Tough hollow composite sections suitable for e.g. highly-stressed parts of bicycle frame

摘要

This is a new hollow profile suitable as e.g. a bicycle frame section, steering tube, or bottom bracket. The section is a composite of preferably two outer casings (1, 2), onto the inner surface of which, a thin mat (3) is adhered. Also claimed is the method of manufacture of low-weight parts subjected to high compressive-, tensile, or flexural stresses, as found e.g. on a bicycle. The impregnated mat covers a flexible tube, which is blown out under internal pressure, against the fixed casing sections. Preferably the casing sections are semi-shells of metal, preferably a light metal such as aluminium and/or of plastic, preferably a thermoplastic. The mats comprise a fibrous composite, which preferably are arranged in accordance with their fibre orientation between the casings. The mats are carbon-, cellulose- or polyacrylonitrile fibres, preferably glass fibre reinforced. They are hardened by a resin such as polyester- or epoxy resin. The casings are placed together with gaps or openings, through which excess resin is expressed, when pressure is applied inside the tube at 2-10 bar (2 x10<5> - 10<6> Pa). The assembled shells have openings for the flexible tube to be removed, following hardening of the resin. The tube is silicon and/or is greased before insertion. Hardening is accompanied by heating at 80 deg C-100 deg C, especially 90 deg C.