PSI - Issue 82

Lenka Markovičová et al. / Procedia Structural Integrity 82 (2026) 274 – 280 L. Markovičová et al./ Structural Integrity Procedia 00 (2026) 000–000

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For samples with 10%, 20%, and 30% filler content, five impact strength (a c ) measurements were performed using the Dynstat apparatus. The arithmetic mean of the measurements is considered the final value. The results are presented in Table 2.

Table 2. Impact strength. Filler content (%)

Shore D (0 UV)

Shore D (500 UV)

10 20 30

81 84 85

78 79 84

The evaluation of rheological characteristics consists of monitoring the changes in complex dynamic viscosity η* (hereinafter referred to as viscosity), storage modulus G′, and loss modulus G″ as a function of angular velocity (or frequency) ω in the range of 0.05–500 s⁻¹, in three analyzed layers (250 µm, 500 µm, 750 µm) of the studied materials, Vojsovičová (2012). For polymer materials, it is typical that they exhibit elastic behavior dominating at high frequencies and viscous behavior at low frequencies. At a certain frequency, where the two moduli intersect and are equal, this point is referred to as the break point or cross-over point (COP), Hrašková (2015). The results of the measurements of these characteristics for samples not affected by UV radiation are shown in the graph (Fig. 3).

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Fig. 3. Rheological characteristics of composite samples with different glass fiber contents not affected by UV radiation.

From the curves, the dependence of complex dynamic viscosity η*, storage modulus G′, and loss modulus G″ on angular velocity ω in the range of 0.05–500 s⁻¹ can be observed. The viscosity curves for all three samples exhibit a similar trend. The highest values of complex dynamic viscosity η* were measured for the composite sample containing 30% glass fibers. At lower angular velocity ω values, the composite with 20% glass fiber content shows higher complex dynamic viscosity, while at higher angular velocities, the composite with 10% glass fiber content exhibits higher viscosity values. A shift in the position of the COP point depending on the filler content toward the