Failure of layered composites subject to impacts: constitutive modeling and parameter identification issues

Layered composites subject to impacts can fail by delamination, i.e. by debonding between laminae, if the stress waves cause damaging phenomena to take place mainly within the resin-enriched interlaminar phases. To simulate delamination at the structural level, processes dissipating energy are lumped onto fictitious zero-thickness interlaminar surfaces, and softening interface constitutive laws are adopted to describe the progressive failure of the interlaminar phases. Since delamination occurs inside very narrow regions, results of experimental testing on whole composites need to be accurately and reliably filtered to calibrate the interface constitutive laws. To this aim, here we propose a sigma-point Kalman filter approach. The performances of the proposed methodology, in terms of constitutive parameter estimations and dynamic delamination tracking, are assessed through pseudo-experimental testings on a two-layer composite, and real testings on multi-layer glass fiber reinforced plastic composites.