Tied Foam Core Technology and the achieved impact performance of sandwich constructions based on reinforced foam materials

Transcription

1 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

2 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 Page 2

3 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) Page 3

4 Tied Foam Core Technology»Introduction»Technological Background»Production aspects» Impact Performance»Summary State of the art foam reinforcing technology Airbus development X-Cor/K-Cor TM (cured Pins) good specific mechanical properties expensive process/ raw material Structiso TM (dry yarns) economically interesting moderate increase of specific mechanical performance Tied Foam Core (TFC) (dry rovings) good specific mechanical properties economically interesting production method Page 4

5 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 dry foam preform 3 arranged dry reinforcements needle pushed back Page 5 cutting off the textile

6 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 ) CAD/CAM interface Stade 2012 Page 6

7 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) Page 7

8 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

9 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

10 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

11 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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