The Method of Ply Generating in Composite Laminate in Fibersim

In Fibersim the digital design of the composite preforms laying process begins with the creation of laminates, which define the required preforms and its plies. The digital design of ply-based laying process, zone-based laying process, multi-ply-based laying process, and the methods of multi-ply and zone-based laying process are elaborated.


Overview
Due to the excellent performance, designability, and integrated forming advantages of composite components, they are highly favored in the current military market.However, the complexity of the laying process of composite preforms seriously restricts the efficiency of forming production.The laying manufacturing of composite prefabricated parts is time-consuming and laborious, and with poor quality consistency.There is an urgent need for technological improvement.

Figure 1. Ply generating and adjustment
Figure 2. Ply producibility and flat pattern Based on the digital design and laying manufacturing technology of composite prefabricated component laying process, the required layers are generated.The laying simulation and adjustment are carried out to obtain the expected laying results, till the final laying parts are generated.Each ply of parts can be unfolded and output for cutting by the cutting machine; The digital manufacturing data for layuping can be output to digital manufacturing equipment such as laser laying positioning devices for guiding layuping production through laser laying positioning.Realize the digital design and manufacturing process of large composite preforms and special-shaped components, effectively improving the quality of composite laying design and manufacturing [1][2][3] .

Requirements Analysis
Fibersim is a professional digital design software for composite preforms, which has the best performance in laying design and simulation.Model establishment and data processing require the connection of professional 3D design software UG, CREO, and Catia.By setting and adjusting the required laying information in Fibersim, model modification and design updates are carried out in professional CAD software.
The digital design of the laying process for composite preforms starts with the establishment of a laminate in Fibersim, which is used to define the required preforms and its layup.The basic and advanced module in Fibersim can be used for most types of product laying processes.There are several typical digital design methods such as ply_based laying process, zone_based laying process, multi_ply based laying process, and multi_ply and zone_ based laying process [4] .

The Laying Lrocess Digital Design of Composite Preforms
Analyze the characteristics of composite components and the required layings to construct laminate.The establishment of laminate lays the foundation for smooth generation of subsequent layers.

Define a Demanded Laminate
As shown in Figure 3, in the definition of laminate, it is necessary to link and select the tool surface defined in CAD, and their net boundaries, extended boundaries, etc.We can first creat a solid model of composite components, and then extract the required inner or outer surfaces as the required toolsurface.Pay attention to defining its correct laying direction.
The definition of toolsurface requires that it be a simply connected region.

The Rosette Definition
In the rosette definition as figure 4, it is necessary to link and select its working plane, origin, 0 degree direction, etc. defined in CAD software.There are four mapping types: standard rosette, translating rosette, radial rosette, and curve rosette [4][7][9] .The rosette specifies the 0 degree direction and variation pattern of fibers on a curved surface.Standard rosette is the most commonly used, but in special cases, it is necessary to choose the corresponding appropriate rosette.

Ply_based laying process digital design
Directly generate plies through defined laminates, with the default laying boundary being the net boundary, which can generate a full ply of the laminate as shown in Figure 5.
Wrapped ply can be used for lamination of partially overlapping wrapping areas.In the layer generation dialog box, as shown in Figure 6, select the wrapped ply checkbox, select the appropriate starting and ending curves, and pay attention to the direction of the laying starting.There should be a small overlap area in the laying area without gaps, as shown in Figure 7. Generate a wrapped ply as shown in Figure 8.
Directly generating plies through defined laminate is suitable for situations where the number plies is few and the structure of the laminate is relatively simple [1][5][6] .

3.3.2
Zone_based laying process digital design Firstly, define zones in the toolsurface, generate layers from the zones, and then generate plies from the layers.The definition of the zones corresponds to the design of different layup thicknesses of the product, and requires that all defined zones must cover all areas within the design boundary, that is, there should be no gaps between each zone.as shown in Figure 10.The digital design of laying process based on multiple plies generally starts with defining overlay zones.as shown in Figure 11, The interface that defining a zone and an overlay zone is exactly the same.The difference is that the number of laminate specification or material specification, in the zone definition it corresponds to the total number and information of the layers while in overlay zone it only correspond to the quantity and information of the reinforcement layers.

Multi-ply based laying process digital design
The drop off area from thick to thin is called the transition zone, which can be generated by Fibersim from the zones and laminate specifications without special definition.

Application Case Analysis
As shown in Figure 12, there are four zones in the laminate.If zone_based design is used to define the layer, four closely connected zones can be defined, with corresponding ply quantities of 4, 6, 10, and 12, respectively.If the overlay zones are used to define the layer, as shown in Figure 13, four overlay zones can be defined in sequence, with corresponding 4, 2, 4, and 2 layers respectively.Finally, a consistent layer result is generated, as shown in Figure 12.The preforms layers can be generated using zone_based digital design methods and multi_ply based digital design methods for laying processes, respectively.
As the layers shown in Figure 13, two laminates need to be defined since the overlay zones and zones cannot exist in the same laminate.Three closely connected zones are defined on laminate 1.Then, based on the laminate 2, four overlay zones are defined.Finally, the required layers of the product are generated [7][8][9] .Digital design for laying processes of this preforms is based on zones and multi_ply.

Conclusion
Defining a laminate and using appropriate methods to generate the required layers is the first step towards successful digital layer design in Fibersim.It can be flexibly used according to the laying characteristics of the product.
The definition and application of laminate specifications, material specifications, offset specifications, and splice groups are crucial in digital design for laying processes.Especially in the process design of laying large size and thick prefabricated components, application of various specifications make the design and modification of laying processes more efficient and standardized.
In cases where the product structure is complex or the number of plies is few, a digital design method of ply_based laying process can be used.The producibility of the ply are relatively complex, and manual intervention is generally required.By adding darts on the ply, its laying performance is reasonable .

Figure 3 .
Figure 3. Definition of a laminate Figure 4. Definition of a rosette 3

Figure 7 .
Figure 7. Definition of wrapped ply Figure 8. Generation of wrapped ply