Automated Fiber Placement: Principles and Manufacturing Considerations.
How an AFP head turns programmed paths into a laminate, which process parameters matter most, and the defects that every AFP programme has to plan for.
What AFP Does.
Automated Fiber Placement lays narrow strips of pre-impregnated fibre, called tows, along prescribed paths on a tool using a numerically controlled machine. A compaction roller and a heat source at the head give each tow the pressure and temperature it needs to adhere to the surface below it.
The placement head is carried by an industrial robot or a gantry. Depending on the machine, it places a single tow or a band of several tows side by side, and it can cut and re-feed tows during a course so that plies follow the part boundary instead of being trimmed afterwards.
Published reviews describe AFP as combining strengths of filament winding and automated tape laying: controlled fibre orientation on complex surfaces, with less material waste than cutting plies from broadgoods.
Inside the Placement Head.
- Material delivery: spools or creels feed tows through guides to the head
- Cut and restart: knives cut individual tows at ply boundaries; feed rollers restart them
- Heating: the heat source is chosen for the material system, for example infrared or laser heating, and controls tack or melting
- Compaction: a conformable roller presses the tow onto the substrate
- Motion: the robot or gantry, plus any rotary axis or linear track, moves the head along the programmed path
The Parameters That Govern Quality.
Three parameters dominate layup quality: compaction force, layup speed and temperature. They interact. The review by Sun et al. notes that higher layup speeds require higher layup temperatures to keep tack, and that for thermoplastic tows the combination of compaction pressure, speed and heating governs void content.
Because these parameters depend on the specific tow, resin system and head, a process window has to be developed for each material and machine combination. It is established through trials, not taken from a data sheet alone.
Defects Every AFP Programme Plans For.
Gaps and overlaps
Adjacent tows that do not meet, or that cross. Reviews identify them as the predominant AFP defects, especially on curved or steered paths.
Twisted and missing tows
A tow that rotates during placement or fails to feed. Both change the local fibre architecture.
Wrinkles and puckers
Out-of-plane buckling of a tow, often linked to steering a tow around too tight a radius.
Bridging and voids
Tows that span a concave feature without consolidating, or trapped air between plies.
Foreign objects
Backing paper, debris or other contaminants introduced during layup.
Angle deviation
Fibre direction differing from the design intent, for example where paths converge on a curved tool.
Why Defects Matter Structurally.
Defects change the laminate the designer analysed. Studies summarised by Sun et al. report compression strength reductions of roughly 15 to 20 percent from gaps and overlaps in one test programme, and NASA's defect identity cards record that gaps can reduce local strength while overlaps can behave differently in constant-stiffness laminates.
The practical response is to define which defects are acceptable, at what size and where, before production begins, and to agree how they will be detected and dispositioned.
How AFP Layups Are Inspected.
- Visual and machine-vision inspection of each ply surface
- Laser profilometry for surface gaps and overlaps
- Thermographic monitoring of the newly placed tow against the substrate
- Post-cure non-destructive inspection, selected for the part and its acceptance criteria
Surface methods detect surface defects. Internal defects need volumetric inspection after processing.
AFP Is a Process Window, Not a Button.
AFP rewards engineering discipline: a validated material, a developed process window, toolpaths checked for steering and accessibility, and an inspection plan agreed before the first ply.
That is the approach DANTA is building around its AFP-led manufacturing direction.
- Sun, S., Han, Z., Fu, H., Jin, H., Dhupia, J. S., Wang, Y. (2020). Defect Characteristics and Online Detection Techniques During Manufacturing of FRPs Using Automated Fiber Placement: A Review. Polymers, 12(6), 1337. doi:10.3390/polym12061337
- NASA Technical Reports Server. Automated Fiber Placement Defect Identity Cards: Cause, Anticipation, Existence, Significance, and Progression. NTRS 20200002536.
- McArthur et al. (2024). Current research in automated fibre placement defect rework. University of Strathclyde repository.
Technical articles are general information. They do not replace application-specific engineering analysis, qualified professional advice or approved manufacturing instructions.
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