8 Reinforcement of Recycled Rubber Based Composite with Nano-Silica and Graphene Hybrid Fillers 73 Fig. 8.4 Absorbed energy during charpy impact tests for SG specimens should be origins of the weakening of the matrix–particle interface. The toughness improvement in hybrid rubber based composites should be direct related to the increment of the debonding phenomena that can increase the size of the plastic zone in the structure. This case facilitate the devulcanized rubber based composites to dissipate additional fracture energy. 8.3.3 Charpy Impact Testing Last mechanical characterization was realized to see the impact resistance and energy absorbance capability of the manufactured composites. Each composition group was tested with at least three specimens. Absorbed energies during impact testing of the composites were presented in Fig. 8.4. It seems that the absorbed energy for each specimen during the impact tests is related to the increment of the plastic zone in the structure due to the debonding of the nano particles. Higher dispersion of the values is also related to the test specimens prepared under laboratory conditions; hot compaction, cutting notch effect, etc. 8.3.4 Damage Analysis by Means of Scratch Test and 3d Optical Roughness Meter After completing mechanical tests, tribological characterization of the composites were done by macro scratch tests. Surface damages were observed three dimensionally by an optical surface scanner. The results are presented in the Fig. 8.5. In Fig. 8.6 the volume and surface of the damage trace after scratch calculated from roughness test results are given. It can be said that, by the increase of the reinforcement content, composites become more resistant to wear. In reality, because of the high shear stress at the interfaces the interfacial shear stress should probably be the main reason for damage of the matrix and reinforced filler interfaces. When the indenter is slipping, tangential tensile stress is caused on the surface behind the indenter, while in front of the indenter the tangential stress is compressive. 8.4 Conclusion The hybrid rubber based composites reinforced with nano silica and graphene nano plates (GnPs) have shown enhancements in the mechanical properties, and more significantly, fracture toughness (KIC), which can be explained by synergistic impact coming from the intrinsic physical characteristics of the reinforcements; it means that nano silica and graphene nano plates
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