1. ROHACELL® General Review, Aircraft
Reid Averill, Business Development Manager
Rodrigo Marques Regional Business Development

2. 3. New Product ROHACELL HERO 4. Shaping of ROHACELL 5. Conclusion
1. Evonik supports the composite market
Overview of ROHACELL
3. New Product ROHACELL HERO
4. Shaping of ROHACELL
5. Conclusion

3. Evonik products and expertise in almost all composite sub-components
Composite sandwich system – schematic view
Thermoplastics
VESTAKEEP® VESTAMID® HTplus VESTAMID® L
TROGAMID®
Thermosets
COMPIMIDE® CALIDUR®
Matrix
Interface
Fiber
Foam cores
ROHACELL®
Crosslinker
VESTAMIN® VESTANAT® JAYHAWK™ Dianhydrides
VISIOMER®
Foam Core
Additives/rheological modifier
AEROSIL® Dynasylan® TEGOMER ®
Thermoset modifier
NANOPOX® ALBIPOX® ALBIDUR®
P84®
Adhesive / Sealant
Understanding all aspects of a complex system is important.

4. ROHACELL ® industry breakdown
Wind
Auto
Lifestyle*
Aircraft
*Lifestyle: sports equipment, medical tables, electronics, radomes

5. ROHACELL® locations Positioned to serve a global market
Darmstadt
Mobile
Shanghai
Mobile, Alabama (USA)
Production: Foaming·Cutting·Shaping
Sandwich Technology Center
Darmstadt (Germany)
Production: Casting·Foaming·Cutting·Shaping
Sandwich Technology Center
Shanghai (China)
Production: Cutting facility - in progress
Sandwich Technology Center

6. Composite Sandwich Design Concepts

7. Aircraft Product Portfolio
ROHACELL® Product
Processing Conditions
Special
Properties A
130°C / 0.35MPa
Standard aircraft grade
HERO
180°C / 0.7MPa
Highest elongation at break HF
High frequency transparency, designed for radome applications WF
Most qualified aircraft grade
RIST
Designed for resin infusion, smaller cells
RIMA
Designed for resin infusion, smallest cells XT
220°C / 0.7MPa
Usable with BMI resins EC
Electrically conductive, designed for UAVs and other stealth applications

8. Advantages of Using ROHACELL
Compatible with all composite processes and thermoset resin systems
Prepreg/autoclave, RTM, infusion, Fiber Placement, etc..
100% closed cell foam no resin absorption through thickness
Outstanding Compressive creep resistance, compatible with 180C and 0.7MPa cure cycles
Complex shaping (Thermoforming/Thermoshaping and CNC machining)
High strength to weight ratio
Excellent electrical performance (Radome applications)
Class A Surface finish
No liquid moisture problem
Full blown FAA qualification on WF grade
Date | ROHACELL® HERO

9. Electrical Properties of ROHACELL
ROHACELL’s electrical and mechanical properties make it an excellent core material for Radomes
ROHACELL performs superior to Honeycomb in hail strike performance
ROHACELL behaves isotropic electrically making it a much easier material to electrically model when compared to honeycomb
Evonik also offer’s an electrically conductive grade of ROHACELL called EC for EM shielding and stealth applications
Date | ROHACELL® HERO

10. ROHACELL HERO
The ROHACELL® HERO development challenge:
Improve a proven, high performing foam sandwich core product for use in Class A and B parts.
Add: High damage tolerance & visibility
With: Greatly improved elongation at break
Keep: All existing advantages
Result: Reduced finished part costs

11. Increased elongation at break is key to meeting the damage requirement
Standard ROHACELL® products
Tension
3-4 %
9-10 %
HERO offers the highest elongation at break of any ROHACELL® foam core product
Elongation

12. Introducing: ROHACELL® HERO New design opportunities
Flap Track Fairings
carbon/glass epoxy skins
Wing Leading and Trailing Edge Panels
Access Panels
Pylon Aft Secondary Structure
carbon epoxy or thermoplastic skins
Empennage Leading and Trailing Edges
VTP tip
VTP panels
Dorsal fin
Spoilers / Ailerons
Nose Landing Gear Doors
carbon fiber epoxy skins
Floor panels
carbon epoxy skin
Fuselage Belly Fairing
Main Landing Gear Doors

13. Required damage C-scan
Target: Meet customer’s requirement for damage detectability (Class A & B parts)
Design load requirements
Typical impact damage
If General Visual Inspection selected
If Detailed Visual Inspection selected
k*Limit Load (1<k<1.5)
Ultimate Load UL
Required damage C-scan LL
Limit Load
This is understanding of what our aircraft customers are looking for. The ability to detect damage and be able to assess it.
Hole
Diameter TBD
BVID (DVI)
BVID (GVI)
Large VID
Increasing damage size
DVI (Detailed Visual Inspection)
GVI (General Visual Inspection)
Walk-around Inspection

14. Impact damage visibility test
Testing target:
Prove that a ROHACELL® HERO sandwich provides the same damage visibility after an impact as a honeycomb sandwich
ROHACELL® HERO Sandwich
Density 75 kg/m³
For more information, please refer to test report.
NOMEX Honeycomb Sandwich
Density 48 kg/m³, Cell size 3.2 mm
Testing conducted at Fraunhofer IWM, 2013

15. Impact @ -55°C Impact depth after 48 hours
BVID (DVI) > 0.3 mm

16. Impact 10J @ 23°C – cut specimen
NDT results
Impact 23°C – cut specimen
Foam Sandwich
Honeycomb Sandwich

17. Impact 35J @ -55°C – cut specimen
NDT results
Impact -55°C – cut specimen
Foam Sandwich
Honeycomb Sandwich

18. ROHACELL® HERO solves a known honeycomb in-service problem
Water ingress in honeycomb
Damaged and undamaged areas of honeycomb collect water, porosity in the skins, or leakage paths (cracks in resin or potting)
Effects include
Increase of mass
 Part weight increase
 Higher fuel consumption
CTE (water converts into ice resulting in expansion)
Damage increase
Disbond failure
Repair
 Cost and weight
Additional service costs for airlines
 AOG time to replace parts
 Spare part cost
Water Ingress
Trailing edge screws
Lightening protection strips
Author: Martin Oehike
Manager: Dr. Eckart Nast/ Lufthansa Technik AG

19. ROHACELL HERO Freeze Thaw Test
1) Impact simulates open damage
3) Damage size evaluation by a US scan
Reference defect (PTFE foil)
2) Water is injected into impact areas and then cooled to -18 °C
US scans of impacted panel CM-VTS2 before freeze/thaw cycles
30mm panel 71 ROHACELL®, 2.6 mm CFRP
Source: Testing conducted by OEM

20. Damage size evaluation
US scan after 6, 30 and 60 cycles proves no damage growth. Reason: ROHACELL® can absorb the change in volume during the liquid to solid transition phase of water.
Damage size [US scan]
Collar 6 30
cycle 60
Further testing by an OEM confirms HERO solves the water ingress and freeze damage problems exhibited by honeycomb!

21. Correct Testing Solution:
Single Cantilever Beam test vs of climbing drum peel test (G1C Determination)
Correct Testing Solution:
Single Cantilever Beam (SCB) test is the recommended test method for face sheet bonding to core
DIN – Not applicable
The climbing drum peel test (DIN 53292) for a foam sandwich is not an applicable test method. DIN will not show damage behavior if damage already exists.
Energy required to propagate crack

22. Effective skin to core bonding analysis with fracture toughness test (SCB)
1. Part design determines skin-stiffness, stress leads to compressive strength in the skins (LL).
2. Worst case debonding area due to:
Impact (according to part requirements) determines damage size.
Ronald Krueger
ICASE, Hampton, Virginia
Process failure
3. FEM shows local buckling and the G1 kinetic energy during special load case G1
G1 is the real force that opens the crack. If G1 is less than G1C (Critical) the crack will not open. This is represented by the SCB test. This is the right way to analyze that sandwich structure.
4. If G1 < G1C, the crack will not open (no crack growth)
Source:NASA/CR ICASE Report No /Ronald Krueger
ICASE, Hampton, Virginia
G1= f (~damage size, skin stiffness and in-plane compression)

23. SCB test gives fracture toughness
e.g. G1

24. Fatigue testing
ROHACELL® WF has a long and successful history of usage in aircraft, with more than 25 years in service.
Test procedure (ASTM C393)
Evaluation of the Foam Core Shear Fatigue Performance; Marianne John, IWM Halle

25. HERO outperforms WF Honeycomb in comparison
Cycled fatigue specimens failed due to core shear cracking
~ +52%
CFRP/NOMEX ECA 3.2/48 L*
Shear failure mode is better than skin to core failure
* Fatigue Crack Initiation and Propagation in Sandwich Structures, Magnus Burmann, Report No , 1998, KTH
**Burman M. and Zenkert D., “ Fatigue of Foam Core Sandwich Beams, Part 2: Damaged Specimens” International Journal of Fatigue, Vol. 19, No. 7, pp , 1997

26. Residual strength test – 71 HERO
Shear strength [Mpa]
Fatigue loaded specimen of 55% UL with 5 Mio. load cycles failed in the same force range as the uncycled specimen (= quasi-static test)

27. Proven stability at high temperatures and pressures
Compressive Creep
Compressive creep [%]
180°C/ 0.7MPa
130°C/ 0.35MPa
Curing conditions (2h)
Out-time investigation at 23°C/50%RF and
27°C/70%RF is running.

28. Lay-up / process / part cost
Business case
Lower part cost and weight (up to -25%)
Easy handling
Stable curing process
Fewer production steps
Ready-to-use parts

29. Demonstrator and evaluation part: Nose Landing Gear (NLG) Door
Foam / Infusion
This foam sandwich part was originally constructed as a 71/200 WF core in infusion technique for Do728. Now, it is optimized for 71 HERO/dry fabrics and stay in infusion technique.
Honeycomb / Prepreg
Baseline for the comparison is an NLG door similar to the A320 design and a process using Nomex honeycomb (64 kg/m³, 4,8 mm) and prepreg (Fibredux 913C %).
Foam / Prepreg
Additionally, we compare the foam with an Autoclave (Prepreg) process in a situation where honeycomb is replaced by foam, but the process stays the same.
Partners
Date | ROHACELL® HERO

30. Cost advantage results: Save 21 – 25 % by using foam
Date | ROHACELL® HERO

31. Weight advantage results: Save 19 %
No adhesive film
No need for potting
Date | ROHACELL® HERO

32. The time advantage: Where are the main differences?
Prepreg instead of infusion

33. Shaped ROHACELL® profiles

34. Shaped ROHACELL® profiles

35. HERO outperforms honeycomb
Date | ROHACELL® HERO

36. Conclusion ROHACELL® HERO Solve Honeycomb problems
No water problem, better fit to CRFP
Efficient
part production
Reduce manufacturing costs
Robust
damage behavior
Meet industry requirements for
damage tolerance and visibility
ROHACELL® HERO
Excellent
mechanical properties
and fatigue behavior
Produce reliable structural components
with long service life
AIRBUS Spec. and MIL-PRF-46194a
are in progress
Qualification

37. ROHACELL® Sales and technical support
Reid Averill
Technical Sales Manger ROHACELL North America Phone Mobile
Blake Juhl
Director of Sales and Marketing ROHACELL North America Mobile
Date | ROHACELL® HERO