PSI - Issue 10

A. Sanida et al. / Procedia Structural Integrity 10 (2018) 257–263 A. Sanida et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 1. SEM images for the nanocomposites with 5 phr in (a) Fe 3 O 4 ; (b) (a) BaFe 12 O 19 and (b) SrFe 12 O 19 content.

3.2. Mechanical characterization

The mechanical properties of the fabricated nanocomposites were tested using an Instron 5582 tensile tester. The tensile modulus was calculated as the slope of the stress/strain curve in the elastic region. Figs.2-6 show the value of the elastic modulus and tensile strength for the epoxy nanocomposites with different concentrations of the nanoinclu sions. Errors bars represent the standard deviation of the representative result. The measured modulus for the neat epoxy was 1.86 GPa. The general trend for the elastic modulus is to increase almost monotonously with the addition of the nanoparticles for all systems examined. The increment of tensile modulus is attributed to the reinforcing ability and rigidness of the ceramic nanoparticles and to the strong interfacial bonding between the matrix and the nanoinclusions. The nanocomposites filled with SrFe 12 O 19 demonstrated the highest values of Y oung’s modulus in nearly all con centrations fabricated, reaching 3.71 GPa for the 20phr sample a whopping 100% increase compared to the neat epoxy. The maximum values of Y oung’s modulus and their increas e compared to the pure matrix for each system were:  For the ZnFe 2 O 4 systems E  (20 phr) = 2. 34± 0.12 GPa (25.5% increase)  The Fe 3 O 4 nanocomposites E  (20 phr) = 2. 90± 0.14 GPa (56% increase)  The BaFe 12 O 19 systems E  (20 phr) = 2.68 ± 0.13 GPa (44% increase)  The Y 3 Fe 5 O 12 nanocomposites E  (15 phr) = 2.79 ± 0.14 GPa (49.6% increase) Since no surface treatment was conducted in any of the employed filler types, moreover no substantial differences in the dispersion quality were revealed during the morphological characterization via SEM, the variation of the Young’s modulus values with filler type could be attributed to the intrinsic reinforcing capability of each ferrite and the adhesion between different nanoparticles and the polymer matrix. Typically, hexaferrites exhibit higher modulus values than spinels, which was indirectly confirmed in this study by the results for the SrFe 12 O 19 filled nanocomposites. The lower values for the other hexaferrite/polymer system can be attributed to the presence of hematite in the BaFe 12 O 19 nano powder, as confirmed by the XRD spectra in a previous study (Kanapitsas et al. (2015)).

Fig. 2. (a) Young’s modulus ; (b) tensile strength as a function of concentration, for the nanocomposites with Y 3 Fe 5 O 12 nanoparticles.