# Mechanical and Conductive Behavior of Graphite Filled Polysulfone-Based Composites
## 3 Results and Discussion
### Mechanical Properties
#### 3.3.4 Mechanical Properties' Summary  
Tables 3 and 4 demonstrate the mechanical properties and Young's Modulus of the studied composites as a function of filler content.  
The ability to withstand mechanical forces is better when using AG as a filler than when using NG and EG. This can be attributed to the fact that small-grained fillers make composite materials denser and more durable, which opens the door to the possibility of transferring the mechanical load between the filler and the polymer. When a filler with large granules is used, a compound with gaps between the filler and the polymer is created. The strength of a composite is also increased by the presence of smaller particles. Among other things, optimizing the quantity, size, distribution, and form of filler pellets can result in composite materials with higher mechanical properties. The variation in the mechanical properties can be explained because the adhesion between the polymer and the filler is not always optimal for transfer of the mechanical loads between the matrix and the filler. Compared to the flexural, tensile and compression strengths of the unfilled PSU (Table 1), which are 120 MPa, 75 MPa and 89.6 MPa respectively [35], we can assume as we had mentioned before that using a graphite type filler with polysulfone gives the matrix more brittleness and stiffness properties and reduces the elasticity of the polymer.  
The Young's Modulus increased as filler content increased, which led to more brittle material. In general, Young's Modulus increases linearly with filler content, as we can see in Table 4, demonstrating the higher stiffness of graphite-reinforced composites.  
The flexural strength of NG/resin composites tends to gradually decrease with an increase in NG content from 30 to 60 wt.%, according to the similar findings of [PERSON] and [PERSON] [36]. Flexural strength and modulus fell from 42.67 MPa and 8.4 GPa to 23.43 MPa and 6.8 GPa, respectively, when the proportion of NG was increased from 30 to 60 wt.% by weight. Beyond 50 wt.% of NG content loading, both the flexural strength and modulus drop at dramatically greater rates. This indicates that when the NG concentration increases, weaker bonds form between the graphite flake and the phenolic resin.  
Regarding the general trends, the outcomes here are more satisfactory than those in the work of [PERSON] et al. [37], where there was a fluctuation in tensile strength as the filler content rose. The samples behave somewhat differently in relation to tensile strength. Even though graphite was present and contributed to the tensile strength decline, its presence did not significantly affect the tensile strength. The stress concentration in the polysulfone-carbon graphite particle interface, which causes the membranes to break at lower tensions, could be the cause of the composite membranes' brittleness.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Filler Content wt.\%** & \multicolumn{3}{c}{**Flexural Test**} & \multicolumn{3}{c}{**Tensile Test**} & \multicolumn{3}{c}{**Compression Test**} \\ \hline \multicolumn{8}{c}{**Young’s Modulus GPa**} & \multicolumn{3}{c}{**Young’s Modulus GPa**} & \multicolumn{3}{c}{**Young’s Modulus GPa**} \\ \hline \multicolumn{8}{c}{**N**G**} & **AG** & **EG** & **NG** & **AG** & **EG** & **NG** & **AG** & **EG** \\
30 & 5.32 \(\pm\) 0.2 & 3.82 \(\pm\) 0.12 & 3.89 \(\pm\) 0.4 & 2.23 \(\pm\) 0.1 & 3.71 \(\pm\) 0.14 & 4.14 \(\pm\) 0.22 &