Additive Manufacturing: Continuous Fiber Placement and Continuous fiber 3D Printing?

Updated: Jun 8


Overview

  • Continuous fiber reinforcement is the key to achieve higher strength

  • The resin or matrix holding the fiber should have no voids and is not more than 35-38% of the structure

  • Either high voids or lower percentage reduces the performance exponentially

  • Fiber Placement: Works by pulling strips of fiber-plastic tapes and pressing it onto a predefined simple shape.

  • Fiber Printing: Extruding the filament through a heated nozzle in X-Y layers to create a highly complex shape.

  • Pure polymer printing: Extruding thermoset or thermoplastic plastic through a heated nozzle in X-Y layers to create a highly complex shape.

  • Hybridization: A combination of fiber placement and fiber printing applied to the manufacturing process

  • The best place to use each approach

Fiber

Composites typically comprise a polymer material and a reinforcing material, like continuous fiber. The composite material offers higher strength and stiffness compared to non-reinforced polymers due to the presence of fiber, the polymer plays the role of the stress distribution medium. Continuous fiber ensures the load is distributed across the length without a weak point.

Resin - Polymer -Matrix

The matrix has a key role to play as a structural member in transferring the load between the fiber. In order to be able to do that, the polymer should be

  • Bonded really well to each fiber

  • Bonded within itself really well without air bubbles


Fiber-resin density

As the fiber is the most critical member taking the load, you aiming to maximize the percentage of fiber in given composites. A theoretical maximum for fiber is 66.66% but some of the best composites structures any range between 60-65% is considered ideal.


Fiber Placement

Automated Fiber Placement (AFP) is the additive manufacturing process that uses fiber-polymer tape as input and the AFP head places this fiber-polymer tapes with the help of heat and pressure. This process can result in additively manufactured parts that are two times stronger than steel at one-fifth of the weight (which is excellent); however, the technology traditionally requires million-dollar AFP systems (which is not great). Addcomposites has recently launched its new AFP-XS platform, which utilizes a technology they call “plug-n-produce” automated fiber placement (AFP-XS), that radically reduces the structure and cost of the typical AFP process.


Fiber printing

Fiber printing refers to the extrusion technologies where a fiber-polymer filament is heated and extruded in an X-Y plane. The extrusion technologies have a layer to layer bonding issues as there is no pressure applied at the end of each layer. However, the pointed tip enables much more complex part production.


Pure polymer printing

When the pure polymer (thermoset to thermoplastic) is extruded at a controlled flow rate through a pointed nozzle. The printing nozzle is most often mounted onto the x-y-z platform to create

Hybridization




The best use cases



Getting to Know the Base Materials

First, it is essential to understand that base materials are "mixed" to create these composite materials. Almost all the materials used in this process are a blend of fiber elements, for example, carbon fiber or fiberglass and a polymer such as nylon, PEEK or PEKK. The Fiber platform allows for the blending of these materials in a machine that is small enough and safe enough to use in an office setting.


What are they and how do they differ? Each process has its strengths and weaknesses. We will dive into them and provide insight on which one you should choose for your specific application. Let's get started!


While choosing a technology for your futuristic manufacturing needs, polymer-based additive manufacturing (3D printing) is oftentimes one of the most obvious choices. However, despite their ubiquitous presence and low cost, the technology is still finding its place in the dog-eat-dog world of manufacturing. The main challenge has been the degradation of the 3D printed part over its lifetime, and its structural strength when compared to conventional processes.


In order to address this, one of the most interesting developments in 3D printing has been the advent of composites (fiber-reinforced) 3D printing. The key here is to combine the high-strength, lightweight composites with low-cost, rapid 3D printing manufacturing.


An alternative method of digitized production of composites, which has been gaining popularity only recently, is called Automated Fiber Placement (FP). This method was developed in the 1970s, primarily for producing aerospace structural parts. This meant that the capability to repeatedly produce aerospace-grade parts far outweighed the overall cost, leading to each system costing millions of dollars in acquisition alone. Given the difference in the cost and operational flexibility of 3D printing and AFP, it is worth exploring the validity of composite 3D printing for your needs.



The Fundamental Difference in Manufacturing Composites

The purpose of this article is to bring the differences between composite 3D printing and AFP processes to light, so let's start with briefly defining the technologies.


- Fiber-reinforced 3D printing: Single plan layer of melted material reinforced with fiber is extruded onto a flat mold surface. The two main categories we will focus on are short fiber and continuous fiber. Short fiber printing uses individual sections of fiber, creating a part with decent overall strength, but not great in any one direction. This is similar to creating parts with chopped strand mat glass. Continuous fiber printing uses long fibers that are similar to unidirectional (UD) sheets, and provide excellent strength in tension. The differences are shown below.


- Fiber Placement: Whereas in 3D printing the material is extruded, tape laying works by pulling strips of tape (usually unidirectional) along a surface, where complexity is determined by the tool's capabilities. The tapes can be either pre-impregnated with resin or dry, which are pulled from the laying tool, then heated and pressed onto the shaped mold. There are two main categories here as well: tapes using either thermoset resin or thermoplastic resin. Thermoset resin is the most common type of matrix material used today and is primarily used in aerospace, automotive, or marine applications. Thermoplastic is gaining popularity due to recyclability and development in its strength and is mainly used for pipes in the oil and gas industry.


Pros and Cons of Each Technology

The difference in the fundamental approach to producing fiber reinforced plastic (FRP) components using these processes creates unique results. The table below indicates the key advantages and disadvantages of these two methods.

Comparing Capabilities of 3D Printing & ATL

While each of these technologies uses the same principle of additive manufacturing, they are very different from each other. Neither technology is great at everything, and each provides unique use cases. So how do you know which one to choose? We need to look into the existing market solutions and determine which suits your needs better.



Choosing between AFP and 3D Printing