Tensile fatigue behavior of short and continuous carbon fiber reinforced additively manufactured thermoplastic multiscale composite

Fiber reinforced multiscale composites represent a cutting-edge class of advanced materials that have garnered significant attention in the realm of materials science and engineering. These advanced materials intertwine various fiber reinforcements, meticulously tailored at micro, to macro levels, imparting them with remarkable mechanical, thermal, and functional properties. In this research, an experimental investigation was performed to observe the tensile fatigue behavior of short and continuous carbon fiber reinforced additively manufactured multiscale thermoplastic composites. The multiscale composite was fabricated by combining layers of continuous woven carbon fiber (CCF) with short carbon fiber (SCF) reinforced acrylonitrile butadiene styrene (ABS) laminates which were additively manufactured using the fused filament fabrication technique. It was observed that the multiscale composite exhibits a maximum 127% higher strength and 154% higher Young’s modulus than neat ABS polymer. Based on non-normalized stress-life curves, multiscale composites with four layers of CCF have a higher fatigue strength than multiscale composites with one layer of CCF. However, when the applied stress is normalized by the quasi-static strength, the multiscale composite with one layer of CCF had a longer fatigue life than the four layers of CCF reinforced multiscale composites at high normalized cyclic stress, while the multiscale composite with four layers of CCF exhibited a longer fatigue life at low normalized cyclic stress. The four CCF layers reinforced multiscale composites experienced a different extent of fiber pull-out, matrix cracking, and delamination at different stress levels. Conversely, fatigue failure of the one layer of CCF reinforced multiscale composites primarily occurred due to localized fiber breakage with minimal matrix-related damage.