1. Process Fragility in the Manufacture of Kevlar Wing Root Panels
James Curran
Process Fragility in the Manufacture of Kevlar Wing Root Panels
Location of wing root panel 2m
Complex curvature
Kevlar
Sandwich panel
Geometrical tolerances
Foiling cure
Increased production rate

2. Plan to double production rate
Roll-out in Toulouse
Increasing scrap rate
NDT (ultrasonic, X-ray, geometry)
RED panels further down production line
Unconventional
No destructive analysis
Production item (no interference, limited changes)

3. Simplified cross-section
NDT Failures
14 plies
Simplified cross-section

4. Key operations half-way through build
Vac bag
Ply 8
Adhesive
Honeycomb
Plies 1-7
Steel Tool
Problems:
Bridging
Core (positioning & moisture content)
Volatiles
Filler material
Poor consolidation

5. Steel Tool Areas signalled for more intensive working
Adhesive lay-up modified
Steel Tool
Plies 1-7
Honeycomb
Adhesive
Vac bag
Bleed pack
Bleed pack introduced for improved consolidation

6. Inadequate moisture management
Steel Tool
Plies 1-7
Honeycomb
Vac bag
Plies 8-14
Intensifier
Inadequate moisture management

7. Problems with honeycomb trim under floating intensifier:
Core filler
Problems with honeycomb trim under floating intensifier:
2: Resin bleed
3: Poor consolidation

8. Kevlar prepreg volatile content
19.4
19.6
19.8
20.0
20.2
15:00
15:30
16:00
16:30
17:00
17:30
18:00
Time
Mass (g)

9. Solutions:
New adhesive lay-up
Use of a bleed pack for all consolidation operations
Core moisture control
Core trimming
Core filler control
Kevlar moisture management
Perforated adhesive
Self-adhesive foil / elimination of separate foiling cure
New tooling