hi all! Are composites like carbon fibres (CFRP) the best material for flywheel? There is no doubt on its high strength to density ratio. Regarding the safety consideration, is flywheel made of composites safer than that made of other materials? I've read through some articles claiming that it should be safer in the sense that composite materials would break into many small pieces once broken. Is this a well-proven fact? Also, regarding the manufacturing of flywheel using composites, is it sill difficult? Where are the difficulties? All in all, what material would you consider to be the best material for flywheel? By the way, can anyone tell me what "toughness" actually means? Is titanium alloy tough? are composites tough?