Filament Winding Process Overview and Outlook

 

Filament Winding Process

This paper divides the existing fiber winding process into core-mold fiber winding, coreless fiber winding and space fiber winding.

 

Core-mold fiber winding (Filament Winding, FW) can be divided into traditional fiber winding and robotic fiber winding. In the traditional fiber winding process, after the fiber bundle passes through the resin bath, the speed of the conveying device and the rotation speed of the core mold are controlled to pull the impregnated fiber bundle so that it is wound on the core mold at different angles. After that, the impregnated fiber will be cured under appropriate time and temperature conditions to form a fiber winding product. The schematic diagram of the traditional fiber winding process is shown in Figure 1, which includes a bobbin, a resin bath and a core mold.

 

Filament Winding Process

This paper divides the existing fiber winding process into core-mold fiber winding, coreless fiber winding and space fiber winding.

 

Core-mold fiber winding (Filament Winding, FW) can be divided into traditional fiber winding and robotic fiber winding. In the traditional fiber winding process, after the fiber bundle passes through the resin bath, the speed of the conveying device and the rotation speed of the mandrel are controlled to pull the impregnated fiber bundle so that it is wound on the mandrel at different angles. After that, the impregnated fiber is cured under appropriate time and temperature conditions to form a fiber-wound product. The schematic diagram of the traditional fiber winding process is shown in Figure 1, which includes a bobbin rack, a resin bath, and a mandrel.

 

 

 

The characteristic of robotic fiber winding technology is that it is based on traditional fiber winding technology and uses industrial robots to complete fiber winding.

 

Robotic fiber winding technology is mainly composed of a core mold, a pay-off device, an industrial robot and auxiliary equipment.

 

Robotic fiber winding technology uses a multi-degree-of-freedom robotic arm to rotate a core mold or a pay-off device for fiber winding, which can be divided into two main working modes. One is to pull the fiber through the robotic arm so that it can be wound and fixed on the core mold of the machine tool rotating equipment;

 

The other is to connect the core mold at the end of the robotic arm, and rotate the core mold by the robotic arm to pull the fiber out of the fiber pay-off device and wind it on the core mold,as shown in Figure 2.

 

 

Coreless Filament Winding Coreless filament winding (CFW) was first developed in 2012 by the Institute for Computational Design (ICD) and the Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart, combining engineering methods and computer design.

 

This novel robotic filament winding technology is a construction method that does not require a core mold. It usually uses a customized steel frame (or scaffolding) as a support, and anchor points are arranged on these steel frames (or scaffolding) according to the design requirements of the structure.

 

As shown in Figure 3, the coreless filament winding equipment mainly consists of an industrial robot Figure 3 (a) and a prefabricated frame Figure 3 (b).

 

During the construction process, the robot’s end effector pulls the resin-impregnated fiber filaments, and then continuously performs fiber winding movements around the frame according to the established fiber winding syntax and the robot’s motion planning path; the fiber material moves back and forth and freely crosses between the two anchor points as the robot’s end effector, and forms winding nodes at the anchor points; after repeated stacking and laying of fiber layers layer by layer, a structure with a multi-layer fiber shell is finally formed; after the impregnated fibers are solidified, the frame (or scaffolding) is removed to complete the manufacture of the fiber-wound component.

 

 

Spatial Filament Winding Coreless fiber winding is based on winding the fiber around the anchor point of the prefabricated frame, with the anchor point as the winding node, while spatial fiber winding (SFW) is based on coreless fiber winding and adds fiber winding in space. Spatial fiber winding forms nodes by winding one fiber around another fiber, as shown in Figure 4.

 

 

Coreless fiber winding realizes the construction of components by layered fiber winding, but the interaction between each fiber is limited to the surface contact between each fiber.

 

Spatial fiber winding expands the concept of winding nodes. By winding each fiber to create a winding node with multi-fiber interaction, the dependence on the frame is further reduced, so that components with multiple spatial winding points and large spans can be created.

 

Spatial fiber winding requires that the fibers can move freely in space during the weaving process, so multiple systems are required to work and build together.

 

As shown in Figure 5, a spatial fiber winding device mainly includes an industrial robot and a movable gantry, on which a rigid frame with anchor points is installed.

 

The spatial fiber winding process can create various geometric shapes in the same frame to form multiple winding nodes, and introduces a multi-step curing process, which can iteratively manufacture continuous large-scale spatial frame structures.

 

 

Filament Winding Construction Technology

Since coreless fiber winding technology abandons the expensive core mold required for traditional fiber winding, it releases the space originally occupied by the core mold compared with traditional fiber winding technology, and has the potential to be applied to large-scale buildings and their components.

 

Therefore, some scholars at home and abroad have also begun to use coreless fiber winding technology to build large-span building structures. This paper defines coreless fiber winding technology applied in the field of construction as fiber winding construction technology.

 

It is mainly aimed at the actual field of construction engineering, aiming to use coreless fiber winding technology to achieve fast, accurate and automated construction of large-scale fiber winding buildings and their components.

 

The fiber winding construction system mainly includes winding material system, integrated computing system and autonomous construction robot system, which combines multiple disciplines and technologies such as civil engineering, materials science, computer technology, mechanical equipment and numerical control technology.

 

Basic Principles

The basic principles of fiber winding construction technology are as follows: fiber winding construction technology is based on coreless fiber winding technology. Through comprehensive design and calculation, a fiber winding path planning scheme is generated. Modeling methods are used to simulate the fiber winding construction process and calculate the performance of the fiber winding structure. The fiber winding path is optimized and iterated according to the simulation results. At the same time, the optimized fiber winding path generates instructions to control the robot to perform fiber winding and weaving, and finally realize the automated construction of the fiber winding structure.

 

Fiber winding construction technology adopts a combination of simulation and prototype experiments. By using different winding materials and adjusting the density of the fiber laying layer, it can realize the automated construction of large-scale assembled or integral fiber winding structures, with the characteristics of fast, accurate and automated construction.

 

The most typical application of fiber winding construction technology is the coreless fiber winding research project led and continuously developed by ICD/ITKE of the University of Stuttgart, Germany.

 

Since 2012, ICD/ITKE has discussed a new design strategy and construction method for building structures, the coreless fiber winding technology, based on research in the field of lightweight fiber reinforced composite materials. At the same time, it has carried out continuous research on it, focusing on the comprehensive computational design, simulation and construction process of fiber reinforced composite buildings, and successfully applied the fiber winding construction technology to multiple research projects.

 

Material System

As the raw material for winding, fiber materials have a very important influence on the appearance and performance of the subsequent winding building structure. Fiber winding building structures usually use carbon fiber winding layers as the load-bearing structure of the winding building structure, bearing the main load and making up for the defects of insufficient strength and stiffness of the building structure.

 

The glass fiber winding layer is the outer shell of the winding building structure and serves as the supporting layer for carbon fiber winding. Composite materials composed of resin matrix and traditional reinforcing fibers such as glass fiber and carbon fiber have good performance and have been widely used in fiber winding building structures.

 

However, the problem of environmental pollution and resource waste caused by its non-degradability and difficulty in recycling has become increasingly prominent. In the fiber material system, natural plant fibers have the advantages of wide sources, low prices, low wear on processing equipment, environmental protection and renewability. At the same time, they have excellent properties such as high strength, large modulus, hardness, friction resistance and blister resistance, and play an increasingly important role in the field of new composite materials.

 

Therefore, some scholars have also proposed the use of natural plant fibers (such as cotton, linen, bamboo, wood fiber, etc.) as raw materials for fiber winding construction, aiming to achieve green, environmentally friendly and sustainable construction.

 

Mechanical Equipment

Common fiber winding construction mechanical equipment combinations include robotic arms and end effectors that can adapt to fiber winding requirements, winding frames, etc.

 

Different structural design requirements may require the determination of different construction equipment, as shown in Figures 3 and 6. Since fiber winding construction is aimed at large-scale construction engineering fields, large industrial robots are generally used as the main winding tools, such as KUKA robotic arms.

 

Common industrial robot mechanical systems include: robotic arms, control systems and handheld operation programmers. At the same time, fiber winding construction requires robot motion path planning according to design requirements and building structure forms.

 

 

The Robot Coreless Fiber Winding Device is Shown in Figure 6, Including:

① industrial robot;

② yarn rack;

③ fiber tension mechanism;

④ robot end effector;

⑤ winding frame;

⑥ continuous steel pipe;

⑦ positioner;

⑧ H-shaped steel beam;

⑨ glass fiber;

⑩ carbon fiber.

 

Anchor points are generally designed on the winding frame, and different numbers of anchor points can be designed according to different load-bearing requirements of the structure, as shown in Figure 7 (a) ~ (b).

 

The curve of the winding frame can be subdivided into a sufficient number of anchor points as nodes for fixing and winding the fiber material, and the frame is removed after the fiber material is solidified.

 

In addition, a rotating chassis is sometimes configured at the bottom of the winding frame. When the winding on one side of the structure is completed, the fixed robot arm can continue to wind the fibers on the other side of the structure by rotating the frame, thereby completing the construction of the entire structural component within a limited working range, further improving the flexibility of the robot arm.

 

 

Application of Fiber Winding Construction Technology

In recent years, the rapid development of robotic construction in the construction field has opened up new possibilities for building design and construction. The new fiber winding construction technology generated by the combination of construction robots and fiber winding technologies has successfully applied fiber winding construction technology in the construction field by adopting previously unfeasible process technologies and materials.

 

Monolithic Buildings

Inspired by the principles of bionics, the ICD/ITKE Pavilion 2012 applied the principle of differentiated fiber arrangement in the exoskeleton of arthropods to fiber winding construction, explored the digital simulation of fiber interactions during the manufacturing process and the discretization of carbon fiber and glass fiber to achieve different stiffness gradients, as shown in Figure 14. As the first research project for the application of fiber winding construction technology, the ICD/ITKE Pavilion 2012 demonstrated the great potential of fiber winding construction technology to create lightweight structures.

 

 

In order to overcome the limitation of the working space of the robot device, ICD and ITKE combined the remote working drone with the industrial robot with limited working range, and proposed a multi-machine collaborative construction system using autonomous drones and industrial robots to build long-span composite structures. The industrial robot is responsible for the pulling, tensioning and winding of the winding fibers, while the drone carries the winding fibers along the mold in the range where the two industrial robots cannot work, expanding the robot’s operating area and assisting the two industrial robots to complete the winding and weaving of the long-span structure, as shown in Figure 15 (a) ~ (b).

 

This structure shows that a strong thin-walled structure that can resist local buckling can be constructed through collaborative multi-machine fiber winding construction technology, which is suitable for large-span structures and architectural applications.

 

 

Prefabricated Buildings

Based on the morphological principles of elytra, ICD and ITKE of the University of Stuttgart explored the framework of a comprehensive computational design method that combines materials, structures, manufacturing and morphogenesis principles, and studied integrated design and digital construction processes. The team used fiber winding construction technology to design and successfully built modular components, and assembled them to form the ICD/ITKE Pavilion 2013-14 and the Elytra Pavilion, as shown in Figure 16.

 

 

From 2019 to 2021, ICD and ITKE successively designed and built three fiber winding construction projects, namely the BUGA Fiber Pavilion, the Maison Fiber Pavilion for Research and Prospects of Fiber Winding Construction Technology, and the Liv Mat S Pavilion. At the same time, the research objectives of these three projects are very different, ranging from high-performance large spans to hybrid building systems to alternative fiber materials. All three pavilions are architectural structures based on the assembly of fiber winding components, and all use a dual simulation test method of numerical simulation and mechanical testing of prototype components to prove the safety of the building structure.

 

Other Applications

Andreas Göbert et al. developed the 3D Wood Wind process aimed at using sustainable fiber alternatives. It uses continuous thin wood strips as fiber materials in the fiber winding process. Using a material system composed of adhesives and fibers, the team developed a computational design method for fiber layout and a robotic manufacturing method to successfully manufacture hollow lightweight components.

 

The team also demonstrated 3D Wood Wind manufacturing capabilities through several manufacturing case studies, providing possibilities for possible applications and future research in the construction industry, such as architectural and structural components, furniture, columns, beams, floor slabs, or facade components, as shown in Figure 20.

 

 

Conclusion and Outlook

 

This paper introduces the fiber winding process, especially the basic principles, material systems, mechanical equipment, key technologies and main applications of fiber winding construction, and draws the following three conclusions.

 

The current fiber winding process can be divided into three types according to the characteristics of its manufacturing process: core mold fiber winding, coreless fiber winding and space fiber winding. The biggest feature of core mold fiber winding is that a core mold or mold is required during the winding process; coreless fiber winding uses the anchor points on the frame as nodes for winding and weaving; space fiber winding is based on coreless fiber winding and adds fiber material winding in space;

 

Fiber winding construction technology is based on coreless fiber winding technology, and highly integrates factors such as weaving materials, robot design, winding and weaving algorithms, building forms and structures, demonstrating a new design logic and construction mode, representing a future development direction of building automation construction;

 

Fiber winding construction has been well practiced and applied both at home and abroad. Its application scenarios can be divided into integral buildings, prefabricated buildings and other structural or component forms, but most application scenarios still tend to be ornamental art buildings, and fiber-wound buildings that can be lived in by humans have not yet been realized.

 

Prospects

 

Looking at the existing fiber-wound construction methods and their applications at home and abroad, they all reflect its potential and adaptability in the field of construction. Although some scholars and institutions have also achieved certain research results, there are still some problems and challenges in terms of materials, machinery, computer design and numerical simulation. Regarding the research on future fiber-wound construction, this paper proposes the following research ideas and prospects.

 

Research on the intelligence of fiber-wound construction technology Although the current fiber-wound construction technology can realize the automated construction of structures through autonomous construction robots, its intelligence level needs to be improved. For example, fixed industrial robots are less flexible than mobile robots. The use of multi-machine collaborative construction is one of the future development directions of fiber-wound intelligent construction. In addition, most of the research on fiber-wound construction does not involve monitoring of the construction process and operation stage. Therefore, it is necessary to combine automated monitoring methods and visualization methods to conduct real-time monitoring of the construction process of fiber-wound structures and life cycle assessment of fiber-wound structures.

 

Research on green and sustainable winding materials Most of the research on fiber winding construction still uses glass fiber and carbon fiber as the main materials, which are non-degradable and difficult to recycle, which can easily cause environmental pollution and resource waste. Therefore, in the subsequent research on fiber winding construction, researchers need to pay attention to the recycling and reuse of fiber materials. Plant fiber reinforced composite materials play an increasingly important role in the field of new composite materials. The application of plant fibers instead of traditional reinforcing fibers in fiber winding construction technology can effectively alleviate environmental damage and resource crises while ensuring structural performance requirements.

 

More standardized design and construction At present, fiber winding construction has not yet formed a unified standard and specification system, and is basically blank in terms of technical standards and social and economic benefit evaluation. Therefore, in order to mature the application of fiber winding construction technology, it is necessary to study and formulate a complete set of technical standards and evaluation systems, including material performance standards, mechanical equipment standards, technical and structural evaluation standards, etc.

 

Structural practicality needs to be improved At present, most fiber winding construction applications are limited to ornamental buildings, and there is still a large gap from fiber winding buildings that are truly applied to serve human life. Therefore, researchers need to expand the application scenarios of fiber-wound buildings so that they are no longer limited to ornamental art buildings. At the same time, this also increases the complexity of the building structure and requires more precise design and simulation to promote the rapid development and widespread application of this technology.