J E Gordon wrote in his book New Science of Strong Materials: or why your feet dont fall through the floor.
"Like boron, this fibre has suffered from a great deal of irresponsible Government publicity.
Although frequently described by the newspapers and on television as a wonderfibre of exceptional strength, carbon fibres are not in fact, particularly strong; if anything they are a little weaker than glass fibres. They are however, for their weight, something like eight times as stiff as either glass or the normal engineering metals. As might be expected the resin-fibre composites made from carbon fibres are very stiff but not especially strong in tension. They are also, at present, rather inconveniently weak in compression. While it might be possible, in theory, to put up the compressive strength of carbon fibre composites by using a metal matrix, this does not usually work in practice because of the chemical reactions which occur between the carbon and the metal.
However, for many purposes where weight saving is important but where the strength requirements are not too critical – such as artificial limbs, golf clubshafts or the stiffening of car bodies – carbon fibre composites have been very successful.
When we turn to more exacting applications, like aircraft parts, the trouble is generally lack of toughness. When the composite is made in the conventional way the work of fracture whichis actually achieved is not far short of the calculated theoretical limit – but unfortunately this is, in practice, not sufficiently high."
