This invention relates generally to carbon fiber produced from single-wall carbon nanotube (SWNT) molecular arrays. In one embodiment, the carbon fiber which comprises an aggregation of substantially parallel carbon nanotubes comprises more than one molecular array. Another embodiment of this invention is a large cable-like structure with enhanced tensile properties comprising a number of smaller separate arrays. In another embodiment, a composite structure is disclosed in which a central core array of metallic SWNTs is surrounded by a series of smaller circular non-metallic SWNT arrays.