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A review of bundle theory and the strength of yarns compared to single filaments has been made for several high strength filament materials. The dielectric properties and the statistical distribution of tensile strength have been compared for filaments of glass (Types E and S), graphites, and the high modulus PRD-49 (organic). The review was made in conjunction with the development of a new type of a high modulus line using PRD-49 filaments. The lines were to be used as guys for the antennae system at the Arecibo Observatory in Puerto Rico, the National Astronomy and Ionosphere Center which is operated by Cornell University for the National Science Foundation. The unique requirement for these cables was not only the high modulus for a low total elongation of 20 to 90 ft lengths with low loss tangent and dielectric properties, but the need for rigidity at comparatively low prestrain loads.
Varying sizes and designs were produced experimentally, ranging from 15 to 19 000 lb ultimate strengths. The testing of lines involved both precision optical strain measurements on 1 ft gage lengths as well as 10 ft test lengths for elongation, modulus, and strength measurements. The final design involved 1800 ends of 380 denier Type III, PRD-49 duPont fibers. The finished cable has a nominal modulus of 16. 5 Ç 106 psi capable of supporting a 19 000-lb load with a cable weight 0.04 lb/ft of length. For optimum resistance to weathering, moisture, and ultraviolet effects, outer sheathing with extruded black PVC had been used. Epoxy bonded end fittings were employed to permit tension adjustments at the comparatively low leads.
composite materials, filaments, fibers, cables (ropes), guy wires, mechanical properties, electrical properties, organic particle composites, glass, carbon, yarns
Consulting engineer, Cornell University, Ithaca, N.Y.