Model of fractured medium and nondestructive control of composite materials

Non-destructive testing of composites is an important issue in the modern aircraft industry. Composites are susceptible to the barely visible impact damage which can affect the residual strength of the material and occurs both during production and operation. The continuum model for describing the damaged zone is presented. The slip theory relations used for a continuous distribution of slip planes are applied. At the initial stage, the isotropic background model is used. This model allows the material slippage along the fractures based on the Coulomb friction law with the small viscous addition. In this regime, the govern system of equations becomes rigid. To overcome this difficulty, the explicit–implicit grid-characteristic scheme is proposed. The standard ultrasound diagnostic procedure of damaged composite materials is successfully simulated. Compared with the trivial free-surface fracture model, different reactions on the compression and stretch waves are registered. This approach provided an effective way for the simulation of complex dynamic behavior of damage zones.