Tied Foam Core Technology and the
achieved impact performance of sandwich
constructions based on reinforced foam
materials
Department TX1 Stade
Dr. Gregor Endres
CFK-Valley Stade Convention 2014
Tied Foam Core Technology
»Introduction »Technological Background »Production aspects » Impact Performance »Summary
•
Today‘s sandwich constructions in aircraft are mainly based on honeycomb structures
•
Beside fairing parts, sandwich application in aircraft is limited to secondary structural parts
•
Foam cores are used as manufacturing aid (e.g. stiffner of the pressure bulkhead)

To make extended use of the weight saving potential of sandwich constructions in aircraft
construction alternative sandwich core materials are needed
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Tied Foam Core Technology
»Introduction »Technological Background »Production aspects » Impact Performance »Summary
Pin reinforced foam core materials …
• … have a high flexibility in core mechanics
• … have a huge flexibilty in core shape
• … show crack stopping behavior due to the pins
• … show an improved fatigue behavior
• … don‘t show water ingress due to closed cell foam as bases (might be foam type depending)
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Tied Foam Core Technology
»Introduction
»Technological Background »Production aspects » Impact Performance »Summary
State of the art foam reinforcing technology
Airbus development
X-Cor/K-CorTM (cured Pins)
•
good specific mechanical
properties
•
expensive process/ raw material
StructisoTM (dry yarns)
•
economically interesting
•
moderate increase of specific
Tied Foam Core (TFC)
(dry rovings)
mechanical performance
•
good specific mechanical properties
•
economically interesting production
method
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Tied Foam Core Technology
»Introduction »Technological Background »Production aspects » Impact Performance »Summary
starting point
needle stitched
through the foam
developed for Airbus Group
hooking in the textile
2
3
dry foam preform
needle pushed back
arranged dry reinforcements
Page 5
cutting off the textile
Tied Foam Core Technology
»Introduction »Technological Background »Production aspects » Impact Performance »Summary
Generation 0
(2006/2007)
OTN 2008/09
•
9 generations of functional units till
process stability for industrial purposes
•
size increasement: 750mm x 750mm 
3500mm x 2500 mm
•
full geometrical flexibility (curvatures,
chambfers, cut outs…)
•
Stade 2012
CAD/CAM interface
Page 6
Tied Foam Core Technology
»Introduction »Technological Background »Production aspects » Impact Performance »Summary
• Purpose of the machine: proof of production concept in lab surrounding
• Highest possible flexibility in foam core shape
• Corresponding cooperation of two functional units
• Increase of production speed
• Sample size up to 3500mm x 2500mm x 30mm
• Curvature radius min 2500mm
• CAD/CAM-interface (chamfers, variation in stitching pattern, …)
 Simplification in machine technology for real production possible without problems (increased output; reduced
investment; increased production stability)
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Tied Foam Core Technology
»Introduction »Technological Background »Production aspects
» Impact Performance »Summary
RohacellTM RIMA51
Reinforced RohacellTM HF31
Comparable
core density
~ 50kg/m3
Figures: water coupled ultrasonic scans; impact energies: 0J, 3J, 5J, 7,5J, 10J, 15J, 20J, 25J
 Insertion of pins into the foam results in an enormous decrease of damage size
Tied Foam Core Technology
»Introduction »Technological Background »Production aspects
» Impact Performance »Summary
Figure: damage size
investigation of the tested
impact samples
 On the highest impact energy level the damage size in a reinforced sample is
less than 20% of an unreinforced sample with comparable density
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Tied Foam Core Technology
»Introduction »Technological Background »Production aspects
» Impact Performance »Summary
Figure: CAI-strength
investigation of the tested
impact samples
 On the highest impact energy level a damages sample with pins almost reaches
the CAI-strength of an undamaged sample without pins
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Tied Foam Core Technology
»Introduction »Technological Background »Production aspects » Impact Performance
•
»Summary
Tied Foam Core Technology is a flexible reinforcing technology which can easily be adapted to several
requirements by changing the foam as well as the fiber reinforcement.
•
Using the full given flexibility by tailoring the pin pattern, TFC is a very promising core for weight optimized
construction.
•
For cost reduction different production possibilities have been developed to follow the given material flexibility
with an adequate production technology for a broad application range in different industrial areas e.g.
aerospace, ship building, wind turbine constructions or transport and civil engineering.
•
The performed impact studies have shown that TFC-samples show a decrease in damage size of almost 90 %
when compared to pure foam samples of the same density.
•
In case of the reinforced samples the achieved residual strength values on the highest impact energy level are
still on the level of an undamaged pure foam sample.
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Technology Video
http://www.technology-licensing.com/etl/int/en/What-weoffer/Technologies-for-licensing/Composites-and-Related-ManufacturingTechnologies/STINGTECH.html
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