Tensile and flexural behaviors of additively manufactured continuous carbon fiber-reinforced polymer composites

Continuous carbon fiber-reinforced polymer (CCFRP) composites are lightweight and strong materials that have been used in a wide range of applications in automotive and aerospace industries. Traditional manufacturing processes (e.g., lay-up and out of autoclave techniques) are not capable of fabricating complex composites. Additive manufacturing (AM) has been increasingly used to fabricate composites with complex geometries. In this study, CCFRP with concentric and isotropic carbon fiber infill patterns were additively manufactured using fused deposition modeling (FDM). The microstructures of CCFRP composites with both infill patterns were characterized by an optical microscope and a scanning electron microscope (SEM). The void density was characterized for infill, solid and carbon fiber regions. Four-point flexural tests and tensile tests were conducted to evaluate the effects of carbon fiber concentration and infill patterns on both tensile and flexural behaviors. A stiffness averaging method was used to model the elastic behavior of CCFRP samples with different microstructures by taking into account porosity in infill, solid and carbon fiber bundles. Experimental results have shown that the specimens with the concentric carbon fiber infill pattern exhibit better flexural strength and energy absorption capability than those with the isotropic carbon fiber infill pattern. As carbon fiber concentration and the number of fiber rings increase, the flexural strength of the CCFRP composite increases. The specimen with 48.72 wt% carbon fibers showed the highest flexural strength of 270.63 MPa. In comparison with chopped carbon fiber-reinforced polymer composites, the flexural strength of the CCFRP specimen was increased by 40%. The predicted elastic moduli are in good agreement with experimental data.