Measurement of the elastic properties of epoxy resin/polyvinyl alcohol nanocomposites by ultrasonic wave velocities

The polyvinyl alcohol (PVA) nanofiber mats are produced using the electrospinning method. The epoxy resin (ER)/polyvinyl alcohol (PVA) nanocomposites are obtained by adding PVA nanofiber mats into neat epoxy resin (ER) as 5, 10, and 15 layers. The elastic properties (elastic constants, Young's modulus, Poisson's ratio, and Shear modulus) of the neat ER, and the ER/PVA nanocomposites, are determined by ultrasonic longitudinal wave velocity (V-L) and shear wave velocity (V-S) measurements. The morphology of the neat ER and the ER/PVA nanocomposites is investigated using scanning electron microscopy (SEM). The results obtained from SEM images showed the ER/PVA nanocomposites have a transversely isotropic structure. The V-L value of isotropic neat ER was obtained higher than the value of V-L33 and V-L45 degrees but lower in x(1) direction for V-L11 in the ER/PVA nanocomposites. The velocity values of ultrasonic shear waves propagated in x(1) direction and polarized in y(2) direction in the ER/PVA nanocomposites are determined as higher than the velocity values of ultrasonic shear waves propagated in z(3) and polarized in x(1) direction. Also, the value of E-3 determined in the z(3) direction is found to be significantly higher than the value of E-1 determined in the x(1) direction when the number of PVA layers increased in the ER matrix. The value of shear modulus (G(31)) is found as 1.53, 1.76, and 1.61 GPa for the ER/PVA-5, the ER/PVA-10, and the ER/PVA-15, respectively. The Poisson's ratio values of the ER/PVA nanocomposites are determined as between 0.473-0.502 and 0.247-0.276 for mu(11) and mu(31), respectively. On the other hand, the degree of anisotropy in the ER/PVA nanocomposites is determined using ratios of E-1/E-3 and mu(11)/mu(31). A small degree of anisotropy in dynamic Young's modulus (0.93-0.99) is observed, while a higher ratio is observed for Poisson's ratio (1.71-2.03) with increasing PVA layers in neat ER.

Automated summary

PVA nanofiber mats were produced using electrospinning and used to form ER/PVA nanocomposites. The elastic properties and morphology of the nanocomposites were studied using ultrasonic wave velocity measurements and scanning electron microscopy. The results showed that the nanocomposites have a transversely isotropic structure and exhibit anisotropic behavior.