Localised heating of carbon fibre reinforced thermoplastic tubes in rotary draw bend forming process

This paper presents a localised heating technique using an induction heater and a steel spring mandrel for post-forming of polyamide six carbon (CF/PA6) thermoplastic tubes. During heating, the mandrel is heated up more rapidly than the tube to catalyse tube heating to its formable temperature of 220°C. Upon heating, the tube matrix softens to enable fibre movements when a tube undergoes rotary draw bending (RDB), forming the desired curvature. Four sets of [±60°]₄ CF/PA6 tubes were formed using an induction heater incorporated RDB setup into 45°, 90°, 135°, and 180° bends with a bending ratio of 2. Optical characterisation and micro-computed tomography were performed to analyse tube fibre angle and geometry changes. Results suggest that the presented technique is capable of producing tube bends with significant improvements in efficiency and quality as compared to oven and infrared heating, opening up the potential for rapid post-forming of composite tubes for high performance applications.