Vibration based damage detection in composite beams under temperature variations using Poincaré maps

In this work numerical and experimental study of the vibration of laminated beams with damage, subjected to dynamic loading and temperature variations is presented. The goal of the study is to check the applicability of the damage detection technique based on an analysis of the Poincare maps of the beam response. The geometrically nonlinear version of the Timoshenko beam theory is used to model the beam behavior. The damage is represented as a reduction of the effective elastic modulus of the beam material in a small area of the structure. The beams are subjected to a harmonic loading, leading to large amplitude vibrations and to temperature changes. The main results are focused on establishing the influence of the damage on the vibration response of heated or unheated structures and the change in the time-history diagrams and the Poincare maps, caused by a damage and elevated temperature. The damage detection criterion formulated earlier for nonheated plates, based on analysing of the Poincare maps of the damaged and healthy plate, is modified and tested for the case of beams additionally subjected to elevated temperatures. The importance of taking into account the actual temperature in the process of damage detection is shown. Performed experimental tests (by an optical method) confirm the applicability and sensitivity of the proposed method.