## 4 Results
### Elastic Properties and ILT Strength  
Static results are given in Tables 1 and 2 for the unidirectional generic carbon/epoxy and fabric materials tested, respectively. Five OHC coupons were tested for each material. Full-field DIC strain data recorded during specimen loading is used in the FEMU procedure to extract material parameters (\(E_{11}\), \(E_{33}\), \(\
u_{13}\), \(G_{13}\)). After convergence, the ILTS is obtained from FE stress analysis at the failure load. Tables 1 and 2 also provide the average material parameters and ILT strength values and the associated normalized coefficient of variation (CV). Figure 15: FEMU total weighted RMS strain error for the strain data of the generic unidirectional carbon/epoxy OHC test specimen shown in Figures 12 and 13. The failure mode for all OHC specimen tested in static was consistent with a 6 o'clock and 12 o'clock delamination failure. The average ILT strength obtained from the carbon/epoxy tape specimens was 101 MPa (14.7 ksi), which was consistent with the interlaminar tensile strength measured by the authors in similar legacy carbon/epoxy materials during other programs. The average ILT strength obtained for the carbon/epoxy fabric material was 55.8 MPa (8.09 ksi). The first fabric specimen tested was an outlier that failed earlier compared to the other four specimens tested. Early failure was attributed to the strong presence of defects. The average elastic material constitutive properties obtained using the OHC-ILT method are compared with results from standard tests methods for \(E_{11}\), \(E_{33}\), and \(\
u_{13}\) and from the small-plate twist method [15] for \(G_{13}\) in Tables 3 and 4. As shown in Tables 3 and 4, the average OHC-ILT results are very consistent with results obtained independently for the same materials, but from different test methods and test specimen geometries. \begin{table}
\begin{tabular}{c c c c c} \hline
**Specimen** & \(E_{11}\)**, GPa (Msi)** & \(E_{33}\)**, GPa (Msi)** & \(\
u_{13}\) & \(G_{13}\)**, GPa (Msi)** & **ILTS 53, MPa (ksi)** \\ \hline US-1 & 139 (20.2) & 7.86 (1.14) & 0.295 & 5.47 (0.794) & 99.3 (14.4) \\ US-2 & 135 (19.6) & 8.00 (1.16) & 0.300 & 5.10 (0.740) & 103 (14.9) \\ US-3 & 137 (19.9) & 8.41 (1.22) & 0.345 & 4.68 (0.679) & 90.3 (13.1) \\ US-4 & 147 (21.3) & 9.17 (1.33) & 0.329 & 4.85 (0.704) & 112 (16.2) \\ US-5 & 145 (21.0) & 8.62 (1.25) & 0.320 & 5.21 (0.756) & 102 (14.8) \\ AVG & 140 (20.4) & 8.41 (1.22) & 0.318 & 5.06 (0.734) & 101 (14.7) \\ CV & 3.6\% & 6.1\% & 6.5\% & 6.1\% & 7.6\% \\ \hline \end{tabular}
\end{table} 
Table 1: Elastic constitutive properties and ILT strength for the carbon/epoxy unidirectional tape OHC-ILT specimens. \begin{table}
\begin{tabular}{c c c c} \hline
**Material Property** & **OHC-ILT FEMU Test Method** & **Other Test Method (Standards + Small Plate Twist0** \\ \hline \(E_{11}\), GPa (Msi) & 141 (20.4) & 144 (20.9) \\ \(E_{33}\), GPa (Msi) & 8.41 (1.22) & 8.76 (1.27) \\ \(\
u_{13}\) & 0.318 & 0.329 \\ \(G_{13}\), GPa (Msi) & 5.06 (0.734) & 5.22 (0.757) \\ \hline \end{tabular}
\end{table} 
Table 4: Comparison of average constitutive properties obtained using the OHC-ILT test with other test methods for the fabric material. \begin{table}
\begin{tabular}{c c c c c} \hline
**Specimen** & \(E_{11}\)**, GPa (Msi)** & \(E_{33}\)**, GPa (Msi)** & \(\
u_{13}\) & \(G_{13}\)**, GPa (Msi)** & **ILTS 53, MPa (ksi)** \\ \hline FS-1 & 62.4 (9.05) & 5.93 (0.86) & 0.344 & 4.22 (0.612) & 26.2 (4.80) (early failure due to defects) \\ FS-2 & 70.3 (10.2) & 9.03 (1.31) & 0.396 & 3.82 (0.554) & 67.1 (9.72) \\ FS-3 & 66.7 (9.68) & 9.51 (1.38) & 0.378 & 3.75 (0.544) & 56.8 (8.24) \\ FS-4 & 72.4 (10.5) & 7.79 (1.13) & 0.346 & 3.55 (0.515) & 42.3 (6.13) \\ FS-5 & 64.7 (9.39) & 7.93 (1.15) & 0.309 & 4.30 (0.623) & 57.0 (8.27) \\ AVG & 68.5 (9.94) & 8.55 (1.24) & 0.357 & 3.85 (0.559) & 55.8 (8.09) \\ CV & 5.1\% & 9.7\% & 10.7\% & 8.2\% & 18.2\% \\ \hline \end{tabular}
\end{table} 
Table 2: Elastic constitutive properties and ILT strength for the carbon/epoxy fabric OHC-ILT specimens.