NARMAX model representation and its application to damage detection for multi-layer composites

The estimation of nonlinear autoregressive moving average with exogenous input (NARMAX) models for vibrating multi-layer composite plates is presented and used to assess internal delamination in the plates. Both static and dynamic tests are carried out to investigate the nature of the nonlinearity of the composite system. The nonlinear nature and order of nonlinearity are then approximated, and used to restrict the search space of the potential NARMAX model. After the structure and terms of the NARMAX model are identified, all coefficients are calculated for the intact plate. Delamination in the plate is assessed according to the coefficient variations in the model using the measured input/output data for the damaged system. Results show that the model output prediction is in agreement with the test data. The proposed method is available to discover and assess severity and location of delamination in the composite plates.