Process Fragility in the Manufacture of Kevlar Wing Root Panels

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James Curran
Process Fragility in the Manufacture of Kevlar
Wing Root Panels

• Complex curvature
• Kevlar
• Sandwich panel
• Geometrical tolerances
• Foiling cure
• Increased production rate

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Increasing scrap rate NDT (ultrasonic,
X-ray, geometry)

• RED panels further down production line
• Unconventional
• No destructive analysis
• Production item (no interference, limited
  changes)

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NDT Failures
14 plies
Simplified cross-section
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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

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Kevlar prepreg volatile content
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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