Abstract: The present invention relates to a high elongation, high strength pitch-type carbon fiber which has an improved handleability. The carbon fiber of this invention has a crystalline structure arranged in such a manner that the angle (.phi.) is 24.degree.-38.degree.; the stack height (L.sub.c) is 19-35 .ANG.; and, the interlayer spacing (d.sub.002) of the X-ray structural parameter is 3.45-3.50 .ANG.. The atomic ratio of oxygen to carbon on the surface of the fiber measured by X-ray photoelectron spectrometry is 0.1-0.35. The total oxygen content in the fiber is 0.01-0.2 wt. %; and, the elongation is 1.0% or more. The high elongation, high strength pitch-type carbon fiber prepared in accordance with the present invention can be used, for example, as a reinforcing fiber for light-weight structural material employed in the aerospace, automotive and architectural industries.

Abstract: An elongated lightweight fiber reinforced composite resin pultrusion-formed piece with a rectangular structural shape has an elongated light honeycomb structure body with a rectangular sectional shape and at least one fiber reinforced resin layer formed to cover at least a portion of the outer peripheral surface of the lightweight honeycomb structure body. The fiber reinforced resin layer comprises an axial fiber layer formed by aligning reinforcing fibers parallel to the longitudinal axis of the lightweight honeycomb structure body.