When the B787 was relatively new I asked a stewardess what she thinks of the plane. She said she loves it.
For the fuselage carbon fibre is good because lack of corrosion allows for greater humidity in the cabin.
Carbon fiber is strong, but only in direction of the fibers. Obviously there have to be several layers with different directions. Aluminium alloys are strong in all directions. AFAIK that's one reason carbon fibers are used more in wings than in fuselages.
"Despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable fatigue limit. This means, theoretically, that stress cycle failure
cannot be ruled out. While steel and many other structural metals and alloys do have estimable fatigue or endurance limits, the complex failure modes of
composites mean that the fatigue failure properties of CFRP are difficult to predict and design for. As a result, when using CFRP for critical cyclic-loading
applications, engineers may need to design in considerable strength safety margins to provide suitable component reliability over its service life."https://en.wikipedia.org/wiki/Carbon_fi ... ed_polymer
Is the "complex failure modes of composites" the reason composites are less used in fuselages with their repeated pressurization cycles?
But isn't a wing facing repeated turbulences far more cyclical loaded? Or is one pressurization cycle more comparable to an extreme wing bending in extreme weather?
Glass Laminate Aluminum Reinforced Epoxy (GLARE) is a sandwich of several thin layers of aluminium with glass fiber reinforced plastic in between. It's a FML=Fiber Metal Laminate.
" http://www.compositesworld.com/blog/pos ... e-of-glare
" discussses FML=Fiber Metal Laminate versus CFRP (Carbon Fiber Reinforced Plastic).
"... FML also beats composites on weight saving in small fuselages because the latter “carry a weight penalty, due to minimum thickness for damage tolerance.”
However this is a statement from a web page promoting composites. The main advantage of GLARE is tensile strength. It's good only for certain areas of the plane and it's expensive.
I would like to add some questions which stray from your "A350 size" question, but refer to optimum material:
" http://www.pvcfittingsonline.com/resour ... gth-chart/
" has a discussion about PVC pipe diameters and it's characteristics.
Apparently with increasing pipe diameter the tensile strength increases, but bursting strength (caused by water pressure) decreases.
Is "bursting strength"/ fatigue by repeated pressurization or tensile strength the limiting factor in today's Aluminium/ Lithium fuselage designs? From the DC 8 I assume it's fatigue, but does somebody know for sure?
A321: fuselage 3.95 m outer width, length 44.51m. Length/ diameter = 11.2..
DC 8/61-63: fuselage 3.73 m outer width, length 57.1 m. Length/ diameter = 15.3.. . Very long.
I assume sooner or later somebody will find a way to mass produce CFRP parts.
(Which makes me wonder if Bombardier's C-Series was a bet that by the time of introduction mass production of CFRP would be much cheaper.
In which case both Airbus and Boeing were brave to bet that this won't happen.)
Considering that increased humidity decreases strain on the body: How much more expensive would be a narrowbody with carbon fiber fuselage with today's technology?