Smithers Rapra interviewed Jens Hinrichsen, from Aerospace Advisory Group ahead of GOCarbonFibre

Please give a brief description of your background in composites.

I had the privilege to grow up with the evolution of composite applications at Airbus, departing from primary structures for Airbus A310, with the vertical stabilizer and the rudder representing the most prominent examples. A deep understanding of the interaction between design solutions and strength/dynamic behavior defined "the lessons-to-be-learned". Later on, composite applications for wing boxes represented a cornerstone of those Airbus technology programs I was accountable for. The above "evolution" prepared the organization and me for broadening the scope of CFRP usage for A380. 

What was underlying concept for material cost reduction for carbon fibre at Airbus?

The decision to significantly increase composite applications for primary fuselage structures in the A380 program was based two different factors:
- Evaluation of "cost-of-weight-saving" vs. metal, and 
- Technology readiness in combination with risk mitigation.
Both, center wing box and unpressurized rear fuselage were under review; targeting substitution of metal with IM fiber based CFRP. With the given size of A380, both of these major assemblies required a huge amount of prepreg material supply per ship-set. In order to amplify the material volume effect on prices, material standardization towards exclusive application of IM-fiber material across all subassemblies was envisaged. As a result, composite material cost settled at an affordable level. The application of CFRP delivered significant weight savings.

Which other implications resulted from the decision to apply composite material for center wing box and rear fuselage panels?

The enormous size of bond tools and layup thicknesses added to the complexity faced in manufacture:
Hand-layup was excluded and automated processes had to be chosen: 
- Automated Tape Laying (ATL) for the center wing box
- Automated fiber placement for the rear fuselage.
These automated processes are known for delivering excellent quality.
Another beneficial effect materialized for the rear fuselage: The number of panel joints was reduced by 75% compared with metallic panels for which stretch forming requirements in double-curved fuselage loft lines restrict the sheet size, which in turn drives the number of panel joints up. 
This way, weight savings from material density (gravity) and reduction of joints added up.
Design and manufacture of the center wing box and fuselage panels for A380 prepared Airbus for further composite applications in the A350XWB program.

The latter decision stands for a singular event in the past, but it earmarks "damage resistance" as a major design driver, which is expected to play a paramount role in the evaluation of composite for fuselage panels of new single aisle aircraft.

What are the most important programmes you currently see going on regards using CFRP in aerospace?

- B787 and A350XWB regarding in-service experience (inspections, repairs, etc.)
- Improvements within the B737 and A320 families regarding CFRP wings
- B777 in view of a substitution of metal with composite in the wing box

What role do your see carbon fibre composites playing in the next 10-20 years?

- Composite applications will deliver a crucial contribution to achievements in reducing weight as well as aerodynamic friction drag, which is the overarching challenge of the future

What are the most valuable lessons you learned at Airbus regards using carbon fibre composites in large volumes in your aircraft?

- Material suppliers serve increases in demand
- 1st tier component suppliers ramp up production as required
- Experienced program delays result in loss of confidence in timely "return on invest", which might kick back as reluctance to invest in future programs
- 2nd tier suppliers might fail to invest in-time due to financial weakness
- There might be a hidden problem with the supply of parts (fasteners, brackets, etc.) as we tend to watch the big components and overlook the "tiny parts"

What are the main threats from other materials to sustained future use of carbon fibre?

Other materials, such as aluminum and glass/aluminum hybrids threaten because of:
- Familiar (legacy) inspection/repair procedures
- Future enhancement of fatigue behavior using bonding technologies
- Elimination of widespread fatigue damage through fiber metal laminates
- Better burn-through behavior
- Elimination of hazards from toxicity of epoxy in post-crash fuel pool fire or onboard fire

With airplanes featuring more than 50% composites, the threat is "toothing trouble" with new technologies:
- Missing skills at airline maintenance organizations and MRO facilities
- Increased cost due to longer downtimes for inspections and repairs
- Uncertainties regarding emergency landings and survivability in cash events

What can the carbon fibre industry do to better position themselves against these other materials?

- Material enhancements through research (non-brittle resins, fiber sizing, reduced tolerances for prepreg thickness, less-toxic resins, etc.)
- Enhancement of inspections and repairs
- Enhancement of "design-for-manufacture"
- Enhancement of "design-for-maintenance"

And finally, we are very pleased to have your on board for the conference this year. What are you hoping to gain from your participation?

It is an honor meeting with great characters from the composite community and to participate in a long-lasting learning process. The GOCarbon congress will provide sources of inspiration and motivation to better identify critical factors and to take on the tasks to overcome barriers as we are only "half-way through".