Additive manufacturing technique fused filament fabrication (FFF) has found widespread usage in a variety of sectors, because of its ability to produce parts with arbitrary geometries and intricate internal structures. This study focuses on the characterization of polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) composites under compressive force to learn more about how various nozzle diameter (ND) and infill pattern (IP) affect the fabricated specimens. The specimens are created with various combination of IPs (triangular, honeycomb, and rectilinear) and NDs (0.2, 0.4, and 0.6 mm) utilizing three polymer composites namely carbon fiber filled PLA (CF-PLA), carbon fiber filled PETG (CF-PETG), and multi walled carbon nano tubes filled PLA (MWCNTs-PLA). According to the findings, the higher ND improves the compressive properties of the polymer composites. The IP also has significant impact on the compressive properties of the fabricated specimens. The overall minimum compressive strength of 14.612 MPa at ND 0.2 mm and honeycomb IP for CF-PLA specimen. The overall maximum compressive strength achieved is 45.269 MPa at ND 0.6 mm and rectilinear IP for MWCNTs-PLA specimen.Therefore, the compressive strength is enhanced by 209.81% by modifying the process parameters and filament material. Based on statistical analysis using Taguchi method, the ND contributes highest, 79.61% to compressive strength of MWCNTs-PLA specimens, but for CF-PLA and CF-PETG specimens, IP contributes highest, 52.65% and 57.91%, respectively. The aforementioned findings will be extremely useful to scientists attempting to achieve sustainability through the use of polymer composites and FFF process.compressive behavior, fused filament fabrication, infill pattern, nozzle diameter, polymer composites | INTRODUCTIONAdditive manufacturing (AM) has evolved from a prototyping technique to one employed in the manufacture of finished, consumer-ready goods. Additively manufactured components are increasingly used as structural components in today's technical practise. [1][2][3] The time required to obtain a working component or assembly is drastically reduced using this method. Therefore, it is important to think about how different mechanical loads and the effects of the environment over time will affect the final part's qualities and behavior. The AM of

Additive manufacturing is becoming more and more significant for the production of engineering products. The global community of designers and manufacturers will undoubtedly benefit from identifying the process factors that could lead to superior mechanical behaviour. The incorporation of fibres and nanoparticles in polymer matrix is one of the most significant advancements in polymer fabrication. This study intends to investigate how the flexural behaviour of dissimilar polymer composites viz carbon fibre reinforced poly lactic acid (CF-PLA), carbon fibre reinforced poly ethylene terephthalate glycol (CF-PETG) and multi walled carbon nano tubes reinforced PLA (MWCNTs-PLA) are affected by process parameters viz nozzle diameter (0.2 mm, 0.4 mm, 0.6 mm), and infill pattern (triangular, honeycomb, rectilinear) through fused filament fabrication (FFF). Flexural testing was carried out on the fabricated specimens, and post to the testing, fractography has been carried out and statistical analysis of the observations is performed utilizing analysis of variance and Taguchi method. According to the observations, flexural strength of the polymer composite specimen increases with increase in nozzle diameter (ND). The flexural behaviour is also directly impacted with the variation of infill pattern (IP). Process parameter variations affect target factors differently depending on the fabricating material. For flexural behaviour, IP contributes 68.27% to CF-PLA, while ND contributes 88.96% to CF-PETG and 77.59% to MWCNTs-PLA. Overall, the highest flexural strength, 70.372 MPa, is exhibited by the specimen with ND 0.6 mm and rectilinear IP for MWCNTs-PLA as fabricating filament material. This study will aid researchers and designers in developing FFF-fabricated electrochemical energy storage devices with improved flexural behaviour of functional parts for a wide range of applications.