Podcast
Questions and Answers
What is the most frequently used inspection method in aviation?
What is the most frequently used inspection method in aviation?
Why is it important to thoroughly inspect a damaged composite structure?
Why is it important to thoroughly inspect a damaged composite structure?
What helps in determining whether damage on a composite structure is repairable?
What helps in determining whether damage on a composite structure is repairable?
Which document outlines inspection procedures, damage classification factors, and recommended repair methods?
Which document outlines inspection procedures, damage classification factors, and recommended repair methods?
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What do composite structures require besides ongoing inspection intervals?
What do composite structures require besides ongoing inspection intervals?
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Why do many metal inspection and NDT methods transfer to composite applications?
Why do many metal inspection and NDT methods transfer to composite applications?
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What is a useful tool for visual inspection to detect surface irregularities in composite materials?
What is a useful tool for visual inspection to detect surface irregularities in composite materials?
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Which type of defects can ultrasonic inspection detect in composite materials?
Which type of defects can ultrasonic inspection detect in composite materials?
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What is the purpose of tap testing inspection in composites?
What is the purpose of tap testing inspection in composites?
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In ultrasonic testing, which method involves generating ultrasonic pulses and receiving the return echo displayed on an oscilloscope?
In ultrasonic testing, which method involves generating ultrasonic pulses and receiving the return echo displayed on an oscilloscope?
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What are some defects that visual inspection with a magnifying glass can help detect in composites?
What are some defects that visual inspection with a magnifying glass can help detect in composites?
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Why is a tap testing tool used in composites inspection?
Why is a tap testing tool used in composites inspection?
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What is impact damage?
What is impact damage?
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Why are sandwich panel face sheets very susceptible to impact damage?
Why are sandwich panel face sheets very susceptible to impact damage?
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What is delamination?
What is delamination?
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What can accompany delamination, particularly when it occurs?
What can accompany delamination, particularly when it occurs?
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How does disbonding differ from delamination?
How does disbonding differ from delamination?
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What are the causes of delamination?
What are the causes of delamination?
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What can cause damage to the resin matrix of composite materials?
What can cause damage to the resin matrix of composite materials?
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Why is water intrusion a common problem with high-temperature repairs?
Why is water intrusion a common problem with high-temperature repairs?
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What issue can arise from holes drilled in the wrong location, size, or number in composite materials?
What issue can arise from holes drilled in the wrong location, size, or number in composite materials?
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How does water intrusion impact honeycomb cores in aircraft structures?
How does water intrusion impact honeycomb cores in aircraft structures?
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Which factor contributes to the progression of converting a small area of damage into a larger one during repairs?
Which factor contributes to the progression of converting a small area of damage into a larger one during repairs?
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What can lead to hole damage in composite materials?
What can lead to hole damage in composite materials?
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What is the most desirable type of permanent repair to a composite structure?
What is the most desirable type of permanent repair to a composite structure?
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What is the purpose of potted repairs in composite structures?
What is the purpose of potted repairs in composite structures?
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In the damage assessment and repair process for composites, what is done after laying up and installing the repair?
In the damage assessment and repair process for composites, what is done after laying up and installing the repair?
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What is a disadvantage of filling a hole with a resin-and-filler mixture in composite repairs?
What is a disadvantage of filling a hole with a resin-and-filler mixture in composite repairs?
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Why is it important to inspect the repair site for structural integrity after the repair procedure?
Why is it important to inspect the repair site for structural integrity after the repair procedure?
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What technique is used to assess the extent of damage in composites during the repair process?
What technique is used to assess the extent of damage in composites during the repair process?
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Study Notes
Impact Damage
- Occurs when a foreign object strikes a part, with degree of damage ranging from slight to severe
- Most common cause is careless handling during transportation or storage
- Thin face sheets on sandwich panels are susceptible to impact damage
- Impacted area should be inspected for delamination
Delamination
- Separation of fabric layers in a laminate
- Can occur with no visible indications from the outer skin
- Often accompanies other types of damage, particularly impact damage
- Causes include impact, moisture ingress, and lightning strikes
Disbonds
- Separation of composite material from another material to which it has been adhesively bonded
- Different from delamination, which refers to separation between plies or layers of the composite
Composite Inspection
- Requires ongoing inspection intervals and non-scheduled damage inspection and testing
- Methods include visual inspection, tap testing, and ultrasonic inspection
Visual Inspection
- Most frequently used inspection method in aviation
- Used to detect surface irregularities, resin-rich areas, and edge delamination
- Tools used include strong light and magnifying glass, and sometimes a small microscope
Tap Testing
- Effective way to discover if a finished job/repair has a good bond line or air pockets
- Uses a small tap testing tool
Ultrasonic Inspection
- Most common instrumental NDT method used on composites
- Detects internal damage such as delaminations, core crush, and subsurface defects
- Methods include pulse echo and through-transmission methods
Cracking and Resin Matrix Damage
- Caused by fire, excessive heat, UV rays, paint stripper, impacts, etc.
- Damage to resin matrix can lead to further damage and repair issues
Water and Aircraft Fluid Intrusion
- Especially problematic with honeycomb cores, causing weight gain, contamination, corrosion, and disbonds
- Water intrusion can occur during high-temperature repairs, leading to disbonds and damage expansion
Hole Damage
- Caused by impact damage, over-torqued fasteners, or fastener pullthrough
- Holes can be difficult to repair, and may require lamination of new repair plies in the damaged area
Composites Damage Assessment and Repair Process
- Basic steps include:
- Find the damage and clean the area
- Assess the extent of the damage using visual and NDI techniques
- Define the repair procedure
- Fabricate and install the repair
- Clean up and inspect the repair site for structural integrity
Potted Repairs
- Use a filler to complete the composite repair process
- Provide an alternative to installing a core material plug, but do not provide as much strength
- Filling a hole with a resin-and-filler mixture adds weight and decreases flexibility
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Description
Test your knowledge on composite inspection techniques and non-destructive testing (NDT) methods used for determining the airworthiness of structures, with a focus on composite applications and ongoing inspection intervals.
