## 3 Results and Discussion
The strain associated with the peak resistance value for test coupon 6207-00304 was found to be 81.02% higher than the corresponding failure strain for test coupon 6207-00304. The strain associated with the corresponding failure strains for test coupon 6207-00305 was observed to be 64.13% higher than the corresponding failure strains for test coupon 6207-00305. The resistance values during the tests were found to be higher than the residual resistance values for the one test coupon (6207-00304) and were lower than the resistance values for the other two test coupons (6207-00303 and 6207-00305). Figure 4: Strain-strain behavior of multifunctional test coupons at RTD: (**a**) 6207-00303; (**b**) 6207-00304; and (**c**) 6207-00305. For test coupon 6207-00305, the residual resistance value (41.5 G Ohms) was found to be higher than the values recorded during the tests (37.6 G Ohm, 9.40% lower than 37.6 G Ohms). This may be attributed to material and manufacturing defects. Thus, the reported coefficient of variation (COV) in Table 2 is higher. The slight variation in the values could have been contributed by the lack of electrical shielding as well as the difficulty on the MTS machine to add the electrical shielding system. Resistance versus strain behavior of the test specimens was found to be stable with a small degree of fluctuations. This small degree of fluctuation may have been contributed to by the underlying coupled compression on the top of the coupons and the tension on the bottom of the test coupons while the specimens underwent multifunctional testing. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Coupon ID** & **Ultimate Load (N)** & \begin{tabular}{c} **Deflection at Ultimate** \\ **(m)** \\ \end{tabular} & \
\begin{tabular}{c} **Maximum Flexural** \\ **Stress (MPa)** \\ \end{tabular} &
\begin{tabular}{c} **Maximum Strain,** \\ \(\varepsilon\) \\ \end{tabular} \\ \hline
6207-00303 & 154.7 & 0.0069 & 204 & 0.0166 \\ \hline
6207-00304 & 172.6 & 0.0097 & 268 & 0.0218 \\ \hline
6207-00305 & 178.7 & 0.0089 & 271 & 0.0202 \\ \hline Average & 168.7 & 0.0085 & 247 & 0.0195 \\ \hline Standard Deviation & 12 & 0.0015 & 38 & 0.0026 \\ \hline Coefficient of Variation (COV) & 7.4\% & 17.3\% & 15.3\% & 13.4\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of results of test specimens. Figure 5: Multifunctional flexural-electrical performance of test coupons at RTD: (**a**) 6207-00303; (**b**) 6207-00304; and (**c**) 6207-00305. The linear and non-linear deformations of the 3D printed continuous carbon fiber composites specimens contributed to the slight rise and decrease in electrical resistance property of the test coupons from one layer to another. The onyx coating of the continuous carbon fiber strand also played a vital role in small fluctuations from layer to layer as the specimens underwent multifunctional testing at RTD. The failure modes of the tested coupons, as shown in Figure 2, suggest that the multifunctional flexural-electrical characterization performance at RTD is consistent with the traditional carbon fiber composites. The lack of delamination and voids in the 3D printed coupons compared to the traditional hand-laid up composites may have also contributed to a small degree of fluctuations in the electrical resistance property along the strain variations. Thus, the coupled flexural-electrical evaluation of 3D printed multifunctional composites at ambient temperature proves suitable for aerospace applications. This experimental investigation and its results suggest that the 3D printed continuous carbon fiber solid laminate composites exhibit a multifunctional property appropriate for aircraft, UAS, and spacecraft applications.