Dynamics of cracked composite material structures

As the result of this work models of the finite cracked beam element, delaminated beam element, and also delaminated plate element have been developed. These models have been used for the analysis of the influence of the fatigue cracks and delaminations on the dynamic characteristics of the constructions made of unidirectional composite materials. The method of modelling cracks and delaminations presented in this work enables its easy modification according to specific cases of damage (i.e. oblique crack, two-side crack, inside crack, multiple delaminations etc.). The results obtained from numerical calculations of the presented models are in good agreement with the known influence of damage parameters like: the position and the depth of the crack or the length and the position of the delamination on the natural frequencies. Simultaneously, a strong influence of the material parameters on these changes has been observed, which does not exist in the case of isotropic materials.