# Study of Mechanical Properties of Micron Polystyrene-Tughened Epoxy Resin
## 3 Results and Discussions
### The Flexural Properties of Epoxy Resins with Different PS Weight Fraction  
The results of three-point bending tests for specimens with different mass fractions of PS microspheres doped are shown in Table 3. Based on the data in the table, the flexural strength, flexural modulus and deflection curves were plotted for different weight fractions of PS.  
The flexural strength of the specimens with different PS weight fractions is shown in Figure 10. As shown in the figure, the flexural strength of the specimens increased with the increase in PS weight fraction. When the PS weight fraction was increased to 2.5 wt%, the flexural strength of the specimens reached a peak of 178 MPa, which was 71% higher than that of the specimens without PS addition, with a significant enhancement effect. The bending strength of the specimens showed a decreasing trend when the PS content was increased to 5 wt%, and the bending strength of the specimens was only 96.48 MPa, which was 46% lower than that of the specimens with a PS weight fraction of 2.5 wt% and 9 MPa smaller than that of the specimens without PS addition.  
Figure 11 shows the flexural modulus of specimens with different PS weight fractions. As can be seen from the figure, the variation pattern of flexural modulus is similar to that of flexural strength, showing a trend of rising to the peak and then falling. The specimens with PS weight fraction of 2.5 wt% show the largest flexural modulus, which is 35% higher than that of the specimens without PS addition, with a clear trend of improvement. However, as the PS weight fraction increased again, the flexural modulus of the specimens decreased. When the PS weight fraction increased to 5 wt%, the flexural modulus decreased by 39%  
Figure 10: Flexural strength of specimens with different PS content.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Symbol**} & **PS Weight** & **Flexural** & **Flexural** & **Deflection (mm)** \\  & **Fraction (wt\%)** & **Strength (MPa)** & **Modulus (MPa)** & **Deflection (mm)** \\ \hline
1 & 0 & 105 & 4515 & 22.722 \\
2 & 1.25 & 127 & 5944 & 16.6787 \\
3 & 2.50 & 178 & 6912 & 16.9621 \\
4 & 3.75 & 102 & 4792 & 14.1701 \\
5 & 5 & 96 & 4193 & 15.7122 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Three-point bending test data of epoxy resin colloids with different PS weight fractions.  
compared to the specimens with a PS weight fraction of 2.5 wt% and was 322 MPa smaller than that of the specimens without PS addition.  
Figure 12 shows the load-deflection curves of specimens with different PS weight fractions. As can be seen from the figure, the curve is divided into two parts: the elastic stage and the damage stage. At the beginning of loading, the load-deflection curve is a straight line, and the specimen is in the elastic stage; as the load continues to increase, the specimen deflection reaches its peak; then as the load increases, the curve starts to decline, and the specimen enters the damage stage. The load-deflection curves corresponding to specimens with different PS weight fractions vary greatly. When the weight fraction of PS was 0 wt%, the deflection of the specimen was the largest; as the weight fraction of PS increased, the slope of the curve increased and the peak value increased, but the corresponding range of deflection changes decreased significantly; when the weight fraction of PS increased from 1.25 wt% to 2.5 wt%, the slope and peak value of the curve increased, but the corresponding deflection changes were small or even unchanged; continuing to increase the weight fraction of PS, the slope and peak of the curve show a decreasing trend when the weight fraction of PS is increased. However, the changes in deflection of the specimens mixed with PS were all in the same range, and the deflection was substantially decreased compared with the specimens without PS added.  
Figure 11: Flexural modulus of specimens with different PS content.  
Figure 12: Load-deflection curves of specimens with different PS content.