High-speed symmetric additive manufacturing of continuous carbon fiber reinforced thermoplastic composites

摘要

A symmetric additive manufacturing process is proposed to achieve tool-less fabrication of thermoplastic composites with potentially enhanced productivity, product quality and process applicability. Dual robotic placement heads are configured in a symmetrical manner and move synchronously along predefined trajectories, during which dual robotic heads simultaneously place fiber tapes and apply force and heat for in-situ curing. The effect of placement speed on thermal and mechanical behaviors during symmetric additive manufacturing were systematically investigated, and the influence of placement speed on product quality such as surface roughness, tape misalignment, internal defects, crystallinity and macroscopic mechanical properties were further explored. The thermal coupling effect of symmetric laser heat sources is found to weaken ply by ply within the coupling zone. Moreover, the increase in placement speed results in more severe deviations of temperature and rolling force, which damages the surface roughness, tape misalignment and internal defect ratio. As the cooling rate is increased at a higher placement speed, a decreasing trend in crystallinity is displayed, thereby resulting in degraded mechanical properties. The findings clarify the thermo-mechanical behavior in high-speed symmetric additive manufacturing and its multi-dimensional influence on product quality, providing new insights into thermo-mechanical regulation and pointing out the future research path of high-speed symmetric additive manufacturing. • Symmetric additive manufacturing for tool-less fabrication of carbon fiber reinforced thermoplastics • Progressively degraded thermal coupling effect of symmetric heat sources ply by ply within coupling zone • Negligible thermal coupling effect beyond the coupling boundary ply • More severe deviations of temperature and rolling force attributed to increased placement speeds • Degraded macroscopic properties due to increased defects and reduced crystallinity caused by higher speeds