## 4 Discussion  
The non-isotropic and isotropic filler distribution within the polymer matrix is displayed in Figure 10a. The particle's shape plays a crucial role in the filler distribution. Non-isotropic particles create eddies in the matrix, resulting in some porosity within the volume; however, filler adhesion with polymer resulted stronger. For the isotropic particle, uniform distribution of the filler within the polymer matrix was observed. The mechanism of the filler particle movement within the matrix is explained in terms of simulation and surface images. The adhesion of the filler particles is shown in Figures 11 and 12. It is possible to observe the sedimentation of filler particles towards the bottom of the matrix that may arise from the gravitational pull of attraction. This results in the sedimentation of the larger particles towards the bottom of the polymer matrix. However, regular size particles show uniform distribution without any agglomeration that leads to sedimentation. Spherical shape particles are well dispersed [35; 36], whilst irregularly shaped particles showed an interlocking mechanism of allowing the polymer to enter along the non-uniform edges of the boundary [37]. The boundary area acts as a hook for strong polymer-particle adhesion.  
In the case of regular-shaped particles, the boundary is smooth, thus resulting in weaker adhesion within the matrix. Some voids towards the bottom of the particles were observed, which could be due to the gravitational force attraction [38]. Some particles have good wettability; however, interfacial adhesion of irregular particles has stronger adhesion than regular ones. The inter-particle bonding is stronger that result in agglomeration of the particles in irregularly shaped filler [39]. The irregular particles dispersed in the polymer matrix showed higher apparent viscosity than the case of nearly spherical filler suspension. The viscosity of irregular particles depends not only on the dispersing ability of the medium but also on itself viscosity [40]. Mechanical properties are associated with the resistance of a material to deformation under load. The mechanical properties of polymers are complex due to their viscoelastic nature, which is demonstrated by a strong dependence of the mechanical properties on time and temperature. The mechanical properties of polymers are dependent on many factors, including microstructure, chemical composition, residual stresses, reinforcing particles. In polymer composite reinforced with particles of graphite  
Figure 9: Scheme of the contour pressure (**a**) at lower and (**b**) higher time range for isotropic particle distribution in the polymer matrix.  
and carbonyl iron also influence the microstructure, hardness of the material. The influence of the dispersion state of the particles such as graphite and Carbonyl iron shows well dispersion and distribution in polymer composite. The polymer reinforced with graphite particles shows very softly in structures in compare to CI particles. The lower rigidity of the composite structure may lead to the lower density of the graphite particles (2.26 g/cm\({}^{3}\)). However, CI iron shows better response in mechanical properties that is proved by many researchers [23; 24; 25; 26]. Improving the durability of composite material, an insight view need to develop into the influence of microstructure on the distribution of filler particles and its contribution towards mechanical properties [27; 28; 29; 30; 31].  
The supplementary files (Video S1) displays the graphite and iron filler distribution in the polymer composite. The micro computed tomography investigates the filler distribution within volume of the composite. The inner volume of the composite shows the filler distribution in one by one frame with various planes of distribution. The quality of the composite displays the filler distribution and some voids in the interior areas.  
Figure 10: _Cont._  
Figure 10: Non-isotropic (**Top**) and isotropic (**Down**) filler distribution in polymer composite.