PSI - Issue 10

A. Sanida et al. / Procedia Structural Integrity 10 (2018) 91–96

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

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(Vassilikou-Dova and Kalogeras (2009)). The formalism of electric modulus (M*=1/ ε *) can be employed for more direct comparisons between DMA and DRS results, obtained in the same frequency range.

3. Results and discussion

The dynamic mechanical response of PVDF and the Fe 3 O 4 /PVDF nanocomposites is depicted in Fig.1. The rein forcement of Fe 3 O 4 is demonstrated in the storage modulus curves in the whole temperature range. The vanishing values of storage modulus in all specimens with temperature are attributed to a transition/relaxation which is associated with molecular motion of amorphous parts restricted within the crystalline region or various defect types in crystals and in the crystalline/amorphous interface. This transition/relaxation is evident by the formation of a peak recorded in the loss modulus spectra. Results from static mechanical tests are shown in Fig. 2. Young’s modulus increases with filler content, although at the highest content a leveling off is observed, indicating that the optimum static mechanical performance does not coincide with the maximum filler content. Tensile strength varies with filler content because nanoinclusions can prohibit yielding of the specimen and at the same act as stress raisers.

(a)

(b) Fig. 1. Storage modulus (a) and loss modulus (b) of all studied systems, as a function of temperature at f = 1 Hz.

(a)

(b) Fig. 2. Young’s modulus ( a) and tensile strength (b) of all studied systems, as a function of filler content.