## 4 Results
### Evaluation of Strain Behavior  
To evaluate the strain behavior predicted by the developed PFA method, strain values were compared to those obtained from the DIC. Figures 12 and 13 show the longitudinal strain (\(\varepsilon_{xx}\)) contour obtained from the PFA and DIC results at the fracture moment, respectively. The applied displacement direction is up and down. The strain values were concentrated near the open hole because of the stress concentration induced from the geometric discontinuity. When comparing the PFA and DIC results, the legend range of DIC was matched with the PFA result contour and it can be verified that the overall strain distribution was similar for the PFA and DIC. For the one-open-hole tensile case, the maximum value observed from the PFA result was 0.01873 while the DIC result was 0.01804. Likewise, in all other cases, the strain values obtained from the PFA were compared to those of the DIC; the values were observed similarly. Furthermore, the strain values obtained from the PFA and DIC were compared to the measured values by strain gauges. Figures 14-17 show the maximum longitudinal strain values obtained from the strain gauge, PFA, and DIC at the same point for open-hole tests. Figures 14a, 15a, 16a and 17a show the location of the attached strain gauges. The point was selected based on the position of the strain gauge. Figure 14b,c, Figure 15b,c, Figure 16b,c and Figure 17b,c show the mean values of the strain values measured by the strain gauges. The maximum error was 9.74%, which was observed in the two-open-hole compressive test case; other cases had a lower error. According to this comparison for specific strain values at each location, it can be verified that the developed PFA model is effective in predicting the strain behavior of the notched composite laminate regardless of the tensile or compressive loading conditions and stacking sequences.  
Figure 11: Load-displacement curves for two-open-hole tests and PFA results under (**a**) tensile, and (**b**) compressive loading conditions.  
Figure 10: Compressive load-displacement curves for one-open-hole compressive tests and the PFA.  
Figure 12: Longitudinal strain (\(\varepsilon_{xx}\)) contour at fracture moment obtained from PFA.  
Figure 13: Longitudinal strain (\(\epsilon_{xx}\)) contour at fracture moment obtained from DIC.  
_Appl. Sci._**2019**, \(9\), 5572  
Figure 14: Location of attached strain gauges and longitudinal strain (\(\varepsilon_{xx}\)) value comparison for one-open-hole tensile tests: (**a**) Location of strain gauges, (**b**) strain comparison results for Type 1, and (**c**) strain comparison results for Type 2 stacking sequences.  
Figure 16: _Cont_.  
Figure 15: Location of attached strain gauges and longitudinal strain (\(\epsilon_{xx}\)) value comparison for one-open-hole compressive tests: (**a**) Location of strain gauges, (**b**) strain comparison results for location 1 and 2, and (**c**) strain comparison results for location 3 of the specimens.  
Figure 16: Location of attached strain gauges and longitudinal strain (\(\epsilon_{xx}\)) value comparison for two-open-hole tensile tests: (**a**) Location of strain gauges, (**b**) strain comparison results for location 1, and (**c**) strain comparison results for location 2 and 3 of the specimens.