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Low cost general aircraft composite design and manufacturing integration technology

low cost composite design and manufacturing integration technology has become one of the problems that the world general aircraft manufacturers must face and solve. Adopting digital design and manufacturing technology can improve product development and production efficiency, ensure product quality and reduce product cost [1]. This technology overcomes the waste caused by inaccurate positioning of layers and between layers and excessive material margin in the original composite manufacturing process, which mainly depends on mold line template. High performance continuous fiber composites provide great opportunities for the production of light and high-performance products, but the high material cost, design and product manufacturing complexity offset the use benefits of composites to a large extent. In order to reduce costs, improve the production efficiency of composite materials, shorten the development time of composite products, reduce material waste, reduce tool loss and production time, vistage company of the United States has developed the software fibersim for composite material manufacturing and Analysis on catia[2] software platform

Fibersim is a software toolkit integrated into CAD system, which can make CAD system become a high-performance software tool for designing and manufacturing composite parts. The unique composite simulation technology of fibersim software can predict how composite materials fit with complex surfaces, and visually show the fitting results. Fibersim software supports the whole engineering process of composite materials, enabling designers to make trade-offs between part geometry, materials, structural requirements and process constraints at the same time. Using fibersim software, designers can quickly visualize the ply shape and fiber direction, find manufacturing problems in the design stage, and take corresponding corrective measures; From preliminary design, detailed design to manufacturing workshop, composite parts are finally obtained

research content

1 research on the offset of ply and butt joint area

the prepreg has certain width limit. Through simulation analysis, if the ply exceeds the width limit of the material, the ply needs to be divided at an appropriate position, and the split ply needs to be butt jointed or overlapped. The size of the offset should be designed through software according to the design requirements [3]

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2 research on ply analysis and ply deployment design under complex surfaces

for the ply on complex surfaces, when carrying out two-dimensional deployment, it is often difficult to ensure that the ply can be deployed and that the deployed ply is consistent with the upper boundary of the 3D model. Only when the manufacturing feasibility analysis shows that the fiber deformation is within the acceptable range, the paving can be carried out. The algorithm of ply unfolding has the ability to draw the curve from 3D ply model to ply unfolding, that is, it can draw the tooling positioning hole (tooling cross line) of ply unfolding, as well as the cutting line, reference line and ply hole

it is impossible for the composite curve to determine the extremely accurate layering expansion, and an explanation can be found in the problem of making a world map

in the process of developing and drawing the earth plan, some quite good methods have been produced to accurately draw the area of the surface and the shape of the land block. These conditions are independent of each other, and it is impossible to ensure both shape and area, unless many cuts are added. If there are enough cutouts in a world map, theoretically, the map is quite accurate in shape and area; However, it is difficult for ordinary people to recognize. As for the development of composite laminates, just like drawing maps, the development of composite laminates is to draw each free-form surface into a plan. If too many cuts are applied to a ply, it will be difficult to lay the ply and affect the integrity of the part

(1) optimization of laying starting point

as mentioned earlier, the manufacturing feasibility analysis grid shows that there is minimal deformation around the starting point of placement. Moving the starting point forward reduces or even eliminates the deformation area. When the surface has a large curvature, the starting point offset points to one end of the ply to represent the shape there, and then other techniques are applied to reduce the deformation of the ply

(2) ply splicing

splicing is to butt the two boundaries cut by the ply together. If the two boundaries are external, the ply is cut into two blocks. 1. The positive deviation of the indication is out of tolerance. If one boundary is external and the other is internal, keep one ply. The implementation of the above situation in fibersim calculation is to force the lattice to calculate around the docking, so the continuous constraint of the lattice is broken at a specific position. As a result, there is little fiber deformation on the ply, but the fibers are no longer tangent at the splicing boundary

(3) ply trimming

cutting is similar to splicing, except that cutting only includes a boundary, and continuous fibers are broken between the starting point of placement and the deformation area. The cutting position is located between the starting point of laying and the deformation area, or it may only be closed in the deformation area. At the splice, the fiber is discontinuous at the shear

(4) marker length analysis

this is a technique for measuring the accuracy of ply unfolding. It includes defining marks (curves) between the two features that need to be measured in the unfolded layer, at the typical starting point of laying and the position of tooling holes. When the ply unfolding is defined, the marker will be automatically drawn on the unfolded ply. In the selfly module, the MLA function determines the mark and measures the length difference between 3D and 2D. The allowable difference in length is related to the selected material, which is reflected in the function of ply size and how much material can be stretched. In this case, the maximum allowable difference is defined as 1.27cm

(5) separate and connect

separation and connection technology is the last method. In fact, the paving is most accurate near the starting point of paving. In essence, this technology is to set multiple laying starting points on an unfolded layer, that is, to cut the 3D layer into several pieces. By analyzing the length on the mark, determine the cutting position of the ply to achieve the expected cutting area. The incision point is located where the distance between 3D and 2D begins to deviate significantly. Once the cut-off point is defined, the ply boundary is changed, and the manufacturing analysis lattice will be defined in the main part. One of the grid lines extends into the cut area and is projected onto the laying surface. These curves become fiber direction curves in the cut area, maintaining fiber continuity between the main body and the cut piece. The starting point of laying is set on the curve close to the cutting boundary. The optimized shape is generated at the common position between the two slices of the cutting line. The mark passes through the cut line, and the ply expansion will calculate each area, and different ply expansions will be combined in the plane with the mark

3 cutting position determination technology

for more complex parts, many red areas appear after simulation, which can not meet the requirements of design and manufacturing and affect the quality of parts. If too many cuts are applied to a ply, it will be difficult to lay the ply and affect the integrity of the part. Cutting is similar to splicing, except that cutting only includes a boundary, breaking the continuous fiber between the starting point of laying and the deformation area. The cutting position is located between the starting point of laying and the deformation area, or it may only be closed in the deformation area. At the splice, the fiber is discontinuous at the cutting position, and the correct design of the cutting position can greatly reduce or eliminate the red area

integrated design of design and manufacturing of demonstration and verification parts

1 selection and structure of demonstration and verification parts

general aircraft composite wall panel is selected as the demonstration and verification structure, and the location of demonstration and verification structure is shown in Figure 1

Figure 1 3D solid diagram of composite parts

demonstration and verification structure size 2000mm × 1000mm, it is a honeycomb sandwich structure, and the honeycomb edge is cut at an angle of 30 °. The upper skin adopts a layer of carbon fiber cloth, the lower skin adopts two layers of carbon fiber cloth, and the edge is locally strengthened with carbon fiber prepreg cloth. Due to the different shapes of the upper and lower surfaces of the honeycomb, two mold surfaces are defined respectively for the accuracy of the process simulation. Figure 2 (a) and (b) are the mold surface of the lower surface of the honeycomb and the mold surface of the upper surface of the honeycomb, as well as their static and extended boundaries

(a) lower surface view

(b) upper surface view

Figure 2 digital design surface view

2 layering process

the following is the process feasibility analysis of the demonstration verification piece, and figure 3 is the simulation of the ultra wide layering, which is not allowed and can be solved by the method of Figure 4

Figure 3 design simulation material super width

after simulating the layering according to the above design scheme, through the above design scheme, generate the effect diagram before the simulation of all the layering (see Figure 6), the simulation effect diagram of the layering after the design (see Figure 7), and the design simulation deployment diagram (see Figure 8)

Figure 4 simulation solution ultra wide view

(a) curve a

(b) curve b

Figure 5 Design Simulation Deployment curve

3 digital manufacturing process

Figure 7 is the deployment diagram of all simulation layers, and figure 8 is a DXF file generated by the deployment diagram for automatic blanking machine. The projection file generated according to the boundary of each layer and the blanking file generated according to the unfolding drawing of each layer are input into the projection device and the blanking device respectively. The projection device projects the outline of each layer on the tooling surface, and the automatic blanking machine cuts the flat unfolded shape of each layer on the prepreg according to the information on the blanking file. Finally, each layer cut by the blanking machine is paved according to the outline projected on the tooling, When all layers are paved, they are cured and formed, and the products are finally formed after cutting

Figure 6 effect drawing before simulation

after the three-dimensional model is built, it is used for the design and manufacturing of tooling, and is input into the special design/manufacturing software for composite materials to complete the layering deployment based on the three-dimensional model. Further extract the layering deployment data, generate the layout and blanking file dedicated to the blanking machine through the data interface, directly support the laser projection code of virtek and general scanning laser projection system and the layering file used for fiber placement, and input the above file information to the nesting system, automatic cutting machine, laser layering positioning system, fiber placement machine and other manufacturing equipment through the data interface, so as to automatically optimize the layout Blanking, precise positioning of each layer and fiber placement. The integration of composite material design and manufacturing realizes the seamless integration from the three-dimensional model of parts to manufacturing, greatly reduces the inaccurate laying size and laying direction, improves the product quality, automatically cuts and optimizes the layout, reduces material waste, and laser laying positioning eliminates manual cutting templates and manual laying samples. Figure 9 shows the digital design process of sandwich composite structure []

Figure 7 simulation effect of design and laying

overview of the benefits of the integration of design and manufacturing of general-purpose aircraft

this paper takes a certain type of general-purpose aircraft as an example, the main structure of the body is made of composite materials except for the main lifting ribs of the wing and some connecting structural parts. Taking the carbon fiber prepreg as an example, after the designer submits the theoretical size to the process, the process personnel should give the worker's operation allowance according to the theoretical size, which is more than 150%; Based on the quotation of main prepreg materials of Toray company in Japan, the quotation of main prepreg materials is shown in Table 1; The quotation list of equipment using fibersim software is shown in Table 2. According to table 3, after the design and manufacture of fibersim, some main structures of a single machine can save 52500 yuan, while the prototype machine is made of all composite materials

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