## 4 Conclusions  
This study investigated a new and novel method to evaluate the coupled multifunctional electro-flexural properties of the additively manufactured multifunctional continuous carbon fiber solid laminate composites at ambient temperature. In this study, a new multifunctional test method was proposed to address the coupling effects of the two unit-functional properties (electrical and flexural) in the same component simultaneously. Test coupons were manufactured using a 3D printing technique for printing continuous carbon fiber solid laminate composites. The experimental results showed that the test specimens exhibited average values of ultimate load of 168.7 N with a corresponding deflection at an ultimate load of 0.0085 m, while the average maximum flexural stress was 247 MPa, and the maximum strain was 0.0195 m/m. The reported maximum flexural stress is 271 MPa and the associated maximum strain is 0.0202 m/m. The observed maximum resistance during the multifunctional testing was 55.1 G Ohms (as the multifunctionality property in this investigation). The resistance versus strain behavior of the specimens were shown to be stable, albeit with a small degree of fluctuations that are contributed by the underlying coupled tension effects on the top of the coupons and the compression effects on the bottom of the same test coupons while the specimens underwent the multifunctional testing at the RTD. This study also showed that the coupons' deformations were the contributing factors for small fluctuations in electrical resistance values of the specimens from one layer to another. Another contributing factor for that small fluctuation is the onyx coating of the continuous carbon fiber strand. As the combination of tensile and compressive forces are exerted on the different layers, the onyx coating acts as an insulating agent and thus leading to an increase in resistivity. The residual resistance value of at least 25 plus G Ohms on the test coupons as depicted in the plots of resistance versus strain showed that the test articles can be optimized and tailored to achieve desired multifunctional properties (as both the structural and electrical). Selection of the coating material will play a significant role in optimizing the multifunctional properties of the 3D printed continuous carbon fiber solid laminate composites. This study also investigated the failure modes and mechanisms \begin{table}
\begin{tabular}{c c} \hline
**Coupon ID** & **Maximum Resistance (G Ohms)** \\ \hline
6207-00303 & 55.1 \\ \hline
6207-00304 & 30.8 \\ \hline
6207-00305 & 41.5 \\ \hline Average & 42.5 \\ \hline Standard Deviation & 12.18 \\ \hline Coefficient of Variation (COV) & 28.68\% \\ \hline \end{tabular}
\end{table} 
Table 2: Summary of maximum resistance values of test specimens. of the tested coupons. Those results suggest that the multifunctional electro-flexural characterization at RTD is consistent with the failure modes of the traditionally manufactured carbon fiber composites and that they agree well with the traditional composites failure modes. This agreement with the traditional failure modes signifies the importance of this new and novel method for assessing the multifunctional properties of the 3D printed continuous carbon fiber solid laminates. The relatively negligible amount of delamination and voids in the 3D printed coupons compared to the traditional hand-laid up composites may have also contributed to that small degree of fluctuations in the electrical resistance property along the strain variations. Thus, this investigation's findings suggest that the 3D printed continuous carbon fiber solid laminate composites exhibit a multifunctional property appropriate for aircraft, UAS, and spacecraft applications due to their practicality and significant weight-savings potential. Conceptualization, R.G. ; methodology, R.G. ; investigation, R.G. ; resources, R.G. ; writing--original draft preparation, R.G. ; writing--review and editing, R.G., F.L. ; supervision, F.L. ; project administration, R.G. ; funding acquisition, R.G.