Thermoplastic FRP threaded rod - consisting of main body reinforced with long fibres and skin contg. only short fibres it has thread formed by cold rolling

摘要

Screws or threaded rods are made of fibre-reinforced thermoplastics and their mechanical properties are made optimal by using long fibres (5-10 mm) in the interior and short fibres (0.1-0.15 mm) in the outer part and by cold rolling the thread into the outer skin layer. An alternative to the short fibres is glass microspheres. Pref. the prods. are circular section rods made by coextrusion in which thermoplastic granules with the long fibres are fed into the extruder for the core material (1) whilst a second extruder produces the short fibre-filled skin (2). A twin-component coextrusion extruder can be fed with both mixes so as to produce the desired coaxial system. The core of the rods is primarily thus made with longitudinal fibres, which transmit max. loads but show minimum cold flow. The short-fibre skins transmit shear forces in the threads formed and their fibres permit cold flow. By rolling the thread cold the strength limits in the thread are considerably greater than those of cut threads. Moreover the cold working produces a certain strengthening in the matrix. ADVANTAGE - The prods. have highest feasible mechanical strength.