Development of continuous fiber reinforced polymer composites using in-situ co-extrusion towpreg material extrusion process with optimized cooling and evaluation of their mechanical performance and quality

Polymer composites mainly reinforced with continuous fibers manufactured using the material extrusion technique have gained attention due to their light weight and high-performance capabilities. Thermoplastics reinforced with continuous carbon fiber (CCF) offer exceptional mechanical properties. Polymer composites are fabricated using the material extrusion process, adapting various methods. Manufacturing such composites using fused filament fabrication (FFF) with high quality and reduced air void content is challenging due to the complexity of the process. In this study, in-situ co-extrusion with the towpreg process is used to manufacture CCF reinforced composites using the FFF technique. Two important printing parameters (layer thickness and line width) are considered. Mechanical properties (tensile, shear and compressive) were studied after the manufacturing of the composites. The porosity in the composites was observed using X-ray micro computed tomography scan, and the carbon fiber contents were estimated using the dissolution method, while the fracture analysis was performed using SEM. The results obtained suggested that both the printing parameters have a significant impact on the quality and mechanical properties of the additively manufactured composites. The polymer composite fabricated using a layer thickness of 0.4 mm and a line width of 1 mm showed the highest tensile, shear, and compressive strength of 364.69 MPa, 33.89 MPa, and 121.25 MPa, respectively, with a minimum porosity of 16.14 % and a reinforcement content of 26.12 % volume fraction. This thorough research gave insights into how differences in printing settings affect the structural integrity, mechanical properties, and quality of composites, directing future optimizations for improving the performance and quality of 3D-printed thermoplastic composites. • In-situ co-extrusion FFF with controlled cooling developed for CCF reinforced composites. • Printing with 0.4 mm layers & 1 mm width achieved tensile strength up to 364.69 MPa. • X-ray micro-CT showed porosity as low as 16.14 % in high-performance composite specimens. • Fiber volume fraction up to 26.12 % measured via dissolution, linked to mechanical properties. • Rule of Mixtures predictions matched experiments, validating process-structure-property link.