AFFECT OF ULTRASONIC LOADING FREQUENCIES ON THE BENDING STRENGTH OF POLYMER COMPOSITE MATERIALS
Arbon, glass and organoplastics samples were tested according to a three-point bending scheme after exposure to a low-amplitude loading with an ultrasonic frequency at various number of cycles. It has been established that for all the materials under study, there is a significant decrease in the bending stress limit after exceeding a certain (critical) number of cycles: for carbon fiber - 6 × 10<sup>6</sup>, fiberglass and organoplastics - 3 × 10<sup>6</sup>. At the same time, a stress increase by more than 19 % was found in the subcritical region for the fiberglass. Ultrasonic short-term loading can be used to harden cured fiberglass as part of the final product with a simple geometric shape.