## 5 Results and Discussion
### Effect of the Particle Volume Fraction on the Tensile Properties of the Composites  
Figure 8a shows the equivalent stress cloud map of the SiCP/6061 Al composites with a SiCp volume fraction of 5%, 10%, and 15% at a nominal strain of 0.2%. Figure 8b shows the average equivalent stress of the SiCP/6061 Al composites with different SiCp volume fractions. It was found that the average equivalent stress of the 6061 Al matrix was lower than that of the SiC-reinforced phase, and the bearing effect of the SiC-reinforced phase was more obvious. In this state, the average equivalent stress of the 6061 Al matrix with different SiCp volume fractions was higher than the yield stress (220 MPa) obtained by the nanoindentation experiment and increased with the increase in the SiC volume fraction.  
Figure 9 is the equivalent plastic strain cloud diagram and logarithmic strain cloud diagram of the RVE model of the SiCP/6061 Al composites with different volume fractions at the nominal strain of 0.2%. It can be seen that the equivalent plastic strain was mostly concentrated in the matrix near the particle boundary. This is because the particles bear a load much higher than the matrix, resulting in an increase in the deformation of the matrix near the matrix-particle interface [4]. Combined with the logarithmic strain cloud diagram, it can be found that the strain of the 6061 Al matrix part in the RVE model was higher than that of the SiC reinforcement part.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Interface** & \
\begin{tabular}{c} **Interface Failure Stage** \\ **(Initial Strain Value/\%)** \\ \end{tabular} &
\begin{tabular}{c} **Matrix Damage Stage** \\ **(Initial Strain Value/\%)** \\ \end{tabular} & **Breaking Strain (\%)** \\ \hline Weak & 1.9\% & 3.9\% & 6.8\% \\ Medium & 2.1\% & 4.8\% & 7.5\% \\ Strong & 2.5\% & 8.9\% & 14\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Model strain value and fracture strain value at the beginning of the strong, medium, and weak interface failure stages and matrix damage stages.  
Figure 7: Equivalent plastic strain nephogram of the RVE model with matrix failure.  
Figure 8: (a) The equivalent stress (S) cloud diagram of the RVE model of the SiCP/6061 Al composites with different volume fractions when the nominal strain was 0.2%; (b) the average equivalent stress of each component in the RVE model of the SiCP/6061 Al composites with different volume fractions.  
Figure 9: Equivalent plastic strain (PE) nephogram and logarithmic strain (LE) nephogram for the RVE models of the SiCP/6061 Al composites with different volume fractions when the nominal strain was 0.2%.  
Figure 10a-c show the 5%, 10%, and 15% volume fractions of the SiCp/6061 Al composite RVE model, respectively. Figure 10d is the nominal stress-strain curve of the corresponding volume fraction. Figure 10e-g are the plastic strain cloud map of the SiCp/6061 Al composites with volume fractions of 5%, 10%, and 15% after RVE model fracture, respectively. It can be seen that the yield strength of the SiCp/6061 Al composites increased, and the fracture strain decreased, with the increase in the SiCp volume fraction. The simulation results of the nominal stress-strain curves of SiCp/6061 Al composites with volume fractions of 5%, 10%, and 15% were in good agreement with the experimental results in the nearly whole tensile stage. The tensile strength of the SiCp/6061 Al composites with different volume fractions was not significantly different from the yield strength. This is due to the failure mode of the RVE model. The mesh unit in the fractured region was directly deleted, resulting in a sharp increase in the force amplitude, and the adjacent unit continued to fail rapidly, resulting in the rapid propagation of cracks. This phenomenon has been observed many times in related studies [36]. Although the tensile strength of the material cannot be obtained according to the simulation results, the yield strength results obtained by simulation are still valuable in engineering applications.