Fatigue Cracks and Ineffective Repairs

1
Fatigue Cracks and Ineffective Repairs

• Matthew R. Fox, Ph.D.,
• Materials Laboratory
• Brian K. Murphy, Structures Group Chairman

2
Wing Structure
Skin
3
Repair Doublers
Stringers
Spar cap
Skin
Outboard
Forward
4
Disassembly
16-inch skin crack
Outboard
Forward
5
Fracture Sequence
1) Stringer fracture
Outboard
Forward
6
Fracture Sequence
2) Skin crack
Outboard
Forward
7
Fracture Sequence
2) Skin crack
Outboard
3) Stop-drill holes
Forward
8
Fracture Sequence
4) Doublers installed
Fasteners installed through sealant
Outboard
Forward
9
Fracture Sequence
Outboard
5) Skin cracks link up
Forward
10
Fracture Sequence
Outboard
6) Spar cap fracture
Forward
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