Hollow carbon fibres for high performance polymer composites

A technique for spinning hollow polyacrylonitrile precursor fibres and converting them into high performance carbon fibres has been developed. Although consistency in fibre Structural morphology has been difficult to attain, the constituent carbon is found to be similar to that of high strength, solid carbon fibre. Simple mechanical testing has revealed, however, that although comparable modulus can be realised, the ultimate tensile strength is currently lower than for solid fibres. This is believed to be a consequence of flaws and the lack of structural homogeneity within filaments. Even with such experimental fibres, preliminary compression testing indicates higher strain to first failure in comparison with a commercial fibre. Once the effect of flaws has been minimised and tensile strength improved, these fibres offer the prospect of structural reinforcing fibres that impart compressive strengths in composites approaching or even exceeding the tensile strength. The hollow cores also offer the possibility of added functionality, such as damage sensing and location, smart repair, novel actuation schemes, or communication mechanisms. PRC/1579. (C) 1999 British Crown Copyright.