## 3 Results and Discussion
### Parametric Study
#### 3.2.1 Single Interface Delamination  
In this section, the static analysis is conducted for the same laminates with delaminations of varying size and location. A uniformly distributed pressure load is applied to the plates, ranging from 0 to 3500 kN/m\({}^{2}\), and the maximum displacement is calculated for each load step. The results obtained considering geometric nonlinearity are compared with the corresponding results from the linear analysis. The load vs. maximum displacement curve for nonlinear analysis has been plotted for a delamination size of \(0.1a\times 0.1a\) with various boundary conditions for damage locations at the center, edge, and corner in Figure 5a,b, Figure 5c,d, and Figure 5e,f, respectively. The load vs. maximum displacement curve for nonlinear analysis has been plotted for a delamination size of \(0.2a\times 0.2a\) with various boundary conditions for damage locations at the center, edge, and corner in Figure 6a,b, Figure 6c,d, and Figure 6e,f, respectively. Similarly, the load vs. maximum displacement curve for nonlinear analysis has been plotted for a delamination size of \(0.5a\times 0.5a\) with various boundary conditions for damage locations at the  
Figure 4: Maximum linear and nonlinear deflection of intact composite plates of various boundary conditions and lamina sequences. (**a**) Maximum linear and nonlinear deflection for SSSS boundary condition. (**b**) Maximum linear and nonlinear deflection for CSCS boundary condition. (**c**) Maximum linear and nonlinear deflection for CCCC boundary condition. (**d**) Maximum linear and nonlinear deflection for CFFF boundary condition. center, edge, and corner in Figure 7a,b, Figure 7c,d, and Figure 7e,f, respectively. The plate with the SSSS boundary condition exhibits the highest maximum displacement, followed by CSCS, CFFF, and CCCC, respectively. Moreover, for SSSS and CSCS boundary conditions, the plate with a cross-ply laminate exhibits the maximum displacement, followed by symmetric and anti-symmetric angle-ply laminates. In the case of CFFF and CCCC boundary conditions, the plate with an anti-symmetric laminate exhibits the maximum displacement, followed by a symmetric angle-ply laminate and a cross-ply laminate. All the cases of delaminated laminates show the same trend, except for a few plots (Figure 7b,d) for the delamination size 0.5\(a\). In these cases, the symmetric angle-ply laminate exhibits the maximum displacement, followed by the anti-symmetric angle-ply and cross-ply laminates for the CCCC boundary condition. Overall, in the case of the CFFF boundary condition, the maximum displacements of the laminate vary significantly based on the lamina orientation, while for other boundary conditions, these variations are smaller. Figure 5: Maximum nonlinear deflection of composite plates of various boundary conditions, lamina sequences, and delamination locations with delamination size of a/10. **(a)** Maximum nonlinear deflection for SSSS and CFFF boundary conditions with delamination at center. **(b)** Maximum nonlinear deflection for CCCC and CSCS boundary conditions with delamination at center. **(c)** Maximum nonlinear deflection for SSSS and CFFF boundary conditions with delamination at edge. **(d)** Maximum nonlinear deflection for CCCC and CSCS boundary conditions with delamination at edge. **(e)** Maximum nonlinear deflection for SSSS and CFFF boundary conditions with delamination at corner. **(f)** Maximum nonlinear deflection for CCCC and CSCS boundary conditions with delamination at corner. Next, the effect of nonlinearity on delamination size for the cross-ply laminate has been plotted in terms of percentage changes in maximum deflection vs. load in Figure 8a,b, Figure 8c,d, and Figure 8e,f for damage located at the center, edge, and corner, respectively. In most cases, apart from a few exceptions, it is found that the larger the damage size, the greater the effect of nonlinearity.