Automated Fibre Placement (AFP) is part of a family of manufacturing techniques, which refer to the precise laying of continuous fibre tapes to manufacture multi-layered composite products, typically with significant strength.
These techniques include:
The terms AFP and ATL are commonly used to describe similar manufacturing processes. Both terms fundamentally refer to the process of applying fibre reinforced tapes using a loaded roller system to create a part.
ATL typically refers to the application of a single wide tape to create a product, while AFP systems have greater control of how and where to lay multiple narrow tapes. As ATP uses multiple tapes, they are more easily “steerable” and can be added or removed individually. An AFP machine can cover a surface containing a higher degree of curvature than ATL. However, modern ATL systems now have improved control of tape start, cut and orientation. Therefore, the distinctions between the AFP and ATL techniques are not as clear as they once were.
Over the last 20 years both the processing equipment and the materials they use have advanced significantly. In particular, the demand for increased manufacturing rates and tighter tolerances on the final products have led to major design changes to the equipment and corresponding refinements to the materials.
As AFP moves towards the greater use of thermoplastic tapes changes to the equipment over recent years have seen the emergence of improved technologies such as in situ heating and the consolidation of the tape via laser or infrared technology.
As the materials used by AFP offer lighter weight with equivalent or greater strength than metals, they are being increasingly used in the aerospace sector and specialised industrial sectors such as oil and gas.
Originally, thermosets (typically epoxies) were used exclusively as the polymer matrix in order to bind the fibres together during the manufacturing process. There are many advantages to using thermosets, which include:
However, over recent years thermosets are being replaced by thermoplastic (typically PA6, PP, etc..) for the following reasons:
Although carbon fibre is still widely used as the preferred continuous reinforcement, other fibres such as glass and natural materials are starting to appear in the market.
Although AFP systems are usually bespoke for the particular application, they all consist of the following components:
AFP machines lay down a strip consisting of several individually narrow tapes (typically 3mm to 13mm in width) via a tape laying head in order to build-up the product. The tapes are fed into the head via the tape feeding system, which holds multiple bobbins or spools containing the tape. These spools typically hold around 1000m of tape per bobbin.
These tapes are precisely laid by AFP machines according to a computer program, which has been defined to give the final product the optimum alignment of the fibres based on the expected operational loads of the part being manufactured. The tape laying head is connected to a robot, which guides the head into the correct position during the process.
Over recent years there have been great advances in the optimisation of AFP layups using simulation software such as CGTech’s Vericut package. This type of simulation package has begun to replace the more basic programming software supplied by the machine builders. As a consequence this has allowed end-users to select the best machine for their product, while being able to have one software package to simulate and create suitable layups.
As per computer numerical control (CNC) of machining tools (such as drills, lathes, mills, etc.) it is now possible with AFP to design a part and simulate its manufacture offline. Composite design software tools take into account AFP manufacturing requirements early in the product development cycle allowing the direct transfer to the final manufacturing process.
Compared to other composite fabrication methods there are a number of key advantages and disadvantages of using AFP. These include:
There are a number of suppliers around the world who make equipment for applying fibre reinforced tapes to create a part. The apparatus they sell varies in size, complexity, as well as cost and the requirement for a particular application means that most machines are bespoke for a particular job.
Suppliers of AFP machines include:
The ongoing push for faster deposition rates, the development of new material combinations as well as the downward pressure on cost means that AFP will continue to evolve in the coming years. It is expected that thermoplastics will continue to replace thermosets as the preferred polymer matrix. Also the size of the heads with the compaction rollers will get smaller allowing a greater diversity of products to be made.
Composites Evolution has significant experience in the development and use of fibre reinforced tapes for AFP. Along with our standard Evopreg® Thermoplastic Tapes, we can manufacture pilot-scale quantities of a variety of tapes for initial evaluation, and can provide technical support to assist with application development.
Please feel free to contact us to discuss your requirements.
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About the author
Gary has worked in polymer research and development for over 30 years. After spending 10 years at an analytical instrument company, Gary returned to academia (Universities of London and Exeter), where he helped to develop thermoplastic polymer solutions for a range of industrial clients. In 2005, he joined Smithers Rapra, a supplier of materials testing and consultancy to the plastics, rubber and composite industries. Gary moved to his role of Senior Project Manager in 2013. During this time he has been focusing his efforts in the thermoplastic composites area of the business, helping to develop new material solutions and processes for the composite sector.All articles by this author