## 4 Stress Analysis of Thick Laminated Composite Beams under Bending Load  
After performing the analysis on thin laminates, thick laminated composite beams were modeled and Tsai-Wu failure factors were evaluated accordingly using an analytical approach. The purpose of this study was to evaluate the strength-to-weight ratio of all these materials for their subsequent selection and utilization for design and analysis of the main landing gear strut. The results of the theoretical stress analysis of laminated composite beams under bending load are depicted in Table 4. The applied bending load was kept constant at 35,000 N in all cases. Passing the criterion of a Tsai-Wu failure factor less than or equal to 0.5 was set in order to evaluate the total requirement of material in terms of weight which could sustain the applied load. The aim of this analysis was to select two composite materials, one each from carbon- and glass-fiber families, meeting the stringent requirement of a Tsai-Wu value less than 0.50 with minimum weight. From the results shown in Table 4, it was concluded that T300 carbon fiber/epoxy lamina was the safest material on the basis of the strength-to-weight ratio among all the four beams along with an acceptable deflection value under bending load. Hence, T300 carbon fiber/epoxy composite material was recommended for further analysis from the carbon family. Similarly, it was further observed that the E-glass laminated beam had \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**E-glass/Epoxy**} & \multicolumn{2}{c}{**S-glass/Epoxy**} & \multicolumn{2}{c}{**Carbon (T300)/Epoxy**} & \multicolumn{2}{c}{**Carbon (AS)/Epoxy**} \\ \hline \multirow{2}{*}{**Number of Piles**} & **Tsai-Wu Failure Criteria** & **Number of Piles** & **Tsai-Wu Failure Criteria** & **Number of Piles** & **Tsai-Wu Failure Criteria** \\ \hline
72 & 0.46 & 65 & 0.47 & 51 & 0.47 & 52 & 0.47 \\ \hline \multicolumn{2}{c}{**Mass of the laminated beams/struts (kg)**} & & & & & \\ \hline \multicolumn{2}{c}{**8.26**} & \multicolumn{2}{c}{**6.8**} & \multicolumn{2}{c}{**3.68**} & \multicolumn{2}{c}{**3.83**} \\ \hline \multicolumn{2}{c}{**Deflection of the laminated struts (cm)**} & & & & & \\ \hline
**5.1** & **6.8** & **4.3** & **5.23** \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of thick laminated composite beams under bending load of 35,000 N. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**S-glass/Epoxy**} & \multicolumn{2}{c}{**S-glass/Epoxy**} & \multicolumn{2}{c}{**Carbon (T300)/Epoxy**} & \multicolumn{2}{c}{**Carbon (AS)/Epoxy**} \\ \hline \multirow{2}{*}{**Number of Piles**} & **Tsai-Wu Failure Criteria** & **Number of Piles** & **Tsai-Wu Failure Criteria** & **Number of Piles** & **Tsai-Wu Failure Criteria** \\ \hline
72 & 0.46 & 65 & 0.47 & 51 & 0.47 & 52 & 0.47 \\ \hline \multicolumn{2}{c}{**Mass of the laminated beams/struts (kg)**} & & & & \\ \hline \multicolumn{2}{c}{**8.26**} & \multicolumn{2}{c}{**6.8**} & \multicolumn{2}{c}{**3.68**} & \multicolumn{2}{c}{**3.83**} \\ \hline \hline \multicolumn{2}{c}{**Deflection of the laminated struts (cm)**} & & & & \\ \hline
**5.1** & **6.8** & **4.3** & **5.23** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of Tsai-Wu failure criterion under 200 kN longitudinal and 100 KN transverse loading. a maximum weight of 8.26 kg and was considered as the heaviest among all the beams. Therefore, the E-glass/epoxy pre-preg material was rejected and S-glass/epoxy composite material from the glass fiber family was recommended for further analysis. In the next step, composite beams of recommended material T300 carbon fiber/epoxy and S-glass fiber/epoxy were modeled and analyzed using Abaqus CAE(r). The results of the computational analysis were then compared with the analytical analysis; the comparison is shown in Table 5. The comparison of the theoretical and computational results showed that the results for the deflection of the beams were the same in both the approaches.