Common Defects in Automated Fiber Placement (AFP)

Automated Fiber Placement (AFP) enables precise, repeatable composite layups for complex structures — but like any advanced process, it comes with its own set of challenges.

If not carefully managed, AFP can produce defects that compromise part performance, increase scrap, and reduce production efficiency. In this article, we’ll highlight the most common AFP defects, explain their causes, and show how smart design, simulation, and automation can minimize these risks.

1. Gaps and Overlaps

When adjacent fiber tows are misaligned during placement, small gaps or overlaps can form between them.

Why it matters:

  • Gaps reduce fiber volume fraction and create resin-rich areas, which may weaken the laminate.

  • Overlaps can cause thickness build-up, uneven surfaces, or stress concentrations.

Root causes:

  • Inaccurate path planning

  • Poor machine calibration

  • Excessive compaction pressure or steering radius

Prevention tips:

  • Use accurate simulation tools for tow path generation

  • Optimize placement parameters for curvature and steering

  • Ensure regular maintenance of tow feeding and compaction systems

2. Tow Buckling

Buckling occurs when the tow is compressed during tight steering or rapid changes in curvature, causing it to wrinkle or distort.

Why it matters:

  • Buckled tows create local defects that reduce load-bearing capability

  • They can trap air and resin, leading to delamination or voids during curing

Prevention tips:

  • Limit steering radius for each tow width

  • Adjust tension and compaction force during curved placements

  • Use appropriate path planning strategies to minimize sharp curvature

3. Bridging

Bridging occurs when tows span across a concave surface without fully conforming to it, leaving voids underneath.

Why it matters:

  • Creates out-of-plane defects that reduce structural performance

  • Difficult to detect visually before curing

Common causes:

  • Insufficient compaction pressure

  • Rapid placement over deep contours

  • Improper heat or tack control

How to avoid it:

  • Slow down placement speed over complex geometry

  • Maintain consistent heat and tow tack

  • Design tooling and layup angles to minimize unsupported regions

4. Tow Drops and Misfeeds

Tows may fail to feed correctly due to mechanical issues, spool tension variations, or sensor faults.

Why it matters:

  • Results in missing material or inconsistent layer build-up

  • Can cause serious inconsistencies in fiber coverage and laminate strength

Solutions:

  • Regular machine diagnostics and maintenance

  • Real-time monitoring systems to detect and correct misfeeds

  • Improved spool design and tow handling

5. Fuzzing or Fiber Fray

During tow placement, small fibers may break off or fuzz due to abrasion or poor cutting.

Why it matters:

  • Weakens surface quality and bond with subsequent plies

  • Can lead to voids or poor resin flow during curing

How to reduce it:

  • Maintain sharp cutting blades and clean feeding paths

  • Use cleanroom standards where possible to minimize contamination

  • Inspect and replace damaged tows early

Leveraging Simulation and Process Automation

Many of these defects originate from how the AFP process is planned and executed. Using advanced simulation tools during the design and path planning phase helps identify high-risk areas—such as tight curvatures or conflicting tow paths—before the machine is ever run.

Automated quality monitoring and closed-loop feedback also reduce variation during production. By aligning virtual simulation with physical layup, engineers can minimize trial-and-error and improve first-time-right success rates.

Final Thoughts

While Automated Fiber Placement offers unmatched precision and repeatability, the process isn’t immune to error. By understanding common AFP defects—and proactively addressing them through smart path planning, machine control, and simulation—manufacturers can unlock the full potential of this technology.

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