The technique of model-based identification is proposed to extract a model for damage in composite materials from experimental data. The proposed method is demonstrated on a unidirectional carbon fiber reinforced polymer (CFRP) beam. Impact damage is seeded in the CFRP beam using a spherical punch, causing localized damage. The specimen is evaluated through modal testing before and after the damage is seeded, with the healthy case modeled using the FEM. Finally, a virtual controller is found which eliminates error in response between the healthy model and damaged experimental system. The virtual controller, being in feedback with the healthy model at the FE node where the damage occurs, reflects the effect of the localized damage.
It is found that the seeded impact damage reduces stiffness and is a source of damping inside the composite beam. Interpretation of the local damage is made through the curve fitting of the identified dynamics. To confirm the efficacy of the fit, a closed-loop is made with the healthy model which is then compared to the data from the damaged system.