How to actually fix a defect
Finding a defect is half the job; removing it without damaging what's underneath is the other half, and it's a skilled trade. First decide whether it's a rework job at all: gaps and overlaps that come from the toolpath get fixed in programming. Then fix fast, because adhesion grows with time; peel with heat, evenly, along the fibres; splice shallower than one tow thickness; use laser projection to see where; and on big curved parts, let the machine re-lay just the repair tows.
Predict · at 1:07 in the video
A defect is found two hours after it was laid. Why is it harder to fix than if it had been found two minutes after?
Because the tows keep bonding. The longer you wait, the stronger the adhesion between neighbouring tows. And the harder it is to lift one tow out cleanly, without pulling its neighbours or the ply below.
Automated Fiber Placement: Status, Challenges, and Evolution, Ramy Harik & Alex Brasington.
- Chapter 6, section 3.A
- Chapter 6, section 3.B
Simulations in this lesson are our own. Where the numbers are invented to show a mechanism, the video says so on screen.
