2 Devulcanized Rubber Based Composite Design Reinforced with Nano. . . 15 Fig. 2.3 (a) Fracture surfaces of the 3 different composites tested with 3P-Bending CJ I (b) CJ II (c)CJ III each composition, as presented in Fig. 2.3 with different fracture surfaces taken by SEM. Cavitation and void formation in the rubber matrix with matrix expansion and locally, debonding of nano particles with consequent void growth have been observed in the structure as the improved toughening mechanisms. It seems also an interaction between devulcanized rubber and the epoxy is very fine and there is fusion mutually between them. For this evolution, the mixture of devulcanized rubber (80 wt %) with epoxy (20 wt %) plays an important role. Some of the specimens with homogenous distribution of the nanoparticles have shown a typical debonding of the silica nanoparticles with GnPs that 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. 2.3.3 Drop Weight Testing Drop weight test analyses have been carried out on the three composites for the measurement of the impact resistance and energy absorbance ability of the manufactured composites for wing spar. Four specimens were tested for each composite. Absorbed energies measured with maximum force during impact were presented in Table 2.6.
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