## 4 Discussion  
The method proposed by [PERSON] and [PERSON] includes simplified and general formulas that allow knowing the maximum and distributed values of the normal and shear stresses along with the adhesive. The results obtained with both formulations result in similar values and simplified formulas allow the quick estimation and easy application.  
2D and 3D models have the same boundary conditions, making it possible to make a comparison between the results of the stresses. The 2D model is made for a local analysis allowing a more refined mesh; the stress distribution results obtained demonstrate a slight difference in their extreme values of the adhesive, attributed to boundary singularities of the model.  
\begin{table}
\begin{tabular}{c c c c} \hline  & **Pressure Factor** &
\begin{tabular}{c} **Design Pressure, \(p\)** \\ **(kN/m\({}^{2}\))** \\ \end{tabular} & **Failure Criterion** \\ \hline \(p\) (initial) & 1.000 & 5.160 & 0.540 \\ \(p\) (maximum) & 1.360 & 7.030 & 1.000 \\ \hline \end{tabular}
\end{table}
Table 4: Design limit pressure using the failure criteria.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & & \multicolumn{5}{c}{**FEA**} \\ \cline{3-8}
**Variable** & **Value** & \multicolumn{5}{c}{**A (0,0,0) mm**} & \multicolumn{5}{c}{**B (0,75,0) mm**} \\ \cline{3-8}  & & \(\sigma\) & \(\tau\) & \(\sigma\) & \(\tau\) & \\  & & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** \\ \cline{3-8}  & & **z** & **yz** & **xz** & **z** & **yz** & **xz** \\ \hline \(T\) (N/mm) & 4899 & \(-\)0.006 & - & 8.152 & \(-\)0.006 & - & 8.152 \\ \(V\) (N/mm) & 5127 & 2.330 & 1.020 & - & \(-\)0.610 & 2.480 & - \\ \(P\) (N/mm) & 134 & 0.493 & \(-\)0.393 & - & \(-\)0.014 & 0.023 & - \\ \hline \(\sigma_{z}\) (MPa) & 2.817 & - & - & -0.629 & - & - \\ \(\tau_{yz}\) (MPa) & - & 0.627 & - & - & 2.503 & - \\ \(\tau_{xz}\) (MPa) & - & - & 8.152 & - & - & 8.152 \\ \hline \(Z_{t}\) (MPa) & & 9.500 & & & 9.500 & \\ \(S_{t}\) (MPa) & & 17.950 & & & 17.950 & \\ \hline Interlaminar Stress & & & & & 0.650 & \\ Fraction, \(F_{rc-i}\) & & & & & 0.650 & \\ \hline Failure Criteria & & & & & 0.520 & \\ \hline \end{tabular}
\end{table}
Table 3: Failure criteria the tubular hybrid joint: FEA.  
\begin{table}
\begin{tabular}{c c c} \hline  & **Safety Factor** & **Failure Criterion** \\ \hline F\({}_{rc-i}\) (initial) & 1.540 & 0.540 \\ F\({}_{rc-i}\) (minimum) & 2.080 & 1.000 \\ \hline \end{tabular}
\end{table}
Table 5: Safety factor using the failure criteria.  
Figure 8a shows that applying a horizontal force (\(T\)), the Bigwood and Crocombe formulas do not calculate the normal stress, however, the FEA model shows the normal stress.  
Regarding the points defined in Figure 3, it can be shown in Figure 10 that when the force \(V\) is applied at point A, there is a shear stress value of 1.031 MPa, while at the extreme point B the shear stress is 3.076 MPa, this difference in stress is due to the moment reaction generated at the boundary condition in the adherent 2.  
In Figures 11 and 12, the behavior of the stresses through the laminate and its interfaces is shown. The stresses of the adhesive are like those presented in the first interface of the adherents 1 and 2, therefore the thickness of the interface and the adhesive of the joint must be considered.  
In Figure 12 of the 2D model, high-stress values are presented in the corner of the external laminate of the adherent 1 due to the stress concentration in this corner.  
A tubular hybrid joint (see Figure 6) can be optimized based on the number of layers of the tubular laminate, configuration of the tubular structure, and the limit pressure that the FRP panel and the hybrid tubular joint can support. In cases where it is required to increase the pressure \(p\), the FRP panel laminate should be reviewed utilizing critical layer analysis, and as an option closer vertical pipes can be installed.