Analysis of damage characteristics for cracked composite structures using spectral element method

Structural health monitoring of composites, due to their wide use, has attracted more attention. It is essential to study variations of structural dynamic characteristics caused by the damage. A cracked spectral element model is developed to study dynamics of cracked composite structures. Taking crack location as a boundary, the cracked composite beam is separated into two parts, which are connected by a spring. The spring, whose flexibility can be obtained by laws of fracture mechanics, is used to model axial-flexural coupling effect due to asymmetry of the crack. Calculated natural characteristics are in good agreement with the results of conventional finite element method. Lamb wave reflection and transmission at the crack location are also analyzed to verify the model. Formulations are derived to calculate power reflection and transmission of wave modes. The results indicate that power reflection/transmission ratio of a single mode is monotonic, which may provide some quantitative foundations for structural health monitoring.