Sucker rod

摘要

A rod assembly comprising a core component and a sheath component and having an elongate cross-section, the sheath component consisting of an anisotropic assembly of non-metallic filamentary elements embedded in a polymeric matrix whereby the bending stiffness for deformations about an axis parallel to the major axis of the rod assembly is less than the bending stiffness of the same core and sheath components in a radially symmetrical configuration, and in which the core and sheath components have load-elongation characteristics so that the ratio of the strain to the strain-to-break in the sheath is essentially equal to the ratio of the strain to the strain-to-break in the core throughout the working load range.