On the use of vibration parameters for the estimation of damage in laminated composite plates

The dynamic response of a structure depends on the system's particular characteristics, namely its mass, stiffness and damping properties. Vibration-based damage detection techniques assume that damage will induce a local change on at least one of these characteristics. Hence, the development of techniques that evaluate changes on vibration parameters appeared as way for detecting damage on complex structures at an early stage. Nevertheless, there is still no universal method appropriate for all cases. Composite laminate materials are receiving an increasing attention by the industry, namely by the aeronautical and automotive ones. However, materials such as Carbon Fibre Reinforced Polymers (CFRPs) are extremely sensitive to impacts. Barely Visible Impact Damage (BVID) may occur, constituting an unsafe failure of difficult assessment. To assess (detect, locate and quantify) damage in this kind of materials is still a challenge, especially if a huge amount of sensors or expensive equipments are not available. In this article, some challenges and needs on the use of vibration parameters as features for damage assessment on composite laminate components are discussed. Some results of a technique that makes use of vibration-based parameters for damage detection - the frequency and damping factor - are also presented, concerning the location of damage on CFRPs plates subjected to impacts.