PSI - Issue 79

Agnieszka Chowaniec-Michalak et al. / Procedia Structural Integrity 79 (2026) 198–205

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All coatings containing granite powders exhibited type I damage, however, their resistance (measured as the minimum drop height causing cracking) was clearly higher than that of the reference system (Fig. 4). The highest resistance was observed for the G1-60 mixture, in which localized cracking occurred only at a height of about 80 cm. With increasing G1 powder content, a systematic improvement in impact resistance was observed, indicating a beneficial effect of the fine fraction on the coating’s ability to transfer localized stresses. The G2 powder (with larger particle size) produced slightly lower critical heights, which may result from the less homogeneous structure of the coating. 3.3. Results - type II damage For the 2 kg load, type II damage was observed, characterized by radial cracking and partial detachment of the coating from the substrate. The reference sample (REF) exhibited very low resistance, failure occurred already at a drop height of 20 cm, indicating the limited ability of pure epoxy resin to dissipate impact energy (Fig. 5). The use of granite powders clearly improved the resistance to extensive damage. All modified mixtures achieved higher minimum drop heights compared to the reference sample. The best results were obtained for G2-36 and G2-60, where type II damage appeared only at a height of about 75 cm. This indicates that larger particles (G2) promote more effective impact energy dissipation within the coating structure. For samples containing the finer powder (G1), an increase in resistance was also recorded, though less pronounced, which may suggest that particle size plays a dominant role in the initiation and propagation of cracks.

Type II damage

0 10 20 30 40 50 60 70 80 90

75

75

60

50

50

47.5

20

Minimum drop height [cm]

REF G1-12 G1-36 G1-60 G2-12 G2-36 G2-60

Fig. 5. Minimum drop height causing type II damage for epoxy coatings containing different amounts of granite powders.

3.4. Interpretation of results and discussion To enable comparison of the results obtained for different load masses, the minimum drop heights were converted into the corresponding impact energy for free fall, according to the equation (1). The comparison of the impact energies corresponding to the minimum drop heights for the individual mixtures is presented in Table 1. ܧ ൌ݉ ή݃ ή݄ (1) where: E – impact energy [J], m – mass of the weight [kg], g – gravitational acceleration (9.81 m/s²), h – drop height [m].