Background:
Mechanical degradation of polymer composites is associated with changes in the structure of the material locally or applies to the entire element. Detailed microscopic analyses are necessary to fully understand and characterize the mechanisms of the samples’ destruction during strength loads.

Aim of the study:
To perform microscopic structural assessment and analysis of degradation that occurred in the composite reinforced with artificial fibers as a result of the mechanical tests that were undertaken.

Material and methods:
The research material consisted of a total of 70 samples subjected to the three-point bending test. Observations of fractures of the samples and their sections were made using the Scanning Electron Microscope (SEM).

Results:
Degradations were observed, such as cracks in the fiber-composite interface (debonding), cracks in the composite matrix, delamination and fiber damage. Degradations were local or concerned the whole sample.

Conclusions:
Degradations resulting from the strength tests prove the imperfect bonding of artificial fibers with the composite. Aramid fibers are the best reinforcement because they break longitudinally and transversely, and therefore are able to withstand high mechanical loads.