Effects of Infill Speed and Heat Treatment on Mechanical Properties of Carbon Fiber Reinforced Polyethylene Terephthalate Glycol (CF-PETG) Composites

Abstract

In recent years, conventional metals are replaced with Carbon Fiber reinforced Polyethylene Terephthalate Glycol (CF-PETG) composites in automotive and aerospace industries due to their lightweight, better mechanical strength and hardness. In general, thermoplastic polymer composites are fabricated using compression and injection molding techniques. However, fabricating composite specimens using these techniques is expensive and also, different shapes of molds are required for fabricating different components. However, in recent times, the fused deposition modeling (FDM) technique is being widely used in fabricating thermoplastic polymer composites, most importantly, this technique is cheap and mold is not required to fabricate any shape of a product. Therefore, complex geometrical components can be fabricated easily without the need for a mold. However, FDM printed components exhibited lower mechanical properties, owing to layer-by-layer printing process, moreover, the fabrication time is lengthier which relies on several process parameters, compared to those of compression and injection molding techniques. Therefore, the post-processing of FDM printed components is essential to enhance the mechanical properties. The present study focuses on the effects of FDM infill speed on the mechanical properties of as-built and annealed samples printed with CF-PETG composites, as these are not investigated previously to explore the use of material effectively. The samples were printed using FDM by layers of extruded beads at different infill speeds of 40, 50, and 60mm/s, with the remaining parameters, held constant at optimal values. The infill speed followed by annealing determines the overall mechanical performance. The highest mechanical properties such as hardness, tensile strength, and impact strength were measured when CF-PETG specimens are printed at an infill speed of 40mm/s, compared to samples printed with other infill speeds. When compared to the as-built sample, the interlayer diffusion bonding was increased and the mechanical characteristics were improved by using an appropriate post-processing approach of annealing. The responses in this study provide a useful guideline for making functional parts utilizing CFPETG, and considering 40mm/s infill speed with annealing to obtain optimum mechanical properties, and to replace automobile and aeronautical structural metallic components with these materials in the future.