###### Abstract  
Multifunctional composites offer a higher strength to weight ratio, electrical properties, etc., thereby providing possible solutions for replacing the physical electrical wirings in aircraft. The lack of research on the coupled multifunctional characterization of 3D printed composites flexural-electrical properties is the main reason for its unsuitability in aerospace applications. The proposed method evaluates multifunctional flexural-electrical properties of 3D printed multifunctional carbon fiber composites. Traditional methods for conducting structural and electrical analyses for aircraft certification do not accommodate new technologies that are not yet proven. Such technologies are additive manufacturing (AM) techniques, multifunctional composite structures, and the certification requirements for 3D printed multifunctional carbon fiber composites for use in aircraft. In this study, the multifunctional 3D printed specimens were concurrently evaluated for flexural-electrical properties using three-point bending and electrical conductivity tests. The results showed that the multifunctional properties included the maximum flexural strength of 271 MPa and the maximum electrical resistance of 55.1 G Ohms, with the failure modes and mechanisms found to be consistent with the traditional composites. Due to its infancy, the existing AM techniques, and the use of the multifunctional carbon fiber composites manufactured using those AM technologies, are not implemented on a large commercial scale. coupled flexural-electrical evaluation; 3D printing; multifunctional composites; continuous carbon fiber solid laminate; ambient temperature testing +
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of the carbon fiber concentration and infill patterns on both flexural and tensile properties [4]. While the test results showed that the coupons with the concentric carbon fiber infill pattern exhibited higher flexural strength and energy absorption capability than those with the isotropic carbon fiber infill pattern, the multifunctional properties, with respect to the coupled flexural-electrical evaluation of additively manufactured multifunctional composites at ambient temperature, was not addressed [4]. The multifunctional properties, such as the flexural and electrical properties on the same component, are not addressed yet. They are not matured, thus needing research to analyze the applications of the coupled multifunctional characterization of the multifunctional composites in the aircraft primary and secondary structures. Monofunctional flexural assessment of traditionally manufactured composites using a three-point bending test, and failure analysis using a scanning electron microscope, were conducted [5]. Quasi-static rate of 1 mm/minute was used for in-situ three-point bend tests on glass/epoxy (GE) and carbon nanotubes embedded glass/epoxy (CNT-GE) composites at ambient condition (20 \({}^{\circ}\)C), 70 \({}^{\circ}\)C, 110 \({}^{\circ}\)C, \(-\)80 \({}^{\circ}\)C and \(-\)40 \({}^{\circ}\)C [5]. The experimental results showed that the flexural strength of GE and CNT-GE composites at 110 \({}^{\circ}\)C was significantly decreased by 67% and 81%, respectively, compared with their strength at \(-\)80 \({}^{\circ}\)C [5]. Similarly, 38% and 77% decrease in modulus values were observed for the GE and CNT-GE composites, respectively [5]. Post failure analysis of the fractured specimens was conducted to evaluate various possible failure modes and failure mechanisms using the SEM [5]. Since the scope of this paper was limited to monofunctional composites manufactured using the traditional hand layup method, this paper did not address the multifunctional properties of the 3D printed multifunctional continuous carbon fiber solid laminate composites. Monofunctional three-point bending flexural testing was conducted on continuous glass-fiber reinforced thermoplastic composites test coupons, manufactured using laser-assisted AM technique [6].