing roller according to the normal vector, tangent vector and the central axis of the pressing roller, and the intersection line of the sectional plane and the strip is the projection line.

[0021] According to an embodiment of the present invention, the reference point is set as the geometric center point of the strip.

[0022] According to an embodiment of the present invention, the reference placement pressure is set as the maximum placement pressure on the strip.

[0023] According to an embodiment of the present invention, the projection line intersects with a plurality of prepreg tows in each strip to form a plurality of second intersection points.

[0024] According to an embodiment of the present invention, the step of obtaining the pressing depth at the second intersection point includes:

[0025] Calculate the distance component of the distance between the second intersection point and the first intersection point in the vertical plane of the Cartesian coordinate system, and subtract the pressing depth at the first intersection point from the distance component, so as to obtain the pressing depth at the second intersection point.

[0026] According to an embodiment of the present invention, the step of optimizing the uniformity of the placement pressure on each strip according to the uniformity function includes:

[0027] By adjusting the number of prepreg tows forming each strip to change the number of second intersection points, thereby changing the pressure extreme value and the average placement pressure value on each strip, so that the placement pressure distribution on each strip is uniform.

[0028] According to an embodiment of the present invention, the difference value of the laying pressure is the difference between the maximum value and the minimum value of the laying pressure values at the first intersection point and the second intersection point, and the average laying pressure value is the ratio of the sum of the laying pressure values at the first intersection point and the second intersection point to the number of intersection points including the first intersection point and the second intersection point.

[0029] According to another embodiment of the present invention, the method further includes optimizing the distribution of the laying pressure on the strip by adjusting the number of prepreg tows of the strip at the place with a larger curvature of the curved surface according to the uniformity function, and appropriately increasing the number of prepreg tows of the strip at the place with a smaller curvature according to the optimized number of prepreg tows of the strip at the place with a larger curvature, so as to optimize the distribution of the laying pressure on the strip at the place with a smaller curvature by using the uniformity function.

[0030] According to another embodiment of the present invention, the method further includes laying the optimized multiple strips side by side with each other to form a ply with a uniform laying pressure distribution, and then laying and pressing the multiple plies layer by layer, so as to obtain a large-curvature surface structure with a uniform laying pressure distribution.

[0031] According to another embodiment of the present invention, the forming pressure at the first intersection point and / or the second intersection point is the component of the laying pressure along the normal direction of the curved surface at the first intersection point and / or the second intersection point.

[0032] On the basis of conforming to the common knowledge in the art, the above preferred embodiments can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0033] The positive and progressive effects of the above embodiments of the present invention are as follows:

[0034] 1. A functional relationship between the laying pressure and the pressing depth of the pressing roller is established through a planar structure;

[0035] 2. The laying pressure on the prepreg tows of the strip forming the curved surface structure is analyzed, and a uniformity function of the laying pressure of the strip is established;

[0036] 3. By adjusting the number of prepreg tows of the strip through the established uniformity function of the laying pressure, the uniformity of the laying pressure and / or the forming pressure of the prepreg tows of the entire curved surface structure at a single ply angle is improved, thereby significantly enhancing the actual laying quality and facilitating the manufacture of composite material structural parts with high quality;

[0037] 4. Based on the optimized number of prepreg tows of the strip at the place with a larger curvature, the number of prepreg tows of other strips is adjusted, so that the uniformity of the laying pressure of the strips of each ply is optimized, and at the same time, the number of trial laying times can be effectively reduced. Description of the Drawings

[0038] Figure 1Schematic diagram of automatically laying prepreg tows on a large - curvature curved - surface structure according to a preferred embodiment of the present invention.

[0039] Figure 2 Schematic diagram of automatically laying prepreg tows on a large - curvature curved - surface structure according to a preferred embodiment of the present invention.

[0040] Figure 3 Schematic diagram of automatically laying prepreg tows on a large - curvature curved - surface structure according to a preferred embodiment of the present invention.

[0041] Figure 4 Flowchart of a method for optimizing parameters in the process of automatically laying prepreg tows on a large - curvature curved - surface structure according to a preferred embodiment of the present invention.

[0042] Figure 5 It is Figure 4 Schematic diagram of the projection line of the central axis of the pressure roller on the strip in the method shown.

[0043] Figure 6 It is Figure 4 Schematic diagram of the pressing depths at the first intersection point and the second intersection point on the strip in the method shown.

[0044] Figure 7 It is Figure 4 Schematic diagram of the laying pressure and the forming pressure at the first intersection point and the second intersection point on the strip in the method shown. Detailed implementation manners

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only some embodiments of this application, rather than all embodiments. Based on the embodiments described in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the description of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including", "having", etc. in the description and claims of this application and the above drawings are open-ended terms. Therefore, "including", "having", for example, one or more steps, has one or more steps, but is not limited to only having this one or more steps. The terms "first", "second", etc. in the description and claims of this application or the above drawings are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship. In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include one or more of such features.

[0047] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the description and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments.

[0048] As mentioned above, it should be emphasized that when the term "including / comprising" is used in this specification, it is used to clearly indicate the presence of the described feature or component, but does not exclude the presence or addition of one or more other features, steps, or groups of features, steps. As used in this application, the singular forms "a", "an", and "the" also include the plural forms unless the context clearly indicates otherwise.

[0049] The term "and / or" in this application is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally represents an "or" relationship between the associated objects before and after.

[0050] The automated fiber placement technology has advantages such as high material utilization rate and large laying freedom, so it is increasingly widely used in the production and manufacturing of composite structural parts in the aerospace field. However, for a large-curvature panel curved surface structure such as the leading edge of a wing, such as Figures 1-3As shown, during the laying process, the pressure roller 4 conforms to the curved surface shape of the conforming surface 1, and the pressing depth is the largest at the prepreg tow 3 closest to the central axis 41 of the pressure roller 4. Therefore, the laying pressure F on this prepreg tow 3 is also the largest, and correspondingly, the forming pressure on this prepreg tow 3 is also the largest. It can be seen from this that the farther away from the central axis 41 of the pressure roller 4, the smaller the pressing depth generated by the pressure roller 4 on the prepreg tow 3, the smaller the laying pressure F received by the prepreg tow 3, and correspondingly, the smaller the forming pressure on this prepreg tow 3. Therefore, along the direction of the central axis 41 of the pressure roller 4, the distribution of the laying pressure and the forming pressure on the prepreg tows 3 in the strip 2 is uneven.

[0051] Currently, for the automatic fiber placement preforming of similar large-curvature surface structures, the number of prepreg tows 3 in the strip 2 is usually set based on engineering experience during the programming stage, and the optimal number of prepreg tows 3 in the strip 2 is finally determined through multiple actual trial layings, so as to adjust the laying pressure and the forming pressure of the prepreg tows 3 on the strip 2. In addition, during the actual trial laying process, the bonding quality between the edge or outermost prepreg tow 3 and the surface of the curved surface 1 is improved by increasing the laying pressure or raising the laying heating temperature.

[0052] However, increasing the temperature will increase the tendency of the fiber placement material to age, and increasing the pressure will also cause greater deformation of the fibers in the prepreg tow 3 closer to the central axis 41 of the pressure roller 4, thus affecting the laying quality. At the same time, the method of improving the laying quality by increasing the laying pressure and the laying temperature requires, on the one hand, multiple trial layings for verification, and on the other hand, it will increase the uneven force and heat on the entire formed curved surface structure, thus having a certain impact on the final performance of the large-curvature composite material curved surface structure. Moreover, for the automatic fiber placement forming of curved surface structures, a large number of literatures have shown that the uniformity of the laying pressure and / or the forming pressure distribution of the strip 2 has a great influence on the performance of the large-curvature composite material curved surface structure after forming.

[0053] Therefore, in view of the above problems, the present invention provides a method for optimizing the parameters during the automatic laying of prepreg tows 3 on a large-curvature surface structure. This method analyzes the laying pressure of the prepreg tows 3 forming the large-curvature surface structure during the fiber placement programming stage, obtains the laying pressure uniformity function of the strip 2, and optimizes the uniformity of the laying pressure on the strip 2 in a single ply. By optimizing the number of prepreg tows 3 in the strip 2 at the location with a larger curvature, the uniformity of the laying pressure received by the prepreg tows 3 in a single ply is improved, which is beneficial to improving the actual laying quality while reducing the number of trial layings.

[0054] Figure 4 The flowchart of the method for optimizing the parameters during the automatic laying of prepreg tows 3 on a large-curvature surface structure according to a preferred embodiment of the present invention is shown. AsFigure 4 As shown, the method includes the following steps: establishing the functional relationship between the laying pressure and the pressing depth of the pressing roller; dividing each ply into multiple strips 2 on a computer and determining the trajectory line of each strip 2; calculating the reference laying pressure and the reference pressing depth at the intersection of the projection line of the central axis 41 of the pressing roller 4 on each strip 2 and the corresponding trajectory line; calculating the pressing depth and the laying pressure at the intersection of the projection line and the center line of the prepreg tow 3 of the strip 2; establishing the uniformity function of the laying pressure on each strip 2 according to the laying pressure of each intersection obtained by calculation, and optimizing the uniformity of the laying pressure distribution on each strip 2 according to the uniformity function. The specific process will be further described in detail below with reference to the accompanying drawings of the specification.

[0055] Reference Figures 1-7 , as Figure 4 shown, first, establish the functional relationship between the laying pressure and the pressing depth of the pressing roller. The specific process includes: according to the given fiber placement material system, based on the material and properties of the selected material of the pressing roller 4, changing the pressing depth of the pressing roller 4 acting on the planar structure during the process of automatic fiber placement on the planar structure, and measuring the laying pressure on the planar structure corresponding to each pressing depth to establish the functional relationship between the laying pressure and the pressing depth of the pressing roller. For the planar structure, the forming pressure of the prepreg tow 3 is equal to the set laying pressure F.

[0056] In the given fiber placement material system, each prepreg tow 3 is the same, that is, the material and properties of each prepreg tow 3, as well as the length, width, and thickness, are the same. Set the width of each prepreg tow 3 to be w 0 , then the width of n prepreg tows 3 arranged side by side is nw 0 . At the same time, in the automatic fiber placement technology, the material of the pressing roller 4 can be an elastic elastomer material with different hardness and elastic modulus, such as silicone rubber. However, different materials of the pressing roller 4 have different sensitivities to the laying pressure. Therefore, the establishment of the functional relationship between the laying pressure and the pressing depth of the pressing roller needs to be based on the material and properties of the selected material of the pressing roller 4.

[0057] Under the given fiber placement material system, select the material of the pressing roller 4, and as Figure 5 shown, set the radius of the pressing roller 4 to be R. Preferably, the length of the pressing roller 4 is greater than or equal to the maximum width that the fiber placement head of the automatic fiber placement machine can lay at one time, and this maximum width corresponds to the maximum number of prepreg tows 3 that can be arranged side by side. Exemplarily, the number of tows of the fiber placement head can be 16, then the maximum width that the fiber placement head of this automatic fiber placement machine can lay at one time is the width formed by 16 prepreg tows 3 arranged side by side, and at the same time, the length of the pressing roller 4 is greater than the width formed by 16 prepreg tows 3 arranged side by side.

[0058] Subsequently, each ply is divided into a plurality of strips 2 on a computer, and the trajectory line of each strip 2 is determined. The specific process includes: based on the length of the compaction roller 4 and the maximum width that the fiber placement head of the automatic fiber placement machine can lay at one time, each ply is divided into a plurality of strips 2 on the computer and the trajectory line of each strip 2 is generated. The trajectory line of each strip 2 corresponds to the path that the automatic fiber placement machine passes through to complete the laying of this strip 2. There is a trajectory line for each strip 2, and this trajectory line is formed by a series of trajectory control points. In the actual laying process, a single ply usually includes a plurality of strips 2, and each strip 2 is formed by a plurality of prepreg tows 3 arranged side by side. The compaction roller 4 completes the laying of the strip 2 along the trajectory line. Exemplarily, each strip 2 includes at most 4 prepreg tows 3. Generally, the more prepreg tows 3 in the strip 2, the higher the laying efficiency.

[0059] Exemplarily, based on the automatic fiber placement software or other fiber placement trajectory programming software such as Fibersim software, for the large curvature hyperbolic panel surface structure, such as Figure 5 shown, according to the shape and size of the surface 1 and the compaction roller 4, each ply is divided into a plurality of strips 2, and the trajectory line S of each strip 2 is generated. The shape and size of the surface 1 include the length, width and curvature of the surface 1, and the shape and size of the compaction roller 4 include the length and radius of the compaction roller 4. Moreover, according to the divided strips 2 and the trajectory line S of the strips 2, a fiber placement trajectory S for laying a plurality of prepreg tows 3 arranged side by side in the strip 2 is generated 2 , where the fiber placement trajectory S of each prepreg tow 3 in each strip 2 2 corresponds to the center line of this prepreg tow 3. Preferably, the trajectory line S of the strip 2 is set to coincide with the center line of the prepreg tow 3 located at the center position of the strip 2. More preferably, the trajectory line S of the strip 2 is set to coincide with the center line of the strip 2. Set the initial laying pressure magnitude, which is the maximum laying pressure borne by the prepreg tows 3 in the strips 2 of a single ply.

[0060] Preferably, first lay the 0° fiber ply of the large curvature leading edge panel. Based on the surface structure and fiber placement programming, a plurality of strips 2 of the 0° fiber ply are produced, and the trajectory line S of each strip 2 and the center line S of each prepreg tow 3 in each strip 2 are extracted 2 .

[0061] As Figure 5 shown, extract the trajectory line S of the strip 2 and the center line S of the prepreg tow 3 of this strip 2 2 , where the curve equation of the trajectory line S is E(X, Y, Z)=0, and the curve equation of the center line S of the prepreg tow 3 of the strip 2 2 is F(X, Y, Z)=0.

[0062] Then, calculate the reference laying pressure and the reference pressing depth at the intersection of the projection line 42 of the central axis 41 of the pressing roller 4 on each strip 2 and the trajectory line S of each strip 2. The specific process includes: for each strip 2, project the central axis 41 of the pressing roller 4 onto the strip 2 to obtain the projection line 42 of the central axis 41 of the pressing roller 4. For each strip 2, set the intersection of the projection line 42 and the trajectory line S of the strip 2 as the first intersection point, set the first intersection point as the reference point, the laying pressure at the reference point as the reference laying pressure, and use the functional relationship between the laying pressure and the pressing depth of the pressing roller to obtain the reference pressing depth at the first intersection point.

[0063] In this embodiment, one of the multiple strips 2 is as Figure 5 shown, the central axis 41 of the pressing roller 4 is projected onto the strip 2 to form the projection line 42 of the central axis 41 of the pressing roller 4, and the projection line 42 intersects the trajectory line S of the strip 2 to form the first intersection point P i , and at the same time, the projection line intersects the center line S of each prepreg tow 3 of the strip 2 2 to form a plurality of second intersection points Q i . Among them, for each strip 2, the step of forming the projection line 42 of the strip 2 on the central axis 41 of the pressing roller 4 includes: selecting any point on the trajectory line S of the strip 2 as the reference point P i , and at the reference point P i make the normal vector of the surface 1 and the tangent vector of the trajectory line S . According to the reference point P i , the normal vector the tangent vector construct the section plane P of the central axis 41 of the pressing roller 4, the intersection line of the section plane P and the strip 2 is the projection line 42, and the central axis 41 of the pressing roller 4 is also located in the section plane P.

[0064] Exemplarily, the above process of forming the projection line 42 can be realized by extracting the trajectory line S of the strip 2 and the center line S of each prepreg tow 3 in the strip 2 2 and importing them into the CATIA software, generating the above section plane P in the CATIA software, and obtaining the intersection line of the section plane P and the strip 2. Set the laying pressure at the reference point as the reference laying pressure, then use the functional relationship between the laying pressure and the pressing depth of the pressing roller to obtain the reference pressing depth at the reference point, that is, obtain the reference laying pressure and the reference pressing depth at the first intersection point. As Figure 7 shown, the reference laying pressure of the reference point P i on the trajectory line S of the strip 2 is F 1 .

[0065] Another example, the step of forming the projection line 42 of the central axis 41 of the pressing roller 4 includes: selecting any trajectory point P on the trajectory line S of the strip 2i (Xi, Yi, Zi) is the reference point, and the normal vector of surface 1 is drawn through this point and the tangent vector of the trajectory line S The central axis 41 of the pressure roller 4 is perpendicular to the normal vector and the tangent vector And the distance from the reference point is the difference between the radius of the pressing roller 4 and the reference pressing depth, so that the curve equation of the central axis 41 of the pressing roller 4 is obtained as L(X, Y, Z)=0.

[0066] The reference laying pressure at the reference point is set to the laying pressure initially set in programming, and the reference pressing depth at the reference point can be obtained by using the functional relationship between the laying pressure and the pressing depth of the pressing roller, that is, the distance between the central axis 41 of the pressing roller 4 and the reference point. Preferably, the reference point is set to the geometric center point of the strip 2. More preferably, the reference laying pressure is set to the maximum laying pressure on the strip 2.

[0067] like Figure 7 As shown, the first intersection point P on the trajectory line S of strip 2 i The reference laying pressure is F 1 According to the curve equation L(X, Y, Z)=0 of the central axis 41 of the pressing roller 4, the projection line 42 of the central axis 41 of the pressing roller 4 on the curved surface 1 and the curve equation G(X, Y, Z)=0 of the projection line 42 can be obtained.

[0068] Preferably, the above steps are repeated to calculate multiple strips 2 of the ply, obtain the projection line 42 of the central axis 41 of the pressure roller 4 on each strip 2, and calculate the reference laying pressure and pressure depth of the pressure roller at the first intersection on each strip 2.

[0069] Next, for each strip, the pressure depth and placement pressure at the intersection of the projection line 42 of the central axis 41 of the pressure roller 4 on the strip 2 and the center line of the prepreg tow 3 of the strip 2 are calculated. The specific process includes: setting the intersection of the projection line 42 and the center line of each prepreg tow 3 of the strip 2 as the second intersection, and based on the reference pressure depth, calculating the pressure depth at the second intersection according to the distance between the second intersection and the first intersection, and then using the functional relationship between the placement pressure and the pressure depth of the pressure roller to obtain the placement pressure corresponding to the pressure depth at the second intersection. For each strip 2, the projection line 42 intersects with multiple prepreg tows 3 in the strip 2 to form multiple second intersections.

[0070] Exemplarily, the step of calculating the pressure depth at the second intersection includes: calculating in sequence the distances from the intersection of the cutting plane P and the center line of the prepreg tow 3 of the strip 2 to the center axis 41 of the pressing roller 4, and calculating the pressure depth value of the pressing roller at each second intersection according to the radius R of the pressing roller 4, that is, the pressure depth value of the pressing roller corresponding to the center line of different prepreg tows 3 in the strip 2.

[0071] like Figures 6-7 As shown, the second intersection point Q of any prepreg tow 3 in the strip 2 and the projection line 42 is i For example, Q is calculated by the following formula i The roller pressure depth at the intersection point is calculated, and then the laying pressure at the second intersection point is calculated based on the relationship between the laying pressure and the roller pressure depth. Figure 7 As shown, the second intersection point Q i The laying pressure at point is F 2 According to the above steps, the pressing depth and placement pressure of the second intersection point on each prepreg tow 3 in the strip 2 are calculated.

[0072]

[0073] Wherein, R is the radius of the roller 4, h Qi is the distance between the second intersection point and the central axis 41 of the pressing roller 4, h Pi is the distance between the first intersection point and the central axis 41 of the pressing roller 4, P i Q i is the spatial distance between the first intersection point and the second intersection point in Cartesian coordinates, nw 0 It is the width formed by the plurality of prepreg tows 3 arranged in parallel between the first intersection point and the second intersection point.

[0074] Alternatively, for each strip 2, the second intersection point Q formed by the intersection of the projection line 42 and the prepreg tow 3 of the strip 2 is calculated based on the curve equation of the projection line 42 and the curve equation of the center line of the prepreg tow 3 of the strip 2. i (xi, yi, zi). Calculate the distance component of the vertical plane between the second intersection and the first intersection in the Cartesian coordinate system, and subtract the pressure depth at the first intersection from the distance component to obtain the pressure depth at the second intersection, and then calculate the placement pressure at the second intersection based on the relationship between the placement pressure and the pressure depth of the roller. According to the above steps, calculate the pressure depth and placement pressure of the second intersection on each prepreg tow 3 in the strip 2.

[0075] Preferably, the above steps are repeated to calculate multiple strips 2 of the ply, obtain the projection line 42 of the central axis 41 of the pressure roller 4 on each strip 2, and calculate the reference laying pressure and pressure roller pressure depth of multiple second intersection points on each strip 2.

[0076] Then, based on the laying pressures of the first intersection point and all the second intersection points on strip 2 obtained through calculation, a uniformity function of the laying pressure on each strip 2 is established, and the uniformity of the laying pressure distribution on each strip 2 is optimized according to the uniformity function. The specific process includes: obtaining the range and average laying pressure of the laying pressure on strip 2 based on the laying pressures at the first intersection point and the second intersection points, and establishing the uniformity function of the laying pressure on each strip 2 by using the ratio of the range and average laying pressure of the laying pressure, and optimizing the uniformity of the laying pressure on strip 2 according to the uniformity function. Among them, the range value of the laying pressure is the difference between the maximum and minimum values of the laying pressure values at the first intersection point and the second intersection point, and the average laying pressure value is the ratio of the sum of the laying pressure values at the first intersection point and the second intersection point to the number of intersection points including the first intersection point and the second intersection point.

[0077] Specifically, the defined P can be calculated through the following formula i At the point, the uniformity function U of the laying pressure distribution of strip 2 along the central axis direction of the pressure roller 4. Among them, the larger the U value, the more uniform the laying pressure on strip 2.

[0078]

[0079] Among them, F max represents the maximum laying pressure value among all the intersection points, and F min represents the minimum laying pressure value among all the intersection points, and F aver represents the average value of the laying pressures of each intersection point on strip 2.

[0080] According to the laying pressure uniformity function, the laying pressure at any point on the trajectory line S of strip 2 and the laying pressure at any point on the prepreg tow 3 on strip 2 can be calculated, so as to obtain the laying pressure distribution on strip 2. For a ply at a certain angle, taking the strip 2 with the highest laying pressure distribution uniformity (i.e., the largest U value) as a reference, by adjusting the number of prepreg tows 3 in the strip 2 at the place with a larger curvature, the overall laying pressure distribution uniformity of this strip 2 can be improved, so as to ensure the uniform laying pressure distribution of the prepreg tows 3 of the entire curved surface structure.

[0081] Exemplarily, based on the above method, the laying pressure distribution uniformity of the prepreg tows 3 of each strip 2 of the 0° ply can be obtained. By adjusting the number of prepreg tows 3 in the strip 2 at the place with a larger curvature, the U value is increased, so as to improve the uniformity of the laying pressure borne by the prepreg tows of the entire ply. Specifically, the steps of optimizing the uniformity of the laying pressure on each strip 2 according to the uniformity function include: changing the number of the second intersection points by adjusting the number of the prepreg tows 3 forming each strip 2, so as to change the range value and average laying pressure value of the laying pressure on each strip 2, and make the laying pressure distribution on each strip 2 uniform.

[0082] The method further includes optimizing the distribution of the laying pressure on strip 2 by adjusting the number of prepreg tows of the strip at the location with a larger curvature of the surface according to the uniformity function. Then, according to the number of prepreg tows 3 of strip 2 at the location with a larger curvature after optimization, the number of prepreg tows 3 of strip 2 at the location with a smaller curvature is appropriately increased to optimize the distribution of the laying pressure on strip 2 at the location with a smaller curvature by using the uniformity function, so as to ensure the quality of the surface structural member while reducing the number of trial layings.

[0083] The method further includes laying the optimized multiple strips 2 side by side with each other to form a ply with a uniform laying pressure distribution, and then laying and pressing the multiple plies layer by layer, so as to obtain a large-curvature surface structure with a uniform laying pressure distribution.

[0084] In addition, as Figure 7 shown, a normal vector of surface 1 is made through the second intersection point, i.e., point Q i where and the included angle of is θ. When the laying pressure on the prepreg tow 3 at point Q i is F 2 , the forming pressure at point Q i is the component force of the laying pressure F 2 on the straight line where is located, that is, F 2 *cosθ. This force will cause the prepreg tow 3 to slip during the laying process, thus easily generating wrinkles or gaps.

[0085] When the laying pressure on the prepreg tow 3 at point P i is F 1 , the forming pressure at point P i is the component force of the laying pressure F 1 on the straight line where is located. Exemplarily, as Figure 7 shown, the forming pressure at point P i is equal to the laying pressure, both being F 1 . Generally speaking, the forming pressure at the first intersection point and / or the second intersection point on each strip 2 is the component of the laying pressure along the normal direction of the surface at the first intersection point and / or the second intersection point. Preferably, the forming pressure at each second intersection point can be calculated according to the laying pressure at each second intersection point on strip 2.

[0086] When the locus line S of strip 2 coincides with the center line of the prepreg tow 3 at the center position of strip 2 and point P i is any point on the locus line S, or point P i is the geometric center point of strip 2, and Q iWhen the point is located at the edge of the strip 2 or the center line of the outermost prepreg tow 3, the uniformity distribution function U of the forming pressure of the strip 2 S can also be calculated by the following formula.

[0087]

[0088] where F 1 is the forming pressure at point P i , F 2 *cosθ is the forming pressure at point Q i , F saver is the forming pressure at point P i , and the average value of the forming pressures at all points Q i .

[0089] Preferably, by adjusting the number of prepreg tows 3 in the strip 2 at the location with a larger curvature, the value of U S is increased, thereby improving the uniformity of the forming pressure of the prepreg tows 3 in the entire ply. Specifically, the steps of optimizing the uniformity of the forming pressure on each strip 2 according to the uniformity function of the forming pressure include: changing the number and included angle θ of the second intersection points Q i by adjusting the number of multiple prepreg tows 3 forming each strip 2, so as to change the maximum and minimum forming pressure differences and the average forming pressure value on each strip 2, and make the forming pressure distribution of the prepreg tows 3 on each strip 2 uniform.

[0090] Compared with the current method of analyzing the laying pressure or forming pressure distribution in the automatic laying process through finite element analysis or actual measurement, the present invention is based on the functional relationship between the laying pressure and the pressing depth measured in a flat plate structure, and the laying pressure distribution of any strip 2 on a single laying surface and the magnitude of the laying pressure at the center point of the prepreg tow 3 of the strip 2 can be obtained by using the CATIA processing software, making the analysis operation of the laying pressure simple and easy to implement.

[0091] For a single-layer ply, the maximum laying pressure received by the prepreg tow 3 depends on the set laying pressure value in the programming, and the number of prepreg tows 3 in the strip 2 determines the magnitude of the minimum laying pressure received by the prepreg tow 3. Therefore, after the filament laying program is generated, the set value of the laying pressure and the number of prepreg tows 3 in the strip 2 at the location with a larger curvature can be optimized by this method, so as to simply and quickly obtain the strip 2 with uniform laying pressure and forming pressure distribution. Compared with the traditional method of optimizing parameters through multiple trial layings, the method provided by the present invention reduces the workload and effectively improves the iteration efficiency.

[0092] In addition, compared with the method of using finite element analysis or measuring the laying pressure actually, the method provided by the present invention can analyze the laying pressure of the prepreg tow 3 in the curved surface structure quickly and relatively accurately. After the fiber placement path is generated, the uniformity of the laying pressure distribution of the curved surface structure is analyzed, and the setting of the laying pressure and the set value of the number of prepreg tows 3 in the strip 2 are optimized in advance, so as to reduce the number of trial layings and improve the actual laying quality. Moreover, the pressure analysis of the prepreg tow 3 is based on the generated fiber placement path, and the fiber placement path can also be iteratively optimized reversely according to the pressure distribution result of the prepreg tow 3 in a single layer, thus significantly improving the quality of the formed large-curvature composite material structural part and the iterative efficiency of the laying process of the prepreg tow 3.

[0093] Moreover, based on the trajectory line S of the strip 2 forming a single ply and the center line S of the prepreg tow 3 2 of the fiber placement program, the forming pressure distribution of the prepreg tow 3 on each strip 2 in the fiber placement process of the curved surface structure is given. In this way, with reference to the maximum forming pressure value of the strip 2 at a certain fiber angle, by adjusting the number of prepreg tows 3 in the strip 2 at the place with a larger curvature, the uniformity of the forming pressure of the prepreg tow 3 in the whole ply at a fixed fiber angle can be improved, the number of trial layings is reduced, and the damage to the prepreg tow 3 caused by the forming pressure is avoided, thereby ensuring the laying quality and the quality of the formed large-curvature composite material structural part.

[0094] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and the protection scope of the present invention is defined by the appended claims. Without departing from the principle and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A method for optimizing parameters in the process of automatically laying prepreg tows on a large-curvature surface structure, characterized in that, the method includes: Based on the material and properties of the selected pressure roller material, establish the functional relationship between the laying pressure and the pressure roller penetration depth through the process of automatic fiber placement on a planar structure; Divide each ply into multiple strips on a computer, where the trajectory line of each strip corresponds to the path passed by the automatic fiber placement machine to complete the laying of the strip, and each strip is formed by multiple prepreg tows arranged side by side; Project the central axis of the pressure roller onto multiple strips to obtain the projection line of the central axis of the pressure roller. For each strip, set the intersection point of the projection line and the trajectory line of the strip as the first intersection point, set the laying pressure at the first intersection point as the reference laying pressure, and use the functional relationship between the laying pressure and the pressure roller penetration depth to obtain the reference penetration depth at the first intersection point; Set the intersection point of the projection line and the center line of each prepreg tow of each strip as the second intersection point, and based on the reference penetration depth, calculate the penetration depth at the second intersection point according to the distance between the second intersection point and the first intersection point, and then use the functional relationship between the laying pressure and the pressure roller penetration depth to obtain the laying pressure at the second intersection point; Obtain the laying pressure range and average laying pressure on each strip according to the laying pressures at the first intersection point and the second intersection point; Establish the uniformity function of the laying pressure on each strip using the ratio of the laying pressure range and the average laying pressure, and optimize the uniformity of the laying pressure on the strip according to the uniformity function.

2. The method according to claim 1, characterized in that, the pressure roller material is constructed as an elastomeric material with elasticity.

3. The detection device according to claim 1, characterized in that, Use the automatic fiber placement software or other fiber placement trajectory programming software to divide each ply into multiple strips, generate the trajectory line of each strip and the fiber placement trajectory corresponding to the center line of each prepreg tow in each strip.

4. The method according to claim 3, characterized in that, Divide the multiple strips corresponding to each ply according to the shape and size of the large-curvature surface structure and the shape and size of the pressure roller, and generate the trajectory line of each strip.

5. The method according to claim 4, characterized in that, The shape and size of the large-curvature surface structure include the length, width and curvature of the surface, and the shape and size of the pressure roller include the length and radius of the pressure roller.

6. The method according to claim 1, characterized in that, The trajectory line of each strip is configured to coincide with the center line of each strip.

7. The method according to claim 1, characterized in that, The step of forming the projection line of the central axis of the pressure roller includes: Select any point on the trajectory line of each strip as a reference point, make the normal vector of the surface and the tangent vector of the trajectory line at the reference point, and construct the cross-section plane of the central axis of the pressure roller according to the normal vector, tangent vector and the central axis of the pressure roller. The intersection line of the cross-section plane and the strip is the projection line.

8. The method according to claim 7, characterized in that, The reference point is set as the geometric center point of the strip.

9. The detecting device according to claim 8, wherein, the reference laying pressure is set as the maximum laying pressure on the strip.

10. The detecting device according to claim 1, wherein, the projection line intersects with a plurality of prepreg tows in each strip to form a plurality of the second intersection points.

11. The method according to claim 1, wherein, the step of obtaining the indentation depth at the second intersection point includes: calculating the distance component of the distance between the second intersection point and the first intersection point in the vertical plane of the Cartesian coordinate system, and subtracting the indentation depth at the first intersection point from the distance component, so as to obtain the indentation depth at the second intersection point.

12. The method according to claim 1, wherein, the step of optimizing the uniformity of the laying pressure on each strip according to the function model includes: changing the number of the second intersection points by adjusting the number of prepreg tows forming each strip, changing the extreme value of the laying pressure and the average laying pressure value on each strip, so as to make the laying pressure distribution on each strip uniform.

13. The method according to claim 12, wherein, the extreme value of the laying pressure is the difference between the maximum value and the minimum value of the laying pressure values at the first intersection point and the second intersection point, and the average laying pressure value is the ratio of the sum of the laying pressure values at the first intersection point and the second intersection point to the number of intersection points including the first intersection point and the second intersection point.

14. The method according to claim 13, wherein, the method further includes: optimizing the distribution of the laying pressure on the strip by adjusting the number of prepreg tows of the strip at the place with a larger curvature of the surface according to the uniformity function, and appropriately increasing the number of prepreg tows of the strip at the place with a smaller curvature, so as to optimize the distribution of the laying pressure on the strip at the place with a smaller curvature by using the uniformity function.

15. The method according to claim 1, wherein, the method further includes: laying the optimized plurality of strips side by side with each other to form a ply with a uniform laying pressure distribution, and then laying and pressing the plurality of plies layer by layer, so as to obtain a large curvature surface structure with a uniform laying pressure distribution.

16. The method according to claim 1, wherein, the forming pressure at the first intersection point and / or the second intersection point is the component of the laying pressure along the normal direction of the surface at the first intersection point and / or the second intersection point.

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